Determination of Bromate in the Presence of Brominated Haloacetic

Jun 30, 1997 - The tribromoacetic acid was removed using a reverse-phase sample pretreatment cartridge. The overall analysis procedure was evaluated i...
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Environ. Sci. Technol. 1997, 31, 2059-2063

Determination of Bromate in the Presence of Brominated Haloacetic Acids by Ion Chromatography with Inductively Coupled Plasma Mass Spectrometric Detection JOHN T. CREED,* MATTHEW L. MAGNUSON,† AND CAROL A. BROCKHOFF U.S. Environmental Protection Agency, National Exposure Research Laboratory, Human Exposure Research Division, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268

Bromate is a disinfection by product (DBP) in drinking water that is formed during the ozonation of a source water containing bromide. Brominated haloacetic acids are DBPs that are anions at near-neutral pHs. The anion character of bromoacetic acid (pKa ) 2.7) is similar to bromate, which causes the two species to coelute when NaOH is used as an eluent. Four columns are evaluated as a means of removing the potential false positives generated by bromoacetic acid. The alkyl quaternary amine based PA-100 guard column separates bromate from bromoacetic acid using 100 mM NaOH, but the analysis time is greater than 12 min. The use of 5 mM HNO3 as an eluent (with the PA100) provides adequate separation of bromate from bromoacetic acid with an analysis time of less than 8 min. The stability of bromate in 5 mM HNO3 was evaluated using a DDI matrix (pH adjusted to 5.5, fortified with bromide) and a drinking water matrix (pH 4-9). The bromate recoveries in these two matrices were 93-105% with less than 4% RSDs. Tribromoacetic acid produces a broad peak that envelops the retention window of bromate. The tribromoacetic acid was removed using a reverse-phase sample pretreatment cartridge. The overall analysis procedure was evaluated in a synthetic chloride, sulfate, and nitrate matrix. In addition, precision and recovery data were collected from five ozonated drinking waters. The percent recoveries in the ozonated waters ranged from 90 to 98% with RSDs of less than 6%. The method detection limit for bromate is 0.8 µg/L.

Introduction Bromate is a disinfection byproduct (DBP) derived from the ozonation of bromide containing source water (1-3). The bromide in the source water is oxidized to bromate by the ozone. The disinfection of drinking water with ozone is becoming more prevalent as the health risks associated with DBPs formed during disinfection via chlorination become better documented (4). Ozonation as a disinfection process has its own set of DBPs including trihalomethanes, bromoacetic acids, bromoacetones and bromoacetonitriles, and bromate (5). This work documents the existence of these compounds, but the ozone treatment utilized was relatively * To whom correspondence should be addressed: telephone (513) 569-7833; fax: (513) 569-7757. † National Research Council Postdoctoral Fellow.

S0013-936X(96)00887-5 This article not subject to U.S. Copyright. Published 1997 by the American Chemical Society.

