Canping Pan

Multiresidue method for the determination of 77 pesticides in wine using QuEChERS sample preparation and gas chromatography with mass spectrometry

A method based on a QuEChERS (quick, easy, cheap, effective, rugged, safe) sample preparation method and gas chromatography with mass spectrometric detection by selected ion monitoring (GC/MS-SIM) was developed for simultaneous determination of 77 pesticide residues in wine. An extraction of 10 ml of sample with acetonitrile followed by liquid–liquid partition formed by the addition of 4 g MgSO4 and 3 g NaCl was applied in the sample preparation. The clean-up was carried out by applying dispersive solid-phase with 150 mg MgSO4 as well as 50 mg primary secondary amine (PSA). One quantitation ion and at least two identification ions were selected in the analytical method for each pesticide compound by GC/MS. The recovery data were obtained by spiking blank samples at two concentration levels (0.05 and 0.2 mg l−1). The recoveries of all pesticides were in the range 70–110%, with intra-day precision of less than 15%, and the inter-day precision of less than 22% and 15% for 0.05 and 0.2 mg l−1 fortification levels, respectively. Linearity was between 0.02 and 2 mg l−1 with determination coefficients (R 2) greater than 0.98 for all compounds. The limits of quantification (LOQs) for the 77 pesticides ranged from 0.003 to 0.05 mg l−1. This method was applied for routine analysis in market products.

Direct analysis in real time mass spectrometry for the rapid identification of four highly hazardous pesticides in agrochemicals

RATIONALE Direct analysis in real time (DART) is a new ion source technique, which is conducted in the open air under ambient conditions, applied to the rapid and direct analysis of any material (gases, liquids, and solids) with minimal or no sample preparation. In order to take advantage of the capacity of DART mass spectrometry for the real-time analysis of hazardous ingredients in commercial agrochemicals, a pilot study of rapid qualitative determination of hazardous pesticides was performed. METHODS Highly hazardous pesticides were identified by DART ionization coupled to a single-quadrupole mass spectrometer (DART-MS). Acetonitrile was chosen for dissolving samples prior to the analysis. Samples were analyzed by this technique in as little as 5 s. RESULTS Phorate, carbofuran, ethoprophos and fipronil were be detected directly from commercial agrochemicals. The ionization-related parameters (DART temperature, grid voltage and MS fragment) of these compounds were optimized to obtain highly response. Isotope patterns were taken into consideration for qualitative identification. Relative standard deviations (RSDs, n = 5) of 2.3-15.0% were obtained by measuring the relative abundance of selected isotopes. CONCLUSIONS This study showed that DART-MS technology was able to qualitatively determine the existence of highly hazardous pesticides in commercial pesticide formulations. It is suggested that this technology should be applied for routine monitoring in the market.

Residue Dynamics Studies of Aluminum Phosphide and Magnesium Phosphide in Stored Rice Utilizing a Sulfuric Acid-Toluene Extraction Coupled with Gas Chromatography Analysis

ABSTRACT A method for determination of aluminum phosphide and magnesium phosphide residues in rice was developed and validated. This work, through good laboratory practices, demonstrated aluminum and magnesium phosphide residue dynamics in stored rice. Rice samples were treated with sulfuric acid, which hydrolyzed phosphides to phosphine (PH3), which was simultaneously trapped in toluene. The organic layer was filtered and then analyzed by gas chromatography with a flame photometric detector. The PH3 calibration curves showed a strong linear relationship in the range of 0.012–1.2 mg/L, with a correlation coefficient of 0.999. The limit of detection of this method was 0.004 mg/kg. The average recoveries from samples fortified with aluminum phosphide and magnesium phosphide ranged from 76.8 to 106.5% with relative standard deviations below 10.2% (n = 5). PH3 was applied separately to rice samples to study dissipation dynamics at application dosages of 9.0 and 12 g/m3, respectively. The results showed half-l...