3.21 - Enzyme Digestion for Speciation of Arsenic

Abstract

Arsenic speciation in biological specimens can provide quantitative data for the evaluation of arsenic toxicity since the toxicity of arsenic can vary significantly depending on the chemical form and oxidation state. Extraction of arsenic from biological specimens is a critical step, prior to arsenic speciation analysis, which often involves high-performance liquid chromatography separation followed by inductively coupled plasma mass spectrometry detection. Mild conditions during extractions are necessary to maintain the integrity of arsenic species originally present in samples, although extraction efficiencies may be compromised under these mild conditions. Enzymatic digestion of biological specimens can be utilized to help improve extraction efficiency. Individual groups of enzymes, such as proteases, lipases, and carbohydrases, as well as various combinations of these enzymes, have been applied for the digestion of proteins, cell lysates, hair, fish tissues, and plant materials. This enzymatic treatment step has been conducted with or without the use of microwave digestion or sonication. The enzyme digestion method not only provides efficient digestion capability to cut matrix macromolecules into small fragments and release arsenic into the extraction solution, but also provides a mild environment in which the chemical integrity of the less stable arsenic species is maintained.