Direct analysis of marine macroalgae for determination of macro minerals by energy dispersive X-ray fluorescence

Determination of the macro mineral composition of macroalgae is important considering the relevant applications and potential consequences of macroalgae. The application of direct solid analysis is attractive, as it decreases costs, consumes less reagents, has higher sample throughput, generates less residue, and avoids analyte loss and contamination. The aim of this study is to propose a method for the direct determination of Ca, K and Mg in marine macroalgae using energy dispersive X-ray fluorescence (EDXRF). This method was calibrated using samples previously analyzed by inductively coupled plasma optical emission spectrometry (ICP OES) as calibration standards. In a parallel procedure applied for comparison purposes, macroalgae samples were also analyzed by ICP OES after an acid digestion procedure. Analysis of three Certified Reference Materials (CRM) of different plant materials was performed to evaluate the accuracy of the method. The coefficients of correlation (R) from the calibration curves, the precision (%), the limit of quantification (mg kg− 1) and the recovery (%) were: Ca (0.961, 2.07, 109.5 and 85.0 to 89.3), K (0.998, 3.82, 207.0 and 126.6 to 129.6) and Mg (0.978, 4.07, 195.6 and 92.7 to 115.4). The proposed method was then applied in the determination of Ca, K and Mg in macroalgae samples collected in Todos os Santos Bay, Bahia, Brazil.