Ultrasonic-induced grafted lanthanum sulfide decorated multi-walled carbon nanotube onto bacterial cellulose applied for adsorption of pesticides in environmental waters

A new biosorbent was fabricated by modification of bacterial cellulose biopolymer grafted with lanthanum sulfide decorated carboxylated multiwall carbon nanotube (La2S3@MWCNT@BC). The sorbent was employed in a green alternative dispersive-solid phase extraction of a variety of 14 pesticides in environmental water samples. The analyses were performed using GC-µECD. The properties and structure of La2S3@MWCNT@BC nanocomposite were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and adsorption-desorption isotherms. The composition of the sorbent was also investigated to evaluate the adsorptive properties of its constituents. The impact of various parameters influencing extraction efficacies such as sorbent dose, adsorption time, sample pH, ionic strength, and desorption conditions was investigated. The method was validated by specificity, matrix effect % (-0.4 to -7.4), enrichment factor (4-10), limits of quantification (0.007-0.31 μg L-1), matrix-matched calibration linearity (0.01-200 µg L-1), determination coefficients (r2=0.9921-0.9998), and precision. The optimized method was applied for the analysis of multiclass pesticides in seven environmental and drinking waters and the recoveries were obtained in the 81-108 % range with RSDs of 2.5-4.7 %. This paper is the first report on the synthesis and use of La2S3@MWCNT@BC nanocomposite to extract pesticides from different water samples. The greenness of the procedure was evaluated by the AGREE protocols.

Rapid method for the detection of rodenticides in contaminated foods

Rodenticides are toxic chemicals used to control rodent populations and are among the most common household toxicants. Ingestion of foods contaminated with rodenticides may cause severe illness or death in humans and animals. A rapid analytical method was developed for the identification of nine common rodenticides in foods using solid-liquid extraction followed by dispersive-solid phase extraction prior to the analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and UV detection. The method validation on a variety of food matrices including cornmeal, peanut, whole wheat flour and pork liver produced average recoveries between 91.2 and 107% with relative standard deviations between 2.6 and 14% for all studied rodenticides. The method detection limits ranged from 2.7 to 8.2 μg/kg (ppb) for eight rodenticides analyzed by LC-MS/MS and between 0.10 and 0.21 mg/kg (ppm) for bromethalin which was analyzed by LC with UV detection. This method could be useful in preparedness for emergency response situations involving widespread food contamination, terrorist acts or for forensic studies.

Graphene Oxide-Based Dispersive-Solid Phase Extraction for Preconcentration and Determination of Ampicillin Sodium and Clindamycin Hydrochloride Antibiotics in Environmental Water Samples Followed by HPLC-UV Detection

In this work, a reusable graphene oxide (GO) based dispersive-solid phase extraction (d-SPE) was synthesized and used for the analysis of trace ampicillin sodium (AMP) and clindamycin hydrochloride (CLI) in water samples followed by high performance liquid chromatography-UV detection (HPLC-UV). Batch experiments were conducted to investigate the effects of pH and volume of the sample solution, contact time, adsorption isotherms, temperature, and desorption conditions. The maximum adsorption capacities of AMP and CLI on GO nanosheets were found to be 33.33 mg g^-1 and 47 mg g^-1, respectively. The adsorption isotherm data can be well fitted by Temkin (AMP and CLI) and Freundlich (AMP), and the adsorption process followed the pseudo-second-order model. The thermodynamic parameters were calculated, indicated that the adsorption process of both analytes were spontaneous and exothermic. In addition, the d-SPE following HPLC analyses showed good linearity in the range of 0.5-200 ng mL^-1 (R²= 0.999) for AMP and 1-200 ng mL^-1 (R²= 0.999) for CLI, with LOD of 0.04 and 0.24 ng mL^-1 for AMP and CLI, respectively. The percent of extraction recoveries, intra and inter-day precisions (expressed as RSD %, n = