Hydride Generation Atomic Absorption Research Articles

Urinary Arsenic Metabolites in Children and Adults Exposed to Arsenic in Drinking Water in Inner Mongolia, China

BackgroundWe report the concentrations and distributions of urinary arsenic (As) metabolites in 233 residents exposed to 20, 90, or 160 μg/L inorganic arsenic (iAs) in drinking water from three villages in Hohhot, Inner Mongolia, China, that formed one control and two exposed groups.MethodsWe used hydride generation-atomic absorption spectrometry (HGAAS) to determine iAs, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA).ResultsThe concentrations of each urinary As species in the two exposed groups were significantly higher than in the control group for both children and adults. Both children and adults in exposed groups had higher percent iAs and MMA and lower percent DMA, and low primary and secondary methylation indices (PMI and SMI, respectively) than those in the control group. However, children showed significant increases in percent DMA and the SMI as well as decreases in the percent MMA when the iAs exposure level increased from 90 to 160 μg/L. In addition, children in the two exposed groups showed lower percent MMA but higher percent DMA and higher SMI than adults in the same exposed group. No significant differences in As metabolite concentrations and distributions were found between males and females in each group. A significant correlation was also found in the SMI between 11 pairs of children and their mothers from the 160-μg/L–exposed group.ConclusionsChildren had higher a capacity for secondary methylation of As than adults when exposed to the same concentrations of iAs in drinking water. Exposure to As may increase the capacity for methylation in children to some extent.

Can sample treatments based on advanced oxidation processes assisted by high-intensity focused ultrasound be used for toxic arsenic determination in human urine by flow-injection hydride-generation atomic absorption spectrometry?

Two advanced oxidation processes (AOPs), based on high-intensity focused ultrasound (HIFU), namely, KMnO 4/HCl/HIFU and H 2O 2/HCl/HIFU are studied and compared for the determination of toxic arsenic in human urine [As(III) + As(V) + MMA + DMA] by flow-injection hydride-generation atomic absorption spectrometry (FI-HG-AAS). The KMnO 4/HCl/HIFU procedure was found to be adequate for organic matter degradation in human urine. l-cysteine (letra minuscula) was used for As reduction to the trivalent state. The new procedure was assessed with seven urines certified in different As species. Results revealed that with KMnO 4/HCl/HIFU plus l-cysteine the toxic arsenic can be accurately measured in human urine whilst the H 2O 2/HCl/HIFU procedure underestimates toxic As. DMA and MMA degradation in urine were observed, due to the effects of the ultrasonic field. Recoveries for As(III), As(V), MMA and DMA were within the certified ranges. Arsenobetaine was not degraded by the AOPs. The new procedure adheres well to the principles of analytical minimalism: (i) low reagent consumption, (ii) low reagent concentration, (iii) low waste production and (iv) low amount of time required for sample preparation and analysis.

Silica modified with zirconium oxide for on-line determination of inorganic arsenic using a hydride generation-atomic absorption system

In the present work, an on-line pre-concentration system, using SiO 2/ZrO 2 as solid phase adsorbent, for the determination of low concentrations of arsenic was developed. In this procedure, total inorganic arsenic present in the sample is reduced to As (III) with l-cysteine and the solution is passed into a glass column ( ϕ i = 3 mm; h = 35 mm) containing 70 mg of SiO 2/ZrO 2 (100–230 mesh) to retain the As (III), with the solution flowing at 3.2 mL min −1. After 2 min, the concentrated species are eluted with 3 mol L −1 HCl (3.2 mL min −1) loading a 150 μL loop while a 1.0% (m/v) sodium borohydride solution loads the other loop of a FI–HG AAS system. The elution step is carried out during 7 s and, at the same time, the SiO 2/ZrO 2 phase is regenerated for the next concentration cycle. The arsine generated is carried with N 2 (flow rate = 90 mL min −1) to a quartz cell where the electrothermal atomization process occurs. Under these conditions, a 20-fold enrichment factor is obtained considering the increase of sensitivity in the analytical curve after the concentration step. The limits of detection and quantification were 0.05 and 0.35 μg L −1, respectively, with an injection frequency of about 28 h −1 and relative standard deviation lower than 8%. Four metallurgical reference materials were analyzed with the proposed method after their acid dissolution. The results obtained were in good agreement with certified values.

