Determination of iron and zinc in adipose tissue by on-line microwave-assisted mineralization and flow-injection graphite furnace atomic absorption spectrometry

Flow injection was used to develop an on-line automated focused microwave assisted procedure for the mineralization of adipose tissue and the determination of iron and zinc by graphite furnace atomic absorption spectrometry. Mineralization of samples was accomplished with a mixture of sulfuric and nitric acid and by the alternative exposition of the sampling unit in the microwave irradiated zone. Additional flows of Triton × -100 and Pd-Mg matrix modifier were introduced to avoid detrimental accumulation of solids on the wall of the tubing and to minimize matrix interference effects, respectively. Selected aliquots of mineralized samples were introduced with a sampling arm assembly, by means of air dispositive displacement, into the graphite tube atomizer. The entire system was controlled by a computer, independent of the spectrometer. The analysis of adipose tissue containing 2.3–8.6 and 1.5–4.4 μg g−1 of iron and zinc, respectively, with good precision and accuracy was possible. The main advantage of the method is that the determination of iron and zinc in adipose tissue is performed in a totally closed system with a minimum of sample manipulation, exposure to the environment and minimum operator attention.