Libro Analisis de Agua Cromatografía

8/14/2019 Libro Analisis de Agua Cromatografa

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D Anions

88 Metrohm Monograph 8.038.5003

Groundwater Houston (a)and groundwater Houston spiked with 1 ppb perchlorate (b)

Peakno.

Component Retention time[min]

Concentrationchromatogram a[ g/L]

Concentrationchromatogram b[ g/L]

1 Perchlorate 13.5 0.35 1.35

Relevant Metrohm literatureIC Application Note S 217 Ultratrace-level perchlorate in reagent water, groundwater, surface water and water containing 3000 ppm of total dissolved solids(US EPA method 314.0)

IC Application Note M 2 Chlorite, chlorate and perchlorate in explosion residueapplying IC/MS coupling

Reprint LC-GC, The Applications Book, September 2004, p. 14; Determinationof trace level perchlorate in different vegetable extracts by Ion Chromatography-Mass Spectrometry, Jay Gandhi, Joe Hedrick

Reprint LC-GC, The Application Notebook, 2005, September. p. 1; Simulta-neous Determination of Bromide and Perchlorate in Vegetables by Ion Chro-matography-Mass Spectrometry, Jay Gandhi, Joe Hedrick


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D2 Chromate Cr(VI) with IC

Analysis of water samples and water constituents with Metrohm instruments 89

Additional literature Agilent Application Note 5989-0816EN The Analysis of Perchlorate by IonChromatography/Mass Spectrometry

US EPA Method 314.0 Determination of Perchlorate in Drinking water usingIon Chromatography

US EPA Method 332.0 Determination of Perchlorate in Drinking water by Ionchromatography with suppressed conductivity and Electrospray Ionization MassSpectrometry


General remarksChromium is considered as an essential trace element. Only the compounds ofhexavalent chromium are toxic because of their oxidative effect on cell constitu-ents. Cr(VI) has mutagenic and carcinogenic properties and can cause skinallergies. It is therefore important to know the chromium content of the differenttypes of water.

The chromium content of surface waters ranges from 0.2 to 20 g/L. The require-ments for drinking water depend on local legislation, the limiting values rangingfrom


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D Anions


b) for chromate determination using post-column derivatization with diphenylcarbazide and VIS detection

MIC-2 or MIC-1 Advanced IC system plus Lambda 1010 UV/VIS detector, 833 Advanced IC Liquid Handling Pump Unit and 6.2836.000 post-column reactor

844 UV/VIS Compact IC (2.844.0120)

Anion exchange column, e.g. Metrosep A Supp 5 100 (6.1006.510) plusMetrosep A Supp 4/5 Guard (6.1006.500), Metrosep Anion Dual 3 (6.1006.120)plus Metrosep RP Guard (6.1011.020), Metrosep A Supp 4 250 (6.1006.430)plus Metrosep A Supp 4/5 Guard (6.1006.500), Phenomenex Star Ion A300(6.1005.100)

ReagentsUse only reagents of highest purity and ultrapure water having a specific resis-tance >18 MOhm cm.

Chromate standard: (chromate) = 1 g/L

Weigh 0.167 g potassium chloride into a 100-mL volumetric flask, dissolve inultrapure water, make up to 100 mL with ultrapure water and mix.

a) for chromate determination using conductivity detection after chemicalsuppression

Eluent containing Na 2CO 3 and NaHCO 3, concentrations depend on the columnused

Suppressor regenerant solution: c(H2SO

4) = 50 mmol/L

Suppressor rinsing solution: ultrapure water (specific resistance >18 MOhm cm)


Eluent containing Na 2CO 3 and NaHCO 3, concentrations depend on the columnused

Reagent for post-column derivatization: dissolve 0.5 g 1,5-diphenyl carbazide in100 mL methanol (HPLC grade). Transfer approx. 600 mL ultrapure water into a1-L volumetric flask, then add 28 mL 98% sulfuric acid. Add the diphenyl carba-zide solution and make up to the mark with ultrapure water. This solution has ashelf life of 5 days.

Sample preparation methods All water samples should be filtered through a filter with 0.45 m pore size.


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AnalysisQuantitation is carried out by means of an external multipoint calibration coveringthe concentration range concerned. To obtain the required concentrations, theabove-mentioned standard is diluted with ultrapure water.

Chromatographic conditions plus example chromatograms

a) for chromate determination using conductivity detection after chemicalsuppression

Instrument 861 Advanced Compact IC

Full Scale 250 S/cm or 50 S/cm

Polarity +

Column Metrosep A Supp 5 100 (6.1006.510) plus Metrosep ASupp 4/5Guard (6.1006.500)

Eluent 3.2 mmol/L Na 2CO 3, 1.0 mmol/L NaHCO 3

Flow 0.7 mL/min

Loop 20 L

Wastewater

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 min

20

40

60

80

100

120

140

160

180

uS/cm

Cond

1

2

3

4 5 6

13 14 15 16 17 18 19 min

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

uS/cm

Cond5

6


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D Anions


Peak no. Component Retention time [min] Concentration [mg/L]

1 Chloride 3.95 84.3

2 Nitrite 4.98 105

3 Nitrate 7.46 3652

4 Sulfate 9.61 53.0

5 not identified 16.1

6 Chromate 17.12 0.11


InstrumentMIC-2 Advanced IC system plus Lambda 1010 UV/VIS detector, 833

Advanced IC Liquid Handling Pump Unit and 6.2836.000 post-column reactor

Lamp Tungsten

Wavelength 540 nm

Column Phenomenex Star Ion A300 (6.1005.100)

Eluent 1.8 mmol/L Na 2CO 3, 1.7 mmol/L NaHCO 3

Eluent flow 1.5 mL/min

Reagentflow 0.5 mL/min

Loop 20 L


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D Anions


D2 Silicate dissolved silicic acid with IC

General remarksSilicates are salts of silicic acid and form a large group of minerals. The earth's

crust cosists to more than 90%, the earth's mantle almost completely of silicates.The silicates occur in dissolved form in virtually all types of water and theirdetermination, for example in drinking water, is of considerable interest.

The silicate ion is also an indicator of the quality of ultrapure water as it is one ofthe first ions that appear in the purified water when the ion exchangers used forwater purification becomes exhausted. The determination at very low levels ofconcentration is therefore very important, for example in thermal power plants.

As silicates are salts of a very weak acid they dissociate only in the alkaline regionand there can be detected by conductivity without chemical suppression.

For the determination of silicate in the low ppb range the preconcentration tech-nique is used.

Recommended accessoriesMIC-1 Advanced IC system

Anion exchange column, e.g. Hamilton PRP-X 100 (6.1005.000) plus HamiltonPRP-X 100 precolumn cartridge (6.1005.020), Phenomenex Star Ion A300(6.1005.100)

Preconcentration column, e.g. Hamilton PRP-X 100 precolumn cartridge(6.1005.020), Metrosep A PCC 1 anion preconcentration column (6.1006.300)


Silicate standard: (silicate) = 1 g/L

Weigh 0.100 g pure silicate (SiO 2) into a 100-mL volumetric flask, dissolve in0.2% NaOH, make up to 100 mL with 0.2% NaOH and mix.

Eluent containing Na 2CO 3 and NaHCO 3, concentrations depend on the column

usedSample preparation methods

All water samples should be filtered through a filter with 0.45 m pore size.


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D2 Silicate dissolved silicic acid with IC


AnalysisQuantitation is carried out by means of an external multipoint calibration coveringthe concentration range concerned. To obtain the required concentrations, theabove-mentioned standard is diluted with ultrapure water.

If one works in the low ppb range using preconcentration, it is recommended toapply inline calibration.

Examples

Silicate in drinking water

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 min

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

mV

ch1

1

2



2 Silicate 4.18 5.32


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Instrument MIC-1 Advanced IC system

Range 1 mS/cm

Full Scale 5 S/cm

Polarity

Column Hamilton PRP-X 100 (6.1005.000) plus Hamilton PRP-X 100precolumn cartridge (6.1005.020)

Eluent 3.2 mmol/L NaOH / 0.5 mmol/L Na 2CO 3

Flow 1.0 mL/min

Loop 100 L

Silicate in boiler feed water (ultrapure water)

0 1 2 3 4 5 6 7 8 9 10 min

20

40

60

80

100

120

140

mV ch1

1

Peak no. Component Retention time [min] Concentration [ g/L]

1 Silicate 3.71 0.89


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D2 Sulfite, sulfate and thiosulfate with IC



Range 1 mS/cm

Full Scale 10 S/cm

Polarity

Column Hamilton PRP-X 100 (6.1005.000) plus Hamilton PRP-X 100precolumn cartridge (6.1005.020)

Preconcentrationcolumn

IC anion preconcentration column Metrosep A PCC 1(6.1006.300)

Preconcentrationvolume

10 mL

Eluent 3.2 mmol/L NaOH / 0.5 mmol/L Na 2CO 3

Flow 1.0 mL/min

Metrohm literature concerning silicate determination with ICIC Application Note N 44 Silicate in tap water

IC Application Note N 54 Borate and silicate in ultrapure water

IC Application Note N 56 Silicate besides fluoride in tap water

IC Application Note N 60 and Q 1 Online monitoring of trace levels of silicate inboiler feed water


General remarksWith ion chromatography the determination of the sulfur species sulfite, sulfateand thiosulfate can be carried out in one run. This determination is of high interestin the analysis of wastewaters, especially in the paper industry, where sulfate- and

sulfite-containing solutions are used for paper production.