high in comparison to normal treatment practices. Bromate is believed to be a cancer causing agent with an estimated lifetime cancer risk of 1 in 104 at 5 ppb based on an average adult’s drinking water intake (6). This carcinogenic risk would require the maximum contaminate level goal (MCLG) of bromate to be zero; therefore, trace determination will allow the MCL to be set closer to the MCLG. The World Health Organization has established a guideline of 25 µg/L and a lifetime cancer risk of 1 in 105 for 3 µg/L for bromate (3). U.S. EPA Method 300.0 is an ion chromatography/ conductivity detection based method for the analysis of bromate in drinking water with a MDL of 20 µg/L (7). The analysis of bromate by ion chromatography coupled with conductivity detection suffers from a near coelution of chloride with bromate. Chloride, a common matrix anion in drinking water, envelops the much smaller bromate signal when a nonspecific detector is utilized producing an MDL of 7 µg/L (8, 9). Recent advances in minimizing this interference have included a column switching system (10) and the use of a silver-containing cartridge as a pretreatment to remove the chloride (11, 12). This approach has an MDL of 1 µg/L using a 5-mL sample volume and the possible disadvantage of analyte losses due to column capacities limitations (9, 13). Gordon et al. (14) used the oxidation of chlorpromazine by bromate as the basis for an ion chromatography detector (15), but this spectrophotometric technique still required chloride removal prior to analysis. Charles et al. (16) used electrospray and ion chromatography in combination with tandem mass spectrometry to achieve sub-parts-per-billion detection limits for bromate in water. Heitkemper et al. (1719) used ICP-MS as a detector for an ion chromatograph for the analysis of bromate in bread. The selectivity of the mass spectrometer allows the detection of 5 ppb bromate in the presence of 1000 ppm chloride (20). This selectivity greatly increases the reliability of the analysis of bromate in drinking water because most finished waters contain less than 1000 ppm chloride (21). However, the borate eluents commonly used with conductivity detection causes the sampling cone of the ICP-MS to clog, leading to poor short-term precision. The detection of bromate in drinking water by IC-ICPMS is not affected by typical drinking water chloride concentration but rather by brominated haloacetic acids (22). The ozonation of source water, which contain bromide and humic material produces brominated haloacetic acids such as DBPs (5). These brominated haloacetic acids (pKa < 2.7) are anions at drinking water pHs. This class of compounds circumvent the selectivity of the ICP-MS. The brominated haloacetic acids anionic character causes separation difficulties with the early-eluting bromate while the trisubstituted haloacetic acids produce broad peaks within the retention window for bromate. The focus of this work is 2-fold: first, the removal of the tribromoacetic acid prior to analysis; second, the separation of the weakly retained bromoacetic acid from the early-eluting bromate using a nitric acid-based eluent system.

Experimental Section Reagents. Reagent-grade NaOH was used to make the 100 mM NaOH (Mallinkrodt, Paris, KY). The 5 mM HNO3 was made from 624 µL of 1:1 HNO3 (Ultrex II, J. T. Baker Inc, Phillipsburg, NJ) diluted to 1 L. All dilutions were made using 18 MΩ water (Millipore, Bedford, MA). The bromate standards were made from sodium bromate (Fisher, Fairlawn, NJ). The NaBrO3 standard did not contain detectable quantities of Br- and was verified against a secondary bromate standard (High Purity, Charleston, SC). The methanol used for the preparation of the RP cartridges (Dionex, Sunnyvale

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CA) was Optima grade (Fisher, Fairlawn, NJ). The haloacetic acid mixture was purchased from Supelco (Bellefonte, PA). The mixture contained 200 µg/mL bromoacetic, chlorodibromoacetic, bromochloroacetic, bromodichloroacetic, and dalapon; 100 µg/mL of dibromoacetic, tribromoacetic, trichloroacetic, 2-bromopropionic; and 300 µg/mL of chloroacetic and dichloroacetic. These concentrations were not verified with a secondary source standard. The synthetic chloride matrix was made from NaCl (J. T. Baker, Phillipsburg NJ), the sulfate matrix was made from K2SO4 (Fisher, Fairlawn, NJ), and the nitrate matrix was made from NaNO3 (J. T. Baker, Phillipsburg NJ). Apparatus. The ICP-MS was a Fisons (Beverly, MA) PQI that has been upgraded with a high-performance interface. The data were collected in single ion monitoring (SIM) mode using the major isotope of bromine, m/z 79. The dwell time was set to 81 ms. The chromatographic peaks were integrated offline using a routine written in SAS (SAS Institute Inc., Cary, NC). This routine uses a quadratic fit to estimate the baseline and uses this baseline to integrate the chromatographic peaks. The plasma, auxiliary, and nebulizer flow rate were 14, 0.8, and 0.7 L/min, respectively. The ICP forward power was 1.3 KW and was not optimized for bromate analysis. The ion chromatograph was a Dionex (Sunnyvale, CA) Model GPM2. The sample pump was a Dionex Model DQP-1. The selfregenerating suppressor (Dionex, Sunnyvale, CA) exchanges the sodium ion in the mobile phase for hydronium ion. This exchange eliminates the deposition of sodium on the ICPMS sampling cone and thereby provides improved long-term precision. The flow rate of the DDI through the selfregenerating suppressor was 1 mL/min. This suppressor was not utilized with the 5 mM HNO3 eluent. The analytical columns used were as follows: IonPac AS10 with a capacity of 170 µequiv and an alkanol quaternary ammonium functional group; IonPac AG10 (a guard column for the AS10); IonPac AS12 with a capacity of 52 µequiv and an alkyl quaternary ammonium functional group; the guard column for the PA-100 with a capacity of 18 µequiv and an alkyl quarternary amine functional group; and the AG7, which has a capacity of 20 µequiv and an alkyl quarternary ammonium functional group. All columns were purchased from Dionex (Sunnyvale, CA). The AG7 is the only column evaluated that is not solvent compatible. The guard columns utilized in this work were found to provide adequate separation of the analyte from known interferences. The samples were pretreated using a RP cartridge (Dionex, Sunnyvale, CA). The cartridges are similar to a C-18 sample pretreatment cartridge. The cartridges were prepared and used according to manufacturer’s recommendations. The chromatographic setup has one unique feature. A 100-µL post-column standard injection loop is used to inject a bromate standard, which does not traverse the column. This standard is used to correct for instrumental drift during the analysis of a batch of samples. This 100-µL standard injection provides a means for synchronizing data collection from the mass spectrometer with the start of the ion chromatograph’s program. This synchronization is necessary solely because the IC and ICP-MS are not connected electronically. The sample is injected onto the column using a 170-µL loop. The flow rate for the 100 mM NaOH and the 5 mM HNO3 was 1.5 mL/min.

