Simultaneous sample digestion and determination of Cd, Cu and Pb in biological samples using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) with slurry sample introduction

Abstract

In a Ni tube placed in an oxidizing air/acetylene AAS flame simultaneous digestion/oxidation of biological samples and powerful trace determinations were performed. A ceramic capillary was used for sample introduction. This capillary acted as a flame-heated thermospray nozzle (TS-FF-AAS). Slurry samples, prepared in 0.3 mol L⁻¹ HNO₃, were transported by a new 0.6 MPa (84 psi) flow injection system through the hot capillary into the flame tube furnace. A nitric acid vapour environment exists inside the tube at temperatures above 1000 °C oxidising the samples. The element traces could then be measured by AAS. For these investigations, 300 µL slurry samples (0.1 to 1.0% w/v) from various biological materials, such as pig kidney (CRM 186), bovine liver (SRM 1577), spinach (SRM 1570), orchard leaves (SRM 1571) citrus leaves (SRM 1572), tomato leaves (SRM 1573) and tomato puree were used. Reference values were additionally obtained by electrothermal atomic absorption spectrometry (ETAAS). The standard deviation (n = 10) was between 3 and 5% using the same slurry and about 10% when the whole process was repeated on subsequent days. The detection limits for Cd, Cu and Pb were found to be 0.5, 4.3 and 3.5 µg g⁻¹, respectively. A t-test showed no differences between the found and certified values at a 95% confidence level. In all experiments the calibration could be performed with aqueous standard solutions.