Determination of Monocrotophos in Camellia Seed Oil and Tap Water by Resonance Light Scattering Spectrometry Based on Iron (Ⅲ) -Nitro-Salophen Complex

A method for the determination of monocrotophos in camellia seed oil and tap water by resonance light scattering spectrometry based on iron (Ⅲ)-nitro-Salophen (I-N-Sal) complex was proposed. The appropriate amounts of ethanol solutions containing 5-nitrosalicylaldehyde and o-phenylenediamine were taken respectively. The mixture were refluxed in water bath at 40 ℃ for 0.5 h, and then a certain amount of ethanol solution containing ferric nitrate nonahydrate was added under the condition of stirring. After reaction for 4 h, the solution was filtrated and dried, and the deep orange-red solid powder was obtained. As shown by the results of UV-Vis spectrometry, Fourier transform infrared spectroscopy, elemental analysis and hydrogen nuclear magnetic resonance spectroscopy, the prepared product was tetradentate Schiff base metal complex, and its chemical formula was C₂₀H₁₂N₄O₆Fe. The prepared I-N-Sal complex (0.700 μmol·L^-1) was reacted with monocrotophos for settling 20 min under the condition of weakly alkaline (pH 8.5), and the formed complex made the system produced strong resonance light scattering signal at 300 nm. It was shown that the I-N-Sal complex showed good selectivity for monocrotophos, and linear relationship between the concentration of monocrotophos and the corresponding resonance light scattering intensity was kept in the range of 0.100-1.100 μmol·L^-1, with detection limit (3s/k) of 30 nmol·L^-1. The method was applied to the determination of monocrotophos in camellia seed oil and tap water samples, it was shown that the results were basically consistent with those obtained by NY/T 761-2008, and the spiked recoveries of monocrotophos were in the range of 97.0%-103%, with RSDs (n=6) of the determined values ranged from 1.5% to 3.8%.