Abstract Arsenic has been determined by β-correction spectrophotometry with ethyl violet (EV) in the presence of sodium nitrite which is an oxidant and effective for removing absorption spectra and increasing analytical sensitivity. Extraction with benzene can separate most other metals ions and concentrate arsenic in wastewater. The β-correction method can eliminate completely the effect of excess EV in its As colored solution to give the real absorbance of the chelate produced. Sensitivity, precision and accuracy are all increased. Beer's law is obeyed over the range 0–2.0 mg l −1 at 630 nm and the detection limit of arsenic is 0.02 mg l −1. The results show that the relative standard deviation was less than 12% with the recovery between 91.0 and 114%.