Kinetics of arsenic methylation by freshly isolated B6C3F1 mouse hepatocytes

The toxic and carcinogenic effects of arsenic may be mediated by both inorganic and methylated arsenic species. The methylation of arsenic III is thought to take place via sequential oxidative methylation and reduction steps to form monomethylarsenic (MMA) and dimethylarsenic (DMA) species, but recent evidence indicates that glutathione complexes of arsenic III can be methylated without oxidation. The kinetics of arsenic methylation were determined in freshly isolated hepatocytes from male B6C3F1 mice. Hepatocytes (>90% viability) were isolated by collagenase perfusion and suspended in Williams’ Medium E with various concentrations of arsenic III (sodium m-arsenite). Aliquots of the lysed cell suspension were analyzed for arsenic species by hydride generation-atomic absorption spectrometry. The formation of MMA III from sodium arsenite (1 μM) was linear with respect to time for >90 min. DMA III formation did not become significant until 60 min. MMA V and DMA V were not consistently observed in the incubations. These results suggest that the glutathione complex mechanism of methylation plays an important role in arsenic biotransformation in mouse hepatocytes. Metabolism of arsenic V was not observed in mouse hepatocytes, consistent with inhibition of arsenic V active cellular uptake by phosphate in the medium. The formation of MMA III increased with increasing arsenic III concentrations up to approximately 2 μM and declined thereafter. The concentration dependence is consistent with a saturable methylation reaction accompanied by uncompetitive substrate inhibition of the reaction by arsenic III. Kinetic analysis of the data suggested an apparent K M of approximately 3.6 μM arsenic III, an apparent V max of approximately 38.9 μg MMA III formed/L/h/million cells, and an apparent K I of approximately 1.3 μM arsenic III. The results of this study can be used in the physiologically based pharmacokinetic model for arsenic disposition in mice to predict the concentration of MMA III in liver and other tissues.

Quantitation of Toxic Arsenic Species and Arsenobetaine in Pacific Oysters Using an Off-line Process with Hydride Generation−Atomic Absorption Spectroscopy

An off-line process-based speciation technique was devised here to quantitatively determine toxic inorganic arsenic (iAs), methylarsonic acid (MA), dimethylarsinic acid (DMA), and the dominant, albeit virtually nontoxic, arsenobetaine (AB) in Pacific oysters (Crassostrea gigas). Oysters were extracted with fresh methanol-water (8+2), and this was replicated three times. They were then evaporated to near dryness and subsequently redissolved in pure water; defatting was then performed with a C18 cartridge. The trace hydride active arsenic species, that is, iAs, MA, and DMA, in the defatted solutions were determined with a sensitive hydride generation-packed coldfinger trap-atomic absorption spectrometric (HG-PCFT-AAS) coupled system. The arsenicals that were desorbed from the cation-exchange resin (Dowex 50W-X8) in the washings of 4 M NH3 were categorized on the basis of AB + DMA. The total quantity of arsenic in the recovered AB + DMA was determined with a commercial hydride generation-atomic absorption spectrometric (HG-AAS) system, and finally, AB was calculated from (AB + DMA) - DMA. The average concentrations of iAs, MA, DMA, AB, and total arsenic (TAs) in the oysters collected from six aquacultural sites along the west coast of Taiwan were, respectively, 0.15, 0.06, 0.64, 6.93, and 13.74 mg kg(-1) of dry weight. AB was the major species, whereas iAs (arsenite + arsenate) were the most toxic species, although the iAs made up only approximately 1% of the TAs in the oysters. The lifetime target cancer risk, as determined by the concentration of iAs on a fresh weight basis in the oysters, was well below the ordinary health protection criteria (10(-6)).

A modified routine analysis of arsenic content in drinking-water in Bangladesh by hydride generation-atomic absorption spectrophotometry.

