microwave assisted acid digestion procedure. About six replicates samples of CRM (0.2 g) and triplicate samples lyophilised fish muscle tissues (0.2 g) of each fish species were directly weighed into Teflon PTFE flasks. Two ml of a freshly prepared mixture of concentrated HNO3 and H2O2 (2:1, v/v) was added to each flask and was kept for 10 min at room temperature. The flasks were then placed in a covered PTFE container. It was then heated following a onestage digestion programmed at 80% of total power (900 W) for 2–3 min, to completely oxidise the organic matrices of fish muscle tissues. The digestion flasks were cooled and diluted to 10.0 ml with 0.1 M HCl as stock sample solution. The quality controls included blank, duplicates and certified reference material (CRM) were made. To determine the detection limit, analytical blanks were prepared in a similar manner without the insertion of a sample. The concentration of total As and inorganic arsenic species (As3+ and As5+) in each sample were calculated from the corresponding regression lines.