On-line separation and determination of trace amounts of manganese in biological samples by flow injection inductively coupled plasma atomic emission spectrometry

A procedure is developed for the determination of Mn in biological samples by FI-ICP-AES acid eluates after preconcentration of the samples. The preconcentration step is performed on a 3 cm x 3 mm column packed with silica gel functionalized with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide (DPTH-gel) and placed in the injection valve of a simple flow manifold. The sorbed element is subsequently eluted with nitric acid. The acid eluate is analyzed by ICP-AES. Five variables (sample flow rate, eluent flow rate, eluent concentration, pH, and buffer concentration) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using Response Surface Methodology (RSM) and based on sequential experimental Doehlert designs. The performance characteristics of the determination of manganese with DPTH-gel was: detection limits, 1.5 ng mL(-1), precision (RSD) 0.5% for 100 ng mL(-1), and enrichment factors, 26 using 60 s preconcentration time. The sampling frequency was 40 h(-1). The accuracy of the method was demonstrated by the analysis of certified reference biological samples. The results showed good agreement with the certified values.