Phenylarsonic Acid Research Articles

Steric Effects of Hydroxy Groupsorthoto the Azo Group on Analytical Behavior of Chromogenic Reagents

Three new azo reagents having different numbers of hydroxy groupsorthoto the azo group, i.e., 2-(2′,4′,6′-trihydroxyphenylazo)-, 2-(2′,4′-dihydroxyphenylazo)-, and 2-(4′-hydroxyphenylazo)benzenearsonic acid, were synthesized. Through comparative studies on the reactions of the three reagents with various metal ions, especially with iron(III), it was found that not only selectivities but also sensitivities of azo reagents can be improved by using the steric effects of groupsorthoto the azo group. The reasons for the improvements were discussed.

Speciation of arsenic animal feed additives by microbore high-performance liquid chromatography with inductively coupled plasma mass spectrometry.

Phenylarsonic compounds have been used as poultry and swine feed additives for the purpose of growth promotion and disease prevention. Owing to the lack of suitable analytical methods, however, knowledge of their metabolism, environmental fate and impact remains incomplete. In order to compensate for this, analytical procedures were developed that allow the speciation of arsenic animal feed additives by using microbore high-performance liquid chromatography (microHPLC) coupled on-line with ICP-MS. More specifically, reversed-phase (RP) chromatographic methods were optimised to achieve the separation of various phenylarsonic acids from each other and from the more toxic inorganic arsenic compounds. This mode of chromatography, however, exhibits limitations, especially in the presence of naturally occurring organoarsenic compounds. The application of RP ion-pairing chromatography eliminates such shortcomings by minimising the co-elution of arsenic species. In general, the microHPLC-ICP-MS methods developed in this study provide high selectivity, extremely good sensitivity, low limits of detection (low-ppb or sub-pg amounts of As), require small sample volumes (< 1 microliter), minimise waste and operate most efficiently under low mobile-phase flow rates (15-40 microliters min-1), which are compatible for use with other types of mass spectrometers, e.g., electrospray. Reference materials containing naturally occurring arsenic compounds were spiked with phenylarsonic compounds and then analysed by using the procedures developed in this study.

Differential effects of various trivalent and pentavalent organic and inorganic arsenic species on glucose metabolism in isolated kidney cells

We have compared the acute toxicities of the trivalent arsenic species arsenite, oxophenylarsine (PhAsO), 2-chlorovinyloxoarsine (ClvinAsO), methyloxoarsine (MeAsO), and of the pentavalent arsenic species arsenate, methyl- and phenyl-arsonic acid in rat kidney tubules (RKT) and Madin-Darby canine kidney (MDCK) cells. In RKT, PhAsO (1 μmol I−1, 60 min) almost completely (>90%) blocked gluconeogenesis without affecting cell viability as assessed by dye exclusion. In MDCK cells, PhAsO (2 μmol I−1) markedly inhibited glucose uptake (60% of controls) within 30 min, while cell viability, as assessed by formazan formation, was not affected within 180 min. MeAsO and CIvinAsO were similarly effective to PhAsO in both RKT and MDCK cells. Estimated IC50 values for the inhibition of gluconeogenesis were 0.55 (PhAsO), 0.69 (CIvinAsO) and 0.99 μmol I−1 (MeAsO) and for the inhibition of glucose uptake 1.23 (PhAsO). 2.62 (CIvinAsO) and 6.99 μmol I−1 (MeAsO). At longer storage times, aqueous solutions of MeAsO and of CIvinAsO, but not of PhAsO, gradually lost toxic activity in RKT and MDCK cells, especially at alkaline pH. Concomitantly, a gradual decrease in content as assessed by HPLC was detected. Roughly 10-fold higher concentrations of arsenite than of PhAsO were required for comparable effects on gluconeogenesis in RKT, whereas in MDCK cells about 100-fold higher concentrations were needed for similar inhibition of glucose uptake. Pentavalent arsenate and phenylarsonate were two orders of magnitude less effective than PhAsO in RKT, while methylarsonate had virtually no influence on gluconeogenic activity. In MDCK cells the pentavalent arsenic species showed effects only in the millimolar range. It is concluded (1) that different mechanisms are involved in the acute toxicity of oxoarsines and inorganic arsenic and (2) that PhAsO offers advantages as a model substance for mono-substituted trivalent arsenicals, because it is more stable and more readily detectable.

