Direct Simultaneous Determination of Iron and Copper Content in Used Greases by X-ray Fluorescence Method

Abstract

Direct simultaneous determination of iron and copper content in used greases by X-ray fluorescence method has been investigated. The following conclusions were obtained from the experimental results.(1) Standard samples containing iron and copper were separately prepared by adding Fe2O3 and Cu-naphthenate to new Li-grease and Na-grease to give 0.003-1.5wt% iron content and 0.002-0.02wt% copper content, respectively. Colorimetric analysis values of iron content and chemical analysis values of copper content in these standard samples were used as standard values. The precision of this method for determining iron and copper content, when using a small sample holder (0.8g grease), was as follows: The standard deviation of the X-ray fluorescence method was 6.5% at the lower range of iron concentrations and 1.5% at the higher range of iron concentrations and that of copper was 2.6%. And also, the standard deviation obtained from the difference between colorimetric and X-ray results was 7.5% at the lower range of iron concentrations and 1.6% at the higher range of iron concentrations, and that of copper was 3.4%.(2) The X-ray fluorescence analytical results of iron and copper content in various grease samples which were used in field test of motor cars checked well with the results of colorimetric analysis. And also, there were no differences between the analytical results obtained using a small holder (0.8g) and these using a large holder (2.0g) in the determination of iron and copper content in used greases by X-ray fluorescence method.(3) As this procedure is a direct method, simultaneously determining iron and copper content in greases without ashing treatment, this is a simple and rapid (20-25 minute/one sample) method suitable for routine analysis.