Mineral elements contained in commercially available milk powders, including seven infant formulae and one adult milk, were analyzed with inductively coupled plasma atomic emission spectrometry (ICP-AES) and laser-induced breakdown spectroscopy (LIBS). The purpose of this work was, through a direct comparison of the analytical results, to provide an assessment of the performance of LIBS, and especially of the procedure of calibration-free LIBS (CF-LIBS), to deal with organic compounds such as milk powders. In our experiments, the matrix effect was clearly observed affecting the analytical results each time laser ablation was employed for sampling. Such effect was in addition directly observed by determining the physical parameters of the plasmas induced on the different samples. The CF-LIBS procedure was implemented to deduce the concentrations of Mg and K with Ca as the internal reference element. Quantitative analytical results with CF-LIBS were validated with ICP-AES measurements and nominal concentrations specified for commercial milks. The obtained good results with the CF-LIBS procedure demonstrate its capacity to take into account the difference in physical parameters of the plasma in the calculation of the concentrations of mineral elements, which allows a significant reduction of the matrix effect related to laser ablation. We finally discuss the way to optimize the implementation of the CF-LIBS procedure for the analysis of mineral elements in organic materials.

No abstract

International audienceIn this work quantitative analysis of minor and trace elements in fly ash by nanosecond laser ablation (LA)-ICP-MS and LA-ICP-OES was investigated in terms of detection limits and accuracy. Different binders and modifiers (silver or chromophores) were added to the fly ash powder to prepare mechanically stable pellets and improve sensitivity (signal to concentration ratio). Maleic acid was found to provide a higher degree of homogeneity between sensitivities across the different fly ashes tested. Ashes were from different origins: domestic waste incinerator or ashes from various coal-fired power plants. A calibration procedure using reference materials as standards was employed, the LAI-CP-MS analysis gave an acceptable accuracy (estimated from NIST 1633), better results were obtained using fused bead preparation. The use of the LA-ICP-OES system gave, when possible (higher concentrations), good results in terms of detection limits (1 to 11 mu g g(-1)) and accuracy