Chlorate Concentrations Research Articles

Occurrence of Chlorate and Perchlorate in Bottled Beverages in Japan

The concentrations of chlorate and perchlorate were examined by ion chromatography-tandem mass spectrometry (IC-MS-MS) in 106 bottled beverages purchased or obtained mainly in the Tokyo area to estimate exposure to these chemicals attributable to bottled beverages. The bottled beverages were classified into 5 categories: water from the water supply (n =5 ), natural water (n = 49), bottled water (n = 10), tea (n = 25), and soft drinks (n = 17) .C hlorate was detected in 85 bottled beverages (highest concentration, 700 µg/l), including all of the samples of bottled water from the water supply at levels ranging from 25 to 120µg/l. Perchlorate was detected above the minimum reporting limit (i.e. ,0 .05µg/l) from 62 bottled beverages, with the highest concentration of 0.92µg/l. As the average consumption of bottled beverages calculated from market statistics is approximately 400 ml/day per person, it seems important to take the amounts of chlorate and perchlorate ingested from bottled beverages into consideration for estimation of total intake of these chemicals.

Effects of electrolyte parameters on the iron/steel cathode potential in the chlorate process

This study focuses on how different electrolyte parameters of the chlorate process affect the cathode potential for hydrogen evolution on iron in a wide current-density range. The varied parameters were pH, temperature, mass transport conditions and the ionic concentrations of chloride, chlorate, chromate and hypochlorite. At lower current densities, where cathodic protection of the electrode material is important, the pH buffering capacity of the electrolyte influenced the potential to a large extent. It could be concluded that none of the electrolyte parameters had any major effects (<50 mV) on the chlorate-cathode potential at industrially relevant current densities (around 3 kA m−2). Certainly, there is more voltage to gain from changing the cathode material than from modifying the electrolyte composition. This is exemplified by experiments on steel corroded from operation in a chlorate plant, which exhibits significantly higher activity for hydrogen evolution than polished steel or iron.

Fate of Chlorate Present in Cattle Wastes and Its Impact on Salmonella Typhimurium and Escherichia coli O157:H7

Chlorate salts are being developed as a feed additive to reduce the numbers of pathogens in feedlot cattle. A series of studies was conducted to determine whether chlorate, at concentrations expected to be excreted in urine of dosed cattle, would also reduce the populations of pathogens in cattle wastes (a mixture of urine and feces) and to determine the fate of chlorate in cattle wastes. Chlorate salts present in a urine-manure-soil mixture at 0, 17, 33, and 67 ppm had no significant effect on the rates of Escherichia coli O157:H7 or Salmonella Typhimurium inactivation from batch cultures. Chlorate was rapidly degraded when incubated at 20 and 30 degrees C with half-lives of 0.1 to 4 days. Chlorate degradation in batch cultures was slowest at 5 degrees C with half-lives of 2.9 to 30 days. The half-life of 100 ppm chlorate in an artificial lagoon system charged with slurry from a feedlot lagoon was 88 h. From an environmental standpoint, chlorate use in feedlot cattle would likely have minimal impacts because any chlorate that escaped degradation on the feedlot floor would be degraded in lagoon systems. Collectively, these results suggest that chlorate administered to cattle and excreted in wastes would have no significant secondary effects on pathogens present in mixed wastes on pen floors. Lack of chlorate efficacy was likely due to low chlorate concentrations in mixed wastes relative to chlorate levels shown to be active in live animals, and the rapid degradation of chlorate to chloride at temperatures of 20 degrees C and above.

