Showing papers on "Arsenic published in 1992"
TL;DR: The evidence assessed here indicates that arsenic can also cause liver, lung, kidney, and bladder cancer and that the population cancer risks due to arsenic in U.S. water supplies may be comparable to those from environmental tobacco smoke and radon in homes.
Abstract: Ingestion of arsenic, both from water supplies and medicinal preparations, is known to cause skin cancer. The evidence assessed here indicates that arsenic can also cause liver, lung, kidney, and bladder cancer and that the population cancer risks due to arsenic in U.S. water supplies may be comparable to those from environmental tobacco smoke and radon in homes. Large population studies in an area of Taiwan with high arsenic levels in well water (170-800 micrograms/L) were used to establish dose-response relationships between cancer risks and the concentration of inorganic arsenic naturally present in water supplies. It was estimated that at the current EPA standard of 50 micrograms/L, the lifetime risk of dying from cancer of the liver, lung, kidney, or bladder from drinking 1 L/day of water could be as high as 13 per 1000 persons. It has been estimated that more than 350,000 people in the United States may be supplied with water containing more than 50 micrograms/L arsenic, and more than 2.5 million people may be supplied with water with levels above 25 micrograms/L. For average arsenic levels and water consumption patterns in the United States, the risk estimate was around 1/1000. Although further research is needed to validate these findings, measures to reduce arsenic levels in water supplies should be considered.
1,097 citations
TL;DR: The mode of toxicity of arsenate is to partially block protein synthesis and interfere with protein phosphorylation but the presence of phosphate prevents this mode of action, and there appears to be a higher affinity for phosphate than arsenate with 4:1.
Abstract: Arsenic has both metallic and nonmetallic properties and is a member of the nitrogen family It occurs as a free element and combined form being widely distributed in sulfide ores The poisonous character of arsenic allowed for its use as a herbicide, cattle and sheep dips, and insecticides The ubiquity of arsenic in the environment, its biological toxicity, and its redistribution are factors evoking public concern This review will cover the chemistry of arsenic and methods curently used to speciate the prevalent chemical forms in various environments The major focus of this review is on the biological transformations of arsenic in both the terrestrial and aquatic systems
459 citations
TL;DR: Arsenic absorption by rice (Oryza sativa, L.) in relation to the chemical form and concentration of arsenic added in nutrient solution was examined in this article, where a 4 × 3 × 2 factorial experiment was conducted with treatments consisting of four arsenic chemical forms [arsenite, As(III); arsenate, As (V); monomethyl arsenic acid, MMAA; and dimethyl arsenic acid (DMAA), three arsenic concentrations [0.05, 0.2, and 0.8 mg As L-1], and two cultivars [
Abstract: Arsenic absorption by rice (Oryza sativa, L.) in relation to the chemical form and concentration of arsenic added in nutrient solution was examined. A 4 × 3 × 2 factorial experiment was conducted with treatments consisting of four arsenic chemical forms [arsenite, As(III); arsenate, As(V); monomethyl arsenic acid, MMAA; and dimethyl arsenic acid, DMAA], three arsenic concentrations [0.05, 0.2, and 0.8 mg As L-1], and two cultivars [Lemont and Mercury] with a different degree of susceptibility to straighthead, a physiological disease attributed to arsenic toxicity. Two controls, one for each cultivar, were also included. Arsenic phytoavailability and phytotoxicity are determined primarily by the arsenic chemical form present. Application of DMAA increased total dry matter production. While application of As(V) did not affect plant growth, both As(III) and MMAA were phytotoxic to rice. Availability of arsenic to rice followed the trend: DMAA
323 citations
TL;DR: ArsC has now been shown to be an arsenate reductase, converting intracellular arsenate to arsenite, which is then exported from the cells by an energy-dependent efflux process.