Recommended accessoriesMIC-2 Advanced IC system or 861 Advanced Compact IC

Anion exchange column, e.g. Metrosep A Supp 3 250 (6.1005.320) plusMetrosep RP Guard (6.1011.020), Metrosep Anion Dual 3 (6.1006.120) plusMetrosep RP Guard (6.1011.020), Metrosep A Supp 4 250 (6.1006.430),Metrosep A Supp 5 150 (6.1006.520) plus Metrosep A Supp 4/5 Guard(6.1006.500)


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Sulfite standard: (sulfite) = 1 g/L

Stabilizing the sulfite requires addition of formaldehyde or 2-propanol (isopro-panol). Accordingly, there are two possibilities of preparing the standard:

a) Weigh 0.157 g sodium sulfite into a 100-mLvolumetric flask and dissolve in0.2 mmol/L NaOH and 0.037% formaldehyde. Make up to 100 mL with thismixture and mix.

b) Weigh 0.157 g sodium sulfite into a 100-mLvolumetric flask and dissolve inultrapure water. Add 10 mL 2-propanol, make up to the mark with ultrapurewater and mix.

Sulfate standard: (sulfate) = 1 g/L; commercially available.

Thiosulfate standard: (thiosulfate) = 1 g/L

Weigh 0.222 g sodium thiosulfate pentahydrate into a 100-mLvolumetric flask,dissolve in ultrapure water, make up to 100 mL with ultrapure water and mix.

Eluent containing Na 2CO 3 and NaHCO 3; possibly also acetone; concentrationsdepend on the column used

Suppressor regenerant solution: c(H 2SO 4) = 50 mmol/L



As wastewaters can contain considerable amounts of organic substances, anadditional sample preparation using an RP cartridge (6.1012.000) is recom-mended.

AnalysisQuantitation is carried out by means of an external multipoint calibration coveringthe concentration range concerned. To obtain the required concentrations, theabove-mentioned standards are diluted with ultrapure water. To stabilize the di-luted sulfite standards, formaldehyde (0.0037%) or 2-propanol (1%) must beadded to them.


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Examples

Sulfite, sulfate and thiosulfate in wastewater

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 min

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

uS/cm

Cond

1

2

34

5

6

7

8


1 Chloride 4.43 38.8

2 System peak 5.80

3 Bromide 6.75 0.34

4 Nitrate 7.88 not quantified

5 Sulfite 10.4 1.54

6 Sulfate 13.61 146

7 Oxalate 16.49 2.02

8 Thiosulfate 25.87 12.7


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Full Scale 50 S/cm

Polarity +

Column Metrosep Anion Dual 3 (6.1006.120) plus Metrosep RP Guard(6.1011.020)

Eluent 1.8 mmol/L Na 2CO 3 / 2.0 mmol/L NaHCO 3 / 15% acetone

Flow 0.8 mL/min

Loop 20 L

Relevant Metrohm literatureIC Application Note S 144 Heat stable salts in scrubber solutions

IC Application Note S 155 Sulfite, oxalate and thiosulfate besides standardanions in process water of paper industry

D2 Organic acids with IC

General remarks

The determination of weak organic acids such as acetic acid or propionic acid iscarried out using ion exclusion chromatography. The completely dissociated acidsare not retained on the stationary phase by Donnan exclusion and therefore elutewithin the dead time.

The determination of short-chain organic acids is applied in wastewater analysis.Compared to gas chromatography, which is also used for this but requires asample derivatization step, ion exclusion chromatography has the advantage ofrequiring significantly less sample preparation effort.

The determination of the organic acids after their separation on an ion exclusioncolumn can be done with direct conductivity measurment or after inverse

suppression with lithium.


Ion exclusion column, e.g. Metrosep Organic Acids 250 (6.1005.200) plusMetrosep Organic Acids Guard (6.1005.250)


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Organic acid standards 1 g/L

In a 100-mL volumetric flask dissolve the corresponding amounts of the salts ofthe organic acids or the acids themselves in ultrapure water. Make up to 100mL with ultrapure water and mix.

Eluent containing a dilute acid, such as sulfuric or perchloric acid, possibly alsoacetone; concentrations depend on the application and the column used

Suppressor regenerant solution: c(LiCl) = 10 mmol/L



It is recommended to pass the samples through a H + cartridge (6.1012.010) toneutralize them and to eliminate the divalent cations.

AnalysisQuantitation is carried out by means of an external multipoint calibration coveringthe concentration range concerned. To obtain the required concentrations, theabove-mentioned standards are diluted with ultrapure water.


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D Anions


Examples

Organic acids in process water with inverse suppression

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 min

46

48

50

52

54

56

58

60

62

64

uS/cm

Cond

1 2 34

5 6

7

8

9



2 Glycolic acid 11.44 3.30

3 Formic acid 12.45 0.97

4 Glutaric acid 14.23 0.93

5 Acetic acid 15.41 724

6 Propionic acid 18.14 530

7 Carbonate 20.04 not quantified

8 Butyric acid 22.32 24.2

9 Sulfide 25.73 not quantified


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Full Scale 250 S/cm

Polarity +

Column Metrosep Organic Acids 250 (6.1005.200) plus Metrosep Organic Acids Guard (6.1005.250)

Eluent 0.5 mmol/L HClO 4

Flow 0.5 mL/min

Loop 20 L

Suppressor 10 mmol/L LiCl as regenerant solution; ultrapure water for rinsing

Relevant Metrohm literatureIC Application Note O 21 Six organic acids in a process water of the paperindustry

IC Application Note O 34 Aliphatic monocarboxylic acids in produced waterusing IC/MS coupling


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D Anions


D3 Chromate/dichromate Cr(VI) with VA

General remarks

Chromium is considered as an essential trace element. Only the compounds ofhexavalent chromium are toxic because of their oxidative effect on cell constitu-ents. Cr(VI) has mutagenic and carcinogenic properties and can cause skinallergies. It is therefore important to know the chromium content of the differenttypes of water.

The chromium content of surface waters ranges from 0.2 to 20 g/L. The require-ments for drinking water depend on local legislation, the limiting values rangingfrom 10 g/L and

catalytic DP stripping voltammetry for contents ranging from 0.02 to 1.5 g/L.

Recommended accessories797 VA Computrace with Dosino

705 UV Digester


a) for the polarographic method:

Cr(VI) standard: (Cr 6+) = 100 mg/LPipet 10.0 mL (Cr 6+) = 1 g/L (commercially available) into a 100-mL volumetricflask, make up to the mark with ultrapure water and mix.

Potassium hydroxide solution: w(KOH) = 45%

Ammonia: w(NH 3) = 5%

Acetic acid: w(CH 3COOH) = 98%

Ethylene diamine: puriss p.a. (CAS 107-15-3)

b) for the stripping-voltammetric method:

Cr(VI) standard: (Cr 6+) = 100 mg/LPipet 10.0 mL (Cr 6+) = 1 g/L (commercially available) into a 100-mL volumetricflask, make up to the mark with ultrapure water and mix.


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Cr(VI) standard: (Cr 6+) = 0.02 mg/LPipet 2.0 mL (Cr 6+) = 100 mg/L into a 100-mL volumetric flask, make up to themark with ultrapure water and mix. In a second 100-mL volumetric flask makeup to the mark 1.0 mL of this solution with ultrapure water and mix. Preparefresh solutions daily (both intermediate and 0.02 mg/L solution).

Sodium hydroxide solution: w(NaOH) = 30%

Base electrolyte:Dissolve 1.64 g sodium acetate, 1.96 g disodium diethylenetriamine pentaace-tate (DTPA, CAS 67-43-6) and 21.3 g sodium nitrate in ultrapure water, makeup to 100 mL with ultrapure water and mix.

