Dynamic Four-step Sequential Extraction Procedure Using a Four-channel Circulating Flow System for Extracting Cd, Cu, Pb, and Zn from Solid Environmental Samples.

ABSTRACT

A method for extracting metals from solid samples was developed. The system had four flow channels (each containing a column packed with a solid sample), a single-flow peristaltic pump, and eight six-port valves. An extractant was passed into each channel for a specified period, then the valves were closed. We evaluated the system by performing a four-step sequential extraction procedure to extract heavy metals from a lake sediment sample. The four extractants were, in order of use, magnesium chloride, ammonium acetate, hydroxylamine hydrochloride, and hydrochloric acid. The concentrations of the analytes extracted agreed well with the concentrations determined using the batch method. The system was also successfully used to analyze heavy metals in a soil sample from a parking lot and fly ash from a domestic waste disposal facility. The total amount of extractant required per sample using the system was two-thirds of the amount required using the batch method.