Isotachophoretic separation of glyphosate, glufosinate, AMPA and MPP with contactless conductivity detection

The potential of isotachophoresis with conductivity detection for the preconcentration, separation and simultaneous determination of two herbicides (glyphosate and glufosinate) and their metabolites (aminomethylphosphonic acid and methylphosphinicopropionc acid) was investigated. A 0.025 μg mL^-1 standard solution of all four analytes was easily detectable in a 40 minute analysis using a volume coupled arrangement of two capillaries connected in series. The conductivity relative step heights (RSHs) were used to assign individual analytes in mixtures. Calibrations were carried out over a dynamic range of three orders of magnitude in concentration, with relative standard deviation in zone length (used to quantify the analytes) shown to be in the range 2-6% at 2.5 μg mL^-1 loading.