Sample preparation methodsWaters moderately loaded with organic substances:

Adjust the sample to a pH value of 5...7. Transfer 10 mL of the resulting mixtureinto a quartz reaction vessel, add 10 L w(H2O 2) = 30% and digest in the UV Di-gester for 1 h at 90 C. Add another 10 L H2O 2 and digest for another 30 min.

Wastewater heavily loaded with organic substances:

This type of wastewater requires wet digestion (e.g. with H 2SO 4 / H 2O 2). After thedigested solution has cooled down, add 10 mL ultrapure water and 2 drops ofc(KMnO 4) = 0.02 mol/L and heat to boiling. Dropwise add permanganate solutionuntil the pink color remains. Keep the solution boiling for approx. 5 min while main-taining the total volume constant by adding small amounts of ultrapure water. Be-fore it has cooled down, adjust the solution to pH = 5...9 with KOH solution. Rinsethe solution into the polarographic vessel with ultrapure water.

Polarographic analysisPreneutralize the sample or the digested solution with KOH solution to pH = 7...8.

To 10 mL sample or digested solution in the polarographic vessel add 20 Lethylenediamine, 150 L acetic acid, 300 L KOH and 200 L ammonia. Ifnecessary adjust the pH value to approx. 9.5 by adding KOH solution or aceticacid, deaerate with nitrogen and record the DP polarogram applying the followingconditions:

Working electrode DME Start potential 80 mV

Stirrer 2000 rpm End potential 400 mV

Mode DP Potential step 6 mV

Deaeration time 600 s Time 0.4 s

Pulse amplitude 50 mV Potential gradient 10 mV/s

Equilibration time 3 s Peak potentialCr(VI)

approx. 250mV


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D Anions


The Cr(VI) content is obtained by means of the standard addition method (in thepresent example: three times 100 L Cr standard, = 100 mg/L).

Stripping voltammetric analysisTransfer 10 mL sample or digested solution (or an aliquot) into the polarographicvessel and add 5 mL base electrolyte. Adjust the pH value of the mixture to 6.20.1 with NaOH solution and record the DP stripping voltammogram applying thefollowing conditions:

Working electrode HMDE

Stirrer 2000 rpm

Mode DP

Deaeration time 300 s

Pulse amplitude 50 mV

Electrolysis under stirring 60 s

Electrolysis withoutstirring

5 s

Preconcentrationpotential

1.0 V

Start potential 1.0 V

End potential 1.45 V

Potential step 10 mV

Time 0.3 s

Potential gradient 33.3 mV/s

Peak potential Cr approx. 1.25 V

The Cr content of the sample was determined by twice adding 100 L (Cr 6+) =0.02 mg/L. The blank value was also determined.


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Examples: Cr content of a wastewater (polarographic) and a surface water(voltammetric)

Relevant Metrohm literature Application Bulletin no. 116 Polarographic/voltammetric determination ofchromium in small quantities


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D Anions


D3 Cyanide with VA

General remarks

The determination of cyanides in waters (e.g. seepage water, electroplatingwastewater before and after detoxification) is highly important. Cyanideconcentrations as low as 50 g/L can be lethal for fish. Depending on thelegislation for drinking water, the maximum allowable cyanide concentrations varybetween 50 and 100 g/L.

The following methods will be described:

DP polarography for cyanide contents of 0.1...10 mg/L and

DP stripping voltammetry for cyanide contents 10...100 g/L.


ReagentsUse only reagents of the highest purity and ultrapure water.

Cyanide standard: (CN -) = 100 mg/LDissolve first 0.6 g KOH and then 0.2503 g KCN in ultrapure water, make up to1 L with ultrapure water and mix.

Cyanide standard: (CN -) = 10 mg/L

Transfer 0.6 g KOH into a 100-mL volumetric flask and dissolve in approx. 50mL ultrapure water. Add 10.0 mL (CN ) = 100 mg/L, make up to the mark withultrapure water and mix. Fresh solution has to be prepared daily.

Ground electrolyte:Dissolve 100 g KOH and 123 g H 3BO 3 in approx. 750 mL ultrapure water.Leave to cool down, make up to 1 L with ultrapure water and mix.

Sample preparation methodsIf only the free cyanide is of interest, the samples can be used directly.

Otherwise one has to distinguish between easily released cyanides (e.g. fromKCN) and the total cyanide content, which also comprises the CN complexes ofheavy metals. Digestion and separation occur according to DIN 38405 D13/D14and are described in detail in Application Bulletin no. 46 Potentiometricdetermination of cyanide.

For the voltammetric analyses, the ground electrolyte is used instead of the NaOHabsorption solution.


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D3 Cyanide with VA


Polarographic analysisTransfer 10...20 mL absorption solution or 1...10 mL sample solution plus 10 mLground electrolyte into the polarographic vessel and deaerate with nitrogen. Re-cord the DP polarogram applying the following conditions:

Working electrode DME Start potential 50 mV

Stirrer 2000 rpm End potential 400 mV

Mode DP Potential step 4 mV

Deaeration time 300 s Time 0.6 s

Pulse amplitude 50 mV Potential gradient 6.6 mV/s

Pulse time 0.04 s

Equilibration time 5 s

Peak potential CN approx. 0.22 V

The cyanide content is determined by means of standard additions.

Stripping-voltammetric analysisTransfer 10...20 mL absorption solution or 1...10 mL sample solution plus 10 mLground electrolyte into the polarographic vessel and deaerate with nitrogen. Re-cord the DP stripping voltammogram applying the following conditions:

Working electrode HMDE Preconcentrationpotential

80 mV

Stirrer 2000 rpm Start potential 80 mV

Mode DP End potential 400 mV

Deaeration time 300 s Potential step 4 mV

Pulse amplitude 50 mV Time 0.4 s

Electrolysis under

stirring

60 s Potential gradient 10 mV/s

Electrolysis withoutstirring

3 s Peak potential CN approx. 0.20 V

The cyanide content is determined by means of standard additions.


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D Anions


Examples: CN content in an artificial wastewater and in drinking water

Relevant Metrohm literature Application Bulletin no. 110 Polarographic determination of free cyanide


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D3 Sulfides and hydrogen sulfide with VA


D3 Sulfides and hydrogen sulfide with VA

General remarks

Sulfides and/or H 2S can be present in reductive ground water, in seepage waterand, under anaerobic conditions, at the bottom of surface waters. Sulfides arevolatile and easily oxidized by atmospheric oxygen. Care has therefore to be takenduring sampling: the samples must be made alkaline with NaOH and be wellsealed for transport.

Sulfides can be easily determined with stripping-voltammetric methods.

The method is suitable for contents ranging from 0.3 to 20 g/L.


ReagentsSodium hydroxide solution: c(NaOH) = 10 mol/LDissolve 80 g NaOH under stirring in approx. 100 mL dist. H 2O. Leave to cooldown, make up to 200 mL with dist. H 2O and mix.

Sodium hydroxide solution: c(NaOH) = 0.1 mol/LTransfer 10 mL c(NaOH) = 10 mol/L into a 1000-mL volumetric flask containingapprox. 800 mL dist. H 2O. Make up to the mark with dist. H 2O and mix.

Sulfide standard: (S 2-) = 1 g/L

Mix 1 mL c(NaOH) = 10 mol/L with 98 mL dist. H 2O and deaerate with nitrogenfor 5 min. Dissolve 700 mg sodium sulfide hydrate (approx. 35% Na 2S) in thissolution and store the resulting solution in a sealed dark bottle in the refrigera-tor. The solution has a storage life of approx. 1 week. To determine its exactcontent, 1 mL of this solution is added to 40 mL c(NaOH) = 0.1 mol/L (O 2-free);nitrogen is passed over the solution while it is titrated with c(AgNO 3) = 0.01mol/L using the Ag Titrode coated with Ag 2S. 1 mL c(AgNO 3) = 0.01 mol/Lcorresponds to 0.16 mg S 2- (see also chapter D1).

Sulfide standard: (S 2-) = approx. 100 mg/LDeaerate approx. 150 mL dist. H 2O plus 2 mL c(NaOH) = 10 mol/L in a 200-mL

volumetric flask with nitrogen. Add 20.0 mL (S2-

) = approx. 1 g/L, make up tothe mark with O 2-free dist. H 2O and mix. Prepare fresh solution daily.

Sulfide standard: (S 2-) = approx. 5 mg/L Add 1 mL c(NaOH) = 10 mol/L to 5.0 mL (S 2-) = approx. 100 mg/L, make up to100 mL with O 2-free ultrapure water and mix. Prepare fresh solution daily.