SYNTHESIS AND MOLECULAR STRUCTURE OF SPIROARSORANES DIFFERING IN RING UNSATURATION. DISTORTION COORDINATES FOR FIVE-COORDINATED ARSENIC

Abstract The new compound 2-phenyl-2,2′-spirobi(1,3,2-naphthodioxarsole), (C10H6O2)2AsPh, 6, was prepared by reacting phenylarsonic acid and 2,3-dihydroxynaphthalene, similar to the preparation of the arsolanes (Me2C2O3)2AsPh, 5, and (C2H4O2)2AsPh, 7. The X-ray structures of 5-7, which were determined, varied from near trigonal bipyramidal (TBP), 5, to an intermediate geometry, 7, to rectangular pyramidal (RP), 6. For phenyl-substituted spirocyclic arsoranes containing like ring atoms directly bound to arsenic, the order of increasing displacement from the TBP toward RP parallels the order of increasing ring electron delocalization. It is found that the structures of arsoranes followed the C2v constraint of the Berry pseudorotational coordinate similar to that reported for phosphoranes. The “limiting” RP for arsoranes has a trans basal angle, θ, of 151.4° similar to that found for other main-group five-coordinated elements. Arsolane 5 crystallizes in the monoclinic space group C21c with a = 11.622 (3) A, ...

Spectrophotometric determination of microamounts of thorium with disodium salt of 2-(2-hydroxy-3,6-disulfo-1-naphthylazo)-benzenearsonic acid (Thorin) as a chromogenic reagent

A sensitive spectrophotometric method has been developed for the determination of microamounts of thorium using 0.05% thorin in a 3M perchloric acid solution as a chromogenic reagent and measuring the absorbance at 544 nm. The complex of thorium thus formed, is stable for more than two months with a constant absorbance of ±0.55%. Beer's law is obeyed from 0 to 25 μg g−1 of thorium in a solution with a molar absorptivity (ɛ544 nm) = 1.69×104 M−1 cm−1 at 26±1 °C. Among the anions tested, only phosphate, acetate and cyanide at >200-fold excess of thorium interfere in the determination, whereas cations like Zn(II), Al(III), Na(I), Mg(II), and Ca(II) do not effect the absorbance. Thorium can be determined in the presence of oxalate, nitrate, tartrate, sulfate, thiosulfate, citrate, and ascorbate. The accuracy of the method has been checked by measuring the known concentration of thorium in the range of 100 μg-5 mg g−1 and found to be in the range of 7.7–0.9%. The method has been applied successfully to determine thorium at μg g−1 level in local ore samples with a precision of ±0.3%. The sensitivity of the method on Sandell's scale is 0.082±0.002 μg g−1 cm−1.

Quantitative aspects of the separation of arsenical species by free solution capillary electrophoresis

Capillary zone electrophoresis has been used for the separation of arsenite, arsenate, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and phenylarsonic acid. The separation was achieved using a fused silica capillary filled with a phosphate buffer. The on-column U.V. detector was operated at 190 nm. The influence of voltage and injected volume, reproducibility of calibration and recovery from a drinking water sample were studied. Using the calibration plot method and phenylarsonic acid as internal standard the mean recoveries for arsenate, MMA and DMA were 104%, 97% and 97% respectively.

