Analytical signal enhancement of moxidectin and abamectin derivatives for their analysis by spectrofluorometry

Due to lack of native fluorescence, moxidectin (MOX) and abamectin (ABA) were derivatized varying the incubation time and the mass of derivatization reagents: trifluoroacetic anhydride (TFAA) and N-methylimidazole (NMI). The effect of those variables on the analytical signal of MOX and ABA was evaluated by spectrofluorometry. There are a few reports of the spectrofluorometric analysis of MOX and ABA. The typical experimental conditions of derivatization were not suitable for the analysis by spectrofluorometry. Therefore, it was necessary to explore the experimental conditions to achieve the analysis. The final conditions were NMI (30 μL), TFAA (45 μL) and incubation time of at least 60 min (λex = 390 nm, λem = 450 nm). The analytical signals achieved with those conditions were more intense than those reported in other works. The conditions were used to analyze solvent standard solutions of MOX and ABA. Also, analyte spectra were obtained in extracts of bovine plasma and peach juice spiked with MOX and ABA, respectively. The derivatization works as pseudo-first-order reaction with rate constants of 0.000056 M−1 s−1 for MOX, and 0.000077 M−1 s−1 for ABA. Spectrofluorometry is easier and cheaper and is an alternative to chromatography to determine these drugs in different types of samples.