Abstract: The arsenic resistance operon of Staphylococcus aureus plasmid pI258 consists of three genes, arsR (encoding the repressor regulatory protein), arsB (the determinant of the membrane efflux protein that confers resistance by pumping arsenic from the cells), and arsC (the small gene whose protein product is required for arsenate resistance only, not for arsenite resistance). ArsC has now been shown to be an arsenate reductase, converting intracellular arsenate [As(V)] to arsenite [As(III)], which is then exported from the cells by an energy-dependent efflux process. The arsenate reductase activity was found in the soluble cytoplasmic fraction in Escherichia coli (and not associated with the periplasmic fraction or the sedimentable cell envelope). Purified ArsC protein coupled in vitro with thioredoxin plus dithiothreitol (but not 2-mercaptoethanol or reduced glutathione) to reduce arsenate to arsenite.
266 citations
TL;DR: In this article, a combination of hydrated lime and ferric chloride was used to remove more than 99% of the original arsenic concentration in a former pesticide facility, where water that was collected during various operations was contaminated with arsenic.
Abstract: The use of arsenic in agriculture, industry, and domestic endeavors since the last century has increased the concentration of arsenic in the environment. During cleanup activities at a former pesticide facility, water that was collected during various operations was contaminated with arsenic and required treatment before discharge. Chemical precipitation was identified as being the most effective means of treatment. Bench-scale treatability testing was completed to determine the effectiveness of various coagulants, including ferric chloride, hydrated lime, sodium sulfide, and alum. A combination of hydrated lime and ferric chloride was able to remove more than 99% of the original arsenic concentration
179 citations
TL;DR: L-Cysteine has been shown to reduce the interference from transition elements and other hydride-forming elements (with the exception of selenium and tellurium) by the presence of L-cysteine in the arsenic solution as mentioned in this paper.
Abstract: L-Cysteine reduces arsenic(V) to arsenic(III) rapidly on warming. In addition, the signal from arsenic(III), after reduction by tetrahydroborate(III), is enhanced by the presence of L-cysteine in the arsenic solution. Interferences from transition elements and other hydride-forming elements (with the exception of selenium and tellurium) are substantially reduced by the presence of L-cysteine
135 citations
TL;DR: The major arsenic compound in fish, crustacea and molluscs has been identified as arsenobetaine, which is an arseno-analog of glycinebetaine, a very common osmo-regulator in living organisms.
129 citations
TL;DR: In this paper, the authors reviewed the thermodynamically unstable species of three metalloids, antimony, arsenic, and selenium, and the rates of their transformation to stable forms.
125 citations
TL;DR: Water-soluble arsenic compounds were extracted with methanol/water (1:1, v/v) from various species of bivalves and also from certified reference materials (NIES No. 6, mussel tissue, and NBS 1566, oyster tissue) as discussed by the authors.
Abstract: Water-soluble arsenic compounds were extracted with methanol/water (1:1, v/v) from various species of bivalves and also from certified reference materials (NIES No. 6, mussel tissue, and NBS 1566, oyster tissue). The extracts were analyzed with a high-performance liquid chromatograph combined with an inductively coupled argon plasma mass spectrometer serving as an arsenic-specific detector. A certified reference material (NIES No. 6) was used to check the reproducibility of the analysis. The relative standard deviations (RSDs) of the peak area of major arsenic compounds among repeated measurements (n = 6) on the same extrct were less than 3.3%, indicating good reproducibility of the technique. The RSDs of some peaks among measurements of independent extracts, on the other hand, were more than 10%, possibly reflecting the heterogeneity of the sample in terms of the chemical species under the present experimental conditions. In many of the samples analyzed in the present study, two arsenic-containing ribofuranosides were detected in addition to arsenobetaine. A compound bearing a glycerophosphoryl glycerol moiety was dominant in such cases. Interestingly, a bivalve living in an estuary (Corbicula japonica) did not contain a detectable amount of arsenobetaine though it had arsenic-containing ribofuranosides. The distribution of arsenic species in the various parts of a clam (Meretrix lusoria) and a mussel (Mytilus coruscum) was also analyzed.
105 citations
TL;DR: A method for the separation and identification of inorganic and methylated arsenic compounds in marine organisms was constructed by using a hydride generation/cold trap/gas chromatography mass spectrometry (HG/CT/GC MS) measurement system as mentioned in this paper.
