4140 INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS*

4140 A. Introduction

Determination of common inorganic anions such as fluoride,

chloride, bromide, nitrite, nitrate, orthophosphate, and sulfate is

a significant component of water quality analysis. Instrumental

techniques that can determine multiple analytes in a single

analysis, i.e., ion chromatography (Section 4110) and capillary

ion electrophoresis, offer significant time and operating cost

savings over traditional single-analyte wet chemical analysis.

Capillary ion electrophoresis is rapid (complete analysis in

less than 5 min) and provides additional anion information, i.e.,

organic acids, not available with isocratic ion chromatography

(IC). Operating costs are significantly less than those of ion

chromatography. Capillary ion electrophoresis can detect all

anions present in the sample matrix, providing an anionic “fingerprint.”

Anion selectivity of capillary ion electrophoresis is different

from that of IC and eliminates many of the difficulties present in

the early portion of an IC chromatogram. For example, sample

matrix neutral organics, water, and cations do not interfere with

anion analysis, and fluoride is well resolved from monovalent

organic acids. Sample preparation typically is dilution with reagent water and removal of suspended solids by filtration. If

necessary, hydrophobic sample components such as oil and

grease can be removed with the use of HPLC solid-phase extraction cartridges without biasing anion concentrations.

4140 B. Capillary Ion Electrophoresis with Indirect UV Detection

1. General Discussion

a. Principle: A buffered aqueous electrolyte solution containing a UV-absorbing anion salt (sodium chromate) and an

electroosmotic flow modifier (OFM) is used to fill a 75-

m-ID silica capillary. An electric field is generated by

applying 15 kV of applied voltage using a negative power

supply; this defines the detector end of the capillary as the

anode. Sample is introduced at the cathodic end of the capillary and anions are separated on the basis of their differences in mobility in the electric field as they migrate through

the capillary. Cations migrate in the opposite direction and are

not detected. Water and neutral organics are not attracted

towards the anode; they migrate after the anions and thus do

not interfere with anion analysis. Anions are detected as they

displace charge-for-charge the UV-absorbing electrolyte anion (chromate), causing a net decrease in UV absorbance in

the analyte anion zone compared to the background electrolyte. Detector polarity is reversed to provide positive mv

response to the data system (Figure 4140:1). As in chromatography, the analytes are identified by their migration time

and quantitated by using time-corrected peak area relative to

standards. After the analytes of interest are detected, the

capillary is purged with fresh electrolyte, eliminating the

remainder of the sample matrix before the next analysis.

b. Interferences: Any anion that has a migration time similar

to the analytes of interest can be considered an interference. This

method has been designed to minimize potential interference

typically found in environmental waters, groundwater, drinking

water, and wastewater.

Formate is a common potential interference with fluoride; it is

a common impurity in reagent water, has a migration time

similar to that of fluoride, and is an indicator of loss of water

purification system performance and TOC greater than 0.1 mg/L.

The addition of 5 mg formate/L in the mixed working anion

standard, and to sample where identification of fluoride is in

question, aids in the correct identification of fluoride.

Generally, a high concentration of any one ion may interfere

with resolution of analyte anions in close proximity. Dilution in

reagent water usually is helpful. Modifications in the electrolyte

formulation can overcome resolution problems but require individual validation for precision and bias. This method is capable

of interference-free resolution of a 1:100 differential of Br to

Cl, and NO2

 and NO3 to SO42, and 1:1000 differential of

Cl and SO4

2.

Dissolved ferric iron in the mg/L range gives a low bias for

PO4. However, transition metals do not precipitate with chromate because of the alkaline electrolyte pH.

c. Minimum detectable concentrations: The minimum detectable concentration for an anion is a function of sample

size. Generally, for a 30-s sampling time, the minimum detectable concentrations are 0.1 mg/L (Figure 4140:2). According to the method for calculating MDL given in Section 1030,

the calculated detection levels are below 0.1 mg/L. These

detection levels can be compromised by analyte impurities in

the electrolyte.

d. Limitations: Samples with high ionic strength may show a

decrease in analyte migration time. This variable is addressed by

using normalized migration time with respect to a reference

peak, chloride, for identification, and using time-corrected area

for quantitation. With electrophoresis, published data indicate

that analyte peak area is a function of migration time. At high

analyte anion concentrations, peak shape becomes asymmetrical;

this phenomenon is typical and is different from that observed in

ion chromatography.

