OPTIMIZATION OF ARSENIC SUPERCRITICAL-FLUID EXTRACTION WITH DETECTION BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

Arsenic has been extracted from a certified reference material (CRM) DORM-1 Dogfish Muscle, National Research Council of Canada, by supercritical fluid extraction. The majority of the arsenic species present in this sample are organic in nature, while the more toxic inorganic forms, As(III) and As(V), are present only in very small amounts. A simple statistical experimental design was used for the optimization of extraction parameters in order to determine the best conditions while performing the minimum number of experiments. The initial parameters investigated were temperature of the extraction chamber and pressure of the supercritical fluid. The amount of methanol modifier added to the supercritical fluid, as well as the total time of extraction, were also investigated. The optimum extraction conditions found for the extraction of arsenic from the CRM DORM-1 include an extraction chamber temperature of 60-degrees-C, supercritical fluid pressure of 5500 psi (1 psi = 68.95 Pa), and the addition of 20% methanol modifier for 10 min extractions. These conditions produce total arsenic recoveries of 57 +/- 8% based on the certified value. Preliminary high-performance liquid chromatography data indicate that at least some of the original arsenic species were maintained throughout the extraction process.