A COMPARISON OF UV AND FLUORESCENCE DETECTORS IN THE LIQUID-CHROMATOGRAPHIC ANALYSIS OF GLYPHOSATE DEPOSITS AFTER POSTCOLUMN DERIVATIZATION

A sensitive and rapid liquid chromatographic method for the analysis o f glyphosate using either post-column ninhydrin derivatization and UV detection (UV-D) or post-column reaction, fluorogenic labelling with o -phthalaldehyde in the presence of 2-mercaptoethanol and fluorescence detection (FD) is described. The sensitivity of the UV-D and two fluor escent detectors (HP-FD and Kratos-FD) were compared and evaluated to analyze glyphosate residues from glass fibre filter (GFF) discs used a s deposit collectors in aerial application. The herbicide was extracte d from the GFF discs using 30.0 mt of phosphate buffer adjusted to pH 2.1, derivatized and quantified. The method was tested initially, opti mized and validated by using glyphosate standards. The average percent recoveries from fortified GFF samples were 93.7 (UV-D), 99.2 (HP-FD) and 94.9 (Kratos-FD). The corresponding standard deviation and coeffic ient of variation (percent) were 6.0 and 6.44; 1.6 and 1.67; and 4.4 a nd 4.59, respectively. The minimum quantifiable limits (ng/50 mu L inj ection) for UV-D, HP-FD and Kratos-FD were 49, 16 and 28, respectively . The study showed that HP-FD was very sensitive compared to the other two detectors. The simplicity of the method allows high sample throug hput for the routine analysis of glyphosate deposits.