Application of laser-induced breakdown spectrometry for direct determination of trace elements in starch-based flours

Abstract

Spatially resolved laser-induced breakdown spectrometry (LIBS) was investigated to evaluate the feasibility as a quick and simple method to analyze trace elemental concentrations in starch-based flour samples. A Nd∶YAG laser beam (λ = 1064 nm, 30 mJ pulse−1) has been used for generation of laser-induced plasma on sample surface under reduced pressure of argon atmosphere. A series of starch powder samples containing different concentrations of Sr, Mg, Al, Cu, Cr, K, Mn, Rb, Cd, and Pb were used to construct the calibration curves and estimate detection limits of measurements. The calibration graphs for all elements show good linearity (correlation coefficient, r > 0.99) in the range 0–160 µg g−1 or within three orders of magnitude. Detection limits achieved were below 18 µg g−1 for all elements studied in this work. The lowest detection limit (0.3 µg g−1) was obtained from Sr measurement. Precision (%RSD) for the selected analysis was in the range 2–10%. The standard addition method was applied to assess the accuracy of LIBS using a NIES standard rice sample. The concentrations of Mg and Mn in NIES standard rice sample determined by spatially resolved LIBS technique have good agreements with those of certified value within an error range. The results indicate that spatially resolved LIBS has been shown to be an accurate technique for determining trace elements of ppm (µg g−1) level in starch-based food samples directly with an acceptable precision without any tedious digestion and dilution procedure.