Inorganic and organic arsenic compounds in Slovenian mushrooms: comparison of arsenic-specific detectors for liquid chromatography

Abstract

After separation of arsenite, dimethylarsinic acid, methylarsonic acid, and arsenate on an Hamilton PRP-X 100 anion-exchange column, arsenic compounds were detected with flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry (GFAAS) or inductively coupled plasma mass spectrometry (ICP-MS). With HPLC-ICP-MS system 0.1 ng of arsenic (100 μL injected) with a relative standard deviation of 10 % could be quantified. The HPLC-FAAS and HPLC-GFAAS require at last three orders of magnitude more arsenic to be reliably quantified.The applicability of the three arsenic-specific detectors was tested with aqueous extracts of mushrooms Laccaria amethystina(~26 mg As/kg dry mass), Laccaria laccata (~ 26 and ~32 mg As/kg dry mass), Boletus cavipes (~12 mg As/kg dry mass), and Thelephora terrestris (~38 mg As/kg dry mass) collected in unpolluted areas in Slovenia. The detection limits obtained with HPLC-FAAS were found to be to high to be used to quantify the arsenic compounds in the aqueous extracts of mushrooms from uncontaminated sites.In the Laccaria amethystina, 97% of the arsenic was found to be dimethylarsinic acid and 3% arsenite. In the related Laccaria laccata, the predominant arsenic compound was arsenate (~80%) and the minor arsenic compounds were arsenite (~14%), and dimethylarsinic acid (~3%). In the Thelephora terrestris, an inedible mushroom with woody structure, only inorganic arsenic compounds were determined (~70% arsenite and ~30% arsenate). In the Boletus cavipes, 50% of arsenic was found to be arsenate, 40% arsenite, and 10% in the form of dimethylarsinic acid.The quantitative results for the four mushrooms obtained with the two systems agree reasonably when the concentrations in the extracts are sufficiently high. Minor arsenic compounds could only be detected with HPLC-ICP-MS.