Applications of Arsine Evolution Methods to Environmental Analyses

Abstract

Because of its biological activity, arsenic is involved in an active global geochemical cycle. Arsenic has been found to be transferred to the atmosphere, at least in part, by evolution of trimethyl arsine and similar methyl arsenic compounds. Because of the environmental importance of the several arsenic forms [inorganic arsenic (III) and (V), methylarsonic acid, dimethylarsenic acid, trimethylarsine, methylarsine, and dimethylarsine], chemical methods for their analysis are needed. Sensitive methods are required because environmental concentrations encountered are generally in the range of 0.01 (or lower) to 3 ppb for natural waters and 1-6 ng As/im3 for arsenic in air. Arsine evolution by pH selective reduction permits specific analyses for inorganic As (III) and As (V). Methylarsenic acids may be reduced to corresponding methylarsines with sodium borohydride after which separation permits specific detection of these arsenic compounds. The most sensitive and selective methods combine reduction, separation, and emission type detectors. The intensity of arsenic atomic emission lines is observed. This type of detector provides a lower limit of detection down to 0.02 ng As per sample. The methods have been applied to a variety of environmental samples. The Analytical ProblemExcept for specific ore deposits, arsenic is generally a trace element present in soils and rocks usually in the low parts-per-million range. Higher concentrations of arsenic are found in sedimentary rocks because of its tendancy to coprecipitate with metal hydroxides, carbonates, and silicates in natural sedimentation processes. Natural fresh waters contain generally less than 1 ppb arsenic, while the sea water content is on the order of 3 ppb despite its removal by sedimentation. Arsenic is involved in a global cycle which includes volatile arsenic compounds.Because of its biological activity one finds methylarsenic type compounds in the environment; methylarsonic acid, dimethylarsinic acid, their acid salts, trimethylarsine, and trimethylarsine oxide. The methylarsenic compounds are generally present only in low concentrations compared to inorganic forms. Nevertheless, in certain locations in the environment exhibiting high biological activity, the methylarsenic compounds may be present in

Accumulation of heavy metals by vegetables grown in mine wastes

“…Calibration of the instrument involved a five‐point calibration curve while checking the calibration every 10 to 20 samples. For analysis of arsenic, hydride generation was used to produce arsine gas, which was subsequently detected in a long path absorbence cell [33]. Reagents used in arsenic analysis were 10 N HCl and a solution containing 0.6% NaBH 4 and 0.5% NaOH.…”

Response: Accuracy, Arsenic, and Cancer

“…This corresponds to 4 ppb blood As (4 pg/l). The 1977 comprehensive and contemporaneous review by Braman (28) for quantitative analysis of various As species via hydride generation summarized various papers showing sensitivity for flame AAS analysis of As after hydride generation is a lower detection limit of 5 ppb on a concentration basis, similar to the reported Kang and Valentine value (27).…”

Epidemiology and Toxicology of Arsenic Poisoning in Domestic Animals

“…In diagnosis of arsenic intoxication, wet chemistry tests, such as the Reinsch test (13), are used as a screening tool; and, if positive, then more definitive chemical analysis must be used to quantitate the levels of arsenic; e.g., arsine evolution (14). A positive test does not conclusively confirm arsenic intoxication, for this test is sensitive to as little as 2 ppm of arsenic.…”