Can Humans Metabolize Arsenic Compounds to Arsenobetaine?

Arsenic compounds were determined in 21 urine samples collected from a male volunteer. The volunteer was exposed to arsenic through either consumption of codfish or inhalation of small amounts of (CH₃)₃As present in the laboratory air. The arsenic compounds in the urine were separated and quantified with an HPLC–ICP–MS system equipped with a hydraulic high-pressure nebulizer. This method has a determination limit of 0.5 μg As dm⁻³ urine. To eliminate the influence of the density of the urine, creatinine was determined and all concentrations of arsenic compounds were expressed in μg As g⁻¹ creatinine. The concentrations of arsenite, arsenate and methylarsonic acid in the urine were not influenced by the consumption of seafood. Exposure to trimethylarsine doubled the concentration of arsenate and increased the concentration of methylarsonic acid drastically (0.5 to 5 μg As g⁻¹ creatinine). The concentration of dimethylarsinic acid was elevated after the first consumption of fish (2.8 to 4.3 μg As g⁻¹ creatinine), after the second consumption of fish (4.9 to 26.5 μg As g⁻¹ creatinine) and after exposure to trimethyl- arsine (2.9 to 9.6 μg As g⁻¹ creatinine). As expected, the concentration of arsenobetaine in the urine increased 30- to 50-fold after the first consumption of codfish. Surprisingly, the concentration of arsenobetaine also increased after exposure to trimethylarsine, from a background of approximately 1 μg As g⁻¹ creatinine up to 33.1 μg As g⁻¹ creatinine. Arsenobetaine was detected in all the urine samples investigated. The arsenobetaine in the urine not ascribable to consumed seafood could come from food items of terrestrial origin that—unknown to us—contain arsenobetaine. The possibility that the human body is capable of metabolizing trimethyl- arsine to arsenobetaine must be considered. © 1997 by John Wiley & Sons, Ltd.     

Study on New Spectrophotometric Determination of Arsenic (V) with Chlorpromazine

IntroductionChlorpromazineasanewchromogenicreagenthasbeenemployedforthedeterminationofvanadium(V)inthislaboratoryi.ItwasfoundthatthisreagentalsogaveasensitivereactionwithheteropolyacidofAs,P,Ge,andStinstronglyacidicmedium.Inthispaper,anewmethodforspectrophotometricdeterminationofarsenic(V)withchlorpromazineisreported.Theoptimumconditionsforcolordevelopmentofthecomplexandtheeffectsofforeignionswerestudied.Itispossibletoestablishasensitiveandselectivespectrophotometricmethodforthedeterminatio…     

Arsenic calamity in the Indian subcontinent What lessons have been learned?

Groundwater arsenic (As) contamination in West Bengal (WB, India) was first reported in December 1983, when 63 people from three villages of two districts were identified by health officials as suffering from As toxicity. As of October 2001, the authors from the School of Environmental Studies (SOES) have analyzed >105 000 water samples, >25 000 urine/hair/nail/skin-scale samples, screened approximately 86 000 people in WB. The results show that more than 6 million people in 2700 villages from nine affected districts (total population approximately 42 million) of 18 total districts are drinking water containing >/=50 mug l(-1) As and >300 000 people may have visible arsenical skin lesions. The As content of the physiological samples indicates that many more may be sub-clinically affected. Children in As-affected villages may be in special danger. In 1995, we had found three villages in two districts of Bangladesh where groundwater contained >/=50 mug l(-1) As. The present situation is that in 2000 villages in 50 out of total 64 districts of Bangladesh, groundwater contains As above 50 mug l(-1) and more than 25 million people are drinking water above >/=50 mug l(-1) As. After years of research in WB and Bangladesh, additional affected villages are being identified on virtually every new survey. The present research may still reflect only the tip of iceberg in identifying the extent of As contamination. Although the WB As problem became public almost 20 years ago, there are still few concrete plans, much less achievements, to solve the problem. Villagers are probably in worse condition than 20 years ago. Even now, many who are drinking As-contaminated water are not even aware of that fact and its consequences. 20 years ago when the WB government was first informed, it was a casual matter, without the realization of the magnitude this problem was to assume. At least up to 1994, one committee after another was formed but no solution was forthcoming. None of the expert reports has suggested solutions that involve awareness campaigns, education of the villagers and participation of the people. Initially, international aid agencies working in the subcontinent simply did not consider that As could be present in groundwater. Even now, while As in drinking water is being highlighted, there have been almost no studies on how additional As is introduced through the food chain, as large amounts of As are present in the agricultural irrigation water. Past mistakes, notably the ceaseless exploitation of groundwater for irrigation, continue unabated today; at this time, more groundwater is being withdrawn than ever before. No efforts have been made to adopt effective watershed management to harness the extensive surface water and rainwater resources of this region. Proper watershed management and participation by villagers are needed for the proper utilization of water resources and to combat the As calamity. As in groundwater may just be nature's initial warning about more dangerous toxins yet to come. What lessons have we really learned?     

