Online element determination in biological and environmental samples by flame AAS coupled with a high-temperature/high-pressure flow digestion system

Abstract

The coupling of a high temperature/high pressure flow digestion system (T_max >300 °C, p_max >30 MPa) to a flame AAS instrument enables an effective and rapid online element determination in biological and environmental matrices. An electrically heated Pt–Ir capillary acts as a digestion tube at a temperature of 320 °C. The reliability of the method is demonstrated by the determination of element traces in various standard reference-materials. The pure digestion time of various matrices (wheat flour, spinach, orchard leaves, tomato leaves, bovine liver, pig kidney, sewage sludge, coal fly ash), as 2% suspensions in 2.5 M HNO₃, is about 1 min, and the time needed for the whole procedure is between 3 and 8 min. Detection limits, based on 2% slurry concentrations, are about 0.25 µg g⁻¹ (Cd), 4.5 µg g⁻¹ (Pb), 2.2 µg g⁻¹ (Cu), 1.4 µg g⁻¹ (Mn) and 0.8 µg g⁻¹ (Zn). Standard deviations were found to be in a range of 2 to 10%. Due to the totally glass-free equipment, samples with a high silicate content can be digested by the addition of hydrofluoric acid.