Direct flame solid sampling for atomic absorption spectrometry: determination of copper in bovine liver

Abstract

In this work a new device for the direct introduction of solid samples into flame atomizers is proposed. The determination of copper in bovine liver reference material by flame atomic absorption spectrometry (FAAS) using a conventional air–acetylene flame was chosen as an example. Between 0.05 and 0.50 mg of the test sample was weighed directly into a small polyethylene vial connected to a glass chamber. A flow of air carries the test sample as a dry aerosol to a T-shaped quartz cell positioned above the burner in the optical path. The atomic vapor generated produces a transient signal of less than 3-s duration; integrated absorbance is used for signal evaluation. Optimized conditions for air flow rate, flame stoichiometry, etc., were evaluated. There was no statistical difference between the results from the proposed system, compared with those obtained by prior sample digestion and determination by conventional FAAS. No excessive grinding of the samples was required and samples with particle size less than 80 μm were used throughout. Background signals were always low and a characteristic mass of 1.5 ng was found for Cu. The proposed system allows the determination of 60 test samples in 1 h and it can be easily adapted to conventional atomic absorption spectrometers.