Abstract: A method for the separation and identification of inorganic and methylated arsenic compounds in marine organisms was constructed by using a hydride generation/cold trap/gas chromatography mass spectrometry (HG/CT/GC MS) measurement system.
The chemical form of arsenic compounds in marine organisms was examined by the HG/CT/GC MS system after alkaline digestion. It was observed that trimethylarsenic compounds were distributed mainly in the water-soluble fraction of muscle of carnivorous gastropods, crustaceans and fish. Also, dimethylated arsenic compounds were distributed in the water-soluble fraction of Phaeophyceae. It is thought that most of the trimethylated arsenic is likely to be arsenobetaine since this compound released trimethylarsine by alkaline digestion and subsequent reduction with sodium borohydride.
The major arsenic compound isolated from the water-soluble fraction in the muscle and liver of sharks was identified as arsenobetaine from IR, FAB Ms data, NMR spectra and TLC behaviour.
The acute toxicity of arsenobetaine was studied in male mice. The LD50 value was higher than 10 g kg−1. This compound was found in urine in the non-metabolized form. No particular toxic symptoms were observed following administration. These results suggest that arsenobetaine has low toxicity and is not metabolized in mice. The LD50 values of other minor arsenicals in marine organisms, trimethylarsine oxide, arsenocholine and tetramethylarsonium salt, were also examined in mice.
99 citations
TL;DR: In this paper, seven molecular forms of arsenic were separated by anion and cation-exchange high-performance liquid chromatography (HPLC) with on-line detection by flame atomic absorption spectrometry (FAAS).
Abstract: Seven molecular forms of arsenic were separated by anion- and cation-exchange high-performance liquid chromatography (HPLC) with on-line detection by flame atomic absorption spectrometry (FAAS). The interfacing was established by a vented poly(tetrafluoroethylene) capillary tubing connecting the HPLC column to the nebulizer of the atomic absorption spectrometer. Arsenite, arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) were separated from each other and from the co-injected cationic arsenic compounds, arsenobetaine (AsB), arsenocholine (AsC) and the tetramethylarsonium ion (TMAs) on an organic polymeric anion-exchange column with 0.1 mol dm–3 carbonate at pH 10.3 as the mobile phase. The three cationic species were separated from each other and from the co-injected anionic species on a silica based cation-exchange column with pyridine at a pH of 2.65 as the mobile phase. The signal-to-noise ratio of the on-line AAS detector was optimized. This involved the use of the hydrogen–argon–entrained air flame, a slotted tube atom trap in the flame for signal enhancement, electronic noise damping and a high-intensity light source. The detection limits in µg cm–3, using 100 mm3 injections of mixtures of arsenic standards into the HPLC system were: arsenite, AsIII 1.1; arsenate, Asv 1.4; MMA 1.4; DMA 0.7; AsB 0.3; AsC 0.5; and the TMAs 0.4. The HPLC–AAS system was used for the analysis of arsenic species in aqueous extracts of soil samples from a polluted land site. Only arsenate was found in the soil extracts. For comparison, inductively coupled plasma mass spectrometry was also used as an on-line detection technique with the same HPLC systems.
TL;DR: In this article, the adsorption of arsenic species in aqueous solutions onto activated carbon with and without chemical impregnation has been studied, and the results of the investigations have shown that the physical adaption is effective only for the arsenic(V) species in water.
Abstract: The adsorption of arsenic species in aqueous solutions onto activated carbon with and without chemical impregnation has been studied. The ability of activated carbon to adsorb arsenic depends on the arsenic oxidation state, the pH of the water, and the activity of the metal used for the activated carbon impregnation. The results of the investigations have shown that physical adsorption is effective only for the arsenic(V) species in water. Activated carbon adsorbs arsenic(V) with a saturation adsorption capacity of 0.27 mmol/g. The chemisorption process is effective for both arsenic species. By impregnation of activated carbon by copper, the sorption process for the arsenic(III) species is significantly improved. The saturation adsorption capacity of the activated carbon impregnated by copper is 0.41 and 0.23 mmol/g for the arsenic(III) and arsenic(V) species, respectively. The pH values of the water are important for both sorption processes because of the change in the ionic forms of both arseni...