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D Anions


Analysis

Stripping-voltammetric method

In the polarographic vessel deaerate 10 mL c(NaOH) = 0.1 mol/L during 5 min with

nitrogen. Depending on the sulfide content, add 1...10 mL sample and mix bysparging with nitrogen, then record the DP stripping voltammogram applying thefollowing conditions:

Working electrode HMDE Electrolysis under stirring 30 s

Stirrer 2000 rpm Electrolysis without stirring 10 s

Mode DP Preconcentration potential 450 mV

Deaeration time 300 s Potential gradient 450 mV to 1000 mV

Pulse amplitude 25 mVPulse time 0.04 s

Peak potential sulfide approx. 730 mV

The content is determined by means of two standard additions. This method issuitable for sulfide contents of 0.3...20 g/L.

Example: Sulfide in ground water (with added sulfide)

Relevant Metrohm literature Application Bulletin no. 199 Polarographic determination of sulfide and sulfite


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D3 Sulfite with VA


Additional literatureHe,Y., Zheng,Y., Locke,D.C. Differential pulse cathodic stripping voltammetricdetermination of nanomolar levels of dissolved sulfide applicable to fieldanalysis of groundwater. Anal.Chim.Acta 459, (2002) 209-217

D3 Sulfite with VA

General remarksSulfite only occurs in wastewaters, for example of the photo and the paperindustries it is not found in industrial water, ground water and surface water.

Ambient oxygen rapidly oxidizes sulfite to sulfate, especially in alkaline solution.This has to be taken into account during sampling and sample treatment.

The method described here allows to determine, in a simple manner, sulfiteconcentrations ranging from 1 mg/L to approx. 10 mg/L by means of DPpolarography.


Reagents Acetate buffer: c(NaOH) = 0.2 mol/L plus c(CH 3COOH) = 0.4 mol/LIn a glass beaker dissolve under stirring 4 g NaOH in approx. 400 mL dist. H 2O.Under stirring then add 12 mL w(CH 3COOH) = 98%. Leave to cool down, makeup to 500 mL with dist. H 2O and mix.

Sulfite standard: (sulfite) = 1 g/LWeigh 161 mg Na 2SO 3 (98%) into a 100-mL volumetric flask and dissolve inapprox. 90 mL O 2-free dist. H 2O, make up with dist. H 2O to 100 mL and mix. Ifstored in a dark bottle and covered with N 2, this solution has a shelf life ofapprox. 1 week.

Sulfite standard: (sulfite) = 200 mg/LPipet 20.0 mL (sulfite) = 1 g/L into a 100-mL volumetric flask, make up to the

mark with O 2-free dist. H 2O and mix. Prepare fresh solution daily.


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D Anions


AnalysisIn the polarographic vessel deaerate 10 mL acetate buffer for 5 min with nitrogen.Depending on the sulfite content, add 1...10 mL sample and mix manually (do notsparge with nitrogen). Record the DP polarogram applying the following

conditions:

Working electrode SMDE

Stirrer 2000 rpm

Mode DP



Pulse time 40 msEquilibration time 10 s

Start potential 400 mV

End potential 850 mV

Potential step 6 mV

Time 0.8 s

Potential gradient 5 mV/s

Peak potential sulfite approx. 610 mV

The content is determined by means of two standard additions (mix manually, donot sparge with nitrogen).

Remarks

In the presence of sulfide there is a peak at approx. 0.45 V.

In the presence of thiosulfate there are two overlapping peaks between 0.14 Vand 0.28 V.


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D3 Sulfite with VA


Example: Sulfite in wastewater

Relevant Metrohm literature Application Bulletin no. 199 Polarographic determination of sulfide and sulfite


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E Cations


E Cations

E1 Titration: Calcium and magnesiumPlease find the detailed procedures for these determinations in the chapter Waterhardness on page 22.

E2 Cation determination with IC

General remarksThe determination of lithium, sodium, ammonium, potassium, calcium, magne-sium, barium und strontium in different water types (drinking water, mineral water,

etc.) is of paramount importance for the assessment of water quality. The determi-nation of these cations by means of ion chromatography is therefore the subject ofvarious standards.


Cation exchange column, e.g. Metrosep Cation 1-2 (6.1010.100), Metrosep C 2 100 (6.1010.210), Metrosep C 2 150 (6.1010.220), Metrosep C 2 250(6.1010.230) plus Metrosep C 2 Guard (6.1010.200)


Eluent containing tartaric acid and dipicolinic acid (2,6-pyridine dicarbonic acid)or nitric acid; concentrations depend on the column used and the application.

1-g/L stock solutions of lithium, sodium, ammonium, potassium, calcium,magnesium, barium, strontium can be obtained especially for ion chromato-graphy from different reagent manufacturers; after appropriate dilution, thesesolutions are used for calibration. The standard solutions are prepared in 2

mmol/L nitric acid (pH value 2.5).PRIMUS standards, the only primary multiion standards for ion chromato-graphy.


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Sample preparation methodsThe samples have to be filtered, for example using Minisart (Sartorius) or dispos-able filter supports (Whatman, formerly Schleicher & Schuell) with a pore size of0.45 m or less. Even seemingly clear solutions can contain very fine particles that

damage the column.The samples can be filtered automatically applying ultrafiltration.

At higher concentrations it may be necessary to dilute the samples.

For water samples containing a high proportion of organic substances we recom-mend to apply dialysis as a sample preparation step that can be completelyautomated.

The pH value of the samples should be adjusted to pH 2.5 by means of nitric acid.

Metrohm offers fully automated IC systems that carry out inline ultrafiltration, inlinedialysis (patented) and also inline dilution. The MISP systems (Metrohm InlineSample Preparation) simplify and improve sample preparation significantly.

AnalysisWhen working in the concentration range 10 ppb to 100 ppm, one normally injects10...100 L sample, which is separated on the cation exchanger column followedby indirect conductometric detection.

If lower detection limits are to be achieved, the sample volume must be increasedmarkedly. Consider, however, that larger sample volumes mean a larger waterpeak, which affects the evaluation of the early-eluting peaks.

Sample preconcentration is a simple method for lowering the detection limit byseveral orders of magnitude. The sample loop is replaced by a preconcentrationcolumn. An increased sample volume, e.g. 10 mL, is passed over the preconcen-tration column, which contains essentially the same material as the separationcolumn. This ensures that all cations contained in the sample solution to be ana-lyzed (e.g. ultrapure water) are kept back on the column and are preconcentrated.The preconcentrated analyte ions are then brought to the separation column bythe eluent flowing counter-current.

Quantitation is performed by means of an external calibration in the concentrationrange concerned. A three-point calibration is recommended for the determination

of cations.


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E Cations


Examples

Cations in wastewater

0 1 2 3 4 5 6 7 8 9 10 11 min

100

200

300

400

500

600

700

800

mV

ch1

1

2

3

4

5


1 Sodium 3.08 7126

2 Ammonium 3.35 450

3 Potassium 4.09 158

4 Calcium 6.24 3049

5 Magnesium 9.87 80


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Range 1.0 mS/cm

Full Scale 50 S/cm

Polarity

Column Metrosep Cation 1-2 (6.1010.100) plus Metrosep C 2 Guard(6.1010.200)

Eluent 4 mmol/L tartaric acid, 1 mmol/L dipicolinic acid (2,6-pyridinedicarbonic acid)

Flow 1.2 mL/min

Loop 10 L

Cations in drinking water

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 min

1

2

3

4

5

6

7

uS/cm

Cond

1

2

34


1 Sodium 4.42 10.1

2 Potassium 7.96 5.61

3 Calcium 9.99 18.3

4 Magnesium 12.7 9.03


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E Cations


Instrument 861 Advanced Compact IC (2.861.0010)

Full Scale 1000 S/cm

Polarity

Column Metrosep Cation 1-2 (6.1010.100) plus Metrosep C 2 Guard(6.1010.200)

Eluent 4 mmol/L tartaric acid, 0.75 mmol/L dipicolinic acid (2,6-pyridinedicarbonic acid)

Flow 1.0 mL/min

Loop 10 L

Cations in mineral water

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 min

10

20

30

40

50

60

70

mV

ch3

1

2

3

4


1 Sodium 5.03 1.96


3 Calcium 14.28 86



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Range 1.0 mS/cm

Full Scale 50 S/cm

Polarity

Column Metrosep C 2 150 (6.1010.220) plus Metrosep C 2 Guard(6.1010.200)

Eluent 4 mmol/L tartaric acid, 0.75 mmol/L dipicolinic acid (2,6-pyridinedicarbonic acid)

