Biomedical subjects

A D Jones

Publications and source records attributed to A D Jones.

At least 55 records · Page 3Linked to original sources

PubMed1998

Copper (II) complexation in northern California rice field waters: an investigation using differential pulse anodic and cathodic stripping voltammetry.

Differential pulse anodic stripping voltammetry (DPASV) and competitive ligand equilibration-cathodic stripping voltammetry (CLE-CSV) demonstrated that > or = 99% of the dissolved copper in five rice field waters, one river water and a catchment basin water collected at sites in northern California is complexed by natural organic matter. Concentrations of natural copper complexing ligands (CL) ranged from 81 to 426 nM determined by CLE-CSV using the competitive ligand 8-hydroxyquinoline and from 156 to 1374 nM using DPASV. Experimental values for conditional stability constants (with respect to free Cu2+) of natural copper-organic ligand complexes (log K'CuL) fell in the range 10.2-11.2 using DPASV and 11.1-11.5 using CLE-CSV. DPASV analyses revealed evidence of organic matter adsorption to the electrode surface at low dissolved organic carbon (DOC) concentrations (i.e. 200 micrograms l-1 DOC for a 10-min deposition period), for some but not all water samples. Examination of lyophilized, filtered rice field water using scanning electron microscopy (SEM) and pyrolysis gas chromatography mass spectrometry (pyr-GC/MS) did not reveal differences that could be associated with surface active material. Uncomplexed copper accounts for only minor amounts of total copper in rice field waters and natural ligands are expected to influence its effectiveness as an agrochemical.

California↗

PubMed1998

Formation of nitric oxide-derived inflammatory oxidants by myeloperoxidase in neutrophils.

Nitric oxide (.NO) plays a central role in the pathogenesis of diverse inflammatory and infectious disorders. The toxicity of .NO is thought to be engendered, in part, by its reaction with superoxide (O2.-), yielding the potent oxidant peroxynitrite (ONOO-). However, evidence for a role of ONOO- in vivo is based largely upon detection of 3-nitrotyrosine in injured tissues. We have recently demonstrated that nitrite (NO2-), a major end-product of .NO metabolism, readily promotes tyrosine nitration through formation of nitryl chloride (NO2Cl) and nitrogen dioxide (.NO2) by reaction with the inflammatory mediators hypochlorous acid (HOCl) or myeloperoxidase. We now show that activated human polymorphonuclear neutrophils convert NO2- into NO2Cl and .NO2 through myeloperoxidase-dependent pathways. Polymorphonuclear neutrophil-mediated nitration and chlorination of tyrosine residues or 4-hydroxyphenylacetic acid is enhanced by addition of NO2- or by fluxes of .NO. Addition of 15NO2- led to 15N enrichment of nitrated phenolic substrates, confirming its role in polymorphonuclear neutrophil-mediated nitration reactions. Polymorphonuclear neutrophil-mediated inactivation of endothelial cell angiotensin-converting enzyme was exacerbated by NO2-, illustrating the physiological significance of these reaction pathways to cellular dysfunction. Our data reveal that NO2- may regulate inflammatory processes through oxidative mechanisms, perhaps by contributing to the tyrosine nitration and chlorination observed in vivo.

Animals↗

PubMed1998

Rapid purification and molecular modeling of AaIT peptides from venom of Androctonus australis.

As recombinant viruses expressing scorpion toxins are moving closer toward the market, it is important to obtain large amounts of pure toxin for biochemical characterization and the evaluation of biological activity in nontarget organisms. In the past, we purified a large amount of Androctonus australis anti-insect toxin (AaIT) present in the venom of A. australis with an analytical reversed-phase column by repeated runs of crude sample. We now report 20 times improved efficiency and speed of the purification by employing a preparative reversed-phase column. In just two consecutive HPLC steps, almost 1 mg of AaIT was obtained from 70 mg crude venom. Furthermore, additional AaIT was obtained from side fractions in a second HPLC run. Recently discovered insect selective toxin, AaIT5, was isolated simultaneously from the same venom batch. It shows different biological toxicity symptoms than the known excitatory and depressant insect toxins. AaIT5 gave 100% mortality with a dose of less than 1.3 micrograms against fourth-instar tobacco budworms Heliothis virescens 24 h after injection. During the purification process, we implemented mass spectrometry in addition to bioassays to monitor the presence of AaIT and AaIT5 in the HPLC fractions. Mass spectrometric screening can unambiguously follow the purification process and can greatly facilitate and expedite the downstream purification of AaIT and AaIT5 eliminating the number of bioassays required. Further, electrospray ionization was compared with matrix-assisted desorption/ionization and evaluated as a method of choice for mass spectrometric characterization of fractions from the venom purification for it provided higher mass accuracy and relative quantitation capability. Molecular models were built for AaIT5, excitatory toxin AaIT4, and depressant toxin LqhIT2. Three-dimensional structure of AaIT5 was compared with structures of the other two toxins, suggesting that AaIT5 is similar to depressant toxins.

