Simultaneous determination of inorganic disinfection by-products and the seven standard anions by ion chromatography

For the first time, an ion chromatographic method for the simultaneous determination of the disinfection by-products bromate, chlorite, chlorate, and the so-called seven standard anions, fluoride, chloride, nitrite, sulfate, bromide, nitrate and orthophosphate is presented. The separation of the ten anions was carried out using a laboratory-made high-capacity anion-exchanger. The high capacity anion-exchanger allowed the direct injection of large sample volumes without any sample pretreatment, even in the case of hard water samples. For quantification of fluoride, chloride, nitrite, sulfate, bromide, nitrate, orthophosphate and chlorate, a conductivity detection method was applied after chemical suppression. The post-column reaction, based on chlorpromazine, was optimized for the determination of chlorite and bromate. The method detection limit for bromate measured in deionized water is 100 ng/l and for chlorite, it is 700 ng/l. In hard drinking water, the method’s detection limits are 700 ng/l (bromate) and 3.5 μg/l (chlorite). The method’s detection limits for the other eight anions, determined by conductivity detection, are between 100 μg/l (nitrite) and 1.6 mg/l (chlorate).     

Use of ion chromatography with post-column reaction for the measurement of tribromide to evaluate bromate levels in drinking water

A user-friendly ion chromatography method in conjunction with a post-column reaction (PCR) achieves practical quantitation limits for the oxyhalides bromate and chlorite of 0.05 μg/l and 0.10 μg/l, respectively. This level of measurement allows for the accurate assessment of bromate contributed to finished drinking waters that have been chlorinated using sodium hypochlorite. The target sensitivity of oxyhalides in the presence of other major ion species typically found in drinking water is achieved by PCR using excess bromide under acidic conditions to form a tribromide species that is detected by ultraviolet spectrometry. The method setup involves non-hazardous materials, as opposed to other recently developed methods that employ somewhat hazardous chemicals for generating the reaction necessary for the detection of bromate at sub-μg/l levels. No pretreatment of the samples is required, other than filtration and quenching of oxidant residual.     

Speciation of iodate and iodide in seawater by non-suppressed ion chromatography with inductively coupled plasma mass spectrometry

A non-suppressed ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP-MS) has been developed for simultaneous determination of trace iodate and iodide in seawater. An anion-exchange column (G3154A/101, provided by Agilent) was used for the separation of iodate and iodide with an eluent containing 20 mM NH₄NO₃ at pH 5.6, which reduced the build-up of salts on the sampler and skimmer cones. The influences of competing ion (NO₃⁻) in the eluent on the retention time and detection sensitivity were investigated to give reasonable resolution and detection limits. Linear plots were obtained in a concentration range of 5.0–500 μg/L and the detection limit was 1.5 μg/L for iodate and 2.0 μg/L for iodide. The proposed method was used to determinate iodate and iodide in seawaters without sample pre-treatment with exception of dilution.     

Germanium dioxide as internal standard for simplified trace determination of bromate, bromide, iodate and iodide by on-line coupling ion chromatography-inductively coupled plasma mass spectrometry

The use of elemental mass spectrometry as detection for ion chromatography allows sensitive determination of several bromine and iodine species at a reasonable time scale. Lowest concentrations observable are 66 ng L(-1) for bromate, 45 ng L(-1) for iodate, 74 ng L(-1) for bromide and 151 ng L(-1) for iodide. A major drawback of previous IC-ICP-MS applications is the high consumption of time and thus the running costs. The use of GeO2 as internal standard not only allows improved external calibration, but also semiquantitative determination of bromate, bromide, iodate and iodide without any calibration procedure. Furthermore, GeO2 can be used for all known types of anion exchange columns regardless of their construction principles. It is shown, that the analyte-to-GeO2 ratio of four bromine and iodine species was nearly constant over 4 months and almost independent from the ICP-MS instrumental settings. The quantification by means of the analyte-to-GeO2 ratio for samples taken from a bromate round robin test shows that the values obtained are in excellent agreement with calibration curve and isotope dilution results.     

