Sequential determination of Sb and Sn in used lubricating oil by electrothermal atomic absorption spectrometry using Ru as a permanent modifier and microemulsion sample introduction

An electrothermal atomic absorption spectrometric (ETAAS) method for the sequential determination of antimony and tin in used lubricating oil was developed. A graphite tube, treated with ruthenium as a permanent modifier, was used in order to make possible pyrolysis of the oil matrix at a high temperature without significant loss of the elements of interest. The permanent modifier also simplified the analytical procedure. The used lubricating oil was introduced into the furnace as an oil-in-water micro-emulsion in order to make possible calibration by direct comparison with aqueous standards as well as to make the sampling easy and repeatable. The determination was performed sequentially using the multi-element sequential routine provided by the atomic absorption spectrometer employed. Good recoveries for Sb (based on spiked samples) and Sn (based on certified reference materials) were achieved, and sub-mu g l(-1) limits of detection (3s(b)) were estimated for both elements.