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PubMed2005

Simultaneous spectrophotometric determination of iodate and bromate in water samples by the method of mean centering of ratio kinetic profiles.

A new and very simple kinetic-spectrophotometric method was developed for the simultaneous determination of binary mixtures of iodate and bromate in water samples, without prior separation steps. The method is based on the mean centering of ratio kinetic profiles, allows rapid and accurate determination of bromate and iodate. The analytical characteristics of the method such as detection limit, accuracy, precision, relative standard deviation (R.S.D.) and relative standard error (R.S.E.) for the simultaneous determination of binary mixtures of iodate and bromate were calculated. The results show that the method was capable of simultaneous determination of 0.05-1.50 microg mL(-1) each of iodate and bromate. The results allow simultaneous determination with the ratio 30:1-1:30 for iodate-bromate. The proposed method was successfully applied to the simultaneous determination of iodate and bromate in several water samples.

Bromates↗
PubMed2006

Etiology of bromate-induced cancer and possible modes of action-studies in Japan.

Renal cell tumors were significantly increased in male and female rats given potassium bromate at 250 and 500 mg/L in drinking water. In at least one other study renal cell tumors were produced in male rats at 125 mg/L. Among male mice given 750 mg/L of potassium bromate, there were no significant differences in renal cell tumors between treated and control groups after 88 weeks on test. In oxidative DNA damage tests 8-oxodeoxyguanosine (8-oxodG also referred to as 8-OH-dG) was induced in DNA in the male rat kidney in 1 week, and in females after 3 weeks at 500 mg/L, and also in both male and female rats at 250 mg/L, but not at 125 mg/L. DNA adducts are considered to be an initial step in the carcinogenesis process, however, the administered doses are not always sufficient to cause mutations, possibly due to DNA repair. In the two-step rat renal carcinogenesis model using N-ethyl-N-hydroxyethylnitrosamine (EHEN) as initiator, promotion activity by potassium bromate was measured using the BrdU labeling index. The promoting activity of bromate in male rats was much greater and extended to doses as low as 60 mg/L in male rats, whereas in females the response was limited to 250 and 500 mg/L. Therefore, it was concluded that the mechanisms contributing to cancer in the male rat were more complex than in the female rat. The accumulation of alpha2mu-globulin in the kidneys of male rats exposed to potassium bromate probably accounts for the greater labeling index in the male rat relative to the female rat. Accumulation of alpha(2mu)-globulin as a result of treatment with chemicals is unique to the male rat and does contribute to carcinogenic responses. Neither humans nor female rats display this response. Nevertheless, bromate must be considered carcinogenic because of the response of the female rats. The better correlation between 8-oxodG formation and tumor response indicates that dose-response information from the female rat would be much more relevant to human risk assessment. The fact that an elevation of BrdU-LI in the kidney of the female rat is consistent with the possibility that cell proliferation observed in female rats resulted from oxidative stress and/or cytotoxic responses in the kidney. Therefore, oxidative stress is most likely the mechanism of interest for cancer risk in humans.

Administration, Oral↗
PubMed2003

Bromate induces loss of heterozygosity in the thymidine kinase gene of L5178Y/Tk(+/-)-3.7.2C mouse lymphoma cells.

Potassium bromate (KBrO(3)) induces DNA damage and tumors in mice and rats, but is a relatively weak mutagen in microbial assays and the in vitro mammalian Hprt assay. Concern that there may be a human health risk associated with bromate, a disinfectant by-product of ozonation, has accompanied the increasing use of ozonation as an alternative to chlorination for treatment of drinking water. In this study, we have evaluated the mutagenicity of KBrO(3) and sodium bromate (NaBrO(3)) in the Tk gene of mouse lymphoma cells. In contrast to the weak mutagenic activity seen in the previous studies, bromate induced a mutant frequency of over 100 x 10(-6) at 0.6mM with minimal cytotoxicity (70-80% survival) and over 1300 x 10(-6) at 3mM ( approximately 10% survival). The increase in the Tk mutant frequency was primarily due to the induction of small colony of Tk mutants. Loss of heterozygosity (LOH) analysis of 384 mutants from control and 2.7 mM KBrO(3)-treated cells showed that almost all (99%) bromate-induced mutants resulted from LOH, whereas in the control cultures 77% of the Tk mutants were LOH. Our results suggest that bromate is a potent mutagen in the Tk gene of mouse lymphoma cells, and the mechanism of action primarily involves LOH. The ability of the mouse lymphoma assay to detect a wider array of mutational events than the microbial or V79 Hprt assays may account for the potent mutagenic response.

