Arsenic species and their transformation pathways in marine plants. Usefulness of advanced hyphenated techniques HPLC/ICP-MS and UPLC/ESI-MS/MS in arsenic species analysis

Abstract

The growing popularity of algae as a foodstuff around the world raises concern for the safety of this food type with respect to arsenic content in algae. The need for determination of total arsenic content and arsenic speciation in algae food has become an important issue. In this paper we have developed a complete analytical procedure for arsenic determination in algae products comprised of 1) total arsenic (tAs) determination in native algae samples after digestion, 2) extraction of As species with the use of two extraction methods with three extracting agents, 3) extracted total arsenic (extracted tAs) determination in algae extracts, 4) bespoke As speciation, 4) mass balance estimation based on extracted tAs and bespoke As speciation results, 5) unknown arsenic (uAs) species identification. Two advanced hyphenated techniques, HPLC/ICP-MS and UPLC/ESI-MS/MS, were employed along with the HPLC/ICP-MS method validation. Total As content in edible algae samples was found to range from (19.28 ± 0.45) mg kg−1 up to (72.6 ± 2.7) mg kg−1. Bespoke arsenic speciation of edible algae samples has revealed the presence of some known inorganic and simple organic As compounds such as As(III) from <LOD to (8.97 ± 0.59) mg kg−1, As(V) from <LOD to (5.95 ± 0.29) mg kg−1 and DMA from <LOD to (0.766 ± 0.040) mg kg−1. Mass balance calculation carried out on the basis of tAs and bespoke As speciation results has shown that the amount of unknown As species in edible algae samples varied from 28% to 100% of extracted tAs. Identification of uAs species in edible algae samples has shown the presence of a high variety of As-sugars (12 compounds) and confirmed the presence of simple inorganic and organic As species such as As(V) and DMA along with 8 more simple organic As compounds. The results obtained in this study have confirmed that the high amounts of tAs do not correspond to the toxicity of algae based food due to the lack of the inorganic As in the tested samples.