RESUMEN
The almost-two-centuries history of spectrochemical analysis has generated a body of literature so vast that it has become nearly intractable for experts, much less for those wishing to enter the field. Authoritative, focused reviews help to address this problem but become so granular that the overall directions of the field are lost. This broader perspective can be provided partially by general overviews but then the thinking, experimental details, theoretical underpinnings and instrumental innovations of the original work must be sacrificed. In the present compilation, this dilemma is overcome by assembling the most impactful publications in the area of analytical atomic spectrometry. Each entry was proposed by at least one current expert in the field and supported by a narrative that justifies its inclusion. The entries were then assembled into a coherent sequence and returned to contributors for a round-robin review.
RESUMEN
This work is focused on rapid quantitative analysis of slag in the steel industry for improved process control. The novel approach in this work is a direct comparison of two methods to calibrate and quantify spectral data from the slags. Calibration was first done with the most prevalent method in quantitative optical emission spectroscopy (OES) of solids, the univariate ratio method. The second method is an advanced multivariate analysis (MVA) algorithm termed Elastic Net, allowing to include several lines for each element in the calibration functions. In both methods, the output is mass fraction ratios of the analyte element (or compound) to a matrix element (compound). The actual mass fractions of each compound are calculated by sum normalization assuming the matrix to make up the difference up to 100%. The metric used to evaluate the performance of the methods in terms of accuracy is the parameter σrel calculated as the ratio of the root mean square (RMS) deviation from values obtained by X-ray fluorescence (XRF) divided by the average mass fraction of the compound, expressed in percent. A bit surprising, the main outcome of the comparison is that there is very little difference in the performance of the two methods. One exception is the analysis of MgO, where the elastic net gives significantly better accuracy. Presumably, this is due to the use of multiple lines for Mg to build the calibration function. This is very encouraging, since MgO is a major compound in most slags that needs to be determined accurately. It is suggested to improve accuracy further by means of separate calibrations for a limited number of slag types.
RESUMEN
This review paper describes the evolution of the quantification procedure for compositional depth profiling (CDP) in glow discharge optical emission spectrometry (GD-OES), based on the constant emission yield concept. The concept of emission yield (EY) is defined and ways of measuring it experimentally are discussed. The history of the development of quantitative CDP is reviewed, which shows that all of the different approaches depend on the assumption that the EY is essentially a matrix-independent quantity. Particular emphasis is placed on the dependence of the EY on the plasma parameters of current, voltage, power and pressure. In short, impedance changes (current voltage) can significantly affect the emission yield and should either be corrected mathematically or the impedance should be kept constant by pressure regulation in order to obtain reliable results from GDOES CDP. On the other hand, the effect of varying the pressure on the emission yield can be considered to be minor within the limits of practical operating conditions for most CDP applications. It is worth, however, bearing in mind that varying the discharge pressure has a significant effect on the plasma processes, and does affect the emission yield when these variations are large. The experimental results obtained for the emission yield are related to the results from theoretical model calculations published on the subject.