The high prevalence of elevated levels of arsenic in drinking-water in many countries, including Bangladesh, has necessitated the development of reliable and rapid methods for the determination of a wide range of arsenic concentrations in water. A simple hydride generation-atomic absorption spectrometry (HG-AAS) method for the determination of arsenic in the range of microg/L to mg/L concentrations in water is reported here. The method showed linearity over concentrations ranging from 1 to 30 microg/L, but requires dilution of samples with higher concentrations. The detection limit ranged from 0.3 to 0.5 microg/L. Evaluation of the method, using internal quality-control (QC) samples (pooled water samples) and spiked internal QC samples throughout the study, and Standard Reference Material in certain lots, showed good accuracy and precision. Analysis of duplicate water samples at another laboratory also showed good agreement. In total, 13,286 tubewell water samples from Matlab, a rural area in Bangladesh, were analyzed. Thirty-seven percent of the water samples had concentrations below 50 microg/L, 29% below the WHO guideline value of 10 microg/L, and 17% below 1 microg/L. The HG-AAS was found to be a precise, sensitive, and reasonably fast and simple method for analysis of arsenic concentrations in water samples.

Speciation of arsenic in ground water samples: A comparative study of CE-UV, HG-AAS and LC-ICP-MS

The performance of capillary electrophoresis-ultraviolet detector (CE-UV), hydride generation-atomic absorption spectrometry (HG-AAS) and liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) have been compared for the speciation of arsenic (As) in groundwater samples. Two inorganic As species, arsenite (As III), arsenate (As V) and one organo species dimethyl arsenic acid (DMA) were mainly considered for this study as these are known to be predominant in water. Under optimal analytical conditions, limits of detection (LD) ranging from 0.10 (As III, AsT) to 0.19 (DMA) μg/l for HG-AAS, 100 (As III, DMA) to 500 (As V) μg/l for CE-UV and 0.1 (DMA, MMA) to 0.2 (As III, As V) μg/l for LC-ICP-MS, allowed the determination of the above three species present in these samples. Results obtained by all the three methods are well correlated ( r 2 = 0.996*** for total As) with the precision of <5% R.S.D. except CE-UV. The effect of interfering ions (e.g. Fe 2+, Fe 3+, SO 4 2− and Cl −) commonly found in ground water on separation and estimation of As species were studied and corrected for. Spike recovery was tested and found to be 80–110% at 0.5 μg/l As standard except CE-UV where only 50% of the analyte was recovered. Comparison of these results shows that LC-ICP-MS is the best choice for routine analysis of As species in ground water samples.

Tissue dosimetry, metabolism and excretion of pentavalent and trivalent monomethylated arsenic in mice after oral administration

Exposure to monomethylarsonic acid (MMA(V)) and monomethylarsonous acid (MMA(III)) can result from their formation as metabolites of inorganic arsenic and by the use of the sodium salts of MMA(V) as herbicides. This study compared the disposition of MMA(V) and MMA(III) in adult female B6C3F1 mice. Mice were gavaged po with MMA(V), either unlabeled or labeled with 14C at two dose levels (0.4 or 40 mg As/kg). Other mice were dosed po with unlabeled MMA(III) at one dose level (0.4 mg As/kg). Mice were housed in metabolism cages for collection of excreta and sacrificed serially over 24 h for collection of tissues. MMA(V)-derived radioactivity was rapidly absorbed, distributed and excreted. By 8 h post-exposure, 80% of both doses of MMA(V) were eliminated in urine and feces. Absorption of MMA(V) was dose dependent; that is, there was less than a 100-fold difference between the two dose levels in the area under the curves for the concentration-time profiles of arsenic in blood and major organs. In addition, urinary excretion of MMA(V)-derived radioactivity in the low dose group was significantly greater ( P < 0.05) than in the high dose group. Conversely, fecal excretion of MMA(V)-derived radioactivity was significantly greater ( P < 0.05) in the high dose group than in the low dose group. Speciation of arsenic by hydride generation-atomic absorption spectrometry in urine and tissues of mice administered MMA(V) or MMA(III) found that methylation of MMA(V) was limited while the methylation of MMA(III) was extensive. Less than 10% of the dose excreted in urine of MMA(V)-treated mice was in the form of methylated products, whereas it was greater than 90% for MMA(III)-treated mice. In MMA(V)-treated mice, 25% or less of the tissue arsenic was in the form of dimethylarsenic, whereas in MMA(III)-treated mice, 75% or more of the tissue arsenic was in the form of dimethylarsenic. Based on urinary analysis, administered dose of MMA(V) did not affect the level of its metabolites excreted. In the tested range, dose affects the absorption, distribution and route of excretion of MMA(V) but not its metabolism.

