DETERMINATION OF TRACE-METALS IN CRUDE-OIL BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY WITH MICROEMULSION SAMPLE INTRODUCTION

A new technique is described for introducing crude oils directly into an inductively coupled plasma mass spectrometer. This technique is based on the formation of oil-in-water microemulsions and greatly simplifies the determination of trace metals in oil. The advantages of the microemulsion ICPMS method include rapid multielement detection, ease of sample preparation, long-term sample stability, and low detection limits. Accuracy and precision are on the order of +/- 3%. Oils that contain metals in the concentration range of 0.1 to several hundred parts per million can be analyzed routinely. The upper end of this range can be extended by simple aqueous dilution of the microemulsion. Because the sample solutions are composed primarily of water, there is no carbon buildup on the mass spectrometer interface. Other petroleum based materials such as gasolines, diesel fuels, lubricating oils, residual oils, and asphaltenes can also be analyzed with this methodology.