The toxicological and biological importance of many metals greatly depend upon their chemical form. The determination of the total amount of an element is not sufficient to assess the toxicity of a considered medium. Arsenic is one of these elements whose speciation (determination of different chemical species involved) is of particular interest because of the wide-ranging levels of toxicity exhibited by the different chemical forms. With direct coupling of HPLC with HR-ICPMS it is possible to determine the arsenic species arsenite, arsenate, monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), arsenobetaine (AsB) and Arsenochinoline (AsC).