HPLC determination of chlorate metabolism in bovine ruminal fluid§

Salmonella and Escherichia coli are two bacteria that are important causes of human and animal disease worldwide. Chlorate is converted in the cell to chlorite, which is lethal to these bacteria. An HPLC procedure was developed for the rapid analysis of chlorate (ClO3 −), nitrate (NO3 −), and nitrite (NO2 −) ions in bovine ruminal fluid samples. Standard curves for chlorite, nitrite, nitrate, and chlorate were well defined linear curves with R2 values of 0.99846, 0.99106, 0.99854, and 0.99138, respectively. Concentrations of chlorite could not be accurately determined in bovine ruminal fluid because chlorite reacts with or binds a component(s) or is reduced to chloride in bovine ruminal fluid resulting in low chlorite measurements. A standard curve ranging from 25 to 150 ppm ClO3 − ion was used to measure chlorate fortified into ruminal fluid. The concentration of chlorate was more rapidly lowered (P < 0.01) under anaerobic compared to aerobic incubation conditions. Chlorate alone or chlorate supplemented with the reductants sodium lactate or glycerol were bactericidal in anaerobic incubations. In anaerobic culture, the addition of sodium formate to chlorate-fortified ruminal fluid appeared to decrease chlorate concentrations; however, formate also appeared to moderate the bactericidal effect of chlorate against E. coli. Addition of the reductants, glycerol or lactate, to chlorate-fortified ruminal fluid did not increase the killing of E. coli at 24 h, but may be useful when the reducing equivalents are limiting as in waste holding reservoirs or composting systems required for intense animal production. §Mention of trade names, proprietary products, or specific equipment is solely for the purpose of providing specific information and does not constitute a guarantee, warranty or endorsement by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.

Total Radioactive Residues and Residues of [36Cl]Chlorate in Market Size Broilers

The oral administration of chlorate salts reduces the numbers of Gram-negative pathogens in gastrointestinal tracts of live food animals. Although the efficacy of chlorate salts has been demonstrated repeatedly, the technology cannot be introduced into commercial settings without first demonstrating that chlorate residues, and metabolites of chlorate remaining in edible tissues, represent a negligible risk to consumers. Typically, a first step in this risk assessment is to quantify the parent compound and to identify metabolites remaining in edible tissues of animals treated with the experimental compound. The objectives of this study were to determine the pathway(s) of chlorate metabolism in market broilers and to determine the magnitude of chlorate residues remaining in edible tissues. To this end, 12 broilers (6 weeks; 2.70+/-0.34 kg) were randomly assigned to three treatments of 7.4, 15.0, and 22.5 mM sodium [36Cl]chlorate dissolved in drinking water (n=4 broilers per treatment). Exposure to chlorate, dissolved in drinking water, occurred at 0 and 24 h (250 mL per exposure), feed was withdrawn at hour 38, water was removed at hour 48, and birds were slaughtered at hour 54 (16 h after feed removal and 8 h after water removal). The radioactivity was rapidly eliminated in excreta with 69-78% of the total administered radioactivity being excreted by slaughter. Total radioactive residues were proportional to dose in all edible tissues with chloride ion comprising greater than 98.5% of the radioactive residue for the tissue (9.4-97.8 ppm chlorate equivalents). Chlorate residues were typically greatest in the skin (0.33-0.82 ppm), gizzard (0.1-0.137 ppm), and dark muscle (0.05-0.14 ppm). Adipose, liver, and white muscle tissue contained chlorate concentrations from 0.03 to 0.13 ppm. In contrast, chlorate concentrations in excreta eliminated during the 6 h period prior to slaughter ranged from 53 to 71 ppm. Collectively, these data indicate that broilers rapidly convert chlorate residues to an innocuous metabolite, chloride ion, and that chlorate residues in excreta remain fairly high during the time around slaughter. Because the target tissue of chlorate is the lower gastrointestinal tract, the relatively high distribution of parent chlorate to inedible gastrointestinal tissues and low distribution to edible tissues is favorable for the biological activity and for food safety considerations. These data, when used in conjunction with a toxicological assessment of chlorate, can be used to determine a likely risk/benefit ratio for chlorate.

Exposure assessment of a burning ground for chemical ammunition on the Great War battlefields of Verdun