Flow 1.0 mL/min

Loop 10 L

Cations in a boiler feed water

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 min

10

20

30

40

50

60

70

80

mV

ch3

1

2 3

45

6


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E Cations



1 Sodium 4.00 0.70

2 Ammonium 4.51 0.123 Potassium 5.81 0.69

4 not identified 8.23 -


6 Calcium 15.53 0.83


Range 1.0 mS/cm

Full Scale 10 S/cm

Polarity


Eluent 2.5 mmol/L nitric acid

Flow 1.0 mL/min

Preconcentra-tion colunm

Metrosep C 2 S-Guard (6.1010.240)

Preconcentra-tion volume

10 mL


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Barium, strontium and magnesium in process water (oil production)

Has a very high sodium content (sea water)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 min

1

2

3

4

5

6

7

uS/cm

Cond

1

2

3


1 Strontium 6.04 34

2 Barium 8.64 54

3 Magnesium 10.32 29


Full Scale 1000 S/cmPolarity

Column Nucleosil 5 SA (6.1007.000) plus Metrosep RP Guard (6.1011.020)

Eluent 4 mmol/L tartaric acid, 0.5 mmol/L dipicolinic acid, 3 mmol/Lethylenediamine, 5% acetone

Flow 1.5 mL/min

Loop 20 L


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E Cations


Relevant Metrohm literature Application Note C 1 Sodium, potassium, calcium and magnesium in drinkingwater

Application Note C 2 Sodium, potassium, calcium and magnesium in coolingwater

Application Note C 12 Determination of alkali and alkaline earth metal cations

Application Note C 14 Sodium, ammonium, potassium, calcium andmagnesium in wastewater

Application Note C 19 Five cations in rain water

Application Note C 33 Four cations in sea water

Application Note C 39 Five cations in offshore water

Application Note C 44 Five cations in tap water

Application Note C 60 Magnesium, strontium and barium in produced water

Application Note C 83 On-line monitoring of trace levels of cations in boilerfeed water

Monograph Practical ion chromatography

Additional literatureDIN EN ISO 14911 Determination of dissolved Li +, Na +, NH 4+, K+, Mn 2+ , Ca 2+ ,

Mg2+

, Sr 2+

and Ba2+

using ion chromatography

E2 Amines, for example methylamine, ethanolaminewith IC

General remarksThe determination of amines such as ethanolamine, diethanolamine, methylamine,dimethylamine, guanidine, etc., can be carried out by means of ion chromatogra-phy. The amines are separated on a cation exchange column and determinedusing indirect conductivity detection.

Recommended accessoriesMIC-1 Advanced or 861 Advanced Compact IC

Cation exchange column, e.g. Metrosep C 2 150 (6.1010.220), Metrosep C 2 250 (6.1010.230) plus Metrosep C 2 Guard (6.1010.200)


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E2 Amines, for example methylamine, ethanolamine with IC



Eluent containing tartaric acid and dipicolinic acid (2,6-pyridine dicarbonic acid)

or nitric acid; organic solvents such as acetone are added if required. Theeluent concentrations depend on the column used and the application.

1-g/L stock solutions of the different amines are prepared by dissolving thecompounds in ultrapure water.


At higher concentrations it may be necessary to dilute the samples.

Dialysis or C18 sample preparation cartridges (6.1012.200) can be used for thepreparation of samples with high organic loads.

AnalysisQuantitation is performed by means of an external calibration in the concentrationrange concerned. A three-point calibration is recommended for the determinationof cations.

Examples

N-Methyldiethanolamine (MDEA), Na, NH 4, K, Ca and Mg in wastewater

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 min

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

uS/cm

Cond

1

2

3 4

5

6


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E Cations



1 Sodium 8.38 680

2 Ammonium 9.59 33

3 Potassium 13.80 12

4 MDEA 14.90 21

5 Calcium 17.18 88

6 Magnesium 26.37 16


Full Scale 1000 S/cm

Polarity Column Metrosep C 2 250 (6.1010.230) plus Metrosep C 2 Guard

(6.1010.200)

Eluent 4 mmol/L tartaric acid, 0.75 mmol/L dipicolinic acid (2,6-pyridinedicarbonic acid) / 10% acetone

Flow 1.0 mL/min

Loop 10 L

Methylamine, guanidine, aminoguanidine, Na+

and NH 4+

in wastewater

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 min

50

100

150

200

250

300

350

400

450

500

550

600

650

mV

ch1

1

2

3 4

5

67


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E2 Amines, for example methylamine, ethanolamine with IC



1 Sodium 4.77 883

2 Ammonium 5.39 465

3 Methylamine 6.63 1.214 Guanidine 9.79 99.6

5 Calcium 11.02 not quantified

6 Magnesium 16.08 not quantified

7 Aminoguanidine 20.02 2.16


Range 1.0 mS/cm

Full Scale 10 S/cm

Polarity


Eluent 4 mmol/L tartaric acid, 0.75 mmol/L dipicolinic acid (2,6-pyridinedicarbonic acid), 5% acetone

Flow 1.0 mL/min

Loop 10 L

Relevant Metrohm literature Application Note C 23 Sodium, ammonium, diethanolamine, diglycolamine andpotassium in wastewater

Application Note C 52 Determination of cations and ethanolamine

Application Note C 56 Sodium, ammonium, methylamine, guanidine andaminoguanidine in wastewater

Application Note C 58 N-Methyldiethanolamine (MDEA) in the presence ofstandard cations in wastewater

Application Note C 78 Ethanolamines besides alkali and alkaline earth metalcations


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E Cations


E2 Transition metals zinc, manganese etc. with IC

General remarksThe determination of transition metals such as zinc, manganese, nickel, etc., can

be carried out by separation on a cation exchange column followed by indirectconductivity detection. This method has the advantage that alkali and alkaline-earth metals can be determined simultaneously.

There is also the possibility of determining the transition metals by means ofUV/VIS detection after post-column derivatization with PAR. The metals formcolored complexes with the PAR reagent, these can be detected at 520 nm. Asthis method is very selective for the transition metals, these can be determinedwithout interferences also in samples with very high alkali-metal concentrations.

Both methods will be described briefly.

Recommended accessoriesa) for the determination of transition metals using indirect conductivity detection

MIC-1 Advanced or 861 Advanced Compact IC

Cation exchange column, e.g. Metrosep Cation 1-2 (6.1010.100), Metrosep C 2 100 (6.1010.210), Metrosep C 2 150 (6.1010.220), Metrosep C 2 250(6.1010.230) plus Metrosep C 2 Guard (6.1010.200)

b) for the determination of transition metals using post-column derivatization withPAR and UV/VIS detection

MIC-1 Advanced IC system plus Lambda 1010 UV/VIS detector, 833 AdvancedIC Liquid Handling Pump Unit and 6.2836.000 post-column reactor

844 UV/VIS Compact IC (2.844.0120)

Cation exchange column, e.g. Metrosep C 2 150 (6.1010.220), Metrosep C 2 250 (6.1010.230) plus Metrosep C 2 Guard (6.1010.200), Nucleosil 5 SA(6.1007.000) plus Nucleosil 5SA precolumn cartridge (6.1007.010)

ReagentsUse only reagents of highest purity and ultrapure water having a specific resis-

tance >18 MOhm cm.Eluent containing tartaric acid and dipicolinic acid (2,6-pyridine dicarbonic acid),oxalic acid, etc. The eluent concentrations depend on the column used and theapplication.

1-g/L stock solutions are prepared by weighing the corresponding amounts ofthe salts and dissolving them in ultrapure water.


