A simple approach for the ultrasensitive detection of paraquat residue in adzuki beans by surface-enhanced Raman scattering.

Paraquat (PQ), a broad-spectrum contact herbicide, has been used in many countries for controlling weed growth in agriculture because of its quick-acting and nonselective contact with green plant tissue. PQ is also toxic to humans, and even contributes to the development of neurodegenerative diseases. However, PQ is generally excluded from pesticide residue monitoring programs due to the lack of suitable determination methods. Thus, this study developed a detection method combined with simple extraction and surface-enhanced Raman spectroscopy (SERS) to rapidly determine and quantify the PQ residue on legumes without destructive procedures and high-cost instruments. Following the extraction procedure of the QuPPe-method, however, we took whole adzuki beans (Vigna angularis) extracted via a mixture of methanol and 1% formic acid at room temperature and followed by a 1 min cleanup by SPE. The PQ values for adzuki beans determined by LC/MSMS showed that regardless of whether extraction was followed by the QuPPe-method or the method we proposed, a consistent and low relative standard deviation (RSD) below <22% was found. In this study, we proposed to extract PQ on the surface of the beans by shaking briefly with solvent, and then the PQ molecules were detected and quantified by depositing Ag nanoparticles (AgNPs) and performing SERS within 10 min. Using a coating of deposited Ag nanoparticles, SERS can achieve a limit of detection (LOD) for PQ on the order of 1 µg L-1 (∼4 × 10-9 M) and a method detection limit (MDL) for adzuki beans of 0.8 µg kg-1 (∼3.3 × 10-9 M). This sensitivity at the ppb level absolutely met the maximum residue limit (MRL) for PQ in dried beans as declared by most countries, including the US (0.3 mg kg-1), Australia (1.0 mg kg-1) and Taiwan (0.2 mg kg-1). Taiwan will ban the use of PQ as a defoliating agent for harvest in adzuki bean fields in 2019; therefore, developing a method for detecting PQ residues in the field or in import markets is necessary for consumer health and for authorities. This study provided an opportunity to utilize SERS in the field of on-site pesticide residue screening.

FaPEx® Multipesticide Residues Extraction Kit for Minimizing Sample Preparation Time in Agricultural Produce.

Background: The quick, easy, cheap, effective, rugged, and safe method, generally applied to the determination of pesticide residues in food, has been recently modified and adopted for the analysis of pesticide residues worldwide, including Taiwan. Objective: The method still needs to be improved, particularly in efficiency and normalization, because the time costs 20-30 min for extraction and cleanup of multiple pesticides in every food. Methods: In this study, we present a highly efficient and simple sample preparation method that was developed for the determination of 380 pesticide residues in food, including mangoes, scallions, bok choy, apples, carrots, and pea seedlings. The homogenized 1 g samples mixed with 5 mL 1.0% acetic acid in acetonitrile were pushed through the FaPEx® (fast pesticide extraction) kits in a dropwise manner to obtain sample extracts. The total processing time was less than 15 min. The extracts were subject to chromatographic separation followed by GC-tandem MS (MS/MS) and LC-MS/MS analysis. Results: For more than 270 pesticide residues in these foods, the test gave acceptable mean recoveries, ranging between 70 and 120%, and relative SDs below 20%. The LOQ was at least 0.01 mg/kg for 380 pesticides. Conclusions: The developed method can greatly reduce the time needed for multiple pesticide residues analysis. Highlights: FaPEx is used for the extraction of pesticide residues that relies on single-use pre-filled sealed cartridges. FaPEx diminishes operation time, glassware demand, and laboratory space requirement. It also significantly decreases the amount of chemical solvents.

Modified QuEChERS method for 24 plant growth regulators in grapes using LC-MS/MS.

A multiresidue analytical method was developed for grapes for the following 24 plant growth regulators: 1-naphthylacetamide, 2,3,5-triiodobenzoic acid, 2,4,5-T, 2-naphthoxyacetic acid, 3-indolylacetic acid, 4-(3-indolyl)-butyric acid, 4-chlorophenoxyacetic acid, 4-nitrophenol, 6-benzylaminopurine, N6-isopentenyladenine, butralin, chlormequat chloride, chlorphonim-Cl, cloprop, forchlorfenuron, gibberellic acid 3, gibberellic acid 4, gibberellic acid 7, inabenfide, mepiquat chloride, paclobutrazol, prohydrojasmon, thidiazuron and uniconizole-P. The compounds were extracted from grape samples using an extraction method modified from the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method. Liquid chromatography - tandem mass spectrometry was used for the detection and quantification of the compounds. Validation of the method was performed by using recovery studies at both intra-day and inter-day intervals, as well as by evaluation of the matrix effect, limit of quantification, trueness and precision. We used matrix-matched calibrations for the quantification of the compounds, which all resulted in determination coefficients (r2) higher than 0.995. The limit of quantification ranged from 0.1 to 5 ng/mL. Recovery studies using three spiking concentrations at varying levels showed recoveries of 70.2-112.6% and 67.5-101.8% at intra-day and inter-day intervals, respectively. Relative standard deviations were below 20% for the recovery studies. The extraction method were further validated by performing recovery study and matrix effect test in six different grape varieties from Taiwan and the United States and all resulted in comparable results. Application of the established method to 50 grape samples, resulted in the detection of chlormequat chloride and forchlorfenuron residues in the tested grapes. The results of the method validation and real sample analysis shows the extraction method is therefore suitable for routine monitoring of residue in grapes.