The destruction of arsenical shells from the 1914/18 war in the vicinity of Verdun (France) during the 1920s resulted in a locally limited but severe soil contamination by arsenic and heavy metals. At the study site, the main part of the contaminant inventory occurs in the upper 20 cm of the topsoil which is essentially composed of combustion residues. Besides, some Cu (cmax.=16,877 mg/kg) and Pb (cmax.=26,398 mg/kg) in this layer, As (cmax.=175,907 mg/kg) and Zn (cmax.=133,237 mg/kg) were detected in very high concentrations. The mobilities of Cu, Mn, Pb and Zn in the soil system were derived from ammonium nitrate eluates. They are strongly influenced by the soil pH and can be described by quadratic regression curves from which threshold pH values were calculated. Below these values more than 10% of the element content was available as mobile species. Within the examined pH range, this method could not be adopted for arsenic, because the mobility of As was only slightly controlled by the soil pH. In the heavily contaminated topsoil, Cu and Pb were fixed by the moderately acidic soil pH which varied from 4.8 to 5.8. No migration to the underlying horizons occurred. A different behavior was observed for As and Zn. The calculated threshold pH of Zn was 5.5, so certain amount of this element was transferred to the subsoil and the leachate (cmax.=350 microg/l). However, a major dispersion of Zn was prevented by a rise of the soil pH in the carbonate-containing subsoil. Elevated concentrations of As were found in all soil horizons up to a depth of 2 m and also in the leachate (cmax.=2377 microg/l). Contrary to Cu, Pb and Zn the mobility of As evidently was less affected by the subsoil. Regarding organic contaminants, nitroaromatic explosives were detected only in minor concentrations in the soil (cmax.=14.7 mg/kg) and the leachate (cmax.=13.5 microg/l). No aromatic organoarsenicals were detected in the soil and the leachate samples. The main hazard of the site is the severe arsenic contamination and the transfer of this carcinogen by leachate, surface runoff and probably by wind. Nevertheless, some studies on the effects of the contaminant inventory on the local vegetation revealed that ammonium nitrate elutable zinc is responsible for the spatial distribution of some tolerant plant species and not arsenic. Previously undetected buried munitions from the former delaboration facility can be an other source of environmental contaminants. This is supported by elevated concentrations of chlorate (cmax.=71 mg/l) and perchlorate (cmax.=0.8 mg/l) detected in the leachate samples. This is the second report about environmental contamination related to post-war ammunition destruction activities along the 1914/18 Western Front.

Pharmacokinetics of ruminally dosed sodium [36Cl]chlorate in beef cattle

The recently recognized potential of sodium chlorate as a possible preharvest food safety tool for pathogen reduction in meat animals has spurred interest in the pharmacokinetics of intraruminally dosed chlorate. Six Loala cattle were assigned (one heifer and one steer per treatment) to one of three intraruminal doses of radiolabeled sodium [36Cl]chlorate (21, 42, or 63 mg/kg body weight) administered in four equal aliquots over a 24-h period. Blood and serum were collected (29 samples in 48 h). Total radioactive residues were measured and the radioactive moieties were speciated. Chlorate appeared rapidly in blood and serum after dosing. For animals administered a dose of 42 or 63 mg/kg, the half-life of absorption was estimated at 0.6-0.9 h. Serum chlorate concentrations progressively increased with aliquot administration until peaking at 6-21 parts per million at 26 h. Between aliquot administrations, serum chlorate levels typically peaked in 3.5 h or less. The half-life of chlorate elimination ranged between 6.9 and 11 h, depending on the dose. Ultimately, absorption of chlorate removes it from its desired site of action, the lower gastrointestinal tract, thereby reducing its efficacy. Further research is needed to develop a chlorate formulation that will allow passage to the lower gastrointestinal tract.