Amino Acid Sequence↗

PubMed1998

Protocol development for biological tracer studies.

Improved instrumentation and the increased availability of labeled compounds have democratized the application of isotope-dilution (tracer) methodology in nutrient metabolism. Still, the most challenging aspects of tracer experimentation reside in the steps that precede the measurement of an isotopically labeled tracer, i.e. the design of a suitably labeled tracer and its isolation and purification from complex biological matrices. Construction of useful mathematical models of nutrient dynamics require methodologies that guarantee that the integrity of the tracer is maintained across the entire sampling and analyte isolation protocol. The ability to provide accurate and reliable data highlights a need for analytical chemists to play a central role in these studies. In this regard, examples and discussion of issues relevant to stable-isotope experimentation are provided.

Carbon Isotopes↗

PubMed1998

Development of an enzyme-linked immunosorbent assay for atrazine mercapturic acid in human urine.

Improved assessments of human exposure to electrophilic chemicals require rapid and inexpensive analytical techniques that can detect specific urinary metabolites at low levels as needed for epidemiological screenings of large populations. The first aim of this study has been to apply rational hapten design strategies to develop a more sensitive and selective enzyme-linked immunosorbent assay for atrazine mercapturic acid. Polyclonal sheep antiserum was generated against an improved hapten, numerous coating antigen chemistries were evaluated, and assay conditions were optimized. An assay was developed with an IC50 of 0.08 +/- 0.02 micrograms/L (K approximately with 10(-)10 M) for atrazine mercapturic acid. The assay exhibited greatest recognition of atrazine mercapturic acid relative to other known urinary metabolites of atrazine as well as other triazine herbicides. The assay was surprisingly selective to atrazine mercapturic acid over the structurally similar simazine mercapturic acid. Urine samples presented matrix effects due in part to the nonspecific effects of urinary salts, but 4-fold dilution of urine achieved an overall method limit of quantitation of 0.3 micrograms/L. Solid-phase extraction strategies were also developed in an attempt to increase the sensitivity of the overall method. However, a weak positive assay response was present in the solid-phase extracts of unspiked urines, resulting in accurate recovery of atrazine mercapturic acid at microgram/L.

Acetylcysteine↗

PubMed1998

Plasma kinetics of an oral dose of [2H4]retinyl acetate in human subjects with estimated low or high total body stores of vitamin A.

The deuterated retinol dilution technique is an indirect method for quantitatively estimating total body stores of vitamin A by using the postequilibration plasma isotopic ratio [2H4]retinol:retinol and the prediction model described by Furr et al (Am J Clin Nutr 1989;49:713-6). Limited data are available on the time required for an oral dose of labeled vitamin A to mix with vitamin A body stores in human subjects. This article describes the plasma retinol kinetics of an oral dose of [2H4] retinyl acetate in 4 healthy adults (2 men and 2 women) and 1 healthy female child in the United States and in 4 Bangladeshi women. After an oral dose of [2H4]retinyl acetate was administered, plasma samples were collected at 6, 12, and 24 h postdose during the first day and at 15 time points during the subsequent 90-d period for measurement of plasma [2H4]retinol:retinol. The mean respective plasma isotopic ratios on day 20 for US and Bangladeshi subjects (0.02 +/- 0.02 and 0.17 +/- 0.12, P = 0.03) and estimated total body vitamin A reserves (1.03 +/- 0.45 and 0.10 +/- 0.11 mmol, P = 0.003) were significantly different. The fraction of dose in plasma was plotted against time, and biexponential equations were fit to the kinetic data by using the time points from 24 h through day 90. The mean equilibration time (time required for the fraction of dose in plasma to reach a plateau) for all subjects was 16.6 +/- 3.8 d (11-23 d). There was no difference in estimated equilibration time between the group of US and Bangladeshi adult subjects (17.5 +/- 4.4 and 16.3 +/- 3.9 d, respectively, P = 0.69). Thus, the size of hepatic vitamin A reserves does not appear to affect equilibration time within the range of values observed.