Results and Discussion Column and Mobile Phase Considerations. The anionic character of brominated haloacetic acids at a neutral pH produces possible chromatographic interferences with bromate when anion chromatography is used as a separation scheme. Bromoacetic acid coelutes with bromate under isocratic conditions using 100 mM NaOH at a flow rate of 1.5 mL/min. Table 1 is a summary of retention times for bromate vs bromoacetic acid for five different columns. Three of the

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TABLE 1. Retention Time of Bromate and Bromoacetic Acid columna,b

bromate retention timec (s)

bromoacetic acid retention timec (s)

AG10 AS10 AS12 AG7d PA-100

38 255 155 261 226

38 232 155 158 136

a The AG10 and AS10 have alkanol quaternary ammonium functional groups while the AS12, AG7, and PA-100 have alkyl quaternary ammonium functional groups. b Mobile phase is 100 mM NaOH at 1.5 mL/min. c Retention time is measured at peak height maximum. d This column is not solvent compatible.

FIGURE 1. Separation of bromate from bromoacetic acid using a 100 mM NaOH eluent and a PA-100 column. Chromatogram represents a 170-µL injection of 20 ppb bromate, 56 ppb bromoacetic acid, and 80 ppb dibromoacetic acid. Chromatogram is a single ion monitoring of mass 79 using a 81-ms dwell time. columns evaluated were unable to adequately resolve bromate from the bromoacetic acid using 100 mM NaOH. The AG7 and PA-100 guard columns separated bromate from bromoacetic. The PA-100 was chosen for further work because of its solvent compatibility. Figure 1 is a chromatogram of bromoacetic acid, bromate, and dibromoacetic acid using PA-100 and isocratic 100 mM NaOH eluent. Figure 1 indicates that bromoacetic acid is easily resolved from bromate while the dibromoacetic acid requires 12 min to elute. Alternative isocratic solvent programs were evaluated in an attempt to minimize the analysis time. The most promising of these was dilute nitric acid. The use of dilute nitric acid was evaluated using a test mixture containing the coeluting species (bromate and bromoacetic acid), bromide (common inorganic anion), and dibromoacetic acid (a somewhat strongly retained haloacetic acid). Figure 2 is a graph of retention times for this test mixture vs millimolar nitric acid. Figure 2 indicates that the separation between bromate and bromoacetic acid decreases as the nitric acid concentration increases. Five millimolar nitric acid allows for a 5-min analysis with a 45-s separation (based on height) of bromate from bromoacetic acid. This separation allows for some matrix-dependent peak retention shifts without causing peak misidentification. Figure 2 also illustrates the shorter retention times obtained for bromide and dibromoacetic acid with increasing HNO3 concentration. The 5 mM HNO3 is a compromise between adequate resolution between bromate and bromoacetic acid and the overall analysis time. The effect of pH on the 5 mM HNO3 separation was investigated using NH4OH to increase the pH of the nitric acid eluent. The 5 mM HNO3 mobile phase has a pH of 2.7. The NH4OH was added to adjust the pH from 2.7 to 3.5 in steps of 0.2 pH unit. The pH change from 2.7 to 3.5 caused the bromoacetic acid retention time

