Development of a one-step microwave-assisted subcritical water extraction for simultaneous determination of inorganic elements (Ba, Ca, Cu, Fe, Mg, Mn, Na, Pb, Sr, Zn) in reference materials by microwave induced plasma spectrometry

A “green” procedure has been developed for the simultaneous extraction of total inorganic elements (Ba, Ca, Cu, Fe, Mg, Mn, Na, Pb, Sr, Zn) in certified reference materials by using pressurized subcritical water extraction. Samples (0.1 g) were subjected to 10 min pressurized microwave-assisted extraction with water modified with 1% (v/v) HNO3 at 280 °C and 90 bar. A Univariate approach and the Simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. The target elements have been simultaneously determined by microwave induced plasma-optical emission spectrometry (MIP-OES). The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σblank criterion, peak height) were in the range of 2.5 to 11 ng mL− 1. The method offers relatively good precision (RSD ranged from 5 to 7%) for liquid samples. Method validation was performed analyzing two certified reference materials (IAEA-336 Trace and Minor Elements in Lichen and CRM No. 12-2-02 Essential and Toxic Elements in Green Algae P-ACHK) and by the aqueous standard calibration technique. The measured contents of elements in reference materials were in satisfactory agreement with the certified values.