Voltammetric investigations of 2-dimethylarsinyl-ethanol sulphide in NaCl and seawater

Dimethylarsinylethanol sulphide (Me2As(S)CH2CH2OH) is produced under anaerobic conditions by some seawater algae. Laboratory prepared Me2As(S)CH2CH2OH was investigated by voltammetric methods. It undergoes an oxidation process around 0V versus Ag/AgCl reference electrode forming a deposit of HgS on mercury electrode. During the subsequent reduction HgS is reduced to Hg0 and S2− or HS− depending on pH. Changes of pH influence both anodic and cathodic processes of Me2As(S)CH2CH2OH. Influence of the additions of humic acid and copper ion was investigated in view of the analytical applications. A method for the separate detection of free sulphide, elemental sulphur and Me2As(S)CH2CH2OH in seawater is given. It is suggested that the possible presence of Me2As(S)CH2CH2OH and similar compounds can play an important role in stabilisation of sulphide in seawater.