FIGURE 2. Retention time vs millimolar nitric acid for bromate test mixture. Retention time is measure based on peak height maximum for (9) bromoacetic acid, (() bromate, (2) dibromoacetic acid, and (0) bromide. All samples were analyzed using the PA-100 guard column and the corresponding nitric acid concentration at 1.5 mL/min flow rate. Chromatogram of 170 µL of 56 ppb bromoacetic acid, 20 ppb bromate, 80 ppb dibromoacetic acid, and 50 ppb bromide using 5 mM HNO3 at 1.5 mL/min. to increase by 20 s while the bromate retention time shifted by less than 5 s. This change in retention time could be attributed to the increasing anionic character of the bromoacetic acid (pKa ) 2.7) as the pH was raised from 2.7 to 3.5. This increased anionic character causes increased interaction with the column. Loss of resolution with the pH led to the use of a 5 mM HNO3 mobile phase. A chromatogram of the test mixture using the 5 mM HNO3 is shown in Figure 2. The use of a 5 mM HNO3 mobile phase has the added advantage that the electronic suppressor, which removes the sodium from the 100 mM NaOH eluent, is not required. Sample pH and Sample Loop Considerations. A unique artifact of using the 5 mM HNO3 mobile phase was discovered when a pH-dependent response difference was observed using a 50 ppb bromate standard made in 18 MΩ water. The response from a 50 ppb bromate standard (pH 5.8) injected using a tefzel loop material was 1.8 ( 0.2 (x ( 2σ) times the response from the same sample adjusted to a pH 10 using NaOH. A similar response difference was observed for a sample loop made of Peek tubing. If this same response ratio is measured using a stainless steel sample loop, the 50 ppb standard (pH 5.8)/50 ppb standard (pH 10) ratio is 1.1 ( 0.1 (x ( 2σ). This indicated that the response difference in 18 MΩ of water is correlated to the sample loop material. Figure 3 investigates this response difference using a peristaltic pump and a small piece of sample loop material. The signal tracing within Figure 3 during the first 5 min is produced by the direct nebulization of a 50 ppb bromate standard (pH 5.8). During this time, the bromate signal is extremely slow in achieving a steady-state response (see min 1-2). After the steady-state signal is achieved, a nitric acid spike is added to the sample bottle (the nitric acid added to the 50 ppb standard solution made the resulting solution 5 mM HNO3). The addition of the acid to the sample caused a flow injectionshaped peak of bromate to elute. If a similar experiment is run substituting NaOH for the nitric acid, a similar FIA-shaped peak of bromate is observed. The signal tracing for the NaOH experiment is also shown in Figure 3. The data in Figure 3 in combination with the relative responses using the tefzel vs the stainless steel loop may indicate that, in a low ionic

FIGURE 3. Effect of HNO3 and NaOH on the adsorption of bromate on sample loop walls in 18 MΩ standard solutions. The standard solution contains 50 ppb bromate in 18 MΩ of water. Single ion monitoring of m/z 79 for both experiments. Sodium hydroxide or nitric acid is added to the 50 ppb standard solution at 5.3 min. strength solution at neutral pHs, the bromate adsorbs to the wall of the tefzel sample loop. This response difference was only observed in standards made of 18 MΩ water. The nitric acid or NaOH solubilizes the adsorbed bromate, and the resulting flow injection shape peak is observed. This adsorption on the tefzel sample loop is believed to cause the response difference between the pH 5.8 standard and the pH 10 standard. The 50 ppb bromate standard (pH 5.8) is adsorbed on the sample loop during the loading process and is eluted when the loop is placed in the 5 mM HNO3 eluent flow stream. The elution process includes the adsorbed bromate on the walls of the sample loop and the 100 µL standard solution that is in the sample loop. The net result is an elevated response for the tefzel loop for a standard in 18 MΩ water at pH 5.8. This adsorption is avoided by adjusting the pH of the standard and blank to 10 prior to analysis. It would be equally valid to adjust the pH to 3, but bromate has been reported to be thermodynamically unstable at lower pHs (23).

