Determination of trace elements in oils and greases with total reflection X-ray fluorescence: sample preparation methods

Abstract

Samples of mineral and vegetable oils are analysed with total reflection X-ray fluorescence (TXRF) using different sample preparation techniques. Direct preparation from diluted solutions of oils as the simplest method yields good results for trace element concentrations above 1 μg g . In the sub ppm range, ashing in a low temperature O 2-plasma is shown to be the method of choice, leading to detection limits of a few ng g and yet requiring not much effort. Two other methods—digestion with nitric acid, and extraction of trace elements into aqueous solution—were tested and rejected as being ineffective. Results of recovery experiments are given, and correctness of results is assured by the analysis of SRM 1634b which yields excellent agreement. The methods are also applicable to greasy sample materials