* Approved by Standard Methods Committee, 2004. Editorial revisions, 2011.

Joint Task Group: 20th Edition—Roy-Keith Smith (chair), James Krol, Yuefeng Xie.

1
2. Apparatus

a. Capillary ion electrophoresis (CIE) system:* Various commercial instruments are available that integrate a negative highvoltage power supply, electrolyte reservoirs, covered sample

carousel, hydrostatic sampling mechanism, capillary purge

mechanism, self-aligning capillary holder, and UV detector capable of 254-nm detection in a single temperature-controlled

compartment at 25°C. Optimal detection limits are attained with

a fixed-wavelength UV detector with Hg lamp and 254-nm filter.

b. Capillary: 75-m-ID 375-m-OD 60-cm-long fused

silica capillary with a portion of its outer coating removed to act

as the UV detector window. Capillaries can be purchased premade* or on a spool and prepared as needed.

c. Data system:

* HPLC-based integrator or computer. Optimum performance is attained with a computer data system and

electrophoresis-specific data processing including data acquisition at 20 points/s, migration times determined at midpoint of

peak width, identification based on normalized migration times

with respect to a reference peak, and time-corrected peak area.

3. Reagents

a. Reagent water: See Section 1080. Ensure that water is

analyte-free. The concentration of dissolved organic material

will influence overall performance; preferably use reagent water

with 50 g TOC/L.

b. Chromate electrolyte solution: Prepare as directed from

individual reagents, or purchase electrolyte preformulated.

1) Sodium chromate concentrate, 100 mM: In a 1-L volumetric flask dissolve 23.41 g sodium chromate tetrahydrate,

Na2CrO4  4H2O, in 500 mL water and dilute to 1 L with water.

Store in a capped glass or plastic container at ambient temperature; this reagent is stable for 1 year.

2) Electroosmotic flow modifier concentrate, 100 mM: In a

100-mL volumetric flask dissolve 3.365 g tetradecyltrimethyl

ammonium bromide (TTAB), mol wt 336.4, in 50 mL water and

dilute to 100 mL. Store in a capped glass or plastic container at

ambient temperature; this reagent is stable for 1 year.

3) Buffer concentrate, 100 mM: In a 1-L volumetric flask

dissolve 20.73 g 2-[N-cyclohexylamino]-ethane sulfonate

* Waters Corp. or equivalent. (CHES), mol wt 207.29, in 500 mL water and dilute to 1 L. Store

Figure 4140:1. Electropherogram of the inorganic anions and typically found organic acids using capillary ion electrophoresis and chromate electrolyte.

Electrolyte: 4.7 mN Na2CrO4/4.0 mM TTAOH/10 mM CHES/0.1 mM calcium gluconate; capillary: 75-m-ID 375-m-OD 60-cm length,

uncoated silica; voltage: 15 kV using a negative power supply; current: 14  1 A; sampling: hydrostatic at 10 cm for 30 s; detection: indirect

UV with Hg lamp and 254-nm filter.

Anion Conc

mg/L

Migration Time

min

Migration Time

Ratio to Cl

Peak Area Time-Corrected

Peak Area

Chloride 2.0 3.200 1.000 1204 376.04

Bromide 4.0 3.296 1.030 1147 348.05

Nitrite 4.0 3.343 1.045 2012 601.72

Sulfate 4.0 3.465 1.083 1948 562.05

Nitrate 4.0 3.583 1.120 1805 503.69

Oxalate 5.0 3.684 1.151 3102 842.14

Fluoride 1.0 2.823 1.195 1708 446.65

Formate 5.0 3.873 1.210 1420 366.61

o-Phosphate 4.0 4.004 1.251 2924 730.25

Carbonate & bicarbonate 4.281 1.338

Acetate 5.0 4.560 1.425 3958 868.01

INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS (4140)/CIE with Indirect UV Detection

2
in a capped glass or plastic container at ambient temperature; this

reagent is stable for 1 year.

4) Calcium gluconate concentrate, 1 mM: In a 1-L volumetric

flask dissolve 0.43 g calcium gluconate, mol wt 430.38, in 500 mL

water and dilute to 1 L. Store in a capped glass or plastic container

at ambient temperature; this reagent is stable for 1 year.