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FIGURE 4. Bromate recovery in an ozonated drinking water matrix vs sample pH. The ozonated drinking water sample is pH adjusted using NaOH or HNO3 and pretreated using a Dionex RP cartridge. All average percent recoveries are reported (2σ and are based on n ) 5 of a 25 ppb bromate spike. Bromate Stability in Acidic Mobile Phases. Bromate has been reported to be thermodynamically unstable at lower pHs in the presence of bromide (23). To investigate the stability of bromate at lower pHs, a solution was made up that contained 1 ppm bromide [this concentration was chosen based on the fact that 95% of the U.S. drinking water supplies contain less than 1 ppm (24)]. The pH was adjusted to 5.5 [this pH would be considered low for drinking water supplies (21), and this sample would have very low buffering capacity]. Therefore, from a drinking water analysis standpoint, this sample would be considered a worst case scenario. This sample was fortified with 25 ppb bromate and analyzed five times using the 5 mM HNO3 eluent. The average recovery (relative to pH 10 standard and blank) and the RSD were 103% and 3.6%, respectively. This recovery indicated that the 5 mM HNO3 eluent does not affect the stability of bromate on the column at sample pHs as low as 5.5. In addition, this recovery data indicate that bromate can be determined in the presence of 1 ppm bromide. The stability of bromate was further investigated using an ozonated drinking water matrix. The pH of the ozonated drinking water was adjusted to evaluate the recovery of bromate in an actual drinking water matrix as a function of pH. The pH of the sample was adjusted from pH 3 to pH 9 using NaOH or HNO3. Figure 4 is a plot of average percent recovery ((2σ) versus drinking water pH. The percent recovery for samples with pHs above 5 are within the 95% confidence bound of 100% recovery. The percent recovery for pH 4 is somewhat lower at 93% ( 5.4. The recovery at a pH of 3 is 86% ( 5.8. This lower percent recovery coincides with a broadening of the bromate peak. This broadening may be caused by bromate’s instability but does not become a factor until the pH of the sample is well below those which are expected in a drinking water matrix (21). Haloacetic Acid Interferences. Figure 5a is a chromatogram of 11 haloacetic acids, seven of which are brominated before RP treatment (see Experimental Section). These haloacetic acids are made in a 18-MΩ distilled water sample. Figure 5a clearly indicates that the baseline during the retention window for bromate (2.5-3.0 min) is obstructed by the coelution of the brominated haloacetic acids. The injection of individual standards of the haloacetic acids indicated that tribromoacetic acid was the source of the slowly eluting interference. In order to remove the tribromoacetic acid (and other trisubstituted haloacetic acids), the sample was pretreated with a Dionex RP cartridge. Figure 5b is a chromatogram of the haloacetic acid mixture plus bromate and bromide after the sample has been treated with a Dionex RP cartridge. The RP cartridge effectively removes the tribromoacetic acid allowing for the determination of bromate in this haloacetic acid mixture.