Animals↗
PubMed2004

Simultaneous prediction of Cryptosporidium parvum oocyst inactivation and bromate formation during ozonation of synthetic waters.

A model was developed to simultaneously assess Cryptosporidium parvum oocyst inactivation and bromate formation during ozonation of synthetic solutions in batch and flow-through reactors. The model incorporated 65 elementary chemical reactions involved in the decomposition of ozone and the oxidation of bromine species and their corresponding rate or equilibrium constants reported in the literature. Ozonation experiments were performed with a laboratory-scale batch reactor to evaluate the model with respect to the rate of ozone decomposition and bromate formation. The model was found to provide a good representation of experimental results when the ozone decomposition initiation reaction with hydroxide ion was assumed to produce superoxide radical instead of the alternatively proposed product hydrogen peroxide. The model was further developed to simulate the performance of a flow-through bubble-diffuser reactor with an external recirculation line. Each compartment of the reactor (bubble column and recirculation line) was assumed to behave as a plug flow reactor as supported by tracer test results, and an empirical correlation was used to represent the rate of ozone gas transfer in the bubble column. Model predictions of the performance of the flow-through ozone bubble-diffuser contactor were in good agreement with experimental results obtained for bromate formation and C. parvum oocyst inactivation under all conditions investigated. Additional model simulations revealed that hydrodynamic conditions had a more pronounced effect on C. parvum oocyst inactivation than on bromate formation. In contrast, pH had a strong effect on bromate formation without affecting the inactivation efficiency of C. parvum oocysts for a given level of exposure to ozone. These findings suggested that bromate formation could be minimized while achieving target inactivation levels for C. parvum oocysts by designing ozone reactors with hydrodynamic conditions approaching that of an ideal plug flow reactor and by lowering the pH of the target water.

Animals↗
PubMed2006

Determination of trace levels of bromate in flour and related foods by ion chromatography.

In this paper, a method of determining trace levels of bromate in flour and related foods by ion chromatography with large volume injection has been proposed. The detection of bromate was performed with a suppressed conductivity detector after separation on an IonPac AS19 column with KOH as the gradient eluent. Parameters affecting the extraction efficiency of bromate, such as the flour-to-water ratio, extraction time, and temperature, were studied in detail. The optimized pretreatment process was then selected. By using the large volume injection technique, the solution detection limit was decreased to 0.5 microg/L. The linear range of this method was from 5 to 1000 microg/L, and the linear correlation coefficient was 0.9998. The method has been applied to the detection of bromate in flour and related foods, and different concentration levels of bromate were detected in various samples. The spiked recoveries ranged from 86 to 110%. The relative standard deviation (RSD) of the bromate peak height for the seven successive injections of the flour sample was 6.4%.

Bromates↗
PubMedDate not supplied

Measurement of bromate in bread by liquid chromatography with post-column flow reactor detection.