Rapid IC-ICP/MS method for simultaneous analysis of iodoacetic acids, bromoacetic acids, bromate, and other related halogenated compounds in water

Haloacetic acids (HAAs) and bromate are toxic water disinfection by-products (DBPs) that the U.S. Environmental Protection Agency has regulated in drinking water. Iodoacetic acids (IAAs) are the emerging DBPs that have been recently found in disinfected drinking waters with higher toxicity than their corresponding chloro- and bromo-acetic acids. This study has developed a new rapid and sensitive method for simultaneous analysis of six brominated and four iodinated acetic acids, bromate, iodate, bromide, and iodide using ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS). Mono-, di- and tri-chloroacetic acids are not detected by this method because the sensitivity of ICP-MS analysis for chlorine is poor. Following IC separation, an Elan DRC-e ICP-MS was used for detection, with quantitation utilizing m/z of 79, 127, and 74 amu for Br, I, and Ge (optional internal standard) species, respectively. Although the primary method used was an external standard procedure, an internal standard method approach is discussed herein as well. Calibration and validation were done in a variety of natural and disinfection-treated water samples. The method detection limits (MDLs) in natural water ranged from 0.33 to 0.72 μg L⁻¹ for iodine species, and from 1.36 to 3.28 μg L⁻¹ for bromine species. Spiked recoveries were between 67% and 123%, while relative standard deviations ranged from 0.2% to 12.8% for replicate samples. This method was applied to detect the bromine and iodine species in drinking water, groundwater, surface water, and swimming pool water.     

Liquid-phase microextraction-gas chromatography-mass spectrometry for the determination of bromate, iodate, bromide and iodide in high-chloride matrix

In the determination of bromate and iodate, any free bromide and iodide present was quantitatively removed by anion exchange with silver chloride exploiting the differences in silver salts solubility product, being AgCl, 1.8 x 10(-10), AgBr, 5.0 x 10(-13), AgI, 8.3 x 10(-17), AgBrO(3), 5.5 x 10(-5) and AgIO(3), 3.1 x 10(-8). The oxyhalides were reduced with ascorbic acid to halides and converted to 4-bromo-2,6-dimethylaniline and 4-iodo-2,6-dimethylaniline by their reaction with 2-iodosobenzoate in the presence of 2,6-dimethylaniline at pH 6.4 and 2-3, respectively. Single drop microextraction (SDME) of the haloanilines in 2 microl of toluene and injection of the whole extract into GC-MS, or liquid-phase microextraction (LPME) into 50 microl of toluene and injection of 2 microl of extract, resulted in a sensitive method for bromate and iodate. The latter method of extraction has been found more robust, sensitive and to give better extraction in shorter period than SDME. Total bromine/iodine was determined without any treatment with silver chloride. High concentration of chloride in the matrix did not interfere. A rectilinear calibration graph was obtained for 0.05 microg-25 mg l(-1) of bromate/bromide and iodate/iodide, the limit of detection were 20 ng l(-1) of bromate, 15 ng l(-1) of iodate, 20 ng l(-1) of bromide and 10 ng l(-1) of iodide (by LPME in 50 microl of toluene). The method has been applied to seawater and table salt. From the pooled data, the average recovery of spiked oxyhalide/halide to real samples was in range 96.7-105.7% with RSD in range 1.6-6.5%.     

Determination of trace concentrations of bromate in municipal and bottled drinking waters using a hydroxide-selective column with ion chromatography

The International Agency for Research on Cancer determined that bromate is a potential human carcinogen, even at low micro/l levels in drinking water. Bromate is commonly produced from the ozonation of source water containing naturally occurring bromide. Traditionally, trace concentrations of bromate and other oxyhalides in environmental waters have been determined by anion exchange chromatography with an IonPac AS9-HC column using a carbonate eluent and suppressed conductivity detection, as described in EPA Method 300.1 B. However, a hydroxide eluent has lower suppressed background conductivity and lower noise compared to a carbonate eluent and this can reduce the detection limit and practical quantitation limit for bromate. In this paper, we examine the effect of using an electrolytically generated hydroxide eluent combined with a novel hydroxide-selective anion exchange column for the determination of disinfection byproduct anions and bromide in municipal and bottled drinking water samples. EPA Methods 300.1 B and 317.0 were used as test criteria to evaluate the new anion exchange column. The combination of a hydroxide eluent with a high capacity hydroxide-selective column allowed sub-microg/l detection limits for chlorite, bromate, chlorate, and bromide with a practical quantitation limit of 1 microg/l bromate using suppressed conductivity detection and 0.5 microg/l using postcolumn addition of o-dianisidine followed by visible detection. The linearity, method detection limits, robustness, and accuracy of the methods for spiked municipal and bottled water samples will be discussed.     