Determination of total inorganic arsenic in water using on-line pre-concentration and hydride-generation atomic absorption spectrometry

A rapid and sensitive method for the on-line separation and pre-concentration of inorganic arsenic in water samples is described. The analyte in the pentavalent oxidation state is reduced to its trivalent form with l-cysteine and the total inorganic arsenic is sorbed onto activated alumina in the acid form in a mini-column coupled to a FI-HG AAS system. Afterwards, it is eluted with 3 mol l −1 HCl. An enrichment factor of 7 was obtained, allowing an analytical flow rate of about 28 determinations per hour. The limits of detection (3 σ) and of quantification (10 σ) were calculated as LOD = 0.15 μg l −1 of As and LOQ = 0.5 μg l −1 of As, respectively. Relative standard deviations ( n = 10) less than 8% were obtained for different arsenic concentrations and the accuracy was verified by analysing certified reference materials. Different kinds of samples, such as mineral water, drinking water, river water and natural spring water were analyzed and good agreement was obtained with the values from spiked experiments.

Use of hydride generation-atomic absorption spectrometry to determine the effects of hard ions, iron salts and humic substances on arsenic sorption to sorghum biomass

At present, there is a great interest in studying new sorbent materials for the removal of arsenic from aqueous solutions because of its high toxicity and adverse effects on human health. In previous research, sorghum biomass was found to be an efficient and economic sorbent for the removal of arsenic from aqueous solutions. In this investigation, the effects of CaCl 2, MgCl 2, FeSO 4, MgSO 4, Fe(NO 3) 3, and humic substances (peat moss, humin and humic acids) on arsenic binding to sorghum biomass were evaluated. Among these compounds, only iron salts were found to positively increase the sorption of arsenic to sorghum biomass. In addition, the sorption equilibrium was reached faster when the reaction mixture contained iron salts. However, an overall reduction of 21% of arsenic sorption to sorghum biomass was observed in the presence of MgSO 4. This interference may be due to the presence of sulfate ions, instead of the hard cations, that could be in competition with As for the same interaction sites or ligands. Peat moss, humins and humic acid, extracted from sphagnum peat moss, significantly decreased the arsenic sorption to sorghum biomass.

Determination of total selenium and selenium distribution in the milk phases in commercial cow?s milk by HG-AAS

A procedure has been developed for determining the selenium in cow's milk using hydride generation-atomic absorption spectrometry (HG-AAS) following microwave-assisted acid digestion. The selenium distributions in milk whey, fat and micellar casein phases were studied after separating the different phases by ultracentrifugation and determining the selenium in all of them. The detection limits obtained by HG-AAS for the whole milk, milk whey and micellar casein were 0.074, 0.065 and 0.075 microg l(-1), respectively. The accuracy for the whole milk was checked by using a Certified Reference Material CRM 8435 whole milk powder from NIST, and the analytical recoveries for the milk whey and casein micelles were 100.9 and 96.9%, respectively. A mass balance study of the determination of selenium in the different milk phases was carried out, obtaining values of 95.5-100.8%. The total content of selenium was determined in 37 milk samples from 15 different manufacturers, 19 whole milk samples and 18 skimmed milk samples. The selenium levels found were within the 8.5-21 microg l(-1) range. The selenium distributions in the different milk phases were studied in 14 whole milk samples, and the highest selenium levels were found in milk whey (47.2-73.6%), while the lowest level was found for the fat phase (4.8-16.2%). A strong correlation was found between the selenium levels in whole milk and the selenium levels in the milk components.