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E Cations


Examples for the determination of transition metals with indirectconductivity detection:

Zinc, manganese in the presence of sodium, ammonium, calcium and magnesiumin an industrial wastewater

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 min

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

uS/cm

Cond

1

23

4

Peak no. Component Retention time [min] Concentration [mg/L]1 Zinc 4.44 2484

2 Sodium 8.98 107

3 Ammonium 10.27 108

4 Manganese 29.75 5688


Full Scale 1000

S/cmPolarity


Eluent 5 mmol/L tartaric acid, 0.11 mmol/L dipicolinic acid (2,6-pyridine dicarbonic acid)

Flow 1.0 mL/min

Loop 10 L

Dilution Sample was diluted 1:500 in 2 mmol/L nitric acid


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Transition metals in boiler feed water, spiked

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 min

5

10

15

20

25

30

35

mV

ch1

1

2

3

4

5

67

8

Peak no. Component Retention time [min] Concentration [ g/L]1 Lithium 7.13 24.4

2 Sodium 8.65 19.3

3 Ammonium 9.72 31.0


5 Zinc 13.64 2.53

6 Iron(II) 24.49 14.6


8 Calcium 46.21 6.08


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E Cations



Range 1.0 mS/cm

Full Scale 50 S/cm

Polarity


Eluent 1.75 mmol/L oxalic acid, 1.75 mmol/L ascorbic acid

Flow 1.0 mL/min

Loop 200 L

Example for the determination of transition metals by means of post-columnderivatization with PAR and UV/VIS detection:

Zinc, manganese, copper in a wastewater

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17min

20

40

60

80

100

120

140

160

180

mAU

Abs.1

1

2

3 4


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1 Copper 3.34 84

2 Zinc 5.55 370


4 Manganese 14.57 64

Instrument 844 UV/VIS Compact IC (2.844.0120)

Wavelength 510 nm

Polarity

Column Nucleosil 5 SA (6.1007.000) plus Nucleosil 5SA precolumncartridge (6.1007.010)

Eluent 70 mmol/L tartaric acid pH 3.3 (adjusted with NH 4+)

Flow 1.0 mL/min

Loop 100 L

Derivatizationreagent

0.15 mmol/L PAR, 0.4 mol/L NH 3, 80 mmol/L HNO 3

Flow ofderivatization

reagent

0.4 mL/min

Relevant Metrohm literature Application Note C 49 Trace cations in power plant feed water stabilized with7 ppm monoethanolamine (MEA)

Application Note C 55 Determination of lead, zinc, indium, cadmium, cobalt,ammonium, potassium, manganese, magnesium and calcium

Poster CIA 2005, UV/VIS Compact IC: Determination of transition metals


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E Cations


E3 VA methods: IntroductionMetrohm has been concerned with voltammetric water analysis for many years.Progress has been remarkable since the introduction of the Polarecord E 261 in1957. This is true for instrument technology as well as for keeping pace withgeneral trends: lower detection limits, higher precision, validation, etc. Today,metal traces down to the ppt level can be determined using voltammetric methods.Further advantages of voltammetric methods are species analyses and last notleast the relatively modest acquisition and running costs.

The important parameters are the type of metal ions, their concentration and thetype of water to be analyzed (wastewater, ground, drinking, lake, river, sea or rainwater). Concentrations ranging from ppt to ppm can be determined. Whenanalyzing surface waters, species analyses are very important to answer thequestion: Are the metals present as free ions or as metal complexes?Voltammetry is an elegant, specific, economic and quite modern tool that allows toanswer this question. The examples given here cannot show the whole spectrumof voltammetric applications but restrict themselves to analysis methods fordetermining the total metal content at the trace level.

Voltammetric methods also allow to determine other species that occur in water attrace levels such as nitrophenols, TNT, iodide/iodate, iodoform, NTA, EDTA, thio-sulfate, organo-tin compounds, etc.

Before we start let's consider a list of recent literature references. This list is by nomeans complete. It is rather meant to demonstrate the broad application spectrumof voltammetric methods in water analysis:

Riesenhofer,E., Adami,G., Favretto,A. Heavy metals and nutrients in costal,surface seawaters (Gulf of Trieste, Nothern Adriatic Sea): an environmentalstudy by factor analysis. (Zn, Cd, Pb, Cu in seawater). Fresenius,J.Anal.Chem.354, (1996) 729-734

Colombo,C., van den Berg,C.M.G. Simultaneous determination of several tracemetals in sea water using cathodic stripping voltammetry with mixed ligands.(Cu, Cd, Pb, Ni, Co, Zn in seawater). Anal.Chim.Acta 337, (1997) 29-40

Sander,S. Simultaneous adsorptive stripping voltammetric determination ofmolybdenum(VI), uranium(VI), vanadium(V), and antimony(III) (Mo, U, V, Sb inpotable water, seawater, slag). Anal.Chim.Acta 394, (1999) 81-89

Morales,M.M., Marti,P., Llopis,A., Campos,L., Sagrado,S. An environmentalstudy by factor analysis of surface seawaters in the Gulf of Valencia (WesternMediterranean). (Zn, Cd, Pb, Ni, Cr in seawater). Anal.Chim.Acta 394, (1999)109-117

(continued on page 2136)


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E3 VA methods: Introduction


This page lists a selection of Application Bulletins that you can obtain free ofcharge from you Metrohm distributor.

AB no. 36 Polarographic analysis half-wave potentials of inorganic substances

AB no. 74 Polarographic and stripping voltammetric analysis methods forthallium, antimony, bismuth and iron (copper, vanadium) (Tl, Sb, Bi,Fe, Cu, V)

AB no. 96 Determination of mercury by stripping voltammetry (Hg) AB no. 113 Determination of lead, cadmium and copper in foodstuffs, wastewater

and sewage sludge by anodic stripping voltammetry after digestion(Cd, Pb, Cu)

AB no. 114 Polarographic determination of five metals (copper, cobalt, nickel, zincand iron) in a single operation (Cu, Co, Ni, Zn, Fe)

AB no. 116 Polarographic/voltammetric determination of chromium in smallquantities (Cr)

AB no. 117 Determination of selenium by stripping voltammetry (Se) AB no. 123 Voltammetric determination of iron and manganese in water samples

(Fe, Mn) AB no. 131 Voltammetric determination of aluminum (Al) AB no. 146 Direct polarographic determination of trace amounts of molybdenum in

water (Mo) AB no. 176 Simultaneous determination of lead and tin by anodic stripping

voltammetry (Sn, Pb)

AB no. 186 Determination of aluminum in water samples by adsorptivevoltammetry (Al)

AB no. 207 Stripping voltammetric determination of silver (Ag) AB no. 220 Voltammetric determination of platinum and rhodium in the ultratrace

range (Pt. Rh) AB no. 231 Voltammetric determination of zinc, cadmium, lead, copper, thallium,

nickel and cobalt in water samples according to DIN 38406 Part 16(Zn, Cd, Cu, Tl, Ni, Co)

AB no. 241 Determination of cadmium and lead at the Ultra Trace graphiteelectrode by anodic stripping voltammetry (Cd. Pb)

AB no. 242 Determination of tungsten at the Ultra Trace graphite electrode byanodic stripping voltammetry (W)

AB no. 243 Determination of chromium at the Ultra Trace graphite electrode bycathodic stripping voltammetry (Cr)

AB no. 254 Determination of zinc, cadmium, lead and copper by anodic strippingvoltammetry using carbon electrodes (Zn, Cd, Pb, Cu)

AB no. 276 Validation of Metrohm VA instruments using Standard OperatingProcedures (SOP)


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E Cations


(continued from page 3H134)

Achterberg,E.P., Braungardt,Ch. Stripping voltammetry for the determination oftrace metal speciation and in-situ measurements of trace metal distributions inmarine waters. (Al, As, Co, Cr, Cu, Fe, Mo, Ni, Pt, Sb, Se, Sn, Ti, U, V, Zn inseawater, speciation). Anal.Chim.Acta 400, (1999) 381-397

Bazzi,A. et al. Chemical speciation of dissolved copper in Saginaw bay, lakeHuron, with square wave anodic stripping voltammetry (Cu in lake water,speciation). J.Great Lakes Res. 28, (2002) 466-478

Liu,J. et al. Speciation analysis of aluminium(III) in natural waters and biologicalfluids by complexing with various catechols followed by differential pulsevoltammetric detection. (Al in river and lake water, speciation). Analyst 127,(2002) 1657-1665

Bowie,A.R. et al. Shipboard analytical intercomparison of dissolved iron insurface waters along a north-south transect of the Atlantic Ocean. (Fe in

seawater). Marine Chemistry 84, (2003) 19-34Mylon,S.E., Twining,B.S., Fisher,N.S., Benoit,G. Relating the speciation of Cd,Cu, and Pb in two Connecticut rivers with their uptake in algae. (Cd, Cu, Pb inriver water, speciation). Environ.Sci. & Technol. 37, (2003) 1261-1267

Sander,S., Koschinsky,A., Halbach,P. Redox speciation of chromium in theoceanic water column of the lesser Antilles and offshore Otago Peninsula, NewZealand. (Cr in seawater, speciation). Marine & Freshwater Research 54,(2003) 745-754

Cobelo-Garcia,A., Prego,R., Nieto,O. Chemical speciation of dissolved lead in

polluted environments. A case of study: the Pontevedra Ria (NW Spain). (Pb inriver water, speciation). Ciencias Marinas 29, (2003) 377-388

Perez-Lopez,M. Lead and cadmium levels in seawater and limpet (Patellavulgata L.) from the Vigo estuary. (Cd, Pb in seawater estuary water). Revistade Toxicologia (Alicante, Spain) 20, (2003) 19-22

