Analysis of S and CI in Waste Oil Using an Ag-anode X-ray Tube

Abstract

Waste oil with high chlorine concentrations is hazardous and must be treated differently than other waste oils. A common problem with the analysis of chlorine by EDXRF is the line overlap with sulfur due to the often-high concentrations of sulfur in waste oils.

Introduction

This data sheet demonstrates that the Epsilon 4 – a benchtop energy dispersive X-ray fluorescence (EDXRF) spectrometer – is capable of analyzing sulfur and chlorine in waste oil, without the need of helium.

Application background

Waste oil with high chlorine concentrations (several countries: > 0.1 wt %) is considered to be hazardous and must be treated differently than other waste oils. A common problem with the analysis of chlorine by energy dispersive XRF is the line overlap with sulfur due to the often high concentrations of sulfur in waste oils. The Epsilon 4 is equipped with a high resolution SDD detector, which improves the separation of S Kα, S Kβ and Cl Kα peaks. This improved separation leads to better quantification of S and Cl down to very low concentration levels, Figure 1. Moreover, use of a Ag-anode X-ray tube overcomes the common problem of tube lines overlapping the S Kα peak. In this way, improved accuracy and lowered limits of detection are achieved, compared to commonly used Rh- or Pd-anode X-ray tubes.

Figure 1. Spectrum detail of standard #4 containing 0.01 wt% Cl and 0.5wt% S, demonstrating separation of S and Cl peaks

Instrumentation

Measurements were performed using the Epsilon 4 EDXRF spectrometer, equipped with a 10 W, 50 kV Ag-anode X-ray tube, 6 filters, a helium purge facility, a high resolution silicon drift detector, a sample spinner and a 10-position removable sample tray.

Sample preparation

A series of commercially available mineral oil standards manufactured by VHG Labs, Inc. (U.S.) were used to set up a calibration with varying amounts of S and Cl. The concentration range of the standards was 0 to 0.5 wt% for S and 0 to 0.05 wt% for Cl. Seven grams of each standard were analyzed in 45 mm diameter disposable sample cells using a 3.5 μm Mylar supporting film.

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