Comparison of three post-column reaction methods for the analysis of bromate and nitrite in drinking water

Three post-column ion chromatographic methods (i.e., a sodium bromide–sodium nitrite method, an o-dianisidine method, and a potassium iodide–ammonium heptamolybdate method) were compared for bromate and nitrite analysis. Also, the effect of direct mixing of the reagents without ion suppressors for the sodium bromide–sodium nitrite method and the potassium iodide–ammonium heptamolybdate method was investigated. For the analysis of bromate, the three methods showed similar method detection limits (0.17–0.24 μg/l) with pneumatic reagent delivery systems. Direct reagent mixing achieved comparable detection limits to the suppressor configuration. The three methods are also compatible with conductivity detection. When used in combination with conductivity detection, this compatibility allows simultaneous analysis of bromate, nitrite, and other common ions in drinking water, such as bromide. It was found that the o-dianisidine method achieves μg/l-level detection of nitrite and bromate with a simpler configuration than the potassium iodide–ammonium heptamolybdate method, while the sodium bromide–sodium nitrite method was not sufficiently sensitive for nitrite analysis at the μg/l level.     

Sequential injection spectrophotometric determination of trace amounts of iodide by its catalytic effect on the 4,4'-methylenebis(N,N-dimethylaniline)-chloramine-T reaction

A simple and sensitive sequential injection spectrophotometric procedure is proposed for the determination of trace amounts of iodide in pharmaceutical preparations. The method is based on the catalytic effect of iodide on the (tetra base) 4,4′-methylenebis(N,N-dimethylaniline)-chloramine-T reaction in acidic solution. The method involves a sequential aspiration of 255 μl sample/standard followed by 170 μl tetra base and then 128 μl chloramine-T solutions into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil towards a detector. The resulting colored compound is measured at 600 nm using an UV/Vis-spectrophotometer. All the parameters that affect the reaction were evaluated and the calibration curve is linear over a range of 0.1–6.0 μg l⁻¹ of iodide concentration with detection limit of 0.05 μg l⁻¹. A sample throughput of 80 samples per hour and relative standard deviation of less than 2.0% was achieved. The method is successfully applied for the determination of iodide in three different samples (tablets).     

Analysis of oxyhalide disinfection by-products and other anions of interest in drinking water by ion chromatography.

The US Environmental Protection Agency is developing regulations for various drinking water disinfection by-products (DBPs). This effort involves developing analytical methods for the DBPs formed as a result of different disinfection treatments and collecting occurrence data for these species. Ion chromatography is one method being used to analyze drinking water samples for the following inorganic DBPs: chlorite, chlorate and bromate. These anions, however, are difficult to separate from common interfering anions of chloride, carbonate and nitrate. A method is therefore presented by which tetraborate/boric acid is used to separate these anions. Method detection limits of the order of 10 micrograms/l, using conductivity and UV detection were obtained. Stability studies of chlorite showing the effectiveness of ethylenediamine as a preservative and summary data for an occurrence of nitrite, nitrate and the DBP precursor bromide are presented.     

Analysis of 500-ng/l levels of bromate in drinking water by direct-injection suppressed ion chromatography coupled with a single, pneumatically delivered post-column reagent

In July 1997, the US Environmental Protection Agency (EPA) began sampling and analyzing drinking water matrices from US municipalities serving populations greater than 100 000 for low-level bromate (>0.20 μg/l) in support of the Information Collection Rule (ICR) using the selective anion concentration (SAC) method. In September 1997, EPA published Method 300.1 which lowered the Method 300.0 bromate method detection limit (MDL) from 20.0 to 1.4 μg/l. This paper describes the research conducted at the EPA’s Technical Support Center laboratory investigating a single post-column reagent, o-dianisidine (ODA), which has been successfully coupled to EPA Method 300.1 to extend the MDL for bromate. Initial studies indicate that this method offers a MDL which approaches the EPA’s SAC method with the added benefit of increased specificity, shortened analysis time and reduced sample preparation. The method provides excellent ruggedness and acceptable precision and accuracy with a bromate MDL in reagent water of 0.1 μg/l, and a method reporting limit of 0.50 μg/l.     

