Direct determination of metals in organics by inductively coupled plasma atomic emission spectrometry in aqueous matrices.

A simple method for the simultaneous determination of up to 21 elements in organic matrices is proposed. Organic samples are simply dispersed in concentrated nitric acid by sonication, and the resulting emulsions/suspensions are directly aspirated into an inductively coupled plasma atomic emission spectrometer (ICP-AES) calibrated with aqueous standards for analysis. Proof of concept was provided by the excellent recoveries for the analysis of a 21-element metallo-organic standard. In addition, the results obtained using this method for a waste oil sample compared favorably with those from a method that utilized microwave digestion for sample preparation. Comparable results were also obtained by dilution in an organic solvent followed by ICP-AES analysis with an ultrasonic nebulizer equipped with a membrane desolvator. Furthermore, the viability and validity of this method were confirmed by the analysis of the National Institute of Standards and Technology standard reference material 1084a Wear-Metals in Lubricating Oil. Spike recoveries ranged from 83 to 105% and the limits of quantitation were 6 microg g(-1) or less for all the elements analyzed.