Solid–liquid extraction of copper from slurried samples using high intensity probe sonication for electrothermal atomic absorption spectrometry

A fast and simple method is proposed for determination of copper by electrothermal atomic absorption spectrometry in biological samples. Pulverized solid samples were placed in autosampler cups, slurried in an acidic diluent and subsequently treated by sonication under optimized conditions. Parameters influencing extraction such as sonication time, ultrasound amplitude, acid concentration and particle size were optimized so that quantitative copper recovery could be achieved. Quantitative recoveries for copper in mussel tissue were obtained using a 3 min sonication time, a 60% ultrasound amplitude, a 3% V/V HNO3 concentration along with a particle size of the solid particles less than 50 μm. Under these extraction conditions, quantitative recovery of copper was also seen to be achieved for several certified reference materials such as BCR 278 mussel tissue, NRCC DORM-2 dogfish muscle and BCR CRM 60 (Lagarosiphon major) aquatic plant. The LOD of copper in the biological samples was 0.16 μg g−1 when a sample mass of 10 mg were slurried in a volume of 1.5 ml. When comparing within- and between-batch precision values no significant differences occurred, hence indicating good homogeneity at the 10 mg mass level. Potential advantages of the method proposed over conventional slurry sampling such as an improved precision, since the representative subsample is the whole mass weighed in the autosampler cup, a decreased build-up of carbonaceous residues inside the graphite tube and the removal of volumetric and sedimentation errors can be anticipated.