Determination of Arsenic in Food Samples by Hydride Generation – Atomic Absorption Spectrometry

A method for the determination of trace amounts of arsenic in food samples using flow injection analysis and atomic absorption spectrometry with hydride generation (FI-HG AAS) was developed. The parameters of the flow injection system and the hydride generation were optimized with respect to reagent concentrations, atomization temperature, injection volume, reaction coil length and carrier flow rate. The limits of detection and quantification were 0.34µgL^–1 and 1.2µgL^–:1, respectively, and the analytical curve is linear up to 30.0µgL^–1 arsenic. The relative standard deviation for 12 replicates varies between 5% for 4.0µgL^–1 As and 1.8% for 30.0µgL^–1 As, with an injection frequency of up to 135h^–1. Interferences from Ni(II), Cu(II), Fe(III), Cr(III), Mo(II), Bi(III), Se(IV), Se(VI), Sb(III) and Sb(V) could be masked with a mixture of ascorbic acid-KI in a 5.0molL^–1 HCl solution. The accuracy of the proposed method was evaluated by using certified reference materials of biological samples, and the method was used to determine the content of arsenic in fish and coffee beans.     

Syntheses and Bioactivity of 4＂-Sulfonate-5-triphenyl silyl Avermectin B1a and Ivermectin B1a Derivatives

Fourteen new derivatives of avermectin B1a, and ivermectin B1a were synthesized from C5-O-triphenyl silylavermectin B1a and ivermectin B1a (yield from 40% to 83%). Their chemical structures were characterized by means of IR. ^1H NMR, ^13C NMR and FAB-MS spectrometries. Some of them show excellent insecticidal activity.     

SPE-HPLC法测定枸杞中阿维菌素B1a残留量

建立了固相萃取前处理净化技术-高效液相色谱(HPLC)法检测枸杞中阿维菌素B1a残留量的方法.样品用乙腈提取,经C18固相萃取柱净化,采用C18柱(250 mm×4.6 mm i.d.,5 μm)分离,以V(甲醇):V(水)=85:15为流动相,在245 nm下进行检测.阿维菌素B1a在0.20～2.00 μg/mL范围呈良好的线性关系(γ=0.9994);该方法检出限(S/N=3)为0.02mg/kg;添加回收率为88.3%～102.5%,相对标准偏差为2.1%～3.8%.     

Impact of Arsenic Trioxide on LS-174T Cell Growth and the Activity of Telomerase

The therapeutic action of arsenic trioxide（ As203 ） on solid tumors has aroused widespread interest among scholars. To study the impact of As2O3 on human colorectal carcinoma cells（ LS-174T cell） and the activity of telomerase, the methods of PCR-ELISA, flow cytometry （FCM） and MTT assay in vitro were utilized. The results show that （1） with an increase in the concentration of As2O3, the ratio of living the cells to dead cells decreases significantly, and the IC50 value is 5.23 μg/mL; （2） the cells of the experimental groups can endure a series of morphological changes similar to the features of apoptosis ; （3） the apoptotic curves of FCM pictures appear after 24 h, and the cells show the apoptosis in a time-dependent manner; （4） As2O3 can inhibit the activity of telomerase of the cell extraction obviously in a concentration-dependent and time-dependent manner after 24 h. It can be concluded from the experiment results in vitro that As2O3 can induce the apoptosis of LS-174T cells and inhibit the telomerase activity. Therefore, it has been proposed, for the first time, that these two factors （the apoptosis of LS-174T cells and the inhibition to the telomerase activity） are important causes of the LS-174T cell death caused by As2O3.     

Determination of Arsenic by Hydride Generation—Laser-Induced Breakdown Spectroscopy: Characterization of Interelement Interferences

In this study, interelement interferences were evaluated for the determination of arsenic in aqueous samples through laser-induced breakdown spectroscopy (LIBS) hyphenated with a hydride generation sample introduction system. Optimum instrumental and chemical parameters were selected and variation in LIBS signal intensity was recorded for As solution in the presence of comparable concentrations of interfering elements. No significant change in the signal intensity of As(I) 228.8?nm line was observed in the presence of alkali/alkali earth metals; however, the presence of hydride-forming elements has shown a noticeable decrease in the line emission strength of arsenic. The least variation in arsenic signal was observed in the presence of Ge, the most volatile of all. However, the signal has decreased to a greater extent in the presence of Sn, Sb, and Pb. The presence of interfering elements on electron temperature and electron number density of arsenic plasma has also been studied. Plasma temperatures calculated using both As and Ar emission lines in the Boltzmann equation were similar, being around 5000?K. The McWhirter criterion for stationary and homogenous plasmas was utilized for the establishment of the local thermodynamic equilibrium under the plasma conditions studied. Applicability of the technique for multielemental analysis of water samples was tested through spiking experiments. Arsenic signal showed 26% decrease in the multielemental mixture solution. LIBS is among a few atomic spectroscopic techniques that facilitate rapid and simultaneous multielemental analysis without extensive sample preparation steps. However, the analytical performance of the technique still requires more serious efforts to compete with other conventional techniques for routine analysis of environmental samples.     

