Determination of imidacloprid in fruits and vegetables by liquid chromatography with diode array and...

A national trend is focusing on expanding usage of environmentally friendly nitrogenous pesticides and herbicides. However, some of these chemicals are undetectable by any gas chromatographic method due to their thermal lability or nonvolatility. Using imidacloprid as a model compound, this laboratory has developed a simple, effective, and reliable liquid chromatography (LC) method to address the inherent difficulties of these chemicals. Focusing on nitro, nitrate, and/or nitrite chromophore groups and components contained in the chemical structure of most nitrogenous compounds, LC with diode array detector and a nitrogen-specific detector in tandem enabled determination and confirmation analyses in series. Furthermore, using 2 mixtures of solvents in conjunction with 2-stage solid-phase extraction cleanup on aminopropyl/Florisil cartridges to eliminate and/or minimize interferences resulting from free amino acids, peptides, proteins, pigments, and lipids in the plant tissues made the qualitative and quantitative analysis simple, fast, and cost effective. This method demonstrated the potential for becoming a viable analysis tool for many other types of nonvolatile nitrogenous chemicals.