Synthetic, Structural and Biochemical Studies of Binuclear Complexes Derived from Heterocyclic Azomethines

Abstract Reactions of equimolar amounts of phenylarsonic acid with tri(isopropoxy)borane result in the formation of PhA0s02B(OPri) type derivatives. The substitution reactions of monoisopropoxy derivatives with azomethines yield the chelated binuclear derivatives in the form of monomeric solids having sharp melting points. These have been characterized by elemental analyses, molecular weight determinations and conductance measurements. On the basis of 1R, 1H, 11B and 13C NMR spectral studies, a tetracoordinated environment around the boron atom may be assigned to these oxo-bridged compounds. The tetracoordinated sites are filled by the two oxo-oxygens of phenylarsonic acid, one azomethine nitrogen and an oxygen or sulfur of the semi- or thiosemicarbazone moiety.

Simultaneous Determination of Transition and Rare Earth Metal Ions in Nd-Fe-B Material by High Performance Ion Chromatography Using Post-Column Chelation Technique

Abstract The transition and lanthanide metal ions of Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in Neodymium-iron-boron (Nd-Fe-B) magnetic material are separated and determined by high performance ion chromatography (HPIC) with spectrophotometric detection using post-column reaction methods. 4-(2-pyridylazo)resorcinol (PAR) and 2-(1,8-dihydroxy-3,6-disulfo-2-naphthylazo)benzenearsonic acid (Arsenazo-III) are used as post-column chelating agents. The reguirements for sample preparation, and characterization of the post-column reaction and the optimum conditions for the sensitive detection of these metal ions after ion chromatographic separation are discussed. The concentration of pH of the chelating medium and the composition of the eluent and the detection limits are investigated.

Synthesis and reactivity of phosphonato, phosphato and arsonato complexes of platinum(II)

Treatment of the complexes cis-[PtCl2L2](L = donor ligand) with phenylphosphonic acid, methylphosphonic acid, phenyl dihydrogenphosphate or phenylarsonic acid in the presence of an excess of silver(I) oxide in refluxing dichloromethane yielded the new metallacycles [[graphic omitted]}L2], [[graphic omitted]}L2], [[graphic omitted]}L2] or [[graphic omitted]}L2] respectively. The X-ray crystal structure of [[graphic omitted]}(PMePh2)2] showed the presence of a slightly puckered metallacyclic ring with the phosphoryl oxygen adopting an equatorial position. A decomposition product of the complex [[graphic omitted]}{P(CH2Ph)Ph2}2] in solution was shown, via an X-ray crystal structure determination, to be the diorthometallated complex cis-[[graphic omitted]Ph2)2].

Three-dimensional structure of murine anti-p-azophenylarsonate Fab 36-71. 1. X-ray crystallography, site-directed mutagenesis, and modeling of the complex with hapten

The structure of the antigen-binding fragment (Fab) of an anti-p-azophenylarsonate monoclonal antibody, 36-71, bearing a major cross-reactive idiotype of A/J mice has been refined to an R factor of 24.8% at a resolution of 1.85 A. The previously solved partial structure of this Fab at a resolution of 2.9 A (Rose et al., 1990) was used as an initial model for refinement against the high-resolution data. The complex with hapten has been modeled by docking the small-molecule crystal structure of phenylarsonic acid into the structure of the native Fab on the basis of a low-resolution electron density map of the complex. In this model, residue Arg-96 in the light chain and residues Asn-35, Trp-47, and Ser-99 in the heavy chain contact the arsonate moiety of the hapten; an additional bond is found between the arsonate group and a tightly bound water molecule. The phenyl moiety of the hapten packs against two tyrosine side chains at positions 50 and 106 in the heavy chain. Residue Arg-96 in the light chain had been implicated as involved in hapten binding on the basis of previous experiments, and indeed, this residue appears to play a crucial role in this model. Experiments employing site-directed mutagenesis directly support this conclusion. The heavy-chain complementarity-determining regions have novel conformations not previously observed in immunoglobulins except for the recently solved anti-p-azophenylarsonate Fab R 19.9 (Lascombe et al., 1989).