TL;DR: Multivariate statistical analysis of the results indicated that the dominating pathway of arsenic and chromium from the factory to the leafy vegetables grown nearby was by direct atmospheric deposition, while arsenic in the root crops originated from both the soil and the atmosphere.
TL;DR: Evidence has been obtained which indicates that arsenic is of physiological importance, especially when methionine metabolism is stressed (e.g. pregnancy, lactation, methamphetamineionine deficiency, vitamin B6 deprivation), any possible nutritional requirement by humans can be estimated only by using data from animal studies.
Abstract: Although numerous studies with rats, hamsters, minipigs, goats and chicks have indicated that arsenic is an essential nutrient, the physiological role of arsenic is open to conjecture. Recent studies have suggested that arsenic has a physiological role that affects the formation of various metabolites of methionine metabolism including taurine and the polyamines. The concentration of plasma taurine is decreased in arsenic-deprived rats and hamsters. The hepatic concentration of polyamines and the specific activity of an enzyme necessary for the synthesis of spermidine and spermine, S-adenosylmethionine decarboxylase, are also decreased in arsenic-deprived rats. Thus, evidence has been obtained which indicates that arsenic is of physiological importance, especially when methionine metabolism is stressed (e.g. pregnancy, lactation, methionine deficiency, vitamin B6 deprivation). Any possible nutritional requirement by humans can be estimated only by using data from animal studies. The arsenic requirement for growing chicks and rats has been suggested to be near 25 ng g−1 diet. Thus, a possible human requirement is 12 μg day−1. The reported arsenic content of diets from various parts of the world indicates that the average intake of arsenic is in the range of 12–40 μg. Fish, grain and cereal products contribute most arsenic to the diet.
TL;DR: The mineral leaching archaebacterium Sulfolobus acidocaldarius strain BC is shown to have the ability to oxidise arsenite to arsenate.
Abstract: The mineral leaching archaebacterium Sulfolobus acidocaldarius strain BC is shown to have the ability to oxidise arsenite to arsenate. Arsenite oxidation activity was 8-fold higher for cells grown in the presence of arsenite when compared with cells grown without arsenite. In cell-free extracts, the arsenite oxidation activity was found in the membrane fraction. The arsenite oxidation activity was sensitive to proteinase K and showed the highest activity at acidic pH. A tetrathionate-dependent arsenate reduction activity was also observed.
TL;DR: The urinary and blood levels of each chemical species of arsenic proved to be significantly correlated with the whole-blood TMA levels (r = 0.376; P<0.01), and the intake of TMA was the largest of all the measured species.
Abstract: We calculated the intake of each chemical species of dietary arsenic by typical Japanese, and determined urinary and blood levels of each chemical species of arsenic. The mean total arsenic intake by 35 volunteers was 195±235 (15.8-1039) μg As day−1, composed of 76% trimethylated arsenic (TMA), 17.3% inorganic arsenic (Asi), 5.8% dimethylated arsenic (DMA), and 0.8% monomethylated arsenic (MA): the intake of TMA was the largest of all the measured species. Intake of Asi characteristically and invariably occurred in each meal. Of the intake of Asi, 45-75% was methylated in vivo to form MA and DMA, and excreted in these forms into urine. The mean measured urinary total arsenic level in 56 healthy volunteers was 129±92.0 μg As dm−3, composed of 64.6% TMA, 26.7% DMA, 6.7% Asi and 2.2% MA. The mean blood total arsenic level in the 56 volunteers was 0.73±0.57 μg dl−1, composed of 73% TMA, 14% DMA and 9.6% Asi. The urinary TMA levels proved to be significantly correlated with the whole-blood TMA levels (r = 0.376; P<0.01).
TL;DR: In this article, X-ray photoelectron spectroscopy (XPS) data were analyzed with spectral deconvolution of GaAs with the use of a spectral deconvolution technique.
