QUANTIFICATION OF GLYPHOSATE AND AMPA BY HPLC-ICP-MS/MS AND HPLC-DAD: A COMPARATIVE STUDY

Glyphosate [N-(phosphonomethyl) glycine)] is an organophosphorus non-selective post-emergent herbicide, which is absorbed by leaves and translocated throughout the plant. Due to its efficiency, it is the main herbicide used in the world and target of several researches. When degraded, glyphosate releases aminomethylphosphonic acid (AMPA) as its main secondary metabolite. For the determination of these compounds, the most used techniques are gas-chromatography (GC) and high performance liquid chromatography (HPLC). However, the absence of chromophoric groups and low volatility of these compounds requires derivatization step before analysis. The goal of this study was a comparison between the triple quadrupole mass spectrometer by inductively coupled plasma (ICP-MS/MS) and the diode arrangement detector (DAD), both coupled to HPLC, for the determination of glyphosate and AMPA. Linearity, detection of limit (LOD), total analysis time, sample preparation time and derivatization step were evaluated for comparison of the detection systems. Analytical curves at the concentrations of 1, 2, 4, 6 and 8 mg L-1 were prepared for analysis by HPLC-DAD and 5, 10, 20, 30 and 40 μg L-1 for analysis by HPLC-ICP-MS/MS. Both chromatographic systems showed significant linearity through the F-test, normality (Ryan-Joiner), homogeneity (Brown-Forsythe) and independence (Durbin-Watson). HPLC-DAD showed LOD of 300 μg L-1 for the two compounds and the total analysis time was 20 min. The HPLC-ICP-MS/MS showed LOD of 8.2 μg L-1 and analysis time less than 5 min. For HPLC-ICP-MS/MS, the analytical curve was obtained through standard dilution in ultrapure water, with no requirement of derivatization step and an average time of 30 min for sample preparation. In the HPLC-DAD, the derivatization step was necessary to detect the compounds in the visible region by adding the chromophore group using the FMOC-Cl as derivatizing agent. This step used more reagents and an average time of 200 minutes to prepare the analytical curve. The derivatization step sometimes has low reaction yield and formation by-product, also requires more time for sample preparation and expensive reagents. In this context, this study shows the superiority of the HPLC-ICP-MS/MS for trace level determination of glyphosate and AMPA in comparison to HPLC-DAD.