The in vitro reduction of sodium [36Cl]chlorate in bovine ruminal fluid1,2

Sodium chlorate effectively reduces or eliminates gram-negative pathogenic bacteria in the gastrointestinal tracts of live cattle. Limitations to the in vivo efficacy of chlorate are its rapid absorption from the gastrointestinal tract and its presumed reduction to chloride within the gastrointestinal tract. We hypothesized that chlorate would be reduced via ruminal bacteria in a ruminal in vitro system and that the reduction of chlorate would be influenced by the dietary for-age:concentrate ratio; thus, 4 ruminally cannulated steers were fed 20 or 80% concentrate diets in a crossover design. Ruminal fluid was collected in 2 periods and dispensed into in vitro tubes containing sodium [36Cl]chlorate, which was sufficient for 100 or 300 mg/L final chlorate concentrations. The tubes were incubated for 0, 1, 4, 8, 16, or 24 h; autoclaved, control ruminal fluid, fortified with sodium [36Cl]chlorate, was incubated for 24 h. Chlorate remaining in each sample was measured by liquid scintillation counting after [36Cl]chloride was precipitated with silver nitrate. A preliminary study indicated that chlorite, a possible intermediate in the reduction of chlorate, had a half-life of approximately 4.5 min in freshly collected (live) ruminal fluid; chlorite was, therefore, not specifically measured in ruminal incubations. The chlorate dose did not affect in vitro DM digestion (P > or = 0.11), whereas in vitro DM digestibility was decreased (P < or = 0.05) by 80% forage content. By 24 h, 57.5 +/- 2.6% of the chlorate remained in 100-mg/L incubations, whereas 78.2 +/- 2.6% of the chlorate remained in the 300-mg/L incubations. When the data were expressed on a concentration basis (mg/L), diet had no effect (P > or = 0.18) on chlorate reduction; however, when chlorate reduction was expressed on a percentage basis, chlorate reduction tended to be greater (P > or = 0.09) at 8 and 16 h in the incubations containing the low-concentrate diet. Chlorate remaining in autoclaved controls at 24 h was intermediate (P < 0.01) between chlorate remaining in live ruminal fluid samples incubated for 0 or 24 h. Attempts to isolate chlorate-respiring bacteria from 2 sources of ruminal fluid were not successful. These data indicate that microbial-dependent or chemical-dependent, or both, reduction of chlorate occurs in bovine ruminal fluid and that dietary concentrate had a negligible effect on chlorate reduction.

Effect of Sodium [36Cl]Chlorate Dose on Total Radioactive Residues and Residues of Parent Chlorate in Growing Swine

An experimental chlorate-based product has been shown to be efficacious in eliminating economically important, Gram-negative human pathogens in the gastrointestinal tracts of food animals. Prior to the commercial marketing of such a product, the magnitude and chemical nature of residues remaining in edible tissues must be determined. Thus, the objective of this study was to determine the tissue distribution and elimination of sodium [36Cl]chlorate in orally dosed swine. Three sets of pigs, each consisting of a barrow and a gilt, were orally dosed with a total of 20, 40, or 60 mg of sodium [36Cl]chlorate per kg body weight via the drinking water. Urine and feces were collected throughout the 30 h study. Twenty-four hours after the last exposure to [36Cl]chlorate, each pig was harvested and both edible and inedible tissues were collected. Urine and tissue samples were analyzed for total radioactive residues and for chlorate metabolites. Elimination of radioactivity in urine averaged 81.6, 83.7, and 83.9% of the total dose for the low, medium, and high doses, respectively. Fecal elimination of radioactivity averaged 1.1% of the dosed radiochlorine across all doses. Parent chlorate always represented greater than 97.4% of the urinary radiochlorine with the remaining radiochlorine being excreted as chloride ion. Chlorate represented 39-77% of fecal radioactivity, depending upon dose. Chlorate concentrations in edible tissues ranged from 0.01 to 0.49 ppm, with residues in liver and skeletal muscle generally lower than those in kidney and adipose tissue. Chlorate residues were concentrated in thyroid tissues (7.7-25.4 ppm) relative to edible tissues. No evidence for the presence of chlorite was observed in excreta or in tissues. Results of this study suggest that further development of chlorate as a preharvest food safety tool in swine merits consideration.

Benzene Degradation Coupled with Chlorate Reduction in a Soil Column Study

Perchlorate and chlorate are electron acceptors that during reduction result in the formation of molecular oxygen. The produced oxygen can be used for activation of anaerobic persistent pollutants, like benzene. In this study chlorate was tested as potential electron acceptor to stimulate benzene degradation in anoxic polluted soil column. A chlorate amended benzene polluted soil column was operated over a period of 500 days. Benzene was immediately degraded in the column after start up, and benzene removal recovered completely after omission of chlorate or a too high influent chlorate concentration (22 mM). Mass balance calculations showed that per mole of benzene five mole of chlorate were reduced. At the end of the experiment higher loading rates were applied to measure the maximal benzene degradation rate in this system; a breakthrough of benzene was not observed. The average benzene degradation rate over this period was 31 micromol l(-1) h(-1) with a maximal of 78 micromol l(-1) h(-1). The high degradation rate and the necessity of chlorate indicate that oxygen produced during chlorate reduction indeed is used for the activation of benzene. This is the first column study where benzene biodegradation at a high rate coupled with anaerobic chlorate reduction is observed.

