Evaluation of a Dry Extract System Involving NIR Spectroscopy (DESIR) for Rapid Assessment of Pesticide Contamination of Fruit Surfaces

Abstract

The dry-extract system for (near) infrared (DESIR) technique was implemented using reflectance near-infrared spectroscopy in context of detection of contact pesticide residues on fruit. Based on chemical structure, spectra features and regression statistics for PLSR models, a product containing metiram and pyraclostrobin was chosen from six pesticides for further consideration. Regression models based on spectra of dry extracts of aqueous solutions and either acetone or water washes of contaminated fruit were encouraging (RMSECV of approximately 0.03 -0.06 mg a.i.). This level of analytical performance would support the use of the technique as a rapid screening tool, with suspect samples then subject to the reference GC-MS analysis method. However, the PLSR model performance was poor across populations of fruit, suggesting that matrix changes in the solvent wash between sets of fruit is problematic. Further work is required to establish whether sufficient variation can be built into a calibration set to overcome this issue, without degrading model performance to the point where it loses practical application.

Evaluation of Dry Extract System Involving NIR Spectroscpoy (DESIR) for Pesticide Residues Detection on Fresh Carabao Mango (Mangifera indica L. cv ‘Carabao’) Fruit

“…Two principal components were retained with eigenvalues of 198.017 and 11.86. (Table V) G. Detection Limit A detection limit similar to the study conducted by Saranwong [9] and Acharya [6] showed results in Table VI for the three different concentrations of profenopos sprayed on the fruit. A detection limit for the lowest concentration for profenopos was 0.0005% active ingredient in a 0.5 mL sample was equivalent to 0.0025 mg of active ingredient.…”

“…The extinction coefficient of these chemicals were the parameters in defining how strongly a substance absorbs light at a given wavelength regardless of its concentration and would decrease in relation to absoprtion per unit concentration in the order presented (cypermethrin > chlorpyrifos = profenopos). Absorption around 1400-1500 nm was consistent with a strong O-H feature 1st overtone [6] with major absorbance peak at 1450 nm [5]…”

“…Solutions The procedure used for the analysis of diluted pesticide solutions was adapted from Chen, et al [4]; Acharya, et al [6] and was described below. Three commonly used pesticides with active ingredients of chlorpyrifos, cypermethrin and profenos were diluted into various concentrations (Table I).…”

“…Water was being used as wash solution instead of acetone because acetone wash carried a range of other chemicals like dissolved cuticular wax that varied in quantity and composition as it was discolored due to the extraction of some of its pigments [9]. Acharya [6] conducted a study and showed comparable results to the pure aqueous solutions using water rather than acetone as the wash solvent. All derived calibration models in Table III showed suitability for screening and other approximate calibrations.…”

“…As Acharya [6] had conducted the dry-extract system (DESIR) technique using reflectance near-infrared spectroscopy in context of detection of contact pesticide residues on fruit. This level of analytical performance would support the use of the technique as a rapid screening tool.…”