Fast multi-element screening of non-digested biological materials by slurry introduction to ICP-AES

Abstract

A fast method for direct multi-element analysis of non-digested biological samples is presented. The only sample preparation needed is 1 min homogenization with a Polytron mixer in a small volume of neutral phosphate buffer saline solution (PBS). The total time for analysis (sample preparation and measurement) is 4 min only. This "mix and measure" method can handle large sample loads of biological samples and thus minimize dilution of trace elements. For example 100% whole blood was introduced without any clogging of the introduction system or extinguishing of the plasma. In 70% (v/v) whole blood reference material 14 of 16 analytes were quantified within +/-10% (Al, B, Ba, Ca, Cu, Fe, Mg, Mn, P, Pb, S, Sr, Ti and Zn) and two semi-quantified within +/-20% (Cd and K). Fresh bovine liver was also analyzed with the same method and 7 of 9 analytes were quantified in 5% (w/v) liver slurry. Three different nebulizers were tested, Glass Expansion Concentric (GEC) of Meinhard type, Cross Flow and Burgener T2100 and they performed roughly equally well in giving quantitative results for the slurries but the sensitivity was better with the GEC. The stability of the plasma was studied by evaluating the ratio of Mg 280.270 nm and Mg 285.213 nm lines. When increasing the sample load from 20 to 100% (v/v) of whole blood and from 0.5 to 10% (w/v) of bovine liver the Mg ratio was constant within a few percent for all of the nebulizer tested. The ratio of the sensitivity between GEC and Burgener T2100 was studied and the ratio increased with the energy sum for atomic and ionic lines separately.