5) Sodium hydroxide solution, NaOH, 100 mM: In a 1-L plastic

volumetric flask dissolve 4 g sodium hydroxide, NaOH, in 500 mL

water and dilute to 1 L. Store in a capped plastic container at

ambient temperature; this reagent is stable for 1 month.

6) Chromate electrolyte solution: Prerinse an anion exchange

cartridge in the hydroxide form with 10 mL 100-mM NaOH followed by 10 mL water; discard the washings. Slowly pass 4 mL

100-mM TTAB concentrate through the cartridge into a 100-mL

volumetric flask. Rinse cartridge with 10 mL water and add to flask.

Figure 4140:2. Electropherogram of 0.1 mg/L inorganic anions at minimum detection level. Seven replicates of 0.1 mg/L inorganic anion standard used to calculate minimum detection

levels, as mg/L, using analytical protocol described in Section 1030E.

Chloride  0.046

Nitrate  0.084

Bromide  0.090

Fluoride  0.020

Nitrite  0.072

Phosphate  0.041

Sulfate  0.032

Figure 4140:3. Representative electropherograms of Youden anion standards. For composition of standards, see Table 4140:I.

TABLE 4140:I. COLLABORATIVE DESIGN AS FOUR YOUDEN PAIR SETS*

Anion

Anion Concentration in Individual Youden Pair Standards

mg/L

1 2 3456 7 8

Cl 0.7 2.0 3.0 15.0 40.0 20.0 50.0 0.5

Br 2.0 3.0 15.0 40.0 20.0 50.0 0.7 0.5

NO2

 3.0 40.0 20.0 15.0 50.0 0.5 2.0 0.7

SO4

2 40.0 50.0 0.5 0.7 2.0 3.0 15.0 20.0

NO3

 15.0 20.0 40.0 50.0 0.5 0.7 2.0 3.0

F 2.0 0.7 0.5 3.0 10.0 7.0 20.0 25.0

PO4

3 50.0 40.0 20.0 0.5 3.0 2.0 0.7 15.0

* The collaborative design is intended to demonstrate performance between 0.1

and 50 mg anion/L, except for fluoride between 0.1 and 25 mg/L. The concentrations among anions are varied so as not to have any one standard at all low or

all high anion concentrations.

INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS (4140)/CIE with Indirect UV Detection

3
(NOTE: This step is needed to convert the TTAB from the bromide

form into the hydroxide form TTAOH. The step can be eliminated

if commercially available 100 mM TTAOH is used.)

To the 100-mL volumetric flask containing the TTAOH add

4.7 mL sodium chromate concentrate, 10 mL CHES buffer

concentrate, and 10 mL calcium gluconate concentrate. Mix and

dilute to 100 mL with water. The pH should be 9  0.1; final

solution is 4.7 mM sodium chromate, 4 mM TTAOH, 10 mM

CHES, and 0.1 mM calcium gluconate. Filter and degas through

a 0.45-m aqueous membrane, using a vacuum apparatus. Store

any remaining electrolyte in a capped plastic container at ambient temperature for up to 1 month.

c. Standard anion solution, 1000 mg/L: Prepare a series of

individual standard anion solutions by adding the indicated amount

of salt, dried to constant weight at 105°C, to 100 mL with water.

Store in plastic bottles; these solutions are stable for 3 months.

(Alternatively, purchase individual certified 1000-mg/L anion standards and store following manufacturer’s directions.)

Anion Salt Amount

g/100mL

Chloride NaCl 0.1649

Bromide NaBr 0.1288

Formate NaCO2H 0.1510

Fluoride NaF 0.2210

Nitrite NaNO2 0.1499* (1000 mg NO2

/L  304.3 mg NO2 N/L)

Nitrate NaNO3 0.1371 (1000 mg NO3

/L  225.8 mg NO3N/L)

Phosphate Na2HPO4† 0.1500 (1000 mg PO4

3/L  326.1 mg PO43P/L)

Sulfate Na2SO4† 0.1480 (1000 mg SO4

2/L  676.3 mg SO42S/L)

* Do not oven-dry, but dry to constant weight in a desiccator over phosphorous

pentoxide.