Differences in the apical and basolateral pathways for glycosaminoglycan biosynthesis in Madin–Darby canine kidney cells

Serglycin with a green fluorescent protein tag (SG-GFP) expressed in epithelial Madin-Darby canine kidney cells is secreted mainly (85%) into the apical medium, but the glycosaminoglycan (GAG) chains on the SG-GFP protein core secreted basolaterally (15%) carry most of the sulfate added during biosynthesis (Tveit et al. (2005) J. Biol. Chem., 280, 29596-29603). Here we report further differences in apical and basolateral GAG synthesis. The less intensely sulfated chondroitin sulfate (CS) chains on apically secreted SG-GFP are longer than CS chains attached to basolateral SG-GFP, whereas the heparan sulfate (HS) chains are of similar lengths. When the supply of 3'-phosphoadenosine-5'-phosphosulfate (PAPS) is limited by chlorate treatment, the synthesis machinery maintains sulfation of HS chains on basolateral SG-GFP until it is inhibited at 50 mM chlorate, whereas basolateral CS chains lose sulfate already at 12.5 mM chlorate and become longer. Apically, incorporation of 35S-sulfate into CS is reduced to a lesser extent at higher chlorate concentrations than basolateral CS, although apical CS is less intensely sulfated than basolateral CS in control cells. Similar to what was found for basolateral HS, sulfation of apical HS was not reduced at chlorate concentrations below 50 mM. Also, protein-free, xyloside-based GAG chains secreted basolaterally are more intensely sulfated than their apical counterpart, supporting the view that separate apical and basolateral pathways exist for GAG synthesis and sulfation. Introduction of benzyl beta-d-xyloside (BX) to the GAG synthesis machinery reduces the apical secretion of SG-GFP dramatically and also the modification of SG-GFP by HS.

TOXIC EFFECTS OF POTASSIUM CHLORATE ON PEANUT GROWTH

Chlorates are a group of oxidizers with strong toxic effects that can cause significant damage to plants. However, chlorates have been used as a non-selective herbicide, defoliant and desiccant. It was found that potassium chlorate can induce flowering in longan (Dimocarpus longan). It has been widely used in longan orchards in recent years, especially in north Thailand and south China, but research has shown that potassium chlorate is toxic to organisms. It can also contaminate soil and water. The aim of this study was to determine the effects of potassium chlorate stress on the growth and physiological response of peanut (Arachis hypogaea).The main method used to induce flower initiation in longan for off-season production is the application of potassium chlorate under the tree canopy. Most research efforts have been devoted to determining the optimum time and amount of application. Little is known about the phytotoxic effects of potassium chlorate on peanut plants, which usually is planted within longan orchards. In this paper, the effects of potassium chlorate on the growth of peanut plants were studied. Using the soil culture method, six potassium chlorate treatments were used to assess its effects on seed germination, chlorophyll content, levels of electrolytic leakage (EL), membrane permeability (MP), and activities of nitrate reductase (NR) and catalase (CAT) in peanut seedling leaves, as well as the biomass and number of Rhizobium, and the transpiration and photosynthetic rates in mature peanut plants. The results showed that: when the concentration of potassium chlorate was higher than 50 mg·L -1 , the germination rates of peanut seeds and root lengths were greatly reduced, while the amount of electrolytic leakage and the activity of CAT were increased significantly. When the concentration of potassium chlorate was higher than 50 mg·kg -1 in soil, its phytotoxic effects resulted in a significant increase in MP in seedling leaves, and a decrease in NR, chlorophyll, biomass and the number of Rhizobium, and a reduction in transpiration and photosynthesis. It can be concluded that soil concentrations of potassium chlorate higher than 50 mg·kg -1 would have a significantly negative effect on the growth of peanut plants.