This method is suitable for the determination of bromate residues in a variety of baked goods. The peer-verified method trial was performed on white bread, multigrain bread, and coffee cake spiked with known levels of potassium bromate. The analytical portion is extracted with deionized water to remove bromate from the bulk of the baked product. The aqueous extract is carried through a series of steps to remove co-extractives that would interfere with the liquid chromatography (LC) in the determinative step or hasten the deterioration of the LC column. The extract is filtered before passing it through a reversed-phase solid-phase extraction (SPE) column and a cation-exchange column in the silver form to remove lipids and chloride, respectively. Ultrafiltration is then used to remove proteins with molecular weights of >30,000 daltons. Finally, a cation-exchange column in the sodium form is used to remove silver ions from the extract. The determinative step uses LC with a reversed-phase column and an ion-pairing agent in the mobile phase. Detection is based on the post-column reaction of bromate with o-dianisidine to form an oxidation product that is quantitated spectrophotometrically at 450 nm. Overall agreement between the submitting and peer laboratories was quite good. For bromate levels of 10-52 ppb, overall mean recoveries were 76.9 and 78.8% for the submitting and peer laboratories, respectively. The standard deviations were higher for the results of the peer laboratory, probably because of the generally higher level of baseline noise present in the chromatograms. The results demonstrate that the method provides adequate accuracy with low-fat as well as high-fat foods. Bromate at levels as low as 5 ppb (ng/g) can be detected with the method.

Bread↗
PubMed2003

Bromate assay in water by inductively coupled plasma mass spectrometry combined with solid-phase extraction cartridges.

Based on selective sorption of bromide, bromoacetic acids (BAA) and bromomethanes on solid-phase extraction (SPE) cartridges, a sensitive and convenient method was developed for the determination of bromate in waters by inductively coupled plasma mass spectrometry (ICP-MS). Dionex OnGuard Ag and reversed-phase (RP) cartridges were tested for retention characteristics for bromide, BAA and bromomethanes. When a sample acidified with nitric acid was passed through an RP cartridge, BAA and bromomethanes were retained, afterwards bromide was absorbed as a precipitate of silver bromide and bromate was unretained when the nearly neutral sample passed a combination of Ag and H cartridges. After SPE pretreatment the recovery of bromate was 96-106%, and bromide remaining in the aqueous phase was found to be less than 0.06 microg L(-1) when the original bromide concentrations were less than 5 mg L(-1). Effectiveness of stacked Ag and H cartridges in removing bromide from chloride-containing samples was also examined. Common cations and other anions did not interfere with bromate determination. The detection limit for bromate is 57 ng L(-1). This method has been applied to analyse waters from various sources, and the recovery of the spiked bromate was in the range of 92-107%.

Journal Article↗
PubMed2004

Potentiometric determination of bromate using an Fe(III)-Fe(II) potential buffer by circulatory flow-injection analysis.

A method for the potentiometric determination of bromate by circulatory flow injection analysis (CFIA) is described. The procedure involves the use of an Fe(III)-Fe(II) potential buffer solution, which is recycled via a reservoir. The analytical method is based on a linear relationship between the concentration of bromate and a very transient potential change in the electrode potential due to the generation of intermediate bromine during the reaction of bromate with the Fe(III)-Fe(II) potential buffer solution, which also contains NaBr, (NH4)6Mo7O24 and H2SO4. An aliquot (5 microl) of a bromate sample solution was injected into the stream of the potential buffer solution, 100 ml of which was circulated at a flow rate of 1 ml/min; the potential buffer solution stream was then returned to the reservoir after passing through a flow-through redox electrode detector. A potential change due to the reaction of the injected sample with the potential buffer in a reaction coil was measured with the detector in the form of a peak signal. The effects of the bromide, sulfuric acid and Fe(III)-Fe(II) concentrations in the potential buffer, and length of the reaction coil on the peak heights were examined in order to optimize the proposed CFIA method. The analytical sensitivities to bromate were 5.6 mV/microM for 1 x 10(-2) M and 30.9 mV/microM for 1 x 10(-3) M in the concentration of Fe(III)-Fe(II) in a potential buffer solution containing 0.35 M NaBr, 0.2% (NH4)6Mo7O24 and 1 M H2SO4. The detection limit of bromate obtained by a 1 x 10(-3) M Fe(III)-Fe(II) potential buffer solution was 0.02 microM (2.5 ppb). The numbers of repetitive determinations in which the relative sensitivities within 5% were regarded as being tolerated were ca. 4000 and 2000 for the use of only 100 ml of 1 x 10(-2) M and 1 x 10(-3) M Fe(III)-Fe(II) potential buffer solution, respectively.

