Matrix importance in animal material pre-treatment for metal determination

A relatively cheap and accessible way to analyze difficult samples without loss of analyte was optimized for determination of Cd, Cr, Cu, Hg, Ni, Pb, V and Zn in animal material. Reference materials with suitable matrix were used: Dorm-2 (Dogfish Muscle), Tort-2 (Lobster Hepatopancreas), and SRM 2976 (Mussel Tissue). The analytical procedure included digestion of the sample in Parr reactor bombs combined with a commercial microwave oven and metals analysis by atomic absorption spectrometry. A weak digestion procedure was optimized to prevent metal losses: a two-step digestion with an aqueous solution of HNO3, each step carried at a microwave power of 340 W during 4 min. With the optimized procedure, metals concentrations in all reference materials matched certified ones (for a 95% level of confidence) with the exception of Cd in Tort-2 and Hg in SRM 2976. The present work reinforces the need to use matrix-matched reference materials and that any digestion protocol needs to be modified to maximize recoveries.