Effect of Sodium [36Cl]Chlorate Dose on Total Radioactive Residues and Residues of Parent Chlorate in Beef Cattle

The objectives of this study were to determine total radioactive residues and chlorate residues in edible tissues of cattle administered at three levels of sodium [36Cl]chlorate over a 24-h period and slaughtered after a 24-h withdrawal period. Three sets of cattle, each consisting of a heifer and a steer, were intraruminally dosed with a total of 21, 42, or 63 mg of sodium [36Cl]chlorate/kg of body weight. To simulate a 24-h exposure, equal aliquots of the respective doses were administered to each animal at 0, 8, 16, and 24 h. Urine and feces were collected in 12-h increments for the duration of the 48-h study. At 24 h after the last chlorate exposure, cattle were slaughtered and edible tissues were collected. Urine and tissue samples were analyzed for total radioactive residues and for metabolites. Elimination of radioactivity in urine and feces equaled 20, 33, and 48% of the total dose for the low, medium, and high doses, respectively. Chlorate and chloride were the only radioactive chlorine species present in urine; the fraction of chlorate present as a percentage of the total urine radioactivity decreased with time regardless of the dose. Chloride was the major radioactive residue present in edible tissues, comprising over 98% of the tissue radioactivity for all animals. Chlorate concentrations in edible tissues ranged from nondetectable to an average of 0.41 ppm in skeletal muscle of the high-dosed animals. No evidence for the presence of chlorite was observed in any tissue. Results of this study suggest that further development of chlorate as a preharvest food safety tool merits consideration.

Phase transition in K(NO3)1−x(ClO3)x bulk samples and thick films

The phase transition in K(NO3)1−x(ClO3)x bulk samples and thick films has been investigated from the dielectric polarisation and temperature dependence of the electrical resistivity. The bulk samples were found to be ferroelectric even at room temperature with an average spontaneous polarisation of 6.72μCcm−2. The spontaneous polarisation increased slightly with increasing chlorate concentration up to x=0.08. The transition temperature of KNO3 bulk samples was found to be 146°C. The transition temperature of the thick films was found to shift to higher values with increasing chlorate ion concentration. The substitution of the nitrate ions with increasing chlorate ions could lead to the formation of Schottky barriers at the grain boundaries with a resultant space charge, which could set up space charge fields. The space charge could lead to polarisation, and consequently, a shift in the transition temperature towards higher values.

Chlorination by-products (CBPs) in drinking water and adverse pregnancy outcomes in Italy

Chlorination by-products (CBPs) in drinking water have been associated with an increased risk of adverse pregnancy outcomes, including small for gestational age at term (term-SGA) and preterm delivery. Epidemiological evidence is weakened by a generally inaccurate exposure assessment, often at an ecological level. A case control study with incident cases was performed in nine Italian towns between October 1999 and September 2000. A total of 1,194 subjects were enrolled: 343 preterm births (26th-37th not completed week of pregnancy), 239 term-SGA (from 37th completed week, and weight less than the lowest 10th percentile) and 612 controls. Exposure was assessed both by applying a questionnaire on mothers' personal habits during pregnancy and by water sampling directly at mothers' homes. Levels of trihalomethanes (THMs) were low (median: 1.10 microg l(-1)), while chlorite and chlorate concentrations were relatively high (median: 216.5 microg l(-1) for chlorites and 76.5 microg l(-1) for chlorates). Preterm birth showed no association with CBPs, while term-SGA, when chlorite levels > or =200 microg l(-1) combined with low and high levels of inhalation exposure are considered, suggested a dose-response relationship (adjusted-Odds Ratios (ORs): 1.52, 95%CI: 0.91-2.54 and 1.70, 95%CI: 0.97-3.0, respectively). A weak association with high exposure levels of either THMs (> or =30 microg l(-1)), or chlorite or chlorate (> or =200 microg l(-1)) was also found (adjusted-OR: 1.38, 95%CI: 0.92-2.07). Chlorine dioxide treatment is widespread in Italy; therefore, chlorite levels should be regularly and carefully monitored and their potential effects on pregnancy further evaluated and better understood.

Biological Reduction of Chlorate in a Gas‐Lift Reactor Using Hydrogen as an Energy Source

Chlorate release into the environment occurs with its manufacture and use. Biological reduction of chlorate offers an attractive option to decrease this release. A hydrogen gas-lift reactor with microorganisms attached to pumice particles was used for the treatment of wastewater containing high concentrations of chlorate. The microorganisms used chlorate as an electron acceptor and hydrogen gas as a reducing agent. After a start-up period of only a few weeks, chlorate reduction rates of 3.2 mmol L(-1) h(-1) were achieved during continuous operation. During this period, a hydrogen consumption rate of 14.5 mmol L(-1) h(-1) was observed. Complete removal of chlorate was maintained at hydraulic retention times of 6 h. This study clearly demonstrates the potential of hydrogen gas-lift bioreactors for the treatment of chlorate-containing waste streams.

