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For the solid sampling techniques laser ablation and the slurry technique, the influence of simultaneous measurement vs. sequential measurement of the signal and background and the internal standard was investigated on an identical data set. The experiments were carried out with an array spectrometer, which generates spectra rather than single points. These spectra, typically measured around the analyte wavelength, are measured simultaneously. The ICP spectrometer used has a `profiling' mode, whereby the entrance slit is moved fourfold and the spectra are recorded with a small spectral shift in a sequential manner. These images are then combined to form a spectrum which is composed of simultaneous and sequential measured data. Hence, by carefully selecting the data points in a measured spectrum, the difference between simultaneous and sequential measurements can be estimated from an identical data set. In the example studied, simultaneous background correction and simultaneous internal standardization (typical for array ICP-OES) gave a mean RSD of 3.6%, sequential background correction and simultaneous internal standardization (typical for simultaneous ICP-OES) produced an average RSD of 6.1% and sequential background correction and sequential internal standardization (typical for sequential ICP-OES) resulted in a mean RSD of 6.4%. The RSDs reflect the solid sampling procedure. Some applications of laser ablation and slurry sampling are presented.
Nölte et al. (Fri,) studied this question.