Mapping of arsenic species and identification of a novel arsenosugar in giant clams Tridacna maxima and Tridacna derasa using advanced mass spectrometric techniques

Because of their symbiotic microalgae, giant clams (Tridacna species) exhibit a unique arsenic metabolism, which has been shown in previous studies to involve a large number of arsenic species. This study demonstrates the application of liquid chromatography (HPLC) online with electrospray tandem mass spectrometry (ES-MS/MS) as well as inductively coupled plasma mass spectrometry (ICP-MS) for arsenic speciation analysis in giant clam extracts. Selected reaction monitoring (SRM) was used for sensitive and selective detection of a large number of arsenic species in a single chromatographic run. Novel aspects are the analysis of 10 tissue fractions from one clam and the analysis of kidney extracts both from T. maxima and T. derasa with the same method thus offering the possibility for direct comparisons. Moreover, HPLC-ES-MS/ MS in the precursor ion scan mode and product ion scan mode allowed the identification of a novel sulfonated dimethylarsenosugar and the partial characterisation of another unknown arsenic species. The results indicate that most arsenic species are accumulated in the kidneys. However, arsenobetaine was found at similar contents in all analysed tissue fractions of one T. maxima clam.