Arsenic Species in Solutions for Parenteral Nutrition

In spite of its high toxicity, arsenic is a common contaminant in pharmaceuticals. This is stated by pharmacopoeias' monographs where it is not generically included with other heavy metals, but has its own specifications. Arsenic should not exceed 0.1 mg/L in most pharmaceutical products for IV administration. This limit, however, was established without taking into consideration the specific arsenic species which contribute to this amount. In this work, the presence of arsenite and arsenate species in solutions of amino acids, salts, vitamins, and lipids commercialized for IV administration was investigated. The measurements were done by hydride generation atomic absorption spectrometry. The results showed that all commercial formulations contain both arsenic species in some level; however, the total arsenic content exceeded the allowed limit in only a few samples. Calcium gluconate, sodium bicarbonate, heparin, and vitamin solutions were the most contaminated, presenting total arsenic concentration ranging from 62 to 249 microg/L. The most important finding, however, was the different ratios As(V)/As(III) among the formulations. Whereas practically only As(V) was found in ampoules containing water for injection and salt solutions (NaCl, KC1, phosphates), As(III) predominated in solutions of vitamins, gluconate, and glucose. As these are reducing substances, we investigated the possibility of their reaction with As(V) and its conversion into As(III). The heating of As(V) in the presence of gluconate, glucose, ascorbic acid, methionine, isoleucine, sodium chloride, and pure water, in autoclave for 15 minutes, showed that, whereas no As(III) was found in pure water and sodium chloride solution, approximately 50% of As(V) was converted into As(III) in the remainder of the solutions. The results showed that As(V), the main species in these formulations, may be converted into As(III), depending on the presence of reducing substances among the formulation constituents.

Direct determination of arsenic in acid digests of plant and peat samples using HG-AAS and ICP-SF-MS

A new analytical procedure for the reliable and direct determination of arsenic (As) in nitric acid digests of ombrotrophic peat samples in the low ng l −1 range has been developed based on hydride generation-atomic absorption spectrometry (HG-AAS). The pre-reduction capabilities of KI/ascorbic acid and of l-cysteine in nitric acid digests of peat and plant samples for the conversion of As(V) to As(III) were tested systematically. Samples were digested with high purity nitric acid in a high-pressure microwave autoclave at 240 °C and subsequently measured using HG-AAS or ICP-SF-MS (inductively coupled plasma-sector field-mass spectrometry). Using KI/ascorbic acid as pre-reductant, the accuracy and precision were poor when digests of complex matrices, such as peat were analyzed for As by HG-AAS. However, 10 g l −1 l-cysteine was successfully employed as pre-reductant in diluted nitric acid digests (∼3%, v/v) of peat samples prior to hydride generation of As with 0.5% (m/v) of NaBH 4 and 7 mol l −1 HCl. The analytical procedure was critically evaluated by analyzing several certified plant reference materials, two in-house peat reference materials and by the determination of As in diluted digests of peat samples with ICP-SF-MS. The results for the determination of As in various peat and plant materials showed excellent agreement with the reference values. The method detection limits for the determination of As by the optimized HG-AAS procedure and by ICP-SF-MS were 23 ng g −1 and 1.4 ng g −1 in solid peat, respectively. The newly developed analytical procedure was applied to the determination of As in selected peat samples. Results for As in these peat samples obtained by the developed HG-AAS procedure and the optimized procedure for the determination of As with ICP-SF-MS were highly correlated ( R 2 = 0.993, n = 12).

Stable isotope-enriched selenite and selenate tracers for human metabolic studies: a fast and accurate method for their preparation from elemental selenium and their identification and quantification using hydride generation atomic absorption spectrometry

Stable isotope tracers are safe and nutritionally relevant tools for the investigation of mineral metabolism in man. Increased research into the functional role of selenium has resulted in a need for well-characterised, isotopically enriched solutions of the element in order to determine the nutritional relevance of selenium fortification of foods. A simple method for the conversion of isotopically enriched elemental selenium (2.5–10 mg) into selenite and selenate, and their accurate characterisation and quantification is described. Analysis of selenite and selenate tracers using continuous-flow hydride generation-atomic absorption spectrometry technique was based on the specificity of the selenium hydride reaction and allowed their precise (RSD<2.5%) and accurate determination in aqueous solutions. The detection and determination limits were at 0.13 and 0.36 μg Se/l, respectively. Isotopically enriched elemental selenium was converted into selenite and selenate by a nitric acid and a combined nitric acid/hydrogen peroxide oxidation, respectively. The conversion was quantitative (>95%) and specific for both inorganic seleno-compounds. Selenite and selenate labels were stable in 0.1 mol/l nitric acid for at least 18 months, i.e. making them ideally suitable for use in long-term metabolic studies. An overview of data relating to the absorption and retention of selenium by humans obtained using the two, well-characterised, tracers is presented and indicates that selenite and selenate are equally well retained in adult men and infants, despite differences in their absorption and urinary excretion characteristics.