Abstract: Oxides of GaAs grown using various oxidation processes were analyzed with X-ray photoelectron spectroscopy (XPS) Oxides investigated were the native (naturally grown or exposed to air), the chemical (grown in boiling deionized water) and the thermal (at 350°C and 500°C in dry oxygen) ones With the use of a spectral deconvolution technique, all types of suboxides of both As and Ga including elemental arsenic were observed in addition to well-known As2O3 and Ga2O3 Elemental arsenic is considered to be one of the oxidized forms of GaAs As2O5 was observed in the thermal oxides In the chemical oxide and the native oxide grown in short exposure to air, elemental arsenic is the main component of oxide, while As2O3 is the dominant species in more highly oxidized films such as the thermal oxide XPS data suggest that oxidation of As bonded in GaAs proceeds as GaAs→elemental As (As0)→As2O (As1+)→AsO (As2+)→As2O3 (As3+)→As2O5 (As5+) Oxidation of Ga bonded in GaAs advances as GaAs→Ga2O (Ga1+)→GaO (Ga2+)→Ga2O3 (Ga3+) Angle-resolved XPS measurements and semiquantitative analyses of these data were performed and an effective thickness of each oxide was also derived with simplified assumptions The native and the chemical oxides were nearly stoichiometric However, the thermal oxide was substantially Ga-rich due to desorption and evaporation of As2O3 from the surface during oxidation
TL;DR: The use of hydride generation in conjunction with a polypropylene-membrane gas-liquid separator to completely eliminate the transport of chloride to the plasma is described.
Abstract: In the determination of arsenic, attention has recently focused on the speciation of As(III) and As(V). Reversed-phase HPLC can be used to efficiently separate these two arsenic species. When inductively coupled plasma mass spectrometry is used for arsenic detection, an isobaric interference at m/z 75 is caused by the presence of chloride in the sample. These experiments describe the use of hydride generation in conjunction with a polypropylene-membrane gas-liquid separator to completely eliminate the transport of chloride to the plasma. A detection limit of 0.46 ppb for As(III) was achieved with this system. The chromatographic resolution of the system was not compromised by the addition of the gas-liquid separator. A determination of the arsenic content of a NIST urine sample was performed to demonstrate the effectiveness of the chloride elimination.
TL;DR: In this article, the authors reviewed and discussed the mechanism of arsenic precipitation from the viewpoint of stoichiometry and showed that these arsenic precipitates affect the device properties of chloride epitaxial-type MESFETS.
Abstract: It is well known that there are many arsenic precipitates in LEC GaAs, the dimensions of which are 500-2000 AA. The authors have recently found that these arsenic precipitates affect the device properties of chloride epitaxial-type MESFETS. They also affect the formation of small surface oval defects on MBE layers. To reduce the density of these arsenic precipitates, a multiple-wafer-annealing (MWA) technology has been developed in which wafers are annealed first at 1100 degrees C and then at 950 degrees C. By this annealing, highly uniform substrates with low arsenic precipitate densities, uniform PL and CL, uniform microscopic resistivity distributions and uniform surface morphology after AB etching can be obtained. These MWA wafers showed low threshold voltage variations for condensed ion-implantation-type MESFETS. In the present paper recent works are reviewed and the mechanism of arsenic precipitation is discussed from the viewpoint of stoichiometry.
TL;DR: In this article, the size distribution of 39 trace elements in urban streams was determined by means of neutron activation analysis to estimate their chemical or physical forms, and the following conclusions could be drawn on the dissolved species of trace elements of urban streams: (1) the dominant dissolved species for alkali and alkaline-earth elements, V, Mn, Al, Sb and Au are regarded as simple inorganic ions; (2) the elements Sc, Cr, Co, Ni, Zn, Se, Mo, W, Ir, U, and arsenic is divided between both species
TL;DR: The results show that, at the concentrations tested, arsenite and arsenate impair lymphocyte stimulation and proliferation and confirm the fact that chronic arsenic exposure can affect the proliferation of whole blood lymphocytes.
TL;DR: It is demonstrated that both arsenobetaine and arsenocholine are unstable when incubated in daylight in the presence of hydrogen peroxide, i.e., an oxidizing environment, and it is tempting to speculate that arsenOBetaine could be converted into hydride-generating arsenic compounds during storage or cooking of seafood.