† Potassium salts can be used, but with corresponding modification of salt

amounts.

d. Mixed working anion standard solutions: Prepare at least

three different working anion standard solutions that bracket the

expected sample range, from 0.1 to 50 mg/L. Add 5 mg formate/L

to all standards. Use 0.1 mL standard anion solution/100 mL working anion solution (equal to 1 mg anion/L). (Above 50 mg/L each

anion, chloride, bromide, nitrite, sulfate, and nitrate are no longer

baseline-resolved. Analytes that are not baseline-resolved may give

a low bias. If the analytes are baseline-resolved, quantitation is

linear to 100 mg/L.) Store in plastic containers in the refrigerator;

prepare fresh standards weekly. Figure 4140:3 shows representative

electropherograms of anion standards and Table 4140:I gives the

composition of the standards.

e. Calibration verification sample: Use a certified performance evaluation standard, or equivalent, within the range of the

mixed working anion standard solutions analyzed as an unknown. Refer to Section 4020.

f. Analyte known-addition sample: To each sample matrix add

a known amount of analyte, and use to evaluate analyte recovery.

4. Procedure

a. Capillary conditioning: Set up CIE system according to

manufacturer’s instructions. Rinse capillary with 100 mM NaOH

for 5 min. Place fresh degassed electrolyte into both reservoirs

and purge capillary with electrolyte for 3 min to remove all

previous solutions and air bubbles. Apply voltage of 15 kV and

note the current; if the expected 14  1 A is observed, the CIE

system is ready for use. Zero UV detector to 0.000 absorbance.

b. Analysis conditions: Program CE system to apply constant

current of 14 A for the run time. Use 30 s hydrostatic sampling

time for all standard and sample introduction. Analysis time is 5

min.

c. Analyte migration time calibration: Determine migration

time of each analyte daily using the midrange mixed working

anion standard. Perform duplicate analysis to insure migration

time stability. Use the midpoint of peak width, defined as midpoint between the start and stop integration marks, as the migration time for each analyte; this accounts for the observed nonsymmetrical peak shapes. (Use of peak apex may result in

analyte misidentification.) The migration order is always Cl,

Br, NO2

, SO42, NO3, F, and PO43. Dissolved HCO3 is

the last peak in the standard (see Figure 4140:1). Set analyte

migration time window as 2% of the migration time determined

above, except for Cl, which is set at 10%. Chloride is always

the first peak and is used as the reference peak for analyte

qualitative identification; identify anions on the basis of normalized migration times with respect to the reference peak, or

migration time ratio. (See Figure 4140:1 and Table 4140:II.)

d. Analyte response calibration: Analyze all three mixed

working anion standards in duplicate. Plot time-corrected peak

area for each analyte versus concentration using a linear regression through zero. (In capillary electrophoresis peak area is a

function of analyte migration time, which may change during

analyses. Time-corrected peak area is a well-documented CE

normalization routine, i.e., peak area divided by migration time.

(NOTE: Do not use analyte peak height.) Calibration is accepted

as linear if regression coefficient of variation, R2

, is greater than

0.995. Linearity calibration curves for anions are shown in

Figures 4140:4 through 6.

e. Sample analysis: After initial calibration run samples in the

following order: calibration verification sample, reagent blank,

10 unknown samples, calibration verification sample, reagent

blank, etc. Filter samples containing high concentrations of

TABLE 4140:II. ANION MIGRATION TIME REPRODUCIBILITY FROM YOUDEN

PAIR STANDARDS

Youden

Standard

Anion Midpoint Migration Time, Average of Triplicate

Samplings

min

Cl Br NO2

 SO42 NO3 F PO43

1 3.132 3.226 3.275 3.405 3.502 3.761 3.906

2 3.147 3.239 3.298 3.431 3.517 3.779 3.931

3 3.138 3.231 3.283 3.411 3.497 3.771 3.925

4 3.158 3.244 3.307 3.434 3.510 3.781 3.963

5 3.184 3.271 3.331 3.435 3.551 3.787 3.981

6 3.171 3.260 3.312 3.418 3.537 3.776 3.964

7 3.191 3.272 3.315 3.437 3.544 3.773 3.978

8 3.152 3.248 3.294 3.418 3.526 3.739 3.954

SD* 0.021 0.015 0.018 0.012 0.20 0.015 0.027

%RSD* 0.67% 0.46% 0.55% 0.36% 0.56% 0.40% 0.68%

* Average SD  0.018 min  1.1 s; average %RSD  0.53%.

INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS (4140)/CIE with Indirect UV Detection

4
Figure 4140:4. Linearity calibration curve for chloride, bromide, and

sulfate. Three data points were used per concentration;

based on Youden pair design.

Figure 4140:5. Linearity calibration curve for fluoride and o-phosphate.

Three data points were used per concentration; based on

Youden pair design.

Figure 4140:6. Linearity calibration curve for nitrite and nitrate. Three

data points were used per concentration; based on Youden

pair design.

Figure 4140:7. Electropherogram of typical drinking water.

Chloride  24.72 mg/L

Sulfate  7.99 mg/L

Nitrate  0.36 mg/L

Fluoride  0.10 mg/L

Carbonate &

bicarbonate  natural

INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS (4140)/CIE with Indirect UV Detection

5
suspended solids. If peaks are not baseline-resolved, dilute sample 1:5 with water and repeat analysis for unresolved analyte

quantitation. Resolved analytes in the undiluted sample are considered correct quantitation. Electropherograms of typical samples are shown in Figures 4140:7 through 9.

5. Calculation

Relate the time-corrected peak area for each sample analyte with

the calibration curve to determine concentration of analyte. If the

sample was diluted, multiply anion concentration by the dilution

factor to obtain original sample concentration, as follows:

C A F

where:

C  analyte concentration in original sample, mg/L,

A  analyte concentration from calibration curve, mg/L, and

F  scale factor or dilution factor. (For a 1:5 sample dilution, F

 5.)

Figure 4140:9. Electropherogram of typical industrial wastewater discharge, undiluted.

Chloride  2.0 mg/L

Nitrite  1.6 mg/L

Sulfate  34.7 mg/L

Nitrate  16.5 mg/L

Formate  0.05 mg/L

Phosphate  12.3 mg/L

Carbonate &

bicarbonate  natural

TABLE 4140:III. COMPARISON OF CAPILLARY ION ELECTROPHORESIS AND OTHER METHODS

Source Statistic

Value for Given Anion

mg/L

Cl NO2

 SO42 NO3 F PO43

Performance

evaluation

standard*

True value 43.00 1.77 37.20 15.37 2.69 6.29

Wet chemical

and ion

chromatography

methods†

Measured mean

Measured SD

43.30

3.09

1.77

0.07

37.00

2.24

15.42

1.15

2.75

0.26

6.38

0.21

CIE using chromate

electrolyte‡

Average (n  18) 43.34 1.64 37.11 14.41 2.64 6.34

CIE/mean 1.003 0.927 1.003 0.935 0.959 0.993

CIE/true value 1.008 0.927 0.996 0.938 0.981 1.008

* Purchased from APG Laboratories, June 1996; diluted 1:100 with deionized water.

† Measured result is the average from numerous laboratories using approved Standard Methods and EPA wet chemistry and ion chromatography methods.

‡ CIE results determined in July 1996 with proposed EPA and ASTM method, operationally identical to 4140; they are the average from four laboratories using the Youden

pair standards for quantitation. These data can be considered known addition of the performance evaluation standard in reagent water; they conform to quality control

acceptance limits given in Section 1020.

Figure 4140:8. Electropherogram of typical municipal wastewater discharge, undiluted.

Chloride  93.3 mg/L

Nitrate  0.46 mg/L

Sulfate  60.3 mg/L

Nitrate  40.8 mg/L

Carbonate &

bicarbonate  natural

INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS (4140)/CIE with Indirect UV Detection

6
6. Quality Control

The QC practices considered to be an integral part of each

method are summarized in Table 4020:I.

a. Analytical performance check: Unless analyst has already

demonstrated ability to generate data with acceptable precision and

bias by this method, proceed as follows: Analyze seven replicates of

a certified performance evaluation standard containing the analytes

of interest. Calculate mean and standard deviation of these data. The

mean must be within the performance evaluation standard’s 95%

confidence interval. Calculate percent relative standard deviation

(RSD) for these data as (SD 100) / mean; % RSD should conform

to acceptance limit given in Section 1020B.

