USGS Scientists Compare Analytical Methods for the Analysis of Imidacloprid in Biological Matrices

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In a recent research project, California Water Science Center scientists compared analytical techniques for the analysis of imidacloprid in biological matrices.

Specifically, the scientists analyzed plasma, liver, and fecal matter from a species of Japanese quail (Coturnix japonica) that were dosed with the pesticide using an enzyme-linked immunosorbent assay (ELISA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Schematic representing the dosing of Japanese quail with imidacloprid-treated wheat seeds

Schematic representing the dosing of Japanese quail with imidacloprid-treated wheat seeds and the analysis of biological tissues by ELISA and LC-MS/MS.​​​​​​​

The pesticide imidacloprid belongs to a new class of insecticides knows as neonicotinoids. Neonicotinoids are chemically related to nicotine. Like nicotine, they act on receptors in the nerves and are generally much more toxic to insects than they are to higher organisms. However, the abundant use of the neonicotinoid imidacloprid has raised concerns that it may have toxic effects on nontarget organisms. To better understand the fate and effects of imidacloprid on nontarget organisms, accurate analytical methods are necessary for quantification of residues in complex matrices.

In their research for this article USGS scientists, Dr. Michael Gross, along with colleagues, Dr. Michelle Hladik and Dr. Emily Woodward, used an enzyme-linked immunosorbent assay (ELISA) kit to analyze biological samples from Japanese quail. Following the dosing of the quail with imidacloprid-treated wheat seeds, samples were analyzed and compared to previous analyses that employed an alternate method -- liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results from both analysis methods were positively correlated but there was poor agreement as to the levels of concentration. Plasma and fecal matter imidacloprid concentrations were higher by ELISA, whereas liver imidacloprid concentrations were higher by LC-MS/MS. ELISA results were confounded by high levels of metabolites present within the samples, which cross react with ELISA antibodies. ELISA provided an effective screening tool for imidacloprid in these biological matrices, though it is suggested that ELISA results for complex samples be confirmed by more selective techniques, such as LC-MS/MS.

Read full article:  Evaluation of ELISA for the analysis of imidacloprid in biological matrices: Cross-reactivities, matrix interferences, and comparison to LC-MS/MS.