柱后衍生离子色谱法同时测定瓶装水中的碘酸根、亚氯酸根和溴酸根

水中的碘酸根、亚氯酸根和溴酸根是重要的消毒副产物,主要通过大体积浓缩后直接电导检测,或通过柱前或柱后化学反应将目标物转化成容易检测的物质后检测。本方法采用大体积进样柱后衍生紫外检测的分析方法,通过条件优化获得了较高的灵敏度和信噪比。利用一套自动分析系统,可以满足饮用水中痕量碘酸根、亚氯酸根、溴酸根的同时监测。碘酸根、亚氯酸根和溴酸根的检出限分别为0.5,0.4,0.1 μg/L。对于不同的加标样品,碘酸根、亚氯酸根和溴酸根的回收率分别为70.8%~98.0%,92.4%~100%和93.2%~104.1%。该方法应用于北京市场上的瓶装饮用水分析,结果显示瓶装纯净水中的碘酸根、亚氯酸根、溴酸根浓度均低于检出限,而瓶装矿泉水中碘酸根、溴酸根的最高含量分别达到9.4 μg/L和78.4 μg/L。     

Speciation of the bio-available iodine and bromine forms in edible seaweed by high performance liquid chromatography hyphenated with inductively coupled plasma-mass spectrometry

A bioavailability study based on an in vitro dialyzability approach has been applied to assess the bio-available fractions of iodine and bromine species from edible seaweed. Iodide, iodate, 3-iodo-tyrosine (MIT), 3,5-diiodo-tyrosine (DIT), bromide and bromate were separated by anion exchange chromatography under a gradient elution mode (175 mM ammonium nitrate plus 15% (v/v) methanol, pH 3.8, as a mobile phase, and flow rates within the 0.5–1.5 mL min⁻¹ range). Inductively coupled plasma-mass spectrometry (ICP-MS) was used as a selective detector for iodine (¹²⁷I) and bromine (⁷⁹Br). Low dialyzability ratios (within the 2.0–18% range) were found for iodine species; whereas, moderate dialyzability percentages (from 9.0 to 40%) were obtained for bromine species. Iodide and bromide were the major species found in the dialyzates from seaweed, although MIT and bromate were also found in the dialyzates from most of the seaweed samples analysed. However, DIT was only found in dialyzates from Wakame, Kombu, and NIES 09 (Sargasso) certified reference material; whereas, iodate was not found in any dialyzate. Iodine dialyzability was found to be dependent on the protein content (negative correlation), and on the carbohydrate and dietary fibre levels (positive correlation). However, bromine dialyzability was only dependent on the protein amount in seaweed (negative correlation).     

Trace analysis of chlorobenzenes in water samples using headspace solvent microextraction and gas chromatography/electron capture detection

In the present work, a rapid method for the extraction and determination of chlorobenzenes (CBs) such as monochlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene and 1,2,4-trichlorobenzene in water samples using the headspace solvent microextraction (HSME) and gas chromatography/electron capture detector (ECD) has been described. A microdrop of the dodecane containing monobromobenzene (internal standard) was used as extracting solvent in this investigation. The analytes were extracted by suspending a 2.5 μl extraction drop directly from the tip of a microsyringe fixed above an extraction vial with a septum in a way that the needle passed through the septum and the needle tip appeared above the surface of the solution. After the extraction was finished, the drop was retracted back into the needle and injected directly into a GC column. Optimization of experimental conditions such as nature of the extracting solvent, microdrop and sample temperatures, stirring rate, microdrop and sample volumes, the ionic strength and extraction time were investigated. The optimized conditions were as follows: dodecane as the extracting solvent, the extraction temperature, 45 °C; the sodium chloride concentration, 2 M; the extraction time, 5.0 min; the stirring rate, 500 rpm; the drop volume, 2.5 μl; the sample volume, 7 ml; the microsyringe needle temperature, 0.0 °C. The limit of detection (LOD) ranged from 0.1 μg/l (for 1,3-dichlorobenzene) to 3.0 μg/l (for 1,4-dichlorobenzene) and linear range of 0.5–3.0 μg/l for 1,2-dichlorobenzene, 1,3-dichlorobenzene and from 5.0 to 20.0 μg/l for monochlorobenzene and from 5.0 to 30 μg/l for 1,4-dichlorobenzene. The relative standard deviations (R.S.D.) for most of CBs at the 5 μg/l level were below 10%. The optimized procedure was successfully applied to the extraction and determination of CBs in different water samples.     

Kinetic study of the iodate—iodide and chlorate—iodide reactions in acidic solutions,and a method for the microdetermination of bromide

The iodate—iodide and chlorate—iodide reactions were studied spectrophotometrically in acidic solutions by stopped-flow techniques. Intermediate products(I⁺)were followed; reaction rate constants and activation energies of the reactions were determined. A method of determining bromide was developed on the basis of its accelerating effect on the iodate—iodide reaction ; microamounts of bromide in the range 16–320 μg (10^-4–2 × 10^-3M) were determined with relative errors and relative standard deviation of about 2%.bl]     

Determination of chlorate at low microgram/l levels by ion-chromatography with postcolumn reaction.