Adolescent↗

PubMed1998

Newborn tissue concentrations of bupivacaine following maternal epidural administration during labor in guinea pigs.

Newborn plasma concentrations of maternally administered bupivacaine are often measured, but it is unclear how well they reflect tissue concentrations. Bupivacaine (0.25%) was administered epidurally (0. 12 ml/kg) 10 min prior to labor induction in 6 term-pregnant guinea pigs. Plasma, brain, heart and liver samples were obtained for bupivacaine analysis from newborns (n = 22) after spontaneous delivery. Liver bupivacaine concentrations were 2-3 times greater than those in the plasma, brain, and heart. A similar pattern of tissue concentrations was seen in a smaller number of newborns delivered by cesarean section. Liver bupivacaine concentration decreased with drug-delivery interval in littermates, while heart and brain concentrations showed no relationship with drug-delivery interval. Blood gases of newborns reflected acidosis, which may have influenced tissue drug concentrations. Under conditions of the study, bupivacaine concentrations in heart and brain, potential sites of bupivacaine action, were lower than those observed in a peripheral blood sample.

Anesthetics, Local↗

PubMed1997

Haloenol lactone: a new synergist of chemotherapy in vitro.

Over-expression of glutathione S-transferases (GST) has been found to play a significant role in multiple drug resistance in cancer chemotherapy. To combat GST-mediated drug resistance, GST inhibitors are being studied as potential synergists for effective cancer chemotherapy. We have designed and synthesized a haloenol lactone derivative as a mechanism-based inactivator of GST-pi isozyme. In the current study, we examined the inhibitory effect of the haloenol lactone compound on GST of a human renal carcinoma cell line UOK130 and found that this compound shows time-dependent GST inhibition in these cancer cells. The enzyme activity lost upon incubation with the haloenol lactone could not be restored by extensive dialysis against buffer. Pretreatment of the cancer cells with 1.0 microM of haloenol lactone increased cytotoxicity induced by cisplatin in the UOK130 cell line. This report further supports the possibility of synergizing alkylating agents in cancer chemotherapy by use of selective GST inhibitors.

4-Butyrolactone↗

PubMed1997

Quantitative profiling of tissue- and gender-related expression of glutathione S-transferase isoenzymes in the mouse.

Cytosolic glutathione S-transferase (GST) isoenzymes from brain, heart, lung, liver, kidney and gonads of male and female CD-1 mice were identified and quantified with a combination of affinity purification, electrospray ionization MS, Edman microsequencing, Western blot analysis and reverse-phase HPLC. The three principal hepatic GST subunits, mGSTA3 (25271 Da), mGSTP1 (23478 Da), and mGSTM1 (25839 Da), were isolated from liver, lung, kidney, testes and female heart, whereas brain, ovaries and male heart contained mGSTM1 and mGSTP1. Additional isoenzymes were detected in tissues, including mu class subunits mGSTM2 (25580 Da) and mGSTM3 (25570 Da), an N-terminally blocked Alpha subunit (25480 Da) assigned as mGSTA4, and proteins of molecular masses 25490, 22540, 24493, 24378 and 25383 Da. Distinct gender differences in expression of GST subunits were observed for liver, heart, kidney and gonads, whereas GST expression was similar in brain and lung for both genders. In contrast with patterns of expression in liver (high ratio of mGSTA3 to mGSTP1 in females relative to males), mGSTP1 was the most abundant subunit in female gonads, whereas mGSTA3 was not present in detectable quantities. The profile of GST expression in kidney was similar to that in liver; however, male kidneys expressed 30% more soluble GST than female kidneys. A striking gender-related difference in GST expression was found in cardiac tissue, where female animals expressed 50% more soluble GST than male tissues, and the GST isoenzyme with the greatest documented activity towards lipid hydroperoxides, mGSTA3, was present in female tissue yet absent from male tissue. These results point to complex gender- and tissue-dependent expression of individual mouse GST isoenzymes.

Animals↗

PubMed1997

Anti-insect toxin 5 (AaIT5) from Androctonus australis.

