NIR spectroscopy detects chlorpyrifos-methyl pesticide residues in rough, brown, and milled rice

Authors: RODRIGUEZ, F - Don Mariano Marcos Memorial State University; Armstrong, Paul; Maghirang, Elizabeth; YAPTENCO, K - University Of The Philippines Los Banos; Scully, Erin; Arthur, Franklin; Brabec, Daniel - Dan; Adviento-Borbe, Arlene; SUMINISTRADO, D - University Of The Philippines Los Banos

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2020
Publication Date: 10/1/2020
Citation: Rodriguez, F.S., Armstrong, P.R., Maghirang, E.B., Yaptenco, K.F., Scully, E.D., Arthur, F.H., Brabec, D.L., Adviento-Borbe, A.A., Suministrado, D.C. 2020. NIR spectroscopy detects chlorpyrifos-methyl pesticide residues in rough, brown, and milled rice. Transactions of the ASABE. 36(6):983-993. https://doi.org/10.13031/aea.14001.
DOI: https://doi.org/10.13031/aea.14001

Interpretive Summary: Rice is the most consumed staple food by humans, particularly in Asian countries, making it imperative that rice safety is given high priority. The presence of pesticide residues in rice and the possible adverse effects on human health associated with consuming residues represent a major concern. Chlorpyrifos-methyl is a commonly used insecticide used to eradicate insects in rice grain warehouses and if improperly applied, can have adverse human health effects. A rapid technique was developed using a commercial near infrared (NIR) instrument to determine the presence of chlorpyrifos-methyl in bulk samples of rough (paddy) rice, brown and milled rice. After rice was treated with different concentrations of chlorpyrifos-methyl based on the maximum residue limits (MRL) for each type of rice, rough, brown and milled, it was possible to quantify the amount of residue in all samples and processing type with reasonable accuracy. Also, samples with high residue amounts could be accurately separated from samples with lower amounts. It thus seems possible that low cost, high volume and more rapid screening would be possible using a NIR instrument compared to currently available methods.

Technical Abstract: A rapid technique that uses near-infrared reflectance (NIR) spectroscopy for simultaneous qualitative and quantitative determination of the presence of varying concentrations of chlorpyrifos-methyl in bulk samples of rough, brown, and milled rice was established. Five rice varieties, free of pesticides, obtained from RiceTec Inc and USDA-ARS Arkansas experimental field were used as rough rice samples and also processed to obtain corresponding brown and milled rice. Rice samples were treated with varying levels of chlorpyrifos-methyl: 0, 1.5, 3, 6, 9, and 12 ppm for rough rice, 0, 0.75, 1.5, 3, 4.5 and 6 ppm for brown rice, and 0, 0.1, 0.2, 0.4, 0.6 and 0.8 ppm for milled rice. Concentrations of applied pesticide were verified using gas chromatography-mass spectrometry analyses. A commercial NIR spectrometer (950-1650 nm wavelength range) was used to obtain spectra of bulk samples. Using partial least squares analysis for quantitative analysis with independent one-variety out validation, chlorpyrifos-methyl pesticide residue concentrations in rough, brown, and milled rice are predictable with R2 ranging from 0.702 to 0.839 and standard error of prediction (SEP) of 1.763 to 2.374 for rough rice, R2 ranging from 0.722 to 0.800 and SEP of 0.953 to 1.168 for brown rice, and R2 ranging from 0.693 to 0.789 and SEP of 0.131 to 0.164 for milled rice. For qualitative analysis obtained using discriminant analysis, rough rice samples with concentrations of 0, 1.5 and 3 ppm pooled as low pesticide level (LPL) is distinguishable to 6, 9, and 12 ppm which were pooled as high pesticide level (HPL). Similarly, for brown and milled rice, the lower three concentrations pooled as LPL is distinguishable from the higher three concentrations pooled as HPL. An independent one-variety out validation showed overall correct classifications ranging from 77.8 to 92.6% for rough rice, 79.6 to 88.9% for brown rice, and 94.4 to 100% for milled rice.