b. Calibration verification: Analyze an independent, certified

performance evaluation standard at the beginning and end of the

analyses, or if many samples are analyzed, after every 10 samples. The determined analyte concentration should be within

10% of the true value, and the migration time of the Cl

reference peak should be within 5% of the calibrated migration

time. If the Cl reference peak differs by more than 5% of the

calibrated migration time, repeat capillary conditioning and recalibrate before proceeding.

c. Water blank analysis: At the beginning of every set of

analyses run a water blank to demonstrate that the water is free

of analyte anions. Dissolved bicarbonate will always be observed

as a positive or negative peak having a migration time greater

than PO4

3 and does not interfere with the analysis. Any negative peak indicates the presence of an anion impurity in the

electrolyte; a positive peak indicates the presence of an impurity

in the reagent water. If this is noted, discard electrolyte and

prepare electrolyte and sample dilutions again with water from a

different source.

d. Analyte recovery verification: For each sample matrix analyzed, e.g., drinking water, surface water, groundwater, or

wastewater, analyze duplicate known-addition samples (¶ 3f).

Analyte recoveries should conform to acceptance limits given in

Section 1020B.

e. Blind check sample: Analyze an unknown certified performance evaluation check sample at least once every 6 months to

verify method accuracy.

TABLE 4140:V. CAPILLARY ION ELECTROPHORESIS KNOWN-ADDITION RECOVERY AND PRECISION OF PERFORMANCE EVALUATION STANDARD

WITH DRINKING WATER

Variable

Value for Given Anion

Cl NO2

 SO42 NO3 F PO43

Milford drinking water

(MDW)

n  3, concentration

as mg/L

24.72  0.18 Not detected 7.99  0.07 0.36  0.05 Not detected Not detected

%RSD 0.73 — 0.91 13.3 — —

Performance evaluation

standard (PES),

concentration as mg/L

43.00 1.77 37.20 15.37 2.69 6.29

MDW  PES,*

n  3, concentration

as mg/L

66.57  0.34 1.74  0.03 45.19  0.17 15.42  0.12 2.62  0.07 5.55  0.31

%RSD 0.51% 1.85% 0.38% 0.79% 2.69% 5.52%

% Recovery 97.9% 98.3% 100.2% 98.1% 97.4% 88.2%

* Performance evaluation standard diluted 1:100 with Milford drinking water. Calculated analyte recovery and precision conform to the quality control acceptance limits

given in Section 1020.

TABLE 4140:IV. CAPILLARY ION ELECTROPHORESIS REPRODUCIBILITY AND PRECISION*

Laboratory No.

Anion Concentration

mg/L

Cl NO2

 SO42 NO3 F

1 (n  5) 43.22  0.22 1.58  0.09 36.39  0.33 14.57  0.12 2.54  0.10

2 (n  5) 43.68  0.61 1.58  0.08 37.01  0.37 13.94  0.09 2.69  0.02

3 (n  5) 43.93  0.39 1.60  0.06 37.68  0.24 15.05  0.11 2.69  0.03

4 (n  3) 42.51  0.22 1.78  0.06 37.34  0.19 14.06  0.07 2.69  0.02

Average (mean  SD) 43.34  0.36 1.64  0.07 37.11  0.28 14.41  0.10 2.64  0.04

%RSD 0.83% 4.5% 0.77% 0.67% 1.61%

* Results from four laboratories analyzing the performance evaluation standard using the Youden pair standards for quantitation. Only one laboratory reported results for

PO4

3 as 6.34  0.02 mg/L on triplicate samplings yielding %RSD of 0.07%. Calculated replicate reproducibility and precision conform to the quality control acceptance

limits given in Section 1020.

INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS (4140)/CIE with Indirect UV Detection

7
f. Sample duplicates: Analyze one or more sample duplicates

every 10 samples.

7. Precision and Bias

Table 4140:III compares results of capillary ion electrophoresis

with those of other approved methods. Precision and bias data are

given in Tables 4140:IV and 4140:V. Comparison of other methods

and capillary ion electrophoresis for wastewater effluent, drinking

water, and landfill leachates are given in Table 4140:VI.