Can an ancillary ligand lead to a thermodynamically stable end-on 1 : 1 Cu-O2 adduct supported by a beta-diketiminate ligand?

The finding that dioxygen binds end-on to the Cu(B) site in the crystal structure of a precatalytic complex of peptidylglycine alpha-hydroxylating monooxygenase has spurred the search for biomimetic model complexes exhibiting the same dioxygen coordination. Recent work has not only indicated that sterically hindered beta-diketiminate ligands (L(1)) could support side-on 1 : 1 Cu-O(2) adducts, but also that an end-on L(1)Cu(THF)O(2) structure occurs as an unstable intermediate in the oxygenation mechanism of the Cu(I) complex. In this work, density functional theory and multireference methods are used to determine the potential of ancillary ligands, X, other than THF to yield thermodynamically stable end-on L(1)CuXO(2) species. A diverse set of ligands X, comprising phosphines, thiophene, cyclic ethers, acetonitrile, para-substituted pyridines, N-heterocyclic carbenes, and ligands bearing hydrogen bond donors, has been considered in order to identify ligand characteristics which energetically favor end-on L(1)CuXO(2) over: a) reversion to the Cu(I) complex and dioxygen, b) isomerization to side-on L(1)CuXO(2), and c) decay to L(1)CuO(2) and X. Ancillary ligands with judiciously chosen degrees and orientation of steric bulk and which bear potential hydrogen bond donors to an end-on bound dioxygen moiety most favor oxygenation of L(1)CuX to yield end-on L(1)CuXO(2). Conversion to the side-on isomer can be deterred through the use of a sufficiently bulky ligand X, such as one that is at least the size of a 5-membered ring. Loss of X to give L(1)CuO(2) can be made prohibitively endergonic by employing ligands X which are highly electron donating and which backbond strongly with and sigma-donate significantly to copper.     

Kinetic and Dynamic Aspects of Arsenic Adsorption by Fe(III)-Loaded Sponge

Nowadays there is a great concern about new adsorbent materials for either the removal or fixation of arsenic species because of their high toxicity and the health problems associated with such species. In this paper the kinetics of absorption of As(V) on Fe(III)-loaded sponge have been studied and the results are compared with those of other natural and synthetic adsorbents. Arsenate was adsorbed very rapidly by Fe(III)-loaded sponge with saturation being reached in less than ten minutes. Arsenate was also adsorbed by Fe(III)-loaded Lewatit-TP-207 and non-loaded Purolite A100S ion-exchange resins but the times required to reach total saturation of the adsorbent were more than 100 minutes. The experimental data followed first-order kinetics. The extraordinarily superior kinetics are postulated to be related to the open-celled internal structure of the sponge material. The effect of flow rate on the dynamic removal of As(V) was studied in a fixed-bed column reactor for Fe(III)-loaded sponge and Fe(III)-loaded resin. The adsorption of As(V) on fixed-bed columns of adsorbent also indicated better kinetic properties for the sponge. Column studies showed a good correlation between the experimental data and the calculated breakthrough curves obtained by the Wolborska and Clark models. Application of the Wolborska model to the data at low C/C ₀ ratios enabled the determination of the kinetic coefficient of mass transfer for the sponge and resin materials at the different flow rates used and gave a good prediction of the 5% breakthrough times. Furthermore, the breakthrough curves were well described by the Clark model at the ratios of concentration of effluent to influent up to 0.5 for the sponge and 0.3 for the Fe(III)-loaded resin. Above these levels, a large deviation occurred for the resin adsorption. Thus, the sponge was found to be kinetically effective and favored for As(V) adsorption from solution over the conventional adsorbents used and for most of the adsorbents reported in the bibliography.     

1, 1‐Dianthrimide as a Reagent for the Spectrophotometric Determination of Boron

Abstract

The optimum conditions for the formation of the blue 1:1 complex by the reaction of 1, 1‐dianthrimide and boric acid in 95% by weight sulfuric acid have been determined. The effect of certain diverse ions are reported. The procedure is applicable to the determination of 1 to 10 μ of boron.     

