Flow injection analysis of selenium by using 4, 5-dimethyl-o-phenylenediamine

Abstract

A flow injection method was studied for the determination of selenium (IV) in water.
A distilled water is pumped as a carrier stream (0.78 ml/min), into which 200μl of sample solution is injected. A 4, 5-dimethyl-o-phenylenediamine solution is also pumped as a reagent stream (0.78ml/min), this allows the formation of 4, 5-dimethylpiaselenol in a reaction coil (5m, 85°C) . The absorbance of the piaselenol is measured at 340 nm.
The linearity of calibration curve was good (r=0.9999), and the relative standard deviation in ten determinations of 5 mg/l and 10mg/l ofselenium (IV) were 0.26% and 0.32%, respectively. A routine sampling rate of 40 determinations per hour can be achieved with thismethod.
This method seems hard to apply directly to the determination of selenium in waste water due to the lackof its sensitivity. So, it needs to use suitable preconcentration method such as co-precipitation when the sample solution containing selenium (IV) lower than ppm level, or containing several interfering ions.