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Copper matrix-matched calibration samples were prepared by doping high purity copper powders (99.999%, 500–600 μm) with multi-element standard solutions with a total of 72 elements, and then the relative sensitivity factors (RSFs) of the 72 elements in both microsecond-pulsed and continuous direct current (dc) modes were determined by using Element GD type glow discharge mass spectrometry (GD-MS). The ability of pulsed and continuous dc-GD-MS to quantitatively determine trace elements in copper was demonstrated after calibration using the RSFs. The results showed that the uncertainty level of GD-MS analysis after calibration was comparable with that of ICP-MS and ICP-OES analysis. In order to standardize calibration sample preparation procedures, the doping concentration, pressed powder tablet compactness and tablet homogeneity were optimized. Good recovery (85% to 115%) was obtained. Good pressed powder tablet compactness and tablet homogeneity were obtained, which were expressed as relative standard deviations (<5%) of 6 times GD-MS analysis. Satisfactory repeatability of about 15% (RSD) for continuous and 10% (RSD) for pulsed dc-GD-MS was obtained by strictly controlling the intensity of the matrix to keep it stable when replacing graphite parts. Good reproducibility (RSD < 10%) was obtained after timely detector calibration, so the determined RSFs could remain constant and valid in an instrument for a long time. Under the optimized conditions mentioned above, the RSFs of the total 72 elements in both continuous and pulsed modes were determined and compared. The comparison of RSFs showed that the general trends of the two sets of RSFs were very similar; however, the RSFs in pulsed mode were 2–40% lower than those in continuous mode in most cases. Therefore, a dedicated RSF table for each mode is recommended to achieve accurate and quantitative analysis. The comparison of RSFs in this work with standard RSFs provided by the manufacturer of Element GD revealed that the accepted uncertainty of a factor of two was met for almost all investigated elements in both modes. The accuracy of the RSFs was validated by analyzing three Cu-matrix CRMs. The relative expanded uncertainties (Urel, k = 2) of measured results by using pulsed dc-GD-MS, including the uncertainty of measurement repeatability and RSF, were less than 20%, which was much lower than those obtained by continuous dc-GD-MS (Urel < 30%). [ABSTRACT FROM AUTHOR]

Glow discharge mass spectrometry (GDMS) with its high resolution, low limit of determination and wide linear dynamic range is a powerful technique for direct analysis of high purity solid metals. Similar to the drawback of other direct solid sampling methods, a drawback of this technique is the lack of appropriate pure certified reference materials to calibrate the instrument, so that it is often used for semi-quantity analysis. A new calibration procedure using synthetic calibration samples by the doping-melting method was developed to obtain more accurate and traceable analytical results. The calibration samples were prepared from high purity copper powder doped with standard solutions of graduated and defined concentration. And then a part of them was melted into bulks and another was pressed to tablets. The homogeneity of both types of samples was measured by GDMS and for the doped tablets, relative deviations of the IBRs of both sides for 45 elements were mostly less than 10%. For the doped bulks, some problems such as the segregation effect and analyte losses happened for most elements; so satisfactory homogeneity was obtained for only 9 elements, for which nearly all relative deviations of the IBRs of both sides were less than 5%. Relative sensitivity factors of 9 and 45 elements in the copper matrix were obtained by calibration of GDMS with doped bulks and doped tablets, respectively. The RSF values obtained by calibration with doped tablets were compared with values derived from standard RSFs and the large differences demonstrated that matrix-adapted calibration was necessary when the impurities were measured accurately by using the instrument, especially for the rare earth elements. Then the 9 RSFs determined using tablets and bulks were compared and the results showed that relative deviations of them in most cases were less than 10%. The correlation coefficients of the calibration curves obtained by using the doping-melting method were better than those obtained using the doping-pressed method and the uncertainties of RSFs were smaller. Several copper CRMs were measured to validate the calibration procedures. The results revealed that the measured values using the two types of calibration samples were in agreement with the certified values. The results revealed that the calibration results of Fe and Ni coming from calibration samples prepared by using the two types of methods were in agreement with the certified values. [ABSTRACT FROM AUTHOR]