On-line photo-oxidation for the determination of organoarsenic compounds by atomic-absorption spectrometry with continuous arsine generation

A method has been developed for on-line conversion of organoarsenicals into arsenate, which is readily detected by atomic-absorption spectrometry with continuous arsine generation. The photoreactor consists of a mercury lamp wrapped with 5 m of PTFE tubing (0.5 mm i.d.). The photo-oxidation conditions were optimized, with a flow-injection analysis procedure, for arsenobetaine, monomethylarsonic acid, dimethylarsinic acid, o-arsanilic acid, and phenylarsonic acid, all organoarsenicals of biological and environmental importance. Solutions were continuously pumped at a flow-rate of 2.0 ml/min and combined with a stream of potassium persulfate (flow-rate 0.6 ml/min) before entering the photo-reactor. With reactor dwell times of 36 sec, conversion efficiencies for these compounds were above 95% under these conditions. Interfacing of this flow-through conversion and detection system with a chromatographic inlet permits real-time analysis of mixtures of these organoarsenic compounds, in a manner suitable for environmental or biomedical samples.

Amelioration of selenium toxicity by arsenicals and cysteine.

Young chicks exhibited a 61% reduction in weight gain when a corn-soybean meal diet was supplemented with 15 mg/kg Se provided as Na selenite. The same level of Se provided as selenomethionine depressed weight gain by 32%. Supplementing the high selenite diet with isoarsenous (14 mg/kg As) additions of As2O5, As2O3, phenylarsonic acid, phenylarsine oxide and roxarsone ameliorated the Se-induced growth depression: As2O5 almost totally restored growth rate; As2O3, phenylarsonic acid and phenylarsine oxide gave intermediate responses; and roxarsone gave only a small ameliorative growth response. Arsanilic acid was without effect in stimulating growth rate of selenite-intoxicated chicks. Dietary addition of .4% L-cysteine produced a growth response in selenite intoxicated chicks that was somewhat greater than that obtained with roxarsone; administering both roxarsone and cysteine corrected growth better than either compound given singly. Both roxarsone and As2O5 also effectively ameliorated the Se-toxicity growth depression caused by selenomethionine (15 mg Se/kg) supplementation, but cysteine showed no efficacy against morbidity caused by this form of Se. Liver Se concentration was elevated 10-fold by selenite and 25-fold by selenomethionine supplementation. The arsenic compounds had varying effects on liver Se, whereas cysteine tended to increase Se concentration. These findings suggest that both inorganic and organic arsenicals as well as cysteine ameliorate selenium toxicity by different mechanisms.

Ortho-(Benzoyl)phenylarsonic acid

<i>ortho</i>-(Benzoyl)phenylarsonic acid

Reaction of arylarsonic acids with organylalkoxy- and organylacetoxy-silanes

The reaction of phenylarsonic acid with trialkylalkoxy- or trialkylacetoxysilanes leads to the formation of bis(trialkylsilyl)phenylarsonates. Bis(trimethylsilyl)- and bis(dimethylsilyDphenylarsonates are thermally unstable and decompose upon separation.

Adsorption of short-chained organic acids on stannic oxide

The uptake of styryl phosphoric acid (SPA) by stannic oxide was studied using three independent measures of the adsorption process: (i) adsorption isotherms, (ii) zeta potentials of stannic oxide particles before and after adsorption and (iii) the release of hydroxyl ions from the stannic oxide during SPA uptake. The uptake of structurally similar styryl sulfonic acid, benzene arsonic acid and benzene sulfonic acid was also measured. The results are consistent with exchange chemisorption between phosphonate anions and surface hydroxyl groups being the main adsorption mechanism for SPA between pH 3 and 5.

Potential involvement of vicinal sulfhydryls in stimulus-induced rabbit platelet activation.

