A systematic approach to optimum working conditions with inductively coupled plasma atomic emission spectrometry

Abstract

Optimum experimental factors were determined for the analytical determination of Al, Cd, Fe, Pb, and Zn by ICP atomic emission spectrometry. Based on systematically determined factor levels, working conditions were found that gave similar, and sometimes better results compared with the hitherto used levels of factors. All measurements were performed with a sampling time of 150 ms as often used in routine analysis in the laboratory. This optimization resulted in a reduced outer plasma gas flow from 15 L/min argon to 12 L/min without any relevant changes of the achievable detection limits. A serious problem was that only one analytical line of Al could be used. A comparison with the lower limit of application (comparable with the detection limit) from German directive DIN 38406, part 22 ([1]), showed that the detection limits of Al and Fe are superior, whereas for Cd there was only little improvement. The detection limits of Zn and especially Pb are always higher than the lower range of application under these conditions. Therefore, the use of two device-parameter sets for hard and soft lines, respectively, is strongly suggested. Maps with the observed signal-to-noise-ratios were systematically acquired for each element analyzed in connection with different strategies for optimum search. mon compromise condition (combined analysis) and the limits of quantification demanded in the German directive DIN 38406, part 22 [1]. Only four, but the most important, experimental factors were changed, the other experimental factors were always kept constant (Tables 1 and 2).

Nonmetals in the argon–inductively coupled plasma–optical emission spectrometry: I. Phosphorus, sulfur and carbon

“…It is remarkable that this compromise set is extremely different from the one found for metals in [1]. This is not problematic if the ICP-OES device has two spectrometers like the one used in this investigation.…”

“…However, as shown in [5] even this poor detection limit of about 3 mg/L can be usefully applied to quality control in steel products, where often a content of 25-50 mg/L is of interest. Due to its high detection limit, the weight factor of sulfur was dominant in the weighted compromise conditions (calculated as described in [1]), this can easily be seen in the contour-plots.…”

“…The analysis of the signal-to-noise data and the determination of the optimum followed the procedure described in [1], the weighted optimization was used. To improve readability the resulting contour-plot was normalized to the range 0-100.…”

“…1 Signal-to-noise maps for phosphorus lines tour-plot. In the contour-plots presented here, the x and y-axis are exchanged compared with those cited in [1], this has the advantage that the visual image resembles more the image of a vertical plasma viewed through a narrow optical filter.…”

“…Furthermore, optimal conditions are often reported for only one element, but if high sample throughput is required an efficient compromise must be found. To get such compromise conditions we used here the method published earlier in [1] for multielement optimization with a radially viewed plasma. This method has the advantage that it permits an immediate visual feedback without a factorial design or a simplex method, which are often not available for simultaneous multielement analysis in the existing ICP-OES software.…”