Feasibility study of calibration strategy for direct quantitative measurement of K and Mg in plant material by laser-induced breakdown spectrometry

The calibration and quantitative measurement is the “Achilles heel” of the LIBS technique. This paper deals with a method developed for the direct measurement of K and Mg in plant samples. Instrumental parameters were optimized and the best condition found was a 50 μm spot size, 10 Hz laser repetition rate, 75 accumulated laser pulses with 25 mJ/pulse and 0.25 μs of delay time. For method calibration, the use of synthetic standard calibrating material prepared by the addition of increasing concentrations of K and Mg in wood, filter paper and babassu mesocarp was proposed in order to assess the feasibility of using these various matrices in plant samples analysis. The limits of detection of proposed method were 2–30 and 6–27 μg g⁻¹ for K and Mg, respectively. The use of the carbon emission wavelength at 247.856 nm was used as internal standard to improve the analytical results. Certified reference materials of plants were used to check the accuracy of the proposed method and recovery around 82% and 100% were obtained in all cases.