The potential involvement of vicinal dithiols in the expression of platelet-activating factor (AGEPC)- and A23187-induced alterations in rabbit platelets was explored through the use of phenylarsine oxide (PhAsO) and certain analogous derivatives. PhAsO (As3+) but not phenylarsonic acid (As5+) inhibited markedly at 1 microM concentration the release of arachidonic acid initiated by AGEPC and the ionophore A23187. In contrast, AGEPC-induced phosphatidic acid formation, phosphorylation of 40- and 20-kDa proteins, and Ca2+ uptake from external medium were not inhibited substantially by 1 microM PhAsO. However, these latter metabolic responses to AGEPC were inhibited by PhAsO at higher doses (10 microM). AGEPC- and thrombin-induced platelet aggregation and serotonin secretion also were prevented by PhAsO. The IC50 value of PhAsO was 2.7 +/- 1.2 microM toward AGEPC (5 X 10(-10) M)-induced serotonin release. Further, ATP and cAMP levels in PhAsO-treated platelets were not changed from controls. Interestingly, addition of Ca2+ to platelet sonicates (prepared in EDTA) caused diacylglycerol production and free arachidonic acid formation, even in the presence of 133 microM PhAsO. This would suggest that in the intact platelets PhAsO acted indirectly on phospholipase A2 and/or phospholipase C activities. Finally, a dithiol compound, 2,3-dimercaptopropanol, reversed the inhibition of platelet aggregation and arachidonic acid release effected by PhAsO. On the other hand, a monothiol compound, 2-mercaptoethanol, was not effective in preventing or in reversing the action of PhAsO. These observations suggest that vicinal sulfhydryl residues may be involved in stimulus-induced platelet activation.

Multiple proteases from Streptomyces moderatus: I. Isolation and purification of five extracellular proteases

The presence of multiple proteases in the culture filtrate of Streptomyces moderatus was detected. After preliminary purification by ammonium sulfate precipitation and decolorization using DEAE-cellulose, the fractionation of various proteases was carried out using CM-trisacryl cation-exchange chromatography. By this procedure, four different protease fractions (Fr.) were separated (Fr. I, II, III, and IV). The first fraction was further separated into two different proteolytically active fractions (Fr. Ia and Fr. Ib) by DEAE-trisacryl anion-exchange chromatography. Fraction Ia was purified further by affinity chromatography on N-carbobenzoxy- d-phenylalanyl triethylenetetramine-Sepharose 4B. The second fraction (Fr. Ib) was purified by gel filtration on Ultrogel AcA 44. For the purification of the other protease fractions (Fr. II, III, and IV) single-step affinity chromatography methods were employed. Protease fractions II and III were purified by ϵ-aminocaproyl-4-(4-aminophenylazo)phenylarsonic acid Sepharose 4B and protease fraction IV was purified on ϵ-aminocaproyl trialanine-Sepharose 4B. All five proteases purified were found to be apparently homogeneous by gel electrophoretic methods.

Fluorimetric determination of boron at microgram level

The synthesis, characterization and application of 2-(2-hydroxybenzylidenimine)benzene-arsonic acid (HBBA) as a reagent for the fluorimetric determination of boron are described. This reagent reacts with boric acid in 85% w/w sulphuric acid medium to yield a fluorescent compound. The reagent is not fluorescent in those conditions. Heating at 90° for 45 min is needed for the compound to be formed. The linear calibration range is 0.1–8 μg/ml in the solution measured. The detection limit of the method is 0.01 μg/ml. The method has been applied to determine boron in vegetal material.

Purification of subtilisin by single-step affinity chromatography

The dye 4-(4-aminophenylazo)phenylarsonic acid was coupled to activated CH-Sepharose 4B and the resulting affinity matrix was shown to be highly efficient for the purification of subtilisin. A crystalline subtilisin was purified to homogeneity using this affinity chromatography procedure with a purification fold of 1.4 and with an enzyme activity yield of 98%. Similarly subtilisin from a crude enzyme preparation was purified to 211 fold by this single step procedure with 94% recovery of the enzyme activity. The purified enzymes were shown to be homogeneous by polyacrylamide gel electrophoresis.

Poisoning caused by the combined effects of two phenylarsonic acid growth promotants in pigs

Poisoning caused by the combined effects of two phenylarsonic acid growth promotants in pigs