Abstract: Arsenobetaine and arsenocholine are considered to be non-toxic and are present as a relatively large proportion of total arsenic in seafoods, and they do not respond to hydride generation. The present study describes the effect of seafood consumption on the urinary concentration of hydride-generating arsenic compounds measured by a newly developed flow injection atomic absorption spectrometric (FI-AAS) method. Consumption of plaice, pighvar and tunny resulted in a 2-fold increase, and consumption of mussels produced a 6-fold increase in the urinary level of hydride-generating arsenic compounds. Hence, a person who has consumed mussels may be suspected of being occupationally or environmentally exposed, if the level of consumption of this seafood is unknown. As the FI-AAS method cannot be used to detect arsenobetaine and arsenocholine, the observed increase in urinary concentration of hydride-generating arsenic compounds after consumption of seafood must originate either from hydride-generating arsenic compounds in the seafood or from degraded arsenobetaine or arsenocholine. The present study has demonstrated that both arsenobetaine and arsenocholine are unstable when incubated in daylight in the presence of hydrogen peroxide, i.e., an oxidizing environment. Hence, it is tempting to speculate that arsenobetaine could be converted into hydride-generating arsenic compounds during storage or cooking of seafood. The feasibility of speciation methods based on high-performance liquid chromatographic (HPLC) separation and on-line analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) and FI-AAS was also investigated. The FI-AAS system is approximately 35 times more sensitive to the hydride-generating arsenic species than the ICP-AES system. Consequently, an HPLC–FI-AAS speciation method could be useful in analyses for arsenic species in urine from highly exposed persons, or persons suspected of being unable to, or having a reduced ability to, methylate inorganic arsenic compounds.
TL;DR: A system for on-line treatment of liquid samples in a microwave oven digestor was evaluated for use with cold vapour (CV) and hydride generation (HG) atomic absorption spectrometry (AAS).
Abstract: A system for on-line treatment of liquid samples in a microwave oven digestor was evaluated for use with cold vapour (CV) and hydride generation (HG) atomic absorption spectrometry (AAS). Various oxidation mixtures were tested and those based on bromination (bromate–bromide–acid) and peroxodisulfate (persulfate–acid–complexing agent) were found to be compatible with and most appropriate for CVAAS and HGAAS. The composition of reagents and the analytical conditions were optimized for the determination of mercury, arsenic, bismuth, lead and tin in urine and environmental waters. The limits of detection were 0.01 and 0.2 µg l–1 for mercury, with and without amalgamation, respectively, 0.5 µg l–1 for arsenic, 0.07 µg l–1 for bismuth and 0.1 µg l–1 for tin and the sample throughput was between 13 and 30 h–1.
TL;DR: In this paper, a continuous hydride generator is described which incorporates a combined generator/separator, and the system has been further modified to allow on-line pre-reduction of arsenic(V) to arsenic(III) by L-cysteine.
Abstract: A continuous hydride generator is described which incorporates a combined generator/separator. The low acid concentrations necessary in the tetrahydroborate(III)—L-cystein mediated determination of most hydride-forming elements require that the gas is purged from solution. As the hydride transfer reaction is so rapid, this allows both the hydride-forming reaction and the stripping reaction to take place in the same vessel. The system has been further modified to allow on-line pre-reduction of arsenic(V) to arsenic(III) by L-cysteine. Detection limits for arsenic, germanium and selenium are 4, 0.3 and 8 ng ml–1, respectively, at a sample flow rate of 15 ml min–1. Application of the system to the determination of arsenic in water is described. Concentrations of arsenic in several Ontario waters were found to be in the range 7–600 ng ml–1, Interferences from nickel and palladium, two of the most strongly interfering elements in the continuous hydride generation process, are diminished to a greater extent with the system described here than with the conventional high acid continuous system.
TL;DR: In this article, a method for the on-line prereduction of As(V) was developed in order to determine As(III) and As (V) with the same sensitivity by continuous flow hydride generation.