Occurrence of several arsenic compounds in the liver of birds, cetaceans, pinnipeds, and sea turtles

Concentrations of total arsenic and individual arsenic compounds were determined in livers of birds, cetaceans, pinnipeds, and sea turtles by using hydride generation-atomic absorption spectrometry and high-performance liquid chromatography/inductively coupled plasma-mass spectrometry. Hepatic arsenic concentrations in loggerhead turtles (11.2 +/- 3.0 microg/g dry wt) and black-footed albatrosses (12.2 +/- 10.8 microg/g dry wt) were extremely high among the species examined, and the values were comparable with those of lower trophic marine animals such as fishes, cephalopods, crustaceans, and shellfishes. In all the species, arsenobetaine was the predominant arsenic compound in the livers. Especially, for black-footed albatrosses and black-tailed gull, the mean percentage of arsenobetaine was as high as 97.1 and 87.5, respectively, of extractable arsenic. The present study is among the first on arsenic speciation in avian species. Total arsenic concentration was strongly correlated with the concentration of arsenobetaine, while no significant relationship was observed between total arsenic concentration and other arsenic compounds in these animals. Because arsenobetaine is known to be rapidly excreted into the urine in humans and experimental animals, the observed results suggest that higher trophic marine animals might have a unique metabolism of arsenobetaine and that arsenobetaine plays an important role in the accumulation of arsenic in these animals.

Is arsenobetaine the major arsenic compound in the liver of birds, marine mammals, and sea turtles?

Concentrations of total arsenic and individual arsenic compounds were determined in the livers of birds, marine mammals, and sea turtles by using hydride generation-atomic absorption spectrometry (HG-AAS) and high performance liquid chromatographylinductively coupled plasma-mass spectrometry (HPLCRCP-MS). Marine mammals feeding on cephalopods and crustaceans accumulated higher arsenic concentrations than the species feeding on fishes. No significant age and gender differences in arsenic concentrations were observed for most of the species of marine mammals. Elevated total arsenic concentrations were found in livers of black-footed albatross and loggerhead turtles and these values were comparable to those of lower trophic marine animals. Arsenobetaine was the major arsenical in the livers of most of the species examined. Particularly, in seabirds, mean proportions of arsenobetaine was more than 90% of total extractable arsenic. In contrast, arsenobetaine was a minor constituent in dugong. The compositions of arsenic compounds were different among the species examined. These results might be due to the differences in the metabolic capacity among species and/or the different compositions of arsenic compounds in their preys.

Arsenic methylation and bladder cancer risk in Taiwan.