An insect-selective scorpion toxin (AaIT5) was purified from the venom of the North African scorpion Androctonus australis, and its amino acid sequence was determined by a combination of automated Edman degradation, electrospray-ionization mass spectrometry, and sequence alignment. This insect toxin is very potent against the tobacco budworm, Heliothis virescens (100% lethal dose < 1.8 microg/100 mg body mass) and shows a distinct insect specificity and various symptoms. It is not toxic to mice after subcutaneous injection. The molecular mass of this toxin is 6882 Da and the amino acid sequence is similar to those of Androctonus australis anti-insect toxin 4 (AaIT4), Leiurus quinquestriatus depressant anti-insect toxins (LqhIT2, LqqIT2), and Buthotus judaicus depressant anti-insect toxin (BjIT2).

Amino Acid Sequence↗

PubMed1997

Comparative cytotoxicity of monocrotaline and its metabolites in cultured pulmonary artery endothelial cells.

Metabolites of the pyrrolizidine alkaloid monocrotaline cause progressive development of pulmonary hypertension in rats. The putative reactive intermediate monocrotaline pyrrole (MCTP) has been shown to cause cytotoxicity, hypertrophy, decreased proliferation, and altered synthetic capability in cultured pulmonary endothelial cells. We compared effects of monocrotaline (MCT) at 60 micrograms/ml (0.185 mM) with previously identified metabolites, MCTP 10 micrograms/ml (0.031 mM) and glutathione-conjugated dihydropyrrolizine (GSH-DHP) 60 micrograms/ml (0.135 mM), in cultured bovine pulmonary artery endothelial cells (BPAECs). To determine whether endothelial metabolism might contribute to the mechanism of this toxicity, we used markers of cytotoxicity (LDH release), synthetic activity (PGI2 synthesis), hypertrophy (planimetry), cell density (cell count/area), and Evans blue albumin (EBA) transudation as a marker for loss of fluid barrier integrity. We found changes in all endothelial markers with MCTP only. MCTP caused increased LDH release by 48 hr, augmented PGI2 synthesis by 96 hr, and resulted in hypertrophy and decreased cell density by 48 hr that persisted at least 21 days. There was increased EBA transudation at 24 hr posttreatment. We concluded that, based on markers of endothelial damage, BPAECs showed no apparent ability to metabolize MCT to a reactive intermediate nor to further metabolize GSH-DHP to a toxic species. We also concluded that MCTP can cause a direct effect on fluid barrier integrity of endothelial cell monolayers in the absence of inflammation.

6-Ketoprostaglandin F1 alpha↗

PubMed1997

Assessment of human risks from exposure to low toxicity occupational dusts.

Recent animal studies have demonstrated three separate and distinct mechanisms by which low toxicity dusts can cause important chronic pulmonary effects; through overloading of clearance mechanisms, through increased toxicity associated with ultrafine particle size or by increasing the toxicity of known carcinogens in mixed exposures. The problem to be addressed is how the pathogenicity to man of various airborne dusts should be evaluated, when epidemiological evidence is often insufficient, and the reliability of extrapolation of quantitative risks from animals to man is not established. In this paper we examine the feasibility of evaluating the likely human risks of low toxicity dusts by: (1) semi-quantitative comparisons of the ability of various dusts, in animal studies, to cause overload of clearance and resulting inflammation and fibrosis; (2) postulating that these relativities apply quantitatively to human risks; and (3) estimating approximate human risks by comparisons with reference dusts for which adequate animal and human data are available. Such a decision-making framework appears feasible, provided: (1) comparable and quantitative methods are used consistently in animal studies for the measurement of impairment of clearance leading to overload and resulting inflammation and fibrosis; (2) the quantitative relationships between impairment of clearance leading to overload, and resulting inflammation and fibrosis, can be defined adequately in animals for various dusts; (3) the particle size distributions, including those in the ultrafine range, for dusts to which animals and/or humans are exposed, are taken into account (or are comparable); (4) at least two reference dusts with well-documented activities spanning the range of toxicity can be identified; and (5) the reliability of the predictions of human pathogenicity of a sample of other dusts is tested, in toxicological studies and by observation in humans. Some possible candidate reference and test dusts are identified.

Animals↗

PubMed1997

Association of dehydromonocrotaline with rat red blood cells.