Farghali,O.A. Direct and simultaneous voltammetric analysis of heavy metals intap water samples at Assuit City: an approach to improve the analysis time fornickel and cobalt determination at a mercury film electrode. (Ni, Co in tapwater). Microchem.J. 75, (2003) 119-131

Scoullos,M.J., Pavlidou,A.S. Determination of the lability characteristics of lead,cadmium and zinc in a polluted Mediterranean brackish-marine interfacesystem. (Pb, Cd, Zn in estuary water, speciation). Water, Air, and Soil Pollution147, (2003) 203-227

Huang,Sh., Wang,Z. Application of anodic stripping voltammetry to predict thebioavailable/toxic concentration of Cu in natural water. (Cu in surface waters,speciation). Applied Geochem. 18, (2003) 1215-1223

El Makhfouk,M., Souissi,A., El Meray,M. Speciation of heavy metals dissolvedin the marine environment along the coast of the town of Safi (Marocco). (Cd,Zn, Pb, Cu in seawater, speciation). Bull.Electrochem. 19, (2003) 271-278


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E3 VA methods: Introduction


Vargas Camara,M. et al. Simultaneous determination of chromium(VI) andaluminium(III) by adsorptive stripping voltammetry with pyrocatechol violet. (Cr,

Al in river water). Helv.Chim.Acta 86, (2003) 2434-2440

Pozzi,A. et al. Ultra trace determination of Pt and Rh in wastewater and gullypotsediments from a low pollution area. (Pt, Rh in wastewater and sediments)

Annali di Chimica (Rome) 93, (2003) 181-186

Herzl,V.M.C. et al. Species of dissolved Cu and Ni and their adsorption kineticsin turbid river water. (Cu, Ni in river water, speciation). Estuarine, Coastal andShelf Science 56, (2003) 43-52

Lim,P.E., Mak,K.Y., Mohamed,N., Noor,A.M. Removal and speciation of heavymetals along the treatment path of wastewater in subsurface-flow constructedwetlands. (Zn, Cd, Pb, Cu in groundwater). Water Sci. Technol. 48, (2003) 307-313

Linnik,P.N. Complexation as the most important factor in the fate and transportof heavy metals in the Dnieper water bodies. (Cd, Pb, Zn in river water orgroundwater, speciation). Anal.Bioanal.Chem. 376, (2003) 405-412

Grabarczyk,M., Korolczuk,M. Modification of catalytic adsorptive strippingvoltammetric method for hexavalent chromium determination in the presence ofDTPA and nitrate. (Cr in river and tap water, speciation). Anal.Bioanal.Chem.376, (2003) 1115-1118

van Elteren,J.T., Woroniecka,U.D. Investigation into sorption process in theanodic stripping voltammetric speciation of Cu in natural waters. (Cu in riverwater, speciation). Anal.Chim.Acta 476, (2003) 33-42

Soko,L., Chimuka,L., Cukrowska,E. Pole,S. Extraction and preconcentration ofmanganese(II) from biological fluids (water, milk , blood serum) using supportedliquid membrane and membrane probe methods. (Mn traces in water samples).

Anal.Chim.Acta 485, (2003) 25-35

Jurado-Gonzalez,J.A., Galindo-Riano,M.D., Garcia-Vargas,M. Experimentaldesigns in the development of a new method for the sensitive determination ofcadmium in seawater by adsorptive cathodic stripping voltammetry. (Cd inseawater). Anal.Chim.Acta 487, (2003) 229-241

Riso,R.D., Waeles,M., Garbarino,S., Le Corre,P. Measurement of total seleniumand selenium(IV) in seawater by stripping chronopotentiometry. (Se inseawater, speciation). Anal.Bioanal.Chem. 379, (2004) 1113-1119Korolczuk,M., Moroziewicz,A., Grabarczyk,M., Kutyla,R. Adsorptive strippingvoltammetric determination of cobalt in the presence of dimethylglyoxime andcetyltrimethylammonium bromide. (Co in river water). Anal.Bioanal.Chem. 380,(2004) 141-145

Taher,M.A., Rezaeipour,E., Afzali,D. Anodic stripping voltammetricdetermination of bismuth after solid-phase extraction using Amberlite XAD-2resin modified with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol. (Bi in riverwater). Talanta 63, (2004) 797-801


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Bobrowski,A. et al. Chromium speciation study in polluted waters using catalyticadsorptive stripping voltammetry and tangential flow filtration. (Cr in wastewaterand river water, speciation). Talanta 63, (2004) 1003-1012

Kiptoo,J.K., Ngila,J.C., Sawula,G.M. Speciation studies of nickel and chromiumin wastewater from an electroplating plant ( Ni, Cr in wastewater, speciation).Talanta 64, (2004) 54-59

Mlakar,M. Determination of titanium in water solutions. (Ti in seawater).Electroanalysis 16, (2004) 217-223

Desimoni,E., Brunetti,B. Cattaneo,R. Validation of some procedures forquantifying platinum sub- g/L level in some real matrices by catalytic adsorptivestripping voltammetry. (Pt in tap water). Electroanalysis 16, (2004) 304-310

Grabarczyk,M., Kaczmarek,L., Korolzuk,M. Determination of Cr(VI) by catalyticadsorptive stripping voltammetry with application of nitrilotriacetic acid as amasking agent. (Cr in surface waters, speciation). Electroanalysis 16, (2004)1503-1507Prego,R., Cobelo-Garcia,A. Cadmium, copper and lead contamination of theseawater column on the Prestige shipwreck (NE Atlantic Ocean). (Cd, Cu, Pb inseawater). Anal.Chim.Acta 524, (2004) 23-26

Ensafi,A.A., Khayamian,T., Khaloo,S.S. Application of adsorptive cathodicdifferential pulse stripping method for simultaneous determination of copper andmolybdenum using pyrogallol red. (Cu, Mo in river and tap water).

Anal.Chim.Acta 502, (2004) 201-207

Meylan,S., Odzak,N., Behra,R., Sigg,L. Speciation of copper and zinc in natural

freshwater: comparison of voltammetric measurements, diffusive gradients inthin films (DGT) and chemical equilibrium models. (Cu, Zn in river water,speciation). Anal.Chim.Acta 510, (2004) 91-100

He,Y., Zheng,Y., Ramnaraine,M., Locke,D.C. Differential pulse cathodicstripping voltammetric speciation of trace level inorganic arsenic compounds innatural water samples. (As in groundwater, speciation). Anal.Chim.Acta 511,(2004) 55-61

Paolicchi,I. et al. Application of an optimization procedure in adsorptive strippingvoltammetry for the determination of trace contaminant metals in aqueousmedium (In in waters). Anal.Chim.Acta 511, (2004) 223-229

Cobelo-Garcia,A., Prego,R. Chemical speciation of dissolved copper, lead andzinc in a ria costal system: the role of resuspended sediments. (Cu, Pb, Zn inseawater and sediments, speciation). Anal.Chim.Acta 524, (2004) 109-114


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E3 Determination of Cu, Cd, Pb, Zn with VA



Recommended accessories

797 VA Computrace with Dosino705 UV Digester

ReagentsUse only reagents of highest purity and ultrapure water.

Background electrolyte I: ammonium acetate buffer Add 59 mL w(CH 3COOH) = 96% and 75 mL w(NH3) = 25% to approx. 300 mLultrapure water. Leave to cool down, make up to 500 mL with ultrapure waterand mix. This solution is to be used for samples with a very low chloridecontent.Background electrolyte II: KCl-sodium acetate bufferDissolve 55.9 g KCl and 14.5 g NaOH x H 2O in approx. 300 mL ultrapure water.

Add 14.7 mL w(CH 3COOH) = 96%, leave to cool down, make up to 500 mL withultrapure water and mix. This solution is used for samples with higher chloridecontents.

Standard solutions: (Me) = 1 g/L (Me = Zn, Cd, Pb, Cu)These are commercially available.

Standard solutions: (Me) = 10 mg/L or (Me) = 1 mg/L

Prepare these solutions by diluting the standard solutions (Me) = 1 g/L withultrapure water. Acidify the resulting solutions by adding 0.1 mL w(HNO 3) =65% per 100 mL solution. Ideally the first standard addition should increasethe sample peak height by 50 to 100%. In our example we used a combinedstandard solution with the following analyte concentrations (Me): Zn = 5mg/L, Cd = 0.02 mg/L, Pb = 0.05 mg/L and Cu = 0.5 mg/L.