The mechanism of arsenic detoxification in humans remains unclear. Data are especially lacking for low-level arsenic exposure. We hypothesize that arsenic methylation ability, defined as the ratios of monomethylarsonic acid (MMA(V))/inorganic arsenic (primary arsenic methylation index, PMI) and dimethylarsinic acid (DMA(V))/ MMA(V) (secondary arsenic methylation index, SMI), may modify the association between cumulative arsenic exposure (CAE, mg/L-year) and the risk of bladder cancer. In this study we investigated the relationship among arsenic methylation ability, CAE, and the risk of bladder cancer in a hospital-based case-control study in southwestern Taiwan. From January 1996 to December 1999 we identified 49 patients with newly diagnosed cases of bladder cancer at the National Cheng-Kung University (NCKU) Medical Center; controls consisted of 224 fracture and cataract patients selected from the same medical center. The levels of four urinary arsenic species: arsenite (As(III)), arsenate (As(V)), MMA(V), and DMA(V)) were determined in all subjects by using the high-performance liquid chromatography hydride-generation atomic absorption spectrometry (HPLC-HGAAS). CAE was estimated by using published data collected in a survey from 1974 to 1976. Compared to a CAE < or = 2 mg/L-year, CAE > 12 mg/L-year was associated with an increased risk of bladder cancer (multivariate odds ratio (OR) 4.23, 95% confidence interval (CI) 1.12-16.01), in the setting of a low SMI (< or = 4.8). Compared to women, smoking men (OR 6.23, 95% CI 1.88-20.62) and non-smoking men (OR 3.25, 95% CI 0.95-11.06) had higher risks of bladder cancer. Given the same level of PMI, smoking men (OR 9.80, 95% CI 2.40-40.10) and non-smoking men (OR 4.45, 95% CI 1.00-19.84) had a higher risk of bladder cancer when compared to women. With the same level of SMI, both smoking men (OR 6.28, 95% CI 1.76-22.39) and non-smoking men (OR 3.31, 95% CI 0.84-12.97) had a higher risk of bladder cancer when compared to women. Subjects with low SMI have a substantially increased risk of bladder cancer, especially when combined with high CAE levels.

A novel silica trap for lead determination by hydride generation atomic absorption spectrometry

A novel silica trap for lead determination at concentration levels of ng/l was developed using hydride-generation atomic absorption spectrometry. The device consists of a 7.0-cm silica tubing which is externally heated to a desired temperature. The lead hydride vapor is generated by a conventional hydride-generation flow system. The trap is placed between the gas–liquid separator and silica T-tube; the device traps analyte species at 500 °C and releases them when heated further to 750 °C. The overall efficiency is 49%. The presence of hydrogen gas is required for revolatilization; O 2 gas must also be present. The analytical plot is linear up to 2.0 ng/ml for a collection period of 60 s. The response is also linear with respect to increasing collection periods up to 4 min. For 60-s trapping, the detection limit is 19 ng/l.

Optimisation of sample pre-treatment in the HG-AAS selenium analysis.

A fast and accurate method of pre-treatment for biological materials in the hydride generation-atomic absorption spectroscopy (HG-AAS) selenium determination is described. All procedures of sample pre-treatment were performed in closed-vessels in a microwave oven. After sample decomposition using a HNO3/H2O2 mixture, the pre-reduction and a 'denitrification' step (reduction of interfering nitrogen intermediates) with amidosulfuric acid were combined. Hence, analysis time and the risk of element losses or the emergence of possible contamination are minimised.

Arsenic in breast milk during the first 3 months of lactation

Increased concentrations of arsenic were found in soil and ground water from a military training area in Munster, Lower Saxony, Germany, where chemical weapons were dumped after World War II. In order to assess the possible impact of this contamination for nursing new-borns and infants, samples from breast milk of 36 women were analysed with respect to arsenic content. Study participants came from three different regions: the city of Hamburg, the rural area of Soltau, Lower Saxony, and from Munster, the potentially contaminated area. Breast milk samples were collected immediately before and after nursing on days 2, 5, 15, 30, 45, 60, 75, and 90 post partum. At least 10 ml were required for measurements of arsenic, and 187 samples were of that volume. Samples were analysed with a Perkin-Elmer Type 403 hydride-generation atomic absorption spectrometer, equipped with an arsenic EDL-lamp. Arsenic was not detectable, i.e. below 0.3 microgram/l, in 154 of 187 samples. The highest concentration of 2.8 micrograms/l was measured in a sample from the rural area of Soltau. Geometric means of arsenic concentrations were comparable in the three regions. Concentrations did neither differ in samples obtained before and after nursing nor with respect to age of the infant. The calculated daily intake of arsenic was in the range of 0.02 to 0.06 microgram per kg body weight, which is far below the lower limit of daily permissible intake for adults (WHO/JECFA recommendation 1993) of 15 micrograms/kg/wk. In conclusion, we found concentrations of arsenic in breast milk within the reported safety limits. This was also true for samples from women living in a region which has previously been shown to be contaminated with arsenic from chemical weapons.