LC–MS Quantification of a Sulfosuccinate Surfactant in Agrochemical Formulations

Agrochemical products are a mixture of active ingredient(s) and inerts, which serve as dispersing or wetting agent or as emulsifiers. Varying qualities of these raw materials can have a significant impact on the properties of the final agrochemical product and so its quality has to be controlled. In this work the commercially available mixture of sodium bis(2-ethylhexyl) sulfosuccinate (trade name: Aerosol OT or AOT) and its surface active isomeric by-products sodium 1-carboxy-3-[(2-ethylhexyl)oxy]-3-oxopropane-1-sulfonate and sodium 3-carboxy-1-[(2-ethylhexyl)oxy]-1-oxopropane-2-sulfonate were analyzed. A method using liquid chromatography coupled with time-of-flight mass spectrometry (LC-ToF–MS) with exact mass measurement was developed to quantify these molecules simultaneously. Both by-products were not commercially available and thus were synthesised as analytical standards for method validation. For this purpose, two regio-selective syntheses were developed. Validation was done according to DIN 32645 and recovery and precision for two different matrices were determined. Significant differences were observed in the by-product spectrum of real samples of Aerosol OT of three different suppliers. Their influence on the properties of an agrochemical can now be investigated, as a precise and accurate determination of the target analytes has been developed in this work.