LIBS analysis of crop plants

Abstract

A fast and cheap method for the analysis of macronutrients (K, P, Mg and Ca) in leaves of crop plants (wheat, poppy, barley and rape) using double pulse laser induced breakdown spectrometry (LIBS) is suggested. A commercially available LIBS spectrometer was calibrated with the aid of authentic plant samples previously analysed by AAS and ICP-OES after microwave digestion. The concentration ranges of K, P, Mg and Ca in the calibration standards were 30–66; 2.8–6.6; 1.0–5.6 and 6–24 g kg⁻¹, respectively. Cryogenic grinding and powder pressing to pellets were used as sample preparation steps. Obtained LIBS/ICP-OES recovery values for authentic crop plant samples were 93–109% (K); 93–114% (P); 89–109% (Mg) and 94–110% (Ca). Six certified reference materials (CRMs) of plant tissues were used for the LIBS method validation. Recovery values of 96–101% were obtained for K and P, when the certified concentration of the element in the CRM was inside the concentration range of the used calibration standards. Substantial matrix differences of the CRMs and LIBS calibration standards seem to be a probable reason for the worse recovery results (58–99%) obtained for Mg and Ca.