Trace element determination in leather samples using on-line internal standardization, ultrasonic nebulization and axial view-ICP OES

Abstract

A method has been developed to determine 15 elements in leather samples by ultrasonic nebulization axial view inductively coupled plasma optical emission spectrometry (USN-ICP OES) after calibration by on-line internal standardization (IS). Samples were ground in a lab blender and decomposed following a simple digestion protocol with nitric acid and hydrogen peroxide under microwave heating. Owing to the high chromium content in samples, judicious selection of analytical wavelengths was necessary, as well as the use of internal standardization on-line to compensate for matrix effects caused by sample loading on the nebulizer system and the ICP-source. Low-biased results were obtained by simple external calibration with aqueous standards. Unpredictable plasma-related matrix effects caused signal suppression that cannot be corrected by acid matrix-matched reinforcing of the major role of IS. Even though no reference material for leather samples is commercially available, two certified biological samples were used to estimate the accuracy (dogfish liver and bovine liver) of the proposed procedure. The experimental values achieved showed good agreement with the certified values only if IS was employed throughout. Spike and recovery experiments confirmed that the results of the proposed method were accurate. Fifteen elements were quantified in different leather samples, and indicated the presence of toxic elements, which were mainly Pb, Cd, Zn, V, Ni and Cr.