An Improved Method for the Determination of Residual ABS in Tomato Juice

Abstract

It has been considered that the colorimetric method with methylene blue is one of the best methods for determining very small amounts of anionic surfactants. However, in the case of vegetables and fruits, this method is not necessarily satisfactory owing to interference by methylene blue active substances (MBAS) other than anionic surfactants, contained in vegetables and fruits. Because of the above reason, small amount of a residual surfactant remaining in them cannot be detected precisely, especially when the blank value is high, to give a higher value of the surfactant than an expected value.This paper describes a way of determination of residual alkylbenzene sulfonate in tomato juice by removing MBAS. The procedure is as follows. After evaporating alcohol from the alcohol extract of a sample, the residue is treated with petroleum ether and washed with chloroform. The amount of the surfactant in the aqueous layer is then determined according to the Abbott's method with methylene blue.