## 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 allanions 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 monovalentorganic acids. Sample preparation typically is dilution with reagent water and removal of suspended solids by filtration. If necessary, hydrophobic sample components such as oil andgrease 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 theanode. 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 theydisplace charge-for-charge the UV-absorbing electrolyte anion (chromate), causing a net decrease in UV absorbance inthe analyte anion zone compared to the background electrolyte. Detector polarity is reversed to provide positive mvresponse 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 electrolyteformulation 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 NO 2  

### and NO 3  

### to SO 4 2

 

### , and 1:1000 differential of Cl  

### and SO 4 2





### .

Dissolved ferric iron in the mg/L range gives a low bias for PO 4 

### . However, transition metals do not precipitate with chro

mate because of the alkaline electrolyte pH.

c. Minimum detectable concentrations : The minimum detectable concentration for an anion is a function of samplesize. 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 purgemechanism, 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 actas 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. Opti

mum performance is attained with a computer data system andelectrophoresis-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 m M: In a 1-L volumetric flask dissolve 23.41 g sodium chromate tetrahydrate, Na2

### CrO 4 

###  4H 2

### O, 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 m M: 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 m M: In a 1-L volumetric flask dissolve 20.73 g 2-[N -cyclohexylamino]-ethane sulfonate (CHES), mol wt 207.29, in 500 mL water and dilute to 1 L. Store * Waters Corp. or equivalent. Figure 4140:1. Electropherogram of the inorganic anions and typically found organic acids using capillary ion electrophoresis and chromate electrolyte. Electrolyte: 4.7 m N Na2CrO 4/4.0 m M TTAOH/10 m M CHES/0.1 m M 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 m M: 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 m M: 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-m M NaOH followed by 10 mL water; discard the washings. Slowly pass 4 mL 100-m M 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 detectionlevels, 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. C OLLABORATIVE D ESIGN AS FOUR Y OUDEN PAIR S ETS *

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 NO 2  3.0 40.0 20.0 15.0 50.0 0.5 2.0 0.7 SO 4 2

 40.0 50.0 0.5 0.7 2.0 3.0 15.0 20.0 NO 3  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 PO 4 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 0.1and 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 m M 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 m M sodium chromate, 4 m M TTAOH, 10 m M CHES, and 0.1 m M calcium gluconate. Filter and degas through a 0.45-  m aqueous membrane, using a vacuum apparatus. Storeany 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 NaCO 2H 0.1510 Fluoride NaF 0.2210 Nitrite NaNO 2 0.1499* (1000 mg NO 2  /L  304.3 mg NO 2 

 N/L) Nitrate NaNO 3 0.1371 (1000 mg NO 3  /L  225.8 mg NO 3 

 N/L) Phosphate Na2HPO 4 † 0.1500 (1000 mg PO 4 3

 /L  326.1 mg PO 4 3



 P/L) Sulfate Na2 SO 4 † 0.1480 (1000 mg SO 4 2

 /L  676.3 mg SO 4 2



 S/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/Lto 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 themixed 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 m M 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 migrationtime 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  

### , NO 2  

### , SO 4 2

 

### , NO 3  

### , F  

### , and PO 4 3

 

### . Dissolved HCO 3  

### 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 analytequalitative 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 peakarea 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, R 2 

### , 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 Y OUDEN PAIR S TANDARDS

Youden Standard Anion Midpoint Migration Time, Average of Triplicate Samplings min

Cl  Br  NO 2  SO 4 2

 NO 3  F  PO 4 3



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

4Figure 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 analytequantitation. 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. C OMPARISON OF C APILLARY I ON ELECTROPHORESIS AND O THER METHODS

Source Statistic Value for Given Anion
mg/ L

Cl  NO 2  SO 4 2

 NO 3  F  PO 4 3



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 u sing 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 theanalyses, 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 thecalibrated 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 PO 4 3

 

### and does not interfere with the analysis. Any nega

tive 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 (¶ 3 f

). 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. C APILLARY I ON ELECTROPHORESIS KNOWN-ADDITION RECOVERY AND PRECISION OF PERFORMANCE EVALUATION S TANDARD

WITH D RINKING WATER

Variable Value for Given Anion

Cl  NO 2  SO 4 2

 NO 3  F  PO 4 3


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. C APILLARY I ON ELECTROPHORESIS REPRODUCIBILITY AND PRECISION *

Laboratory No. Anion Concentration
mg/ L

Cl  NO 2  SO 4 2

 NO 3  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 PO 4 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. B ONN . 1993. Capillary Electrophoresis of Small Molecules and Ions. VCH Publishers, New York, N.Y.

TABLE 4140:VI. C OMPARISON OF C APILLARY I ON ELECTROPHORESIS WITH C HROMATE ELECTROLYTE WITH O THER METHODS FOR THE D ETERMINATION 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

8TABLE 4140:VI. C ONT

.

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-SO 4 2

 .E); nitrite  nitrate (total)— cadmium reduction method (4500-NO 3  .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

9