Ability of Fourier Transform-Near Infrared Spectroscopy to Detect Organophosphate (OP) Pesticides and Reduction of OP using a Washing Process

Since December 2020, the Thai Department of Agriculture (Thai DOA) placed chlorpyrifos on the banned chemical list, based on evidence the organophosphate (OP) class of pesticides was shown adverse effects on human health and environment. However, the use of this organophosphate class of pesticides have been found contamination in vegetable and fruit such as grave imported from China. The Fourier transform-near infrared (FT-NIR) spectroscopy combined with the dry extract system for infrared (DESIR) technique have been succeeded on detecting chlorpyrifos and ethion residues in spiked Chinese kale, head cabbage and green chili spur pepper employed as a vegetable model. Chinese kale, head cabbage and green chili spur pepper was spiked with chlorpyrifos and ethion at 0.44 - 111.29 mg/kg were detected using the quick, easy, cheap, effective, rugged and safe (QuEChERS) method coupled with gas chromatography-mass spectrometry (GC-MS). Partial least squares regression (PLSR) was used to develop a calibration equation. FT-NIR combined with DESIR and PLSR produced an equation that showed good performance and provided the best calibration equations based on values for R2 (0.88 - 0.94), SEP (7.65 - 11.36 mg/kg), RMSEP (7.68 - 11.80 mg/kg), bias (−3.83 to 3.32 mg/kg) and RPD (3.03 - 4.10). These statistics revealed no significant difference between FT-NIR-predicted values and actual values at a confidence interval of 95 %. After applying ozonated water (1 mg/L) and EO water (available free Cl2 at 70 mg/L) for 10 min resulted in 67 % reduction in chlorpyrifos and ethion levels in Chinese kale, head cabbage and green chili spur pepper. Since this developed method was limit to predict the amounts of residues (≤ 30 mg/kg) but it could be applied to monitor pesticide residues at harvesting, or inspection of incoming raw materials before entering food chain to ensure the safety of the vegetable for human consumption. HIGHLIGHTS Common Thai fresh produce: Chinese kale (Brassica oleracea var alboglabra), head cabbage (Brassica oleracea capitate) and green chili spur pepper (Capsicum annuum Linn. var acuminatum Fingerh) are common green, and top 10 leafy vegetable for consumption in Thailand. Organophosphate (OP) pesticides contamination: OP pesticides are a class of insecticides have been approved in vegetable crop production in Thailand. Since 2020, they were prohibited to use but the OP residue contamination in Thai fresh vegetable have still been reported. Due to their acute toxicity and widespread use, there are global concerns about trace residues may pose significant long-term health risks. Detection of OP pesticide residues in vegetable by Fourier transform-near infrared (FT-NIR) spectroscopy: FT-NIR combined with the dry-extract system for near infrared (DESIR) technique and Partial least squares regression (PLSR) showed good performance in detecting chlorpyrifos and ethion residues in vegetable. The best calibration equations provided good prediction based on values for R2, SEP, RMSEP, bias and RPD. No significant difference between FT-NIR-predicted values and actual values at a confidence interval of 95 %, with agreeable results presented at pesticides residue levels of more than 30 mg/kg. Washing process with oxidizing water: Ozonated water (1 mg/L) and electrolyzed oxidizing (EO) water (available free Cl2 at 70 mg/L) for 10 min were applied to wash spiked samples and resulted in 67 % reduction of chlorpyrifos and ethion levels in Chinese kale, head cabbage and green chili spur pepper. GRAPHICAL ABSTRACT