Landau–de Gennes theory for a −1 boojum in a degenerate hybrid-aligned nematic cell

Within Landau–de Gennes theory, the texture of a cylindrically confined degenerate hybrid nematic cell containing a ?1 boojum has been investigated using a three-dimensional finite-difference iterative method. We impose strong anchoring conditions, with the nematic director perpendicular to the upper plate and planar degenerate at the lower plate. The director distribution of a degenerate hybrid-aligned nematic cell with a ?1 defect is known to have no axial symmetry. The axially symmetric characteristic of the biaxial distribution is surprising. The geometric confinement and boundary condition induce an order reconstruction. The influences of cell thickness on the frustrated cell and eigenvalue exchange solution for a sufficiently small thickness with order reconstruction nucleus have been analysed. Defect rings appear when cell thickness is sufficiently small.     

Synthesis of a (1→6)-β-Linked N-Acetyl-d-glucosamine Oligosaccharide1

Abstract

1,6-Anhydro-2-deoxy-3,4-di-O-benzyl-2-phthalimido-β-d- glucopyranose (5) was synthesized from 1,6-anhydro-β-d-mannopyranose (1) in five steps. Compound 5 was polymerized under cationic conditions and selectively yielded glucosamine oligomers (degree of polymerization 5-7). Copolymerization of 5 with 1,6-anhydro-2,3,4-tri-O-benzyl-β-d-glucopyranose indicated the low reactivity of 5 with the active cation derived from 5. Deprotection of 2-deoxy-3,4-di-O-benzyl-2-phthalimido-(1→6)-β-d-glucopyranan (7) and N-acetylation gave 2-acetamido-2-deoxy-(1→6)-β-d-glucopyranan (9).     

Syntheses and Bioactivity of 4″-Sulfonate-5-triphenylsilyl Avermectin B_(1a) and Ivermectin B_(1a) Derivatives

IntroductionAvermectins occuring in nature are macro-cyclic lactones with important anthelmintic,insec-ticidal and miticidal activities.Avermectins andtheir many analogues,such as ivermectins( 2 2 ,2 3-dihydroavermectin B1) and4″- epi- ( methylamino) -4″- deoxyavermectin B1benzoate[1] ,bind to verte-brates′ and invertebrates′ γ- gaminobutyric acid( GABA ) - gated and invertebrate glutamate- gatedchloride channels to increase ion conductance,thereby disrupting inhibitory or excitatory ac…     

Total synthesis of a lacto—ganglio series glycosphingolipid,M1−XGL-1

First total synthesis of a novel “lacto—ganglio series” glycosphingolipid M1⁻XGL-1 was achieved regio- and stereoselectively.     

Comparison of neutron capture spectra taken by a constellation Xe-110 detector and a 1″×1″ NaI(Tl) crystal

Constellation Technology Corporation has developed a spectroscopic nuclear detector called the Xe-110 that is well suited for downhole use in oil and gas well logging. The advantages possessed by this detector over traditional technologies such as NaI(Tl) scintillators are summarized. We discuss an analysis of gamma-ray spectra taken by the Xe-110, which suggests that the superior energy resolution and low background level of this detector enables identification of important features in neutron activation spectra of hydrocarbons that might not be identifiable using an NaI(Tl) crystal.     

Determination of Inorganic Arsenic Species by Electrochemical Hydride Generation Atomic Absorption Spectrometry with Selective Electrochemical Reduction

A new direct procedure for the determination of inorganic arsenic species was developed by electrochemical hydride generation atomic absorption spectrometry （EcHG-AAS） with selective electrochemical reduction. The determination of inorganic arsenic species is based on the fact that As（Ⅲ） shows significantly higher absorbance at low electrolytic currents than As（Ⅴ） in 0.3 mol·L^-1 H2SO4. The electrolytic current used for the determination of As（Ⅲ） without considerable interferences of As（Ⅴ） was 0.4 A, whereas the current for the determination of As（Ⅲ） and As（Ⅴ） was 1.2 A. For equal concentrations of As（Ⅲ） and As（Ⅴ） in a sample, the interferences of As（Ⅴ） during the As（Ⅲ） determination were smaller than 5%. The absorbance for As（Ⅴ） could be calculated by subtracting that for As（Ⅲ） measured at 0.4 A from the total absorbance for As（Ⅲ） and As（Ⅴ） measured at 1.2 A, and then the concentration of As（Ⅴ） can be obtained by its calibration curve at 1.2 A. The methodology developed provided the detection limits of 0.3 and 0.6 ng·mL^-1 for As（Ⅲ） and As（Ⅴ）, respectively. The relative standard deviations were of 3.5% for 20 ng·mL^-1 As（Ⅲ） and 3.2% for 20 ng·mL^-1 As（Ⅴ）. The method was successfully applied to determination of soluble inorganic arsenic species in Chinese medicine.