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FIGURE 5. Effects of brominated haloacetic acids on the determination of bromate. Single ion monitoring of m/z 79 using PA-100 column and 5 mM HNO3 at 1.5 mL/min. Sample matrix is 18 MΩ of water fortified with 20 ppb bromate and haloacetic acid mixture after a 2000-fold dilution. See reagent section for individual HAA concentrations. 100 ppb bromide has been added to the sample prior to pretreatment with RP cartridge. Pretreated using Dionex RP preparatory cartridge. Detection Limit and Precision and Recovery. The carcinogenic risk associated with a lifetime exposure to 5 ppb bromate in drinking water is 1 in 104, which is relatively high in comparison to other disinfection byproducts (6). This carcinogenic risk factor would imply the need to monitor bromate below 1 ppb in drinking water. A method detection limit as defined by the U.S. EPA is a measure of the reproducibility of a low level standard that has been treated in the same manner as a sample (25). The method detection limit for IC-ICP-MS based on seven replicate analyses is 0.8 ppb. This direct analysis would provide the capability of measuring bromate at a concentration with an associated cancer risk of 1 in 104-105. The recovery of bromate in a synthetic chloride, sulfate, and nitrate matrix was evaluated using 100 ppm Cl-, 500 ppm SO42-, and 10 ppm NO3-. These three anions were chosen based on their occurrence in drinking supplies data and their potential interferences with IC detection of bromate (8, 9, 21). These synthetic matrices do not represent the maximum concentrations reported in drinking water. The average percent recovery of 25 ppb bromate in a 100 ppm chloride, 500 ppm sulfate, and 10 ppm nitrate matrices were 97, 108, and 99, respectively, with %RSD of 3.7, 6.7, and 8.5, respectively. These results were based on five replicate analyses. Bromate retention time shift (based on peak height) produced by the matrix relative to the standard is 4 s for chloride, 10 s for sulfate, and 1 s for nitrate. These recoveries and small retention time shifts indicate that realistic chloride, sulfate, and nitrate concentrations in a drinking water sample do not cause interference effects on the determination of bromate.

TABLE 2. Bromate Recovery in Ozonated Drinking Watersa water

concnb (µg/L)

% RSD

1 2 3 4 5

2.0 8.2

22.5 7.4

av % recoveryb,c (25 µg/L)

% RSD

98 97 99 94 90

3.2 1.5 5.0 1.9 5.9

a All analysis were performed using PA-100 column and 5 mM HNO . 3 Based on five replicate injections. c Fortified with 25 ppb and BrO3-; 10 ppb bromoacetic acid, bromodichloroacetic acid, and chlorodibromoacetic acid; 5 ppb 2-bromopropionic acid, dibromoacetic acid, and tribromoacetic acid. b

Table 2 contains precision and recovery for five ozonated drinking waters. These data were collected using the RP cartridge prior to analysis and the PA-100/5 mM HNO3. The precision at 3-10 times the MDL (2-8 ppb) is demonstrated by the percent RSDs of 22.5 and 7.4 for waters which after ozonation contain 2.0 and 8.2 ppb bromate, respectively. These RSDs demonstrate the low level performance of the IC-ICP-MS method. The samples were then fortified with bromate and brominated haloacetic acids in order to verify the recovery of bromate in the presence of the haloacetic acid interferences. The percent recovery of bromate in the five drinking waters ranged from 90 to 99 with % RSDs of 2-6. This recovery was determined based on five replicate analyses of a sample fortified with 25 ppb bromate. These recoveries indicate that bromate can be determined using ICP-MS in drinking water samples that contain brominated haloacetic acids. The detection of bromate in ozonated drinking waters via IC-ICP-MS does not suffer from the chloride interference associated with IC conductivity detection, but the instrumental costs are high. The chromatographic interferences of concern in drinking water are the anionic haloacetic acids. The use of a PA-100 guard column with a 5 mM HNO3 mobile phase allows for the separation of bromoacetic acid from bromate with analysis times of less than 8 min. The removal of other bromine-containing trisubstituted haloacetic acids is necessary because of their broad peaks that interfere with the integration of the bromate peak. These interferences can be removed using a RP cartridge prior to analysis. This pretreatment with the RP cartridge and analysis using a 5 mM HNO3 eluent and ICP-MS detection provides a means of minimizing the impact of haloacetic acids as false positives in bromate analysis in ozonated drinking waters. The recoveries of bromate in ozonated waters spiked with bromate and haloacetic acids indicate this capability.

Literature Cited (1) Haag, W. R.; Holgne, J. Environ. Sci. Technol. 1983, 17, 261. (2) vonGunten, U.; Hoigne, J. Environ. Sci. Technol. 1994, 28, 1234. (3) Guidelines for drinking water quality; WHO: Geneva, 1993; p 96.

