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Evaluation of arsenic speciation in rainbow trout and fathead minnows from dietary exposure
Citation:
Jenson, C., T. Lahren, J. Fernandez, D. Kuehl, R. Erickson, D. Mount, D. Hoff, T. Highland, AND R. Hockett. Evaluation of arsenic speciation in rainbow trout and fathead minnows from dietary exposure. Presented at Society of Toxicology, October 22, 2012.
Impact/Purpose:
not applicable
Description:
The concentration of total arsenic and various arsenic species were measured in food and fish tissue samples from two dietary arsenic exposures to juvenile fish. For arsenic speciation, samples were extracted with 10% MeOH and analyzed by HPLC/ICPMS. Total arsenic concentrations in the original sample and at various steps in the extraction were measured to evaluate speciation method performance. For one exposure, fathead minnows were fed oligochaete worms that had been exposed to various levels of arsenite in water. Arsenic in the worms was extracted with approximately 75% efficiency. 98% of the arsenic in the food extract remained in an inorganic form, with some being arsenate due to oxidation during storage. For the fish, the extraction efficiency was only 43%. The majority of the final fish extract was an unidentified organoarsenic species (AsX) and only 10% was in an inorganic form, with the remainder being dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA). For the other exposure, rainbow trout were fed a pellet diet spiked with arsenite, DMA, or MMA. For food, arsenic was extracted with 72-100% efficiency and remained in the original form except for ca. 10% conversion of arsenite and MMA to arsenate. For fish, extraction efficiencies were 69-87%. In the fish extracts, the predominant species for the MMA and DMA treatments were the original forms, but there was substantial conversion to AsB and AsX. For the arsenite treatment, 40% of the measured arsenic in the extract remained inorganic, with about 30% being converted to MMA and lesser conversions to DMA and AsX. This differs markedly from the arsenic species distribution for fathead minnow. The fish species also differed in that quantified peaks in the chromatogram accounted for all the total arsenic in the fathead minnow extracts, but less than half for rainbow trout, indicating other species not measured in the latter species.