Journal Article↗
PubMed2002

Determination of bromate in drinking water by zone electrophoresis-isotachophoresis on a column-coupling chip with conductivity detection.

The use of capillary zone electrophoresis (CZE) on-line coupled with isotachophoresis (ITP) sample pretreatment (ITP-CZE) on a poly(methylmethacrylate) chip, provided with two separation channels in the column-coupling (CC) arrangement and on-column conductivity detection sensors, to the determination of bromate in drinking water was investigated. Hydrodynamic and electroosmotic flows of the solution in the separation compartment of the chip were suppressed and electrophoresis was a dominant transport process in the ITP-CZE separations. A high sample load capacity, linked with the use of ITP in this combination, made possible loading of the samples by a 9.2 microL sample injection channel of the chip. In addition, bromate was concentrated by a factor of 10(3) or more in the ITP stage of the separation and, therefore, its transfer to the CZE stage characterized negligible injection dispersion. This, along with a favorable electric conductivity of the carrier electrolyte solution, contributed to a 20 nmol/L (2.5 ppb) limit of detection for bromate in the CZE stage. Sample cleanup, integrated into the ITP stage, effectively complemented such a detection sensitivity and bromate could be quantified in drinking water matrices when its concentration was 80 nmol/L (10 ppb) or slightly less while the concentrations of anionic macroconstituent (chloride, sulfate, nitrate) in the loaded sample corresponding to a 2 mmol/L (70 ppm) concentration of chloride were still tolerable. The samples containing macroconstituents at higher concentrations required appropriate dilutions and, consequently, bromate in these samples could be directly determined only at proportionally higher concentrations.

Bromates↗
PubMed1989

Effects of sodium bromate on ionic concentrations and osmolalities of the cochlear fluids in guinea pigs.

Effects of sodium bromate on cochlear potentials and electrolyte composition of the cochlear fluids in guinea pigs were investigated following administration of sodium bromate into the cochlea, using perilymphatic perfusion. Cochlear microphonics and the whole nerve action potential of the auditory nerve were markedly suppressed. The K+ and Cl- activities in the endolymph as well as the endocochlear dc potential (EP) decreased significantly and irreversibly, in proportion to the concentration of sodium bromate. A negative EP never developed during the monitoring of 120 min. Microsamples of the endolymph showed substantial decreases of K+ and Cl- concentrations and an increase in the concentration of Na+. Osmolality of the endolymph was much lower than that of the perilymph. The severe edema of the stria vascularis and collapse of Reissner's membrane were histologically evident. These events suggest a breakdown of the endolymph-perilymph barrier, coincident with an inhibition of the strial active transport, as a result of the ototoxic action of sodium bromate. The possible ion and water movement across the endolymph-perilymph barrier in the presence of sodium bromate is discussed.

Acoustic Stimulation↗
PubMed2006

The multiple influences of glutathione on bromate genotoxicity: implications for the dose-response relationship.

Glutathione displays multiple roles in the oxidative genotoxicity of potassium bromate. On the one hand, reduced glutathione has a demonstrated role in the activation of bromate to species capable of oxidising DNA. However, if this activation should occur within the gut or extracellularly once bromate is absorbed, this may limit the ability of the chemical to oxidise cellular DNA in vivo. Moreover, glutathione may offer protection against the damaging species produced by its interaction with bromate. Finally, if bromate exposure of cells is sufficiently high to deplete glutathione, a secondary oxidative stress and associated DNA damage may occur. These observations would suggest non-linearity in the dose-response to DNA damage in vivo.

Animals↗
PubMed2004

Effect of medium-pressure UV irradiation on bromate concentrations in drinking water, a pilot-scale study.

