Ultrasensitive and selective determination of mercury in water, beverages and food samples by EDXRF and TXRF using graphene oxide modified with thiosemicarbazide.

[Display omitted] • Highly selective and ultrasensitive determination of mercury ions. • Very low detection limits using benchtop EDXRF and TXRF instruments. • Simple and robust analysis of waters, beverages, seafood, plants, etc. • Green approach based on reducing the reagent usage and sample preparation time. The paper presents novel analytical methods for sensitive mercury determination in various samples, i.e., waters, beverages, seafood, plants, and biological samples. The procedure is based on selective preconcentration/separation of Hg(II) ions using graphene oxide/thiosemicarbazide in dispersive micro-solid phase extraction (DMSPE) and detection by energy-dispersive (EDXRF) and total-reflection X-ray fluorescence spectrometry (TXRF). The DMSPE/EDXRF and DMSPE/TXRF procedures are characterized by very high enrichment factors and low detection limits (LODs). DMSPE/TXRF allows obtaining LODs of 2.1 pg mL−1 for liquids and 1.8 ng g−1 for solid samples. In the case of DMSPE/EDXRF, the LODs are higher, 60 pg mL−1 for liquid and 73 ng g−1 for solid samples, due to the worse sensitivity of EDXRF measurement. The method was validated using spiked samples (water, apple juice, beer, wine) and certified reference materials (seawater, groundwater, wastewater, herring, cormorant and cod tissues, pig kidney, lobster, tobacco, scallion, celery, and spinach). [ABSTRACT FROM AUTHOR]