8. Bibliography

ROMANO, J. & J. KROL. 1993. Capillary electrophoresis, an environmental method for the determination of anions in water. J. Chromatogr.

640:403.

JANDIK, P. & G. BONN. 1993. Capillary Electrophoresis of Small Molecules and Ions. VCH Publishers, New York, N.Y.

TABLE 4140:VI. COMPARISON OF CAPILLARY ION ELECTROPHORESIS WITH CHROMATE ELECTROLYTE WITH OTHER METHODS FOR THE

DETERMINATION OF ANIONS

Anion Matrix

Sample

No.

Concentration by Given Method*

mg/L

Wet Chemical or Other

Method† IC‡ CIE

Chloride Effluent 1 — 149 147

2 — 162 161

3 — 152 151

4 — 139 139

5 — 111 110

6 — 109 107

7 — 3.6 3.5

Drinking water 1 5.5 5.1 5.0

2 5.5 5.0 5.0

3 5.3 5.2 5.2

4 5.5 5.1 5.1

5 5.3 5.0 5.1

6 5.3 4.9 4.9

7 5.5 4.9 4.9

Landfill leachate 1 0.1 0.1 ND

2 230 245 240

Fluoride Effluent 1 1.7 1.2 1.5

2 0.9 0.6 0.6

3 0.8 0.5 0.6

4 0.8 0.4 0.7

5 0.9 0.5 0.8

6 0.9 0.5 0.7

7 0.1 ND 0.1

Drinking water 1 1.2 0.9 0.9

2 1.3 0.9 0.9

3 1.3 0.9 0.9

4 1.3 0.9 0.9

5 1.3 0.9 0.9

6 0.9 0.6 0.6

7 1.3 0.9 0.9

Landfill leachate 1 0.2 ND ND

2 16 10.6 10.9

INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS (4140)/CIE with Indirect UV Detection

8
TABLE 4140:VI. CONT.

Anion Matrix

Sample

No.

Concentration by Given Method*

mg/L

Wet Chemical or Other

Method† IC‡ CIE

Sulfate Effluent 1 98 87.5 86.4

2 110 95.3 95.9

3 130 118 115

4 130 139 136

5 110 113 110

6 100 107 106

7 6 5.6 5.8

Drinking water 1 6 5.8 6.0

2 6 5.8 6.0

3 6 5.9 6.1

4 6 5.9 6.1

5 5 5.8 6.2

6 4 3.0 3.4

7 5 5.8 6.1

Landfill leachate 1 1 ND ND

2 190 211 201

Nitrite & nitrate§ Effluent 1 0.3 ND ND

(as N) 2 — ND ND

3 — ND ND

4 — ND 0.5

5 — 2.1 2.4

6 2.4 1.9 2.2

7 0.7 0.3 0.4

Drinking water 1 0.6 0.3 0.4

2 0.6 0.3 0.4

3 0.4 0.3 0.4

4 0.6 0.3 0.3

5 0.6 0.3 0.4

6 0.3 0.1 0.1

7 0.5 0.3 0.4

Landfill leachate 1 — ND ND

2 — ND ND

Orthophosphate (as P) Effluent 1 3.4 ND 2.8

2 4.9 ND 4.4

3 4.7 ND 4.5

4 5.3 ND 4.2

5 3.0 ND 3.0

6 2.9 ND 2.3

7 0.1 ND 0.04

Drinking water 1 0.1 ND ND

2 0.1 ND ND

3 — ND ND

4 0.1 ND ND

5 0.1 ND ND

6 — ND ND

7 — ND ND

Landfill leachate 1 0.1 ND 0.1

2 2.2 1.6 1.4

* —  test not performed; ND  not detected.

† Methods used were: chloride—iodometric method (4500-Cl.C); fluoride—ion selective electrode method (4500-F.C); sulfate—turbidimetric method (4500-SO4

2.E);

nitrite  nitrate (total)— cadmium reduction method (4500-NO3

.E); orthophosphate—ascorbic acid method (4500-P.E).

‡ Single-column ion chromatography with direct conductivity detection (4110C).

§ Each technique gave separate nitrite and nitrate values; because of their interconvertability, results were added for comparison purposes.

INORGANIC ANIONS BY CAPILLARY ION ELECTROPHORESIS (4140)/CIE with Indirect UV Detection

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