Separation and Identification of Degradation Products in Abamectin Formulation Using LC, LTQ FT-MS, H/D Exchange and NMR

This paper describes the analysis of abamectin and the characterization of its degradation products in formulation. A fast and selective reversed-phase HPLC was developed and validated for the quantitation of degradation products. Two major degradation products observed in stress study samples were isolated and characterized using chromatography and high resolution FT-MS. Abamectin and its degradation products presented similar masses at m/z 873.49848 Da, and were further distinguished by MSn studies, H/D exchange studies, 1H, 13C and 2D NMR experiments. The interpretation of analytical data positively identified unknown 1 as the stereoisomer 2-epi-abamectin and unknown 2 as the regioisomer Δ2,3-abamectin. The developed HPLC method was found to be precise, accurate and detector response was linear for the analysis of known degradation products at the identification threshold.