The association of radiolabeled monocrotaline pyrrole (DHM) with red blood cell (RBCs) ghosts, globins, and heme was examined to determine their role in the transport and stabilization of this hepatic produced putative toxic metabolite of the pyrrolizidine alkaloid monocrotaline (MCT). Rats were administered 5 mg of DHM/kg, i.v., and RBCs and plasma were harvested at 4 and 24 h. Extensive washing of the RBCs with isotonic phosphate buffer did not decrease the amount of radioactivity associated with the cells. The level of DHM equivalents recovered in the RBCs did not decrease between 4 and 24 h, while the plasma levels, which were 29- and 75-fold lower, respectively, decreased from 5.0 to 2.2 nmol of DHM equiv/g of plasma. Globin chains were found to contain 383 and 453 pmol of DHM equiv/mg of protein, respectively. Rats receiving 10 mg of DHM/kg, i.v., with RBCs collected at 2 h, had approximately double the level of radioactivity associated with their RBCs in addition to 2 times the amount of adducts on the globin chains. Globins and ghosts plus heme (2 h) contained 69% and 2% of the radioactivity, respectively. Globin chains treated with an acidic ethanol solution containing AgNO3 resulted in the removal of 31% of the associated radioactivity. GC/ MS and TLC separation of AgNO3-displaced material revealed the presence of the ethyl ether derivatives of 7-hydroxy-1-(hydroxymethyl)-6,7-dihydro-5H-pyrrolizine. The HPLC separation of globin chains revealed that the majority of radioactivity coeluted with the beta-chains. In conclusion, this study found that the administration of radiolabeled DHM resulted in extensive radioactive labeling of RBCs; similar findings have been reported for [14C]MCT.

Animals↗

PubMed1997

Evidence of quinone metabolites of naphthalene covalently bound to sulfur nucleophiles of proteins of murine Clara cells after exposure to naphthalene.

Naphthalene-induced Clara cell toxicity in the mouse is associated with the covalent binding of electrophilic metabolites to cellular proteins. Epoxide and quinone metabolites of naphthalene are proposed to be the reactive metabolites responsible for covalent binding to proteins. To identify the nature of reactive metabolites bound to proteins (cysteine residues), we alkaline-permethylated proteins obtained from mouse Clara cells incubated with 0.5 mM naphthalene in vitro. Alkaline permethylation of protein adducts produced (methylthio)naphthalene derivatives detected by GC-MS. 3,4-Dimethoxy(methylthio)naphthalene was observed to be a predominant (methylthio)naphthalene derivative formed in the alkaline-permethylated protein sample obtained from Clara cells after exposure to naphthalene. This indicates that 1,2-naphthoquinone is a major metabolite covalently bound to cysteine residues of the cellular proteins. We have developed an immunoblotting approach to detect 1,2-naphthoquinone covalently bound to cysteine residues of proteins [Zheng, J., and Hammock, B. D. (1996) Chem. Res. Toxicol. 9, 904-909]. To identify 1,2-naphthoquinone covalently bound to sulfur nucleophiles of proteins, homogenates obtained from naphthalene-exposed Clara cells were separated by SDS-PAGE followed by Western blotting and immunostaining with the antibodies. Two protein bands with 24 and 25 kDa were detected by the antibodies, further supporting the view that 1,2-naphthoquinone is a reactive metabolite of naphthalene which binds to Clara cell proteins in vitro.

Animals↗

PubMed1997

Characterization of epoxide hydrolase activity in Alternaria alternata f. sp. lycopersici. Possible involvement in toxin production.

Using trans-diphenylpropane oxide (tDPPO) as a substrate, we measured epoxide hydrolase (EH) activity in subcellular fractions of Alternaria alternata f. sp. lycopersici (Aal), a fungus that produces host-specific toxins. The activity was mainly (> 99.5%) located in the soluble fraction (100,000 x g supernatant) with the optimum pH at 7.4. An increase of toxin production between days 3 and 9 found in a Aal liquid culture over a 15 days period was concomitant with a period of high EH activity. EH activity remained constant during the same period in an Alternaria alternata culture, a fungus which does not produce toxin. In vivo treatment of Aal culture with the peroxisome proliferator clofibrate stimulated EH activity by 83% and enhanced toxin production 6.3 fold. Both 4-fluorochalcone oxide (4-FCO) and (2S,3S)-(-)-3-(4-nitrophenyl)-glycidol (SS-NPG) inhibited EH activity in vitro with a I50 of 23 +/- 1 microM and 72 +/- 19 microM, respectively. The possible physiological substrate 9,10-epoxystearic acid was hydrolyzed more efficiently by Aal sEH than the model substrates trans- and cis-stilbene oxide (TSO and CSO) and trans- and cis-diphenylpropane oxide (tDPPO and cDPPO).

