Determination of carbaryl and 1-naphthol in english apples and strawberries by combined gas chromatography-fluorescence spectrometry

A Simple and Reliable Dispersive Liquid-Liquid Microextraction with Smartphone-Based Digital Images for Determination of Carbaryl Residues in Andrographis paniculata Herbal Medicines Using Simple Peroxidase Extract from Senna siamea Lam. Bark

A simple and reliable dispersive liquid-liquid microextraction (DLLME) coupled with smartphone-based digital images using crude peroxidase extracts from cassia bark (Senna siamea Lam.) was proposed to determine carbaryl residues in Andrographis paniculata herbal medicines. The method was based on the reaction of 1-naphthol (hydrolysis of carbaryl) with 4-aminoantipyrine (4-AP) in the presence of hydrogen peroxide, using peroxidase enzyme simple extracts from cassia bark as biocatalysts under pH 6.0. The red product, after preconcentration by DLLME using dichloromethane as extraction solvent, was measured for blue intensity by daily life smartphone-based digital image analysis. Under optimized conditions, good linearity of the calibration graph was found at 0.10–0.50 mg·L⁻¹ (r² = 0.9932). Limits of detection (LOD) (3SD/slope) and quantification (LOQ) (10SD/slope) were 0.03 and 0.09 mg·L⁻¹, respectively, with a precision of less than 5%. Accuracy of the proposed method as percentage recovery gave satisfactory results. The proposed method was successfully applied to analyze carbaryl in Andrographis paniculata herbal medicines. Results agreed well with values obtained from the HPLC-UV method at 95% confidence level. This was simple, convenient, reliable, cost-effective and traceable as an alternative method for the determination of carbaryl.

N-doped mesoporous carbon as a new sorbent for ultrasonic-assisted dispersive micro-solid-phase extraction of 1-naphthol and 2-naphthol, the biomarkers of exposure to naphthalene, from urine samples

This study aimed to optimize a new sample preparation method using N-doped mesoporous carbon sorbent for simultaneous measurement of 1-naphthol and 2-naphthol, the biomarkers of exposure to naphthalene. The samples were analyzed using high-performance liquid chromatography supplied with ultraviolet detector (HPLC-UV). N-doped mesoporous carbon sorbent was obtained via the hard template procedure. The synthesized nanosorbent was then characterized by transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and elemental analysis (CHN). The effective factors in the extraction of the studied biomarkers were examined by the Box-Behnken (BBD) methodology. Regarding the optimum conditions, the sketched calibration curve for naphthols was linear in the concentration levels of 1-600 µg L^-1 for human urine samples. The accuracy and reproducibility of the introduced method were determined using the relative recovery (RR %) and relative standard deviation (RSD %) tests on the fortified urine samples. RR% and RSD% were found to be 97.0-101.2% and 3.1-9.0%, respectively. The calculated method detection limit of the optimized procedure was 0.3 µg L^-1 and 0.5 µg L^-1 for 1-naphthol and 2-naphthol, respectively.

Spectrophotometric determination of carbaryl pesticide and its hydrolysis product in soil and strawberry samples

A spectrophotometric method for the determination of carbaryl in soil and strawberry fruit samples is described. The method is based on the coupling of 1-naphthol obtained from hydrolysing carbaryl with diazotised sulphanilic acid in an alkaline medium to form p-(4-hydroxyl-1-naphtylaza)benzenesulphonic acid which has a maximum absorbance at 475 nm. Beer's law is obeyed in the range of 0.01-0.1 ppm of carbaryl. The proposed method is sensitive and rapid. The average carbaryl content of strawberry fruits was 6.03 ppm and the average 1-naphthol content of soil samples was 16.29. The samples were obtained from their sources during 1 day after approx. 24 h of rain.

Validation of a congener specific method for ortho and non-ortho substituted polychlorinated biphenyls in fruit and vegetable samples

An on-line procedure has been developed and validated for the clean-up and fractionation of ortho and non-ortho-PCBs in fruit and vegetable samples. The procedure combines silica/acid and carbon/glass fibre columns with gas chromatography-mass spectrometry. Chromatography on carbon/glass fibre allowed collection of mono-ortho/di-ortho and non-ortho-PCB fractions, which were determined separately by GC-MS. The method was validated by replicate analyses and by inter-laboratory comparison of data for PCB congeners determined in fruit and vegetable samples collected in South Wales. The concurrent determination of ortho and non-ortho substituted PCBs is reported with recoveries ranging from 55-95% and a mean intra-laboratory precision (%COV) of 9.5% for apple extracts.