A new method for the determination of low concentrations of chlorate in natural waters is described. Chlorate is analyzed by ion-chromatography followed by an osmate-catalyzed postcolumn reaction of chlorate with iodide and UV-detection of triiodide. The new osmate catalysis allows to carry out the oxidation of iodide by chlorate at pH 3 instead of 6 M HCl for the uncatalyzed reaction. A detection limit of 5 nM (0.4 microgram/l) chlorate is achieved. The method also allows the simultaneous determination of chlorite, bromate, and nitrite at the low microgram/l level.     

A simplified method for the amplification of iodine

The sample solution is treated so that all iodine is present in the elemental state. This iodine is extracted into chloroform and thereby separated with very high selectivity from almost any matrix. Until now, in order to apply amplification via oxidation to iodate and reaction with iodide, a reextraction into a sodium hydroxide solution was necessary. In the new procedure the organic phase is shaken with bromine water. Thereby, the iodate formed moves completely into the water phase while the bromine accumulates in the chloroform. Remaining bromine in the water is destroyed with some formic acid. No buffer is needed, because the acid establishes the correct conditions for this reaction and also that between iodate and iodide. The iodine formed in sixfold amount can now be titrated visually or photometrically with thiosulfate or subjected to a second amplification cycle. The new procedure eliminates the reextraction, and the addition of some reagents especially sodium hydroxide which is the main contributor of extraneous iodine. Thus, the blank is reduced by a factor of 10 or more and is also more constant. Iodine at lower levels (< 1 μg/ml) can be determined and with higher reliability.     

Determination of iodide in seawater using C30 column modified with polyoxyethylene oleyl ether in ion chromatography

An ion chromatographic method for rapid and direct determination of iodide in seawater samples is reported. Separation was achieved using a laboratory-made C30 packed column (100 mm × 0.32 mm i.d.) modified with polyoxyethylene oleyl ether, with an aqueous solution of 300 mM sodium chloride as eluent and using UV detection at 220 nm. Samples containing iodate, nitrate, iodide and thiocyanate were eluted within 8 min, and the relative standard deviations of the retention time, peak area and peak height were all smaller than 4.19% for all of the analyte anions. Effects of eluent composition on retention behavior of inorganic anions have been investigated. Both cation and anion of the eluent affected the retention time of analytes. When inorganic eluents, such as ammonium chloride, ammonium sulfate, lithium chloride, sodium chloride, sodium sulfate, magnesium chloride and magnesium sulfate were used, the retention time of analytes increased with increasing eluent concentration. The limit of detection of iodide was 19 μg l⁻¹ (S/N = 3), while the limit of quantitation was 66 μg l⁻¹ (S/N = 10). The present method was successfully applied to the rapid and direct determination of iodide in seawater samples.     

Flow-injection amplification for the spectrophotometric determination of iodide

A flow manifold is described in which iodide (0.05–15 μg ml^?1) in a 50-μl sample is oxidized by bromine water to iodate, most of the excess of bromine is reduced by formic acid, and the iodate is reacted with more iodide to form triiodide, which is determined spectrophotometrically. Six-fold amplification is achieved. The relative standard deviation is ca. 1%).     

Spectrophotometric determination of bromide (and iodide) in a flow system after oxidation by peroxodisulphate

The peroxodisulphate method for the determination of bromide has been modified. A flow-injection system for the spectrophotometric finish has been developed and the size of the ion-exchange column in the preconcentration step has been scaled down. The sum of bromate and iodate produced in the oxidation is determined by treating the oxidized sample with iodide in hydrochloric acid. The iodate is separately determined by applying the reaction in acetic acid. The working range of the spectrophotometric finish is 1-15muM and the limit of determination (10 sigma) is 0.7muM for iodate and for iodate plus bromate. The enrichment factor in the preconcentration step is 50, yielding a limit of determination of 15nM for bromide in natural waters. Eighteen samples of water from the Baltic, with salinity ranging from 3 to 33%. have been analysed. A Br/Cl ratio of (1.53 +/- 0.02) x 10(-3) was found. A comparative study of the original and the new preconcentration step has been made with three river waters, rich in humic substances. The results agreed within +/- 1. 5%.