Alternaria↗

PubMed1997

Assessment of vitamin A status by the deuterated-retinol-dilution technique and comparison with hepatic vitamin A concentration in Bangladeshi surgical patients.

Hepatic stores of vitamin A were estimated in 31 Bangladeshi surgical patients (15 males and 16 females) by the deuterated-retinol-dilution (DRD) technique and by analysis of the vitamin A concentration of a liver biopsy specimen obtained during previously scheduled abdominal surgery. Patients ranged in age from 21 to 65 y and had an average body mass index (BMI: in kg/m2) of 17.7 +/- 3.4. They received 0.753 mumol [2H4]retinyl acetate/kg body wt orally 9-11 d before surgery. Hepatic vitamin A reserves were estimated according to Furr et al (Am J Clin Nutr 1989;49:713-6) by using a single plasma isotopic-ratio measurement (18-25 d postdose). Estimated mean hepatic vitamin A stores were similar by both techniques, 0.110 +/- 0.072 mmol (by DRD) compared with 0.100 +/- 0.067 mmol (by biopsy). Regression analysis was used to compare results of the DRD and biopsy techniques. A significant linear relation was found between the two techniques (r = 0.75, P < 0.0001), and the least-squares regression line was not significantly different from y = x (P = 0.09). The results indicate that the DRD technique provided a very good estimate of hepatic vitamin A reserves for this population. However, a wide prediction interval was observed for estimates of hepatic vitamin A reserves for individual subjects. Thus, further refinement of the prediction model is necessary to improve estimates of hepatic vitamin A reserves for individual subjects.

Abdomen↗

PubMed1997

The carcinogenic potential of the gas phase of environmental tobacco smoke.

Female strain A/J mice were exposed to unfiltered or HEPA-filtered environmental tobacco smoke (ETS). Total suspended particulates (TSP) in the full smoke exposure chamber was 78.5 mg/m3 and in the filtered smoke chamber 0.1 mg/m3; nicotine concentrations in the full and filtered smoke chamber were 13.4 and 3.1 mg/m3, respectively. Animals exposed to filtered ETS (6 h a day, 5 days a week) and killed after 5 months had a higher lung tumor incidence and multiplicity than controls maintained in filtered air, although the differences were not statistically significant. Animals exposed to filtered and full ETS and allowed to recover in air for 4 months had an average of 1.2 +/- 0.3 tumors per lung and 1.3 +/- 0.3 tumors per lung, respectively. Air exposed control animals had an average tumor multiplicity 0.5 +/- 0.1 tumors per lung. Increased immunostaining for CYP 1A1 was not evident in the lung of animals exposed to filtered smoke. Based on the chamber concentrations of selected nitrosamines and polycyclic aromatic hydrocarbons, the possible maximum uptakes by the mice of NNK, NNN and benzo[a]pyrene during the 5 months exposure period were three to six orders of magnitude below doses reported in the literature to produce 1 lung tumor in strain A/J mice. It was concluded that the gas phase of ETS is as carcinogenic as is full ETS. The carcinogenicity of the gas phase may be due to some as yet unidentified, yet highly potent carcinogens or by placing a substantial, possibly free radical-mediated oxidative stress on the lung.

Animals↗

PubMed1996

Speciation of arsenic oxides using laser desorption/ionization time-of-flight mass spectrometry.

Positive and negative ion mass spectra of arsenic trioxide (As2O3) and arsenic pentaoxide (As2O5) have been obtained by single-step laser desorption/ionization time-of-flight mass spectrometry. Pulsed UV radiation at 266 nm was used for the simultaneous desorption and ionization of the solid sample. High-mass cluster ions that are unique to the oxidation state of each oxide sample appear in the negative ion mass spectra. The As2O3 produces As3O5-, while the As2O5 yields As3O8-. The formation of unique negative cluster ions presents the capability for arsenic oxidation state speciation by laser desorption/ionization mass spectrometry. The ability of time-of-flight mass spectrometry to examine the relative amounts of each arsenic oxide present in a series of mixtures is discussed. Application of our speciation technique to a model incinerator sample is demonstrated.

Arsenic Trioxide↗