A method for the determination of the thickness and composition of zinc‐based coatings on steel has been developed. The method is based on direct current glow discharge optical emission spectroscopy (GD‐OES). Six different types of coated materials supplied by five major European steel producers have been used to develop and evaluate the method. The types of coatings are hot‐dipped zinc, electroplated zinc, electroplated ZnNi, Galvanneal (electroplated and annealed ZnFe), Galfan (hot‐dipped Zn95Al5 alloy) and Aluzink (hot‐dipped Zn43Al55Si2 alloy). In the research phase, the range of suitable analytical conditions for these materials was established. Based on these results, a preliminary standard method was established. The method is based on calibration of the emitted light per unit weight of each element. It is recommended that Certified Reference Materials (CRM/s) are used for calibration, and a range of alloy types can be used (multi‐matrix calibration). An interlaboratory comparison based on the preliminary standard method was carried out, involving 12 laboratories from eight countries, using nine different types of glow discharge spectrometers. The results show that the method works very well for accurate and rapid determination of the major element (Zn) and the coating thickness. The concentrations of alloying elements also could be determined very accurately, but the interlaboratory variations were generally too high. Based on these results, several amendments to the standard method have been suggested. Copyright © 1999 John Wiley & Sons, Ltd.

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Large-volume injection using a system consisting of packed column GC, serially connected to capillary GC, and coupled to a microwave-induced plasma atomic emission spectrometric (MIP-AES) detector is described. The greater sample capacity of the packed column is exploited to allow large-volume injections to be accommodated. Preliminary chromatographic separation of the solvent and mercury species on the packed pre-column permits selective transfer of the analytes to a capillary GC system. There, the mercury species can be focused and further separated on the analytical column, minimizing the risks of extinguishing the plasma due to excess solvent reaching the MIP, and stationary phase or detector fouling, which accompany large-volume injections using alternative methods. Application to the determination of mercury species in natural waters following solid-phase extraction on a dithiocarbamate resin, elution into acidic thiourea, complexometric extraction into hexane and Grignard derivatization is used to illustrate the benefits and limitations of this approach. The relative limit of detection obtained for methylmercury is 8 pg 1-1 utilizing 50 pl injection on to the packed pre-column, compared with 40 pg 1-1 for direct injection of 13 pl into the capillary GC-MIP-AES system. This improved performance has enabled more detailed kinetic studies of the uptake of methylmercury from humic-rich natural waters on the dithiocarbamate resin to be undertaken, and shows that incipient and added analyte behave differently during enrichment, which may have implications for the use of spiking during method development.

SwedenGlow discharge optical emission spectroscopy (GD-OES) as a depth profiling teohnique is briefly reviewed, The quantification technique based on emission yields, defin8d as the analytical signal per unit weight of the analyte, is described. Current standardisation work on applications to zinc and aluminium based metallic ooatings is reviewed. Recent work on non-conduotive applications using radio frequency (RF) sources is presented. It is shown that practioal possibilities to determine disoharge parameters exist, but is more complex to use than for the DC source. Furthermore, the strong influence of hydrogen on emission yields is demonstrated. A "matnx correction" technique to deal with this probl8m is discussed. It is also shown that in spite of all the corrective measures, there still exist artefacts not completely understood, making it neoessary to do "matrix-matched" calibrations for certain applications. For thin film applications, it is demonstrated that state-of-the-art GD-OES system8 are capable of a depth resolution similar to e.g. SIMS and AES. For quantifioation of very thin layers, the hydrogen corr80tion must be considered, In addition, it is shown that short-lived molecular emission oan influence the analyiioal results. A method to deal with this effect is presented and discussed,