[Determination of anionic synthetic detergent in drinking water by methylene blue spectrophotometry]

To develope a method for rapid determination of anionic synthetic detergent in drinking water by methylene blue spectrophotometry.

Added 20. 0 mL water sample into 50 mL plastic tube, then added 10. 0 mL chloroform and 200 μL methylene blue solution, oscillatied 1 min, layering, suck out the upper solution, calibrated zero using chloroform, determinated the absorbance of the bottom extraction solution at 650 nm wavelength.

The regression equations of the rapid determination method showed a good linearity and the correlation coefficient was 0. 9995. The method minimum mass detection concentration was 0. 05 mg/L. The recoveries were between 92. 7% and 98. 3%, and the relative standard deviations were between 4. 8% and 5. 7%(n=6). Compared with the national standard method by significance test, the significant difference had no statistical significance(P=0. 79). The detection time(30 samples) was only 2 h which needed a day by using national standard method. The concentration range of anionic synthetic detergent of 30 samples in the Yanqing urban areas of Beijing were<0. 05-0. 26 mg/L.

This method is simple, sensitive, accurate and efficient, and it is suitable for basic level laboratories rapid determination and drinking water surveillance.