(4) Mughal, F. H. J. Environ. Pathol. Toxicol. Oncol. 1992, 11 (5,6), 287-292. (5) Siddiqui, M. S.; Amy, G. L. J. Am. Water Works Assoc. 1993, 63. (6) Fed. Reg. 1994, Part 136, 59 (145), 38709. (7) EPA Method 300.0. Methods for the Determination of Inorganic Substances in Environmental Samples; EPA/600/R93/100; U.S. EPA: Washington, DC, 1993. (8) Hautman, D. P.; Bolyard, M. J. Chromatogr. 1992, 602, 65. (9) Joyce, R. J.; Dhhillon, H. S. J. Chromatogr A. 1994, 671, 165. (10) Hautman, D. Analysis of Trace Bromate in Drinking Water Using Selective Anion Concentration and Ion Chromatography. Presented at the American Water Works Association Water Quality Technology Conference, Toronto, Canada, 1992; American Water Works Association: Denver, CO, 1993; p 993. (11) Joyce, R. J.; Dhillon, H. S. Part-Per-Billion Level Determination of Bromate in Ozonated Drinking Water Using Ion Chromatography. Presented at the International Ion Chromatography Symposium, Baltimore, MD, 1993. (12) Weinberg, H. J. Chromatogr. A. 1994, 671, 141. (13) Koudjonou, B.; Muller, M. C.; Costentin, E.; Racaud, P.; Van der Jagt, H.; Vilaro, J. S.; Hutchinson, J. Ozone Sci. Eng. 1995, 17, 561. (14) Gordon, G.; Bubnis, B.; Sweetin, D.; Juo, C. Ozone Sci. Eng. 1994, 16, 79. (15) Gordon, G.; Bubnis, B. Ozone Sci. Eng. 1995, 17, 551. (16) Charles, L.; Pepin, D.; Casetta, B. Anal. Chem. 1996, 68, 2554. (17) Heitkemper, D. T.; Kaine, L. A.; Jackson, D. S. Determination of Residual Bromate in Baked Goods by Ion Chromatography with ICP-MS Detection. Presented at the 1994 Winter Conference on Plasma Spectrochemistry, San Diego, CA, January 10-15, 1994. (18) Heitkemper, D. T.; Kaine, L. A.; Jackson, D. S.; Wolnik, K. A. J. Chromatogr. A. 1994, 671, 101. (19) Heitkemper, D. T.; Kaine, L. A. Application of IC-ICP-MS/AES in Foods and Dietary Supplements. Presented at the Twentysecond Annual Conference of the Federation of Analytical Chemistry and Spectroscopy Societies, Cincinnati, OH, October 15-20, 1995. (20) Creed J. T.; Magnuson, M. L.; Brockhoff, C. A. J. Chromatogr. 1996, 753, 261. (21) Chemical Analysis of Interstate Carrier Water Supply Systems; U.S. EPA: Washington, DC, 1976; EPA-430/9-75-005. (22) Creed, J. T.; Magnuson, M. L.; Brockhoff, C. A. The Determination of Bromate in the Presence of Haloacetic Acids by Ion Chromatography Inductively Coupled Plasma Mass Spectrometry. Presented at the 38th Rocky Mountain Conference on Analytical Chemistry, Denver, CO, 1996; Abs 191. (23) Gordon, G. The Chemical Aspects of Bromate Ion Control in Ozonated Drinking Water Containing Bromide Ion; International Workshop Bromate and Water Treatment: Paris, 1993; pp 4149. (24) Amy, G.; Siddiqui, M.; Zhai, W., Debroux, J.; Odem, W. NationWide Survey of Bromide Ion Concentrations in Drinking Water Sources. In Proceedings of the 1993 Annual Conference of the American Water Works Association; AWWA: San Antonio, TX, June 6-10, 1993. (25) Glaser, J. A.; Foerst, D. L.; McKee, G. D.; Quave, S. A.; Budde, W. L. Environ. Sci. Technol. 1981, 15, 1426.

Received for review October 14, 1996. Revised manuscript received January 30, 1997. Accepted March 6, 1997.X ES960887S X

Abstract published in Advance ACS Abstracts, May 15, 1997.

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