Determination of traces molybdenum by catalytic adsorptive stripping voltammetry

A reliable and very sensitive procedure for the determination of ultra trace of molybdenum is proposed. Molybdenum was determined by cathodic stripping differential pulse voltammetry based on the adsorption collection of the Mo(VI)–Tiron complex on a hanging mercury drop electrode (HMDE). The variation of peak current with pH, concentration of Tiron and chlorate, plus several instrumental parameters such as accumulation time, accumulation potential and scan rate, were optimized. Under optimized condition, the relationship between the peak current and molybdenum concentration is linear in the range of 0.010–21.0 ng ml −1. The limit of detection was found to be 0.006 ng ml −1. The relative standard deviation for 10 replicates determination of 0.6 and 10 ng ml −1 Mo(VI) is equal to 1.3 and 0.9%, respectively. The method was applied to the determination of molybdenum in river water, tap water, well water, plant foodstuff samples such as cucumber, tomato, carrot, and certified steel reference materials.

Kinetics and mechanism of chloride based chlorine dioxide generation process from acidic sodium chlorate

The reaction between sodium chlorate and sodium chloride in presence of aqueous sulfuric acid is studied in a well stirred reactor at various temperatures and molar concentrations of chlorate, chloride and acid. The reaction rate is evaluated by analyzing the consumption of chlorate or chloride iodometrically or argentometrically. The rate law is established. Reaction has been found first and second order with respect to chlorate and chloride concentration, respectively. Reaction order is found about 13–14 with respect to molar concentration of sulfuric acid but it reduced to 2.4 when acidity function, h_, is substituted in place of molar concentration. The temperature dependence of the reaction is also investigated and pre-exponential Arrhenius parameter as well as activation energy are determined. It has been observed that ClO 2/Cl 2 ratio is markedly affected by chlorate to chloride ratio. Reaction mechanism compatible with the reaction kinetics is proposed.

Determination of bromate and chlorinated haloacetic acids in bottled drinking water with chromatographic methods

Disinfection by-products of interest such as bromate, chlorate and chlorinated haloacetic acids in 10 representative brands of bottled drinking water were investigated with ion chromatography. With the developed method, the detection limits of the disinfection by-products were in sub-μg l −1 level. It was observed that bromate, chlorate and dichloroacetic acid could be detected in some water samples. In the bottled natural water, the concentrations for the three compounds were 0.1, 0.9 and 0.6 μg l −1, respectively. The total concentration of disinfection by-products in the natural water sample was the highest among all the bottled drinking waters. The concentrations for the sum of disinfection by-products in the four types of bottled drinking water investigated were natural water > mineral water > spring water > purified water. The generation of disinfection by-products was much influenced by the original components and process procedure of the source water. The concentrations of bromate and chlorate in the bottled water samples hardly degraded with the increasing storage time. For dichloroacetic acid, with the prolonging of storage time, the concentration was much decreased.

Bioremediation of chlorate or perchlorate contaminated water using permeable barriers containing vegetable oil.

A scale model of an in situ permeable barrier, formed by injecting vegetable oil onto laboratory soil columns, was used to remove chlorate and perchlorate from flowing groundwater. The hypothesis that trapped oil would serve as a substrate enabling native microorganisms to reduce chlorate or perchlorate to chloride as water flowed through the oil-rich zone had merit. Approximately 96% of the 0.2 mM chlorate and 99% of the 0.2 mM perchlorate present in the water was removed as water was pumped through columns containing vegetable oil barriers. The product formed was chloride. When nitrate at 1.4 mM was added to the water, both nitrate and chlorate were removed. High concentrations of chlorate or perchlorate can be treated; 24 m M chlorate and 6 mM perchlorate were completely reduced to chloride during microcosm incubations. Microorganisms capable of reducing perchlorate are plentiful in the environment.