Abstract: A method for the on-line prereduction of As(V) was developed in order to determine As(III) and As(V) with the same sensitivity by continuous flow hydride generation. In this procedure, the sample is continuously mixed with concentrated hydrochloric acid and a potassium iodideascorbic acid solution, flows through a heated PTFE-tube and is determined by hydride generation atomic absorption spectrometry in a heated quartz cell. The selective analysis of As(III) is carried out by continuous mixing of the sample with acetic acid and hydride generation. The method allows the rapid determination of inorganic arsenic species at concentrations down to 1 μg/l. A manual sample preparation is not required.
TL;DR: Arsenic dimers and multilayers are shown to exist on (001)GaAs surfaces under atmospheric pressure (AP) organometallic chemical vapor deposition (OMCVD) conditions.
Abstract: Arsenic dimers and multilayers are shown to exist on (001)GaAs surfaces under atmospheric pressure (AP) organometallic chemical vapor deposition (OMCVD) conditions. We obtained reflectance‐difference spectra from surfaces in AP H2 that are equivalent to those obtained from the (2×4) and disordered‐c(4×4) reconstructions prepared in ultrahigh vacuum by molecular beam epitaxy. Implications for models of OMCVD growth.
TL;DR: In this paper, a method for the selective determination of trivalent and pentavalent inorganic arsenic, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in urine was developed.
Abstract: In studies on arsenic exposure and its monitoring, a method for the selective determination of trivalent and pentavalent inorganic arsenic, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in urine was developed. The method is based on the ion-pair chromatographic separation of arsenic species and continuous hydride generation for the determination of arsenic in the chromatographic effluent by atomic absorption spectrometry. The chromatographic separation was completed within 4 min by using tetrabutylammonium ion in phosphate buffer as the ion-pairing agent and a C18 reversed-phase column. The detection limits were 1.0, 1.6, 1.2 and 4.7 µg dm–3 of arsenic for AsIII, AsV, MMA and DMA, respectively. These detection limits are not low enough to detect the lowest levels of these arsenic species in the urine of unexposed subjects. However, accurate measurement of the concentrations due to occupational exposure is easily achieved.
TL;DR: Arsenic compounds examined in the experiments and their sources and purifies are listed in Table 1 and human peripheral blood was obtained by venipuncture using a heparinized syringe.
Abstract: Arsenic has been documented as a human carcinogen of the skin and lungs. However, attempts to induce tumors in experimental animals with inorganoarsenic compounds have mostly failed except in a few studies in which animals were given arsenic trioxide by intratracheal instillation. Moreover, inorganoarsenics are either inactive or too weak to induce gene mutations in vitro. The mechanism of arsenic carcinogenicity has not yet been discovered. Most mammals including human are able to methylate inorganoarsenic compounds to methylarsonic acid and dimethylarsenic acid. However, the genotoxicity of organoarsenic compounds has hardly been examined. The authors therefore decided to study this genotoxicity, including the frequency of sister chromatid exchange (SCE) of nine organic and three inorganic arsenic compounds. Observation of the metaphases in the SCE test revealed that only DMA of the organo- and inorgano-arsenic compounds induces tetraploids and mitotic arrest. This indicates that the role of DMA may be important in arsenic genotoxicity and may give a clue to the carcinogenic mechanism of arsenic.
TL;DR: In this article, a GaAs epilayer was grown by molecular beam epitaxy under normal conditions, except a substrate temperature of 250°C was used instead of the normal 600°C.
Abstract: GaAs epilayers were grown by molecular beam epitaxy under normal conditions, except a substrate temperature of 250 °C was used instead of the normal 600 °C. This results in an excess of arsenic of about 1.5% in the epilayer. The epilayers also contained regions that were delta doped with silicon, beryllium, and indium. Samples were annealed for 30 s at 600, 700, and 800 °C to investigate the effects of the Si, Be, and In impurities on the precipitation of the excess As. It was found that the As precipitates form preferentially on planes of Si while forming preferentially between planes of Be. The isoelectronic impurity In appeared to have no effect on the precipitation process.