Rapid and direct determination of glyphosate, glufosinate, and aminophosphonic acid by online preconcentration CE with contactless conductivity detection

Rapid and direct online preconcentration followed by CE with capacitively coupled contactless conductivity detection (CE-(CD)-D-4) is evaluated as a new approach for the determination of glyphosate, glufosinate (GLUF), and aminophosphonic acid (AMPA) in drinking water. Two online preconcentration techniques, namely large volume sample stacking without polarity switching and field-enhanced sample injection, coupled with CE-(CD)-D-4 were successfully developed and optimized. Under optimized conditions, LODs in the range of 0.01-0.1 mu M (1.7-11.1 mu g/L) and sensitivity enhancements of 48- to 53-fold were achieved with the large volume sample stacking-CE-(CD)-D-4 method. By performing the field-enhanced sample injection-CE-(CD)-D-4 procedure, excellent LODs down to 0.0005-0.02 mu M (0.1-2.2 mu g/L) as well as sensitivity enhancements of up to 245- to 1002-fold were obtained. Both techniques showed satisfactory reproducibility with RSDs of peak height of better than 10%. The newly established approaches were successfully applied to the analysis of glyphosate, glufosinate, and aminophosphonic acid in spiked tap drinking water.