Determination of enantiomeric fractions of cypermethrin and cis-bifenthrin in Chinese teas by GC/ECD

Method Development and Validation of Seven Pyrethroid Insecticides in Tea and Vegetable by Modified QuEChERS and HPLC-MS/MS

This study developed a quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure for determining seven pyrethroid pesticide residues in tea, cucumber, and tomato via high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The overall average recoveries of the seven pyrethroids were 72%-104% (relative standard deviation (RSD); 2.0%-16.1%, 89%-109% (RSD; 0.7%-17.3%), 82%-110% (RSD; 1.6%-17.1%) for tea, cucumber and tomato, respectively. The determination coefficient (R²), the limit of detection (LOD), and the limit of quantification (LOQ) were ≥ 0.99, 0.007-1.875 μg kg^-1, and 0.025-6.250 μg kg^-1, respectively. The method was successfully used to monitor the pyrethroid pesticide residues in market samples. HPLC-MS/MS rapidly, sensitively, and accurately determined the pyrethroid pesticide residues.

Monitoring and risk assessment of pesticide residues in selected herbal medicinal products in Ghana

The high patronage of herbal medicinal products in Ghana for the treatment of diverse disease conditions raises concerns about patient safety, given that much of the raw materials for production are obtained from the wild or farmlands potentially exposed to varied agrochemical residues. Therefore, the work sought to investigate the contamination of herbal medicinal products with pesticide residues and assess the potential risk posed to patients. As a result, validated gas chromatography with mass spectrometry as a detector was used to determine forty-two pesticides in thirty herbal medicinal products. The performance parameters of the method such as linearity, accuracy, and precision were found as acceptable. Pesticide residues such as chlorpyrifos and/or bifenthrin were found in 4/30 herbal medicinal products. Specifically, 3/30 herbal medicinal products contained only one pesticide, while 1/30 was contaminated with both pesticide residues. The levels of pesticide residue contamination ranged between 2.5 and 5.0 µg/kg. The acute hazard quotient and chronic hazard quotient for the two pesticide residues were evaluated and ranged between 0.21 and 0.92% and between 8.21 × 10^-4 and 5.88 × 10^-3%. The detected pesticide residue levels are below the maximum residue limit values, which may not cause acute and chronic health risks due to intake of the selected herbal medicinal product. Nevertheless, patient safety and potential public health risk can be reduced by regular monitoring, and regulation of pesticide residue levels in herbal medicinal products.

Stereoselective Analysis of Chiral Pyrethroid Insecticides Tetramethrin and α-Cypermethrin in Fruits, Vegetables, and Cereals

This manuscript presents an effective and robust method for simultaneous stereoselective determination of two pyrethroid insecticides, tetramethrin and α-cypermethrin in different food products by high-performance liquid chromatography. Enantioseparation was carried out using reversed-phase chromatography, and the influences of four polysaccharide-based chiral columns, mobile phase composition, and column temperature on retention were fully investigated. Satisfactory separation was obtained on Chiralpak IG column using acetonitrile-water (75:25, v/v) under isocratic conditions. To extract and purify the target analytes from food matrices, matrix solid-phase dispersion was employed with C₁₈ as dispersant and primary secondary amine as well as graphitized carbon black as cleanup sorbents. Response surface method based on Box-Behnken design was implemented to assist optimization of the extraction variables. Then, method validation was done in real samples including specificity, linearity, sensitivity, trueness, precision, as well as stability, and its analytical performance fulfills the criteria recommended by the European Union SANTE/11945/2015, demonstrating its applicability in studying the stereochemistry of chiral tetramethrin and α-cypermethrin in food products.

Enantiomeric separation of type I and type II pyrethroid insecticides with different chiral stationary phases by reversed-phase high-performance liquid chromatography

The enantiomeric separation of type I (bifenthrin, BF) and type II (lambda-cyhalothrin, LCT) pyrethroid insecticides on Lux Cellulose-1, Lux Cellulose-3, and Chiralpak IC chiral columns was investigated by reversed-phase high-performance liquid chromatography. Methanol/water or acetonitrile/water was used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase composition, column temperature, and thermodynamic parameters on enantiomer separation were carefully studied. Bifenthrin got a partial separation on Lux Cellulose-1 column and baseline separation on Lux Cellulose-3 column, while LCT enantiomers could be completely separated on both Lux Cellulose-1 and Lux Cellulose-3 columns. Chiralpak IC provided no separation ability for both BF and LCT. Retention factor (k) and selectivity factor (α) decreased with the column temperature increasing from 10°C to 40°C for both BF and LCT enantiomers. Thermodynamic parameters including ∆H and ∆S were also calculated, and the maximum R_s were not always obtained at lowest temperature. Furthermore, the quantitative analysis methods for BF and LCT enantiomers in soil and water were also established. Such results provide a new approach for pyrethroid separation under reversed-phase condition and contribute to environmental risk assessment of pyrethroids at enantiomer level.

Sucrose as chiral selector for determining enantiomeric composition of metalaxyl by UV-vis spectroscopy and PLS regression

This study revealed that it was possible to determine the enantiomeric composition of with multivariate regression models of spectral data obtained by ordinary UV-vis spectrophotometry of enantiomeric guest-host complexes. The total 60samples involving three concentration levels of metalaxyl as low, medium and high were prepared for spectral collecting. Four methods of modeling were subsequently proposed and compared including two common ways and two compensating ways for variations in total analyte concentration. Firstly, without normalization robust modeling was failed to achieve while employing the medium concentration levels as calibration and the other two levels as a validation. The same case occurred when full-cross validation was conducted. Besides, two enhanced methods were developed to account for the systematic variation. One of which normalized the spectra with respect to the total concentration of enantiomeric, along with spectral data, as a variable in the statistical analysis. The other one ignored variations in total concentration, relying on the specific band normalization to sort out any variations due to total concentration differences. The results clearly demonstrated that the spectra according to concentration provided the acceptable predictive ability in determining enantiomeric composition.

[Determination of 88 pesticide residues in tea using gas chromatography-tandem mass spectrometry]

A multi-residue method for the determination of 88 pesticides in tea using gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed. The target compounds were extracted with acetonitrile by accelerated solvent extraction (ASE), and the extracts were cleaned up by solid phase extraction (SPE) with a Carbon/NH2 cartridge and eluted with acetonitrile-toluene (3:1, v/v) before the identification and quantification of the residues by GC-MS/MS. Performance characteristics, such as accuracy, precision, linear range, limits of detection (LODs) and limits of quantification (LOQs), for each pesticide were determined. At low concentration level spiked (6.4 microg/kg), the average recoveries were in the range of 70%-100% for 87.5% analytes and the relative standard deviations (RSDs) were lower than 15% for 87.5% analytes. The quantification of analytes was carried out using the most sensitive transition for every compound and by matrix-matched standards calibration. The LOQs (S/N = 10) were less than 10 microg/kg for 86.4% analytes. The method is sensitive, accurate, reliable and suitable for the simultaneous determination of multi-residue pesticides in green tea, Woolong tea, black tea and Puer tea.