Application of MgF2 as a new sorbent for preconcentration and isolation of sulphur in food samples before the determination by molecular absorption spectrometry

Abstract

This study proposes, for the first time, the development of an analytical method using the new sorbent - magnesium fluoride (MgF2) and ultrasound-assisted dispersive micro solid-phase extraction (UA DMSPE) for accurate preconcentration and isolation of sulphur in food samples. The further determination was conducted with high-resolution continuum source electrothermal molecular absorption spectrometry (HR-CS ET MAS). The main UA DMSPE parameters were investigated. Satisfying extraction efficiencies were obtained using 10 mL of sample solution, 20 mg of MgF2 and 20 s extraction time. The limit of detection and the preconcentration factor were 0.001 μg mL−1 and 18, respectively, and no matrix effect was observed. The relative standard deviation (RSD) was 2–13%. The proposed method was applied, inter alia, to corn flakes and flour, dried raisins and goji berries as well as different types of tea leaves. The accuracy of the developed method was evaluated by analysis of certified reference materials: mixed polish herbs (INCT-MPH-2), soya bean flour (INCT-SBF-4), tea leaves (INCT-TL-1), wheat (NCS ZC73009) and corn (NCS ZC73010). Sulphur concentrations determined in these materials were in satisfactory agreement with the certified values (recoveries in the range of 94% to 101%).