Blending procedure for the cytosolic preparation of mussel samples for AAS determination of Cd, Cr, Cu, Pb, and Zn bound to low molecular weight compounds

摘要

Simple methods for the determination of Cd, Cr, Cu, Pb, and Zn fractions bound to low molecular weight compounds (presumably metallothionein-like proteins) in mussels (Mytilus edulis) have been developed. The methods involve the novel application of using a blending (Stomacher) rather than a cutting mixer device to perform the homogenization between the fresh mussel tissue and the extractant solution [10 mM TRIS-HCl buffer at pH 7.4 with 5 mM 2-mercaptoethanol (2-MCE), 0.01 mM phenylmethylsulfonyl fluoride (PMSF), and 25 mM sodium chloride]. Optimum conditions for the cytosolic preparation (after an experimental design approach) were a ratio of sample weight: extracting volume of 0.2 g/mL and a blending time of 5 min. The Cu and Zn concentrations bound to low molecular weight compounds (LMW proteins) were measured by flame atomic absorption spectrometry using a high performance nebulizer, while Cd, Cr, and Pb levels in the cytosolic solutions were assessed by electrothermal atomic absorption spectrometry. A microwave-assisted acid digestion procedure was also applied to determine the total metal concentration. The limits of detection (LOD) for Cd, Cr, and Pb were 0.7, 3.0, and 6 6 ng g(-1) respectively and for Cu and Zn they were 0.05 and 0.01 mug g(-1) respectively. The methods were applied to 16 mussel samples from the Ria de Arousa estuary. [References: 20]