LIQUID-CHROMATOGRAPHIC DETERMINATION OF GLYPHOSATE AND AMINOMETHYLPHOSPHONIC ACID (AMPA) IN ENVIRONMENTAL WATER - COLLABORATIVE STUDY

A new method for determination of glyphosate and aminomethylphosphonic acid (AMPA) residues in environmental water was collaboratively studied by 6 laboratories. The method is simpler and shorter than previous methods. A filtered volume of water is evaporated to dryness and the residue is dissolved in a buffered EDTA solution. Glyphosate and AMPA are determined by liquid chromatography with postcolumn reaction detection. The method was validated over the range 0.50-5000 ppb, although one of the collaborating laboratories could not reliably quantitate below 1.0 ppb. Statistical analysis of the results showed that typical reproducibility relative standard deviations (RSD(R)) ranged from 11 to 20% for both glyphosate and AMPA, which compares very well with predicted values for this concentration range. Total variability (as measured by s(R)) increased with increasing fortification level. The method has been adopted official first action by AOAC.