Analysis of alcohol ethoxylates and alkylamine ethoxylates in agricultural soils using pressurised liquid extraction and liquid chromatography-mass spectrometry.

Nonionic surfactants e.g. alcohol ethoxylates (AEOs) and alkylamine ethoxylates (ANEOs) are commonly utilised as adjuvants in pesticide formulations to enhance their effectiveness. In this study, analytical methods for AEO and ANEO determination in soil samples using pressurised liquid extraction (PLE) were developed and used in connection with LC-MS. The recovery of the method, which was highly dependent on the soil properties, varied in the range 47-106% for AEO and 27-109% for ANEO. Detection limits (LOD) were 7-13 microg kg(-1) for AEO and 24-43 microg kg(-1) for ANEO. The developed method has been applied to determine AEOs and ANEOs in surface soil samples from fields sprayed with glyphosate herbicides. Tallowalkylamine ethoxylates (an ANEO) were detected in the soil before and after pesticide application, with increasing concentrations after treatment. The highest concentration in the soil samples was observed for the ANEO homologues with the longest ethoxy chains; in the clay soil the concentration decreased with the length of the ethoxy chain. ANEOs added to pesticide formulations as a technical mixture will, as demonstrated in this study, behave as individual homologues, which is reflected in their behaviour in the environment.