An automatic method for the determination of anionic surface-active material in water

Abstract

An automatic version of the methylene-blue procedure for determining alkylbenzenesulphonates in fresh and saline waters on the AutoAnalyzer is described. Results have been examined statistically and compared with those obtained by the manual methylene-blue method. Student's t-test indicates more than 90 per cent. probability that the manual and automatic methods will give the same value. The sampling rate is 14 per hour, and the standard deviation is 0·04 p.p.m. of Manoxol OT in the range 0 to 4 p.p.m. of Manoxol OT. Whilst chloride, sulphide and sulphate showed no interference when tested, peaty water did interfere with the method. However, the results obtained showed a correlation to the colour (in p.p.m. of platinum) of the water examined. Emulsification, which causes considerable error in the manual method, is completely avoided in the automatic method.