This study investigated the potential for bromate removal from drinking water on irradiation with medium-pressure UV lamps-a technique gaining considerable interest for drinking water disinfection. Waters from two different sources were spiked with 20microg/L of bromate and irradiated with UV fluences up to 718mJ/cm(2) utilizing a pilot-scale reactor (Calgon Carbon Corp.) at a flow of 76L/min (20 gallon/min). Essentially no removal was observed in one of the source waters. Limited bromate removal, up to 19%, was observed in the second source water at high UV fluences (696mJ/cm(2)) and a fluence-response relationship was clearly evident. All removals would be negligible at UV fluences anticipated for drinking water disinfection (< or =40mJ/cm(2)). Different water characteristics, in particular competitive absorption by nitrate and possibly DOC, were most likely responsible for the differences in bromate removal in the waters tested. The source water that did not show any removal had a higher nitrate concentration (4 vs. 0.1mg N/L) and also a higher DOC concentration (4.1 vs. 3.1mg C/L) than the other source water which showed 19% bromate removal.

Adsorption↗
PubMed2004

Modeling of bromate formation by ozonation of surface waters in drinking water treatment.

The main objective of this paper is to try to develop statistically and chemically rational models for bromate formation by ozonation of clarified surface waters. The results presented here show that bromate formation by ozonation of natural waters in drinking water treatment is directly proportional to the "Ct" value ("Ctau" in this study). Moreover, this proportionality strongly depends on many parameters: increasing of pH, temperature and bromide level leading to an increase of bromate formation; ammonia and dissolved organic carbon concentrations causing a reverse effect. Taking into account limitation of theoretical modeling, we proposed to predict bromate formation by stochastic simulations (multi-linear regression and artificial neural networks methods) from 40 experiments (BrO(3)(-) vs. "Ctau") carried out with three sand filtered waters sampled on three different waterworks. With seven selected variables we used a simple architecture of neural networks, optimized by "neural connection" of SPSS Inc./Recognition Inc. The bromate modeling by artificial neural networks gives better result than multi-linear regression. The artificial neural networks model allowed us classifying variables by decreasing order of influence (for the studied cases in our variables scale): "Ctau", [N-NH(4)(+)], [Br(-)], pH, temperature, DOC, alkalinity.

Ammonia↗
PubMed2006

Modeling Cryptosporidium parvum oocyst inactivation and bromate in a flow-through ozone contactor treating natural water.

A reactive transport model was developed to simultaneously predict Cryptosporidium parvum oocyst inactivation and bromate formation during ozonation of natural water. A mechanistic model previously established to predict bromate formation in organic-free synthetic waters was coupled with an empirical ozone decay model and a one-dimensional axial dispersion reactor (ADR) model to represent the performance of a lab-scale flow-through ozone bubble-diffuser contactor. Dissolved ozone concentration, bromate concentration (in flow-through experiments only), hydroxyl radical exposure and C. parvum oocyst survival were measured in batch and flow-through experiments performed with filtered Ohio River water. The model successfully represented ozone concentration and C. parvum oocyst survival ratio in the flow-through reactor using parameters independently determined from batch and semi-batch experiments. Discrepancies between model prediction and experimental data for hydroxyl radical concentration and bromate formation were attributed to unaccounted for reactions, particularly those involving natural organic matter, hydrogen peroxide and carbonate radicals. Model simulations including some of these reactions resulted in closer agreement between predictions and experimental observations for bromate formation.

Animals↗
PubMed2000

Comparison of on-line coupling of ion-chromatography with atmospheric pressure ionization mass spectrometry and with inductively coupled plasma mass spectrometry as tools for the ultra-trace analysis of bromate in surface water samples.