Sample preparation After sampling, immediately filter the water samples through a microfilter (0.45 m)and acidify by adding 1 mL w(HNO 3) = 65% per 1 L.

Add 100 L w(H2O2) = 30% to 10 mL sample and digest in the UV Digester for60 min at 90 C.


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AnalysisIn the polarographic vessel add 5 mL ultrapure water and 1 mL backgroundelectrolyte to 10 mL digested sample solution and deaerate for 5 min withnitrogen. After this, record the ASV voltammogram applying the followingconditions:


Stirrer 2000 rpm

Mode DP



Pulse time 0.04 sElectrolysis under stirring 160 s


Preconcentration potential 1150 mV

Potential gradient 1150 mV to 20 mV

Peak potential Zn approx. 960 mV

Peak potential Cd approx. 560 mV

Peak potential Pb approx. 60 mVPeak potential Cu approx. 100 mV

The content is determined by means of two standard additions.

Remarks

Tap water that has been at rest in the piping for a longer time can contain up to2 mg/L Zn. Under these circumstances, zinc is determined by polarography.

The blank values of the chemicals used (including those used for digestion) must

be determined and taken into account when calculating contents.


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Example: Zn, Cd, Pb and Cu in river water


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--------------------------------------------------------------------------------

Method parameters

--------------------------------------------------------------------------------

Method : Co, Ni.mth

Title : Co, NiRemark1 :

Remark2 :

Calibration : Standard addition

Technique : Batch

Addition : Manual

Sample ID : river water

Sample amount (mL): 10.000

Cell volume (mL): 10.600

Voltammetric parameters

--------------------------------------------------------------------------------

Mode : DP - Differential Pulse

Highest current range : 10 mA

Lowest current range : 100 nA

Electrode : HMDE

Drop size (1..9) : 4

Stirrer speed (rpm) : 2000

Initial electr. conditioning : No

No. of additions : 2

No. of replications : 2

Measure blank : No

Addition purge time (s) : 10

Initial purge time (s) : 300

Conditioning cycles

Start potential (V) : 0.000

End potential (V) : 0.000

No. of cycles : 0

Hydrodynamic (measurement) : No

Cleaning potential (V) : -0.700

Cleaning time (s) : 10.000

Deposition potential (V) : -0.700

Deposition time (s) : 30.000


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Start potential (V) : -0.700

End potential (V) : -1.300

Voltage step (V) : 0.006

Voltage step time (s) : 0.400

Sweep rate (V/s) : 0.015Pulse amplitude (V) : 0.050

Pulse time (s) : 0.040

Cell off after measurement : Yes

--------------------------------------------------------------------------------

Peak evaluation

Regression technique : Linear regression

Peak evaluation : Height

Minimum peak width (V.steps) : 5

Minimum peak height (A) : 1.000e-010

Reverse peaks : No

Smooth factor : 4

Eliminate spikes : Yes

Substances

--------------------------------------------------------------------------------

Co : -1.050 V +/- 0.050 V

Standard solution : 1 5.000 g/L

Addition volume (mL) : 0.100

default : Final result (Co) =

Conc * (10.6 / 10) * (1e+006 / 1) + 0 - 0

Ni : -0.970 V +/- 0.050 V

Standard solution : 1 100.000 g/L

Addition volume (mL) : 0.100

default : Final result (Ni) =

Conc * (10.6 / 10) * (1e+006 / 1) + 0 - 0

Solutions

--------------------------------------------------------------------------------

No. Content Predose (mL)

--- ------------------------------------------------ ------------


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Relevant Metrohm literature Application Bulletin no. 231 Voltammetric determination of zinc, cadmium,lead, copper, thallium, nickel and cobalt in water samples according to DIN38406 Part 16

E3 Determination of Co and Ni with VA


705 UV Digester


Background electrolyte: NH 3-NH4Cl bufferUnder stirring add 53 mL w(HCl) = 30% and 112.5 mL w(NH 3) = 25% to approx.300 mL ultrapure water. Leave to cool down, make up to 500 mL with ultrapurewater and mix.

DMG, Na salt (CAS 75006-64-3) in ultrapure water: c(DMG-Na) = 0.1 mol/L.Prepare fresh solution every second day.

Standard solutions: (Me) = 1 g/L (Me = Co and Ni)These solutions are commercially available.

Standard solutions: (Me) = 1 mg/LPrepare these solutions by diluting the standard solutions (Me) = 1 g/L withultrapure water. Acidify the resulting solutions by adding 0.1 mL w(HNO 3) =65% per 100 mL solution. Ideally the first standard addition should increase thesample peak height by 50 to 100%. In our example we used a combinedstandard solution with the following analyte concentrations (Me): Ni = 0.1mg/L, Co = 5 g/L.

Sample preparation

After sampling, immediately filter the water samples through a microfilter (0.45 m)and acidify by adding 1 mL w(HNO 3) = 65% per 1 L.

Add 100 L w(H2O 2) = 30% to 10 mL sample and digest in the UV Digester for60 min at 90 C.


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E3 Determination of Co and Ni with VA


AnalysisIn the polarographic vessel add 0.5 mL background electrolyte and 100 LDMG solution to 10 mL digested sample solution (the pH value of themeasuring solution should be between 8.5 and 9) and deaerate for 5 min with

nitrogen. After this, record the CSV voltammogram applying the followingconditions:


Stirrer 2000 rpm

Mode DP



Pulse time 0.04 s



Preconcentration potential 700 mV

Potential gradient 700 mV to 1150 mV

Peak potential Ni approx. 950 mV

Peak potential Co approx. 1070 mV


Remarks

The blank values of the chemicals used (including those used for digestion)must be determined and taken into account when calculating contents.

According to this method Co and Ni can be determined in the range 20 ng/L to10 g/L. If higher concentrations have to be determined, the samples must bediluted with ultrapure water.


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Example: Co and Ni in river water

Relevant Metrohm literature Application Bulletin no. 231 Voltammetric determination of zinc, cadmium,lead, copper, thallium, nickel and cobalt in water samples according to DIN38406 Part 16

E3 Determination of Fe with VA

General remarksThe method to be described is very sensitive for iron. It is especially useful forinvestigating ground, drinking, surface and cooling waters, where iron concentra-tion is important. The DPCSV method is applied to the triethanolamine complexformed. The determination limit lies at (Fe) = 5 g/L.

The constituents normally occurring in these water types do not interfere with thedetermination of iron.


705 UV Digester


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E3 Determination of Fe with VA


Sample preparation Add 50 L w(HCl) = 30% and 100 L w(H2O 2) = 30% to 10 mL water sample anddigest for 60 min at 90 C in the UV Digester.


Background electrolyte:Dissolve 10 g KBrO 3 and 5 g triethanolamine (CAS 102-71-6) in approx.300 mL ultrapure water, make up with ultrapure water to 500 mL and mix.

Sodium hydroxide solution: w(NaOH) = 30%Standard solution: (Fe) = 1 g/LThis standard solution is commercially available.

Standard solution: (Fe) = 10 mg/L

Add 50 L w(HCl) = 30% to 1.00 mL (Fe) = 1 g/L, make up to 100 mL withultrapure water and mix. Ideally the first standard addition should increase thesample peak height by 50 to 100%.

AnalysisIn the polarographic vessel deaerate 10 mL digested water sample during 5 minwith nitrogen and add 1 mL background electrolyte. Record the DPCSV voltam-mogram applying the following conditions:


Stirrer 2000 rpm

Mode DP



Pulse time 0.04 s



Preconcentration potential 750 mVPotential gradient 700 mV to 1220 mV

Peak potential Fe approx. 1000 mV



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Example: Fe in river water

Relevant Metrohm literature Application Bulletin no. 123 Voltammetric determination of iron and manga-nese in water samples

E3 Determination of Mo with VA

General remarksNatural waters contain only traces of Mo. The determination limit of the presentmethod lies at (Mo) = 50 ng/L.

The method is based on the fact that the molybdate ion MoO 42 forms a complex

with 8-hydroxy-7-iodo-5-quinolinesulfonic acid (H 2L). This complex, which can bewritten as MoO 2L22 , is adsorbed at the Hg electrode and electrochemicallyreduced to the Mo(V) complex. The protons present in the solution oxidize theMo(V) immediately to the Mo(VI) complex, which is then again available for elec-trochemical reduction. This catalytic reaction is the reason for the high sensitivityof the method.


705 UV Digester


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E3 Determination of Mo with VA


Sample preparation Add 50 L w(HCl) = 30% and 100 L w(H2O 2) = 30% to 10 mL water sample anddigest for 60 min at 90 C in the UV Digester.


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