Ion chromatography in combination with atmospheric pressure ionization mass spectrometry (API-MS) as well as with inductively coupled plasma mass spectrometry (ICP-MS) had been compared for trace analysis of bromate. The results indicate that both techniques yield comparable results, which are in excellent agreement with standard methods for bromate determination. Furthermore, both techniques showed almost equal absolute detection limits (approximately 50 pg bromate injected). Contrary to IC-API-MS, IC-ICP-MS can tolerate a higher salt concentration in the mobile phase. This allows the use of high-capacity columns combined with large sample volumes. This lowered the concentration based detection limits by one order of magnitude for IC-ICP-MS compared to IC-API-MS (0.06 microg/l vs. 0.5 microg/l). On the other hand, IC-API-MS is able to allow a positive identification of bromate even in cases when IC does not fully separate bromate from other bromine-containing species. The performance data of both IC-MS techniques have been established by participation in an international round robin test.

Atmospheric Pressure↗
PubMed2000

Eliminating the chlorite interference in US Environmental Protection Agency Method 317.0 permits analysis of trace bromate levels in all drinking water matrices.

A post-column reagent (PCR) method for bromate analysis in drinking water with a method detection limit (MDL) and method reporting limit (MRL) of 0.1 and 0.5 microg/l, respectively, has been developed by the United States Environmental Protection Agency (EPA) for future publication as EPA Method 317.0. The PCR method provides comparable results to the EPA's Selective Anion Concentration (SAC) method used to support the laboratory analysis of Information Collection Rule (ICR) low-level bromate samples and offers a simple, rugged, direct injection method with potential to be utilized as a compliance monitoring technique for all inorganic Disinfectants/Disinfection By-Products (D/DBPs). It has superior sensitivity for bromate compared to EPA Method 300.1, which was promulgated as the compliance monitoring method for bromate under Stage 1 of the D/DBP rule. This paper addresses elimination of the chlorite interference that was previously reported in finished waters from public water systems (PWSs) that employ chlorine dioxide as the disinfectant. An evaluation of Method 317.0 for the analysis of bromate in commercial bottled waters is also reported.

Bromates↗
PubMed1999

Matrix effects in the determination of bromate in drinking water by ion chromatography.

Bromate is a well known by-product produced by the ozonation of drinking water; the allowed concentration for human consumption has to be regulated to low microgram l-1 range. By using a high-capacity anion-exchange column, it should be possible to determine bromate at this low concentration by direct injection of a very large volume (up to 1 ml) without any sample preconcentration and pretreatment. The feasibility of this technique for the determination of bromate in drinking water has been explored in our work. The experimental results showed that matrix effect, due to inorganic ions contained in drinking water, strongly influenced the chromatographic behaviour of the bromate peak. The increase of the total ion content led to a correlated decrease in the efficiency of the analyte peak so that effective detection limits depended on the matrix composition. In this work chromatographic parameters (efficiency, asymmetry and resolution) of bromate peak are discussed in relation to the concentration of the main inorganic anions, and the injection volume (from 250 microliters to 1 ml).

Bromates↗
PubMed2001

Inactivation of Bacillus subtilis spores and formation of bromate during ozonation.

Inactivation of B. subtilis spores with ozone was investigated to assess the effect of pH and temperature, to compare the kinetics to those for the inactivation of C. parvum oocysts, to investigate bromate formation under 2-log inactivation conditions, and to assess the need for bromate control strategies. The rate of B. subtilis inactivation with ozone was independent of pH, decreased with temperature (activation energy of 42,100 Jmol(-1)), and was consistent with the CT concept. B. subtilis was found to be a good indicator for C. parvum at 20-30 degrees C, but at lower temperatures B. subtilis was inactivated more readily than C. parvum. Bromate formation increased as both pH and temperature increased. For water with an initial bromide concentration of 33 microgl(-1), achieving 2-logs of inactivation, without exceeding the 100 microg l(-1) bromate standard, was most difficult at 30 degrees C for B. subtilis and at midrange temperatures (10-20 degrees C) for C. partum. pH depression and ammonia addition were found to reduce bromate formation without affecting B. subtilis inactivation, and may be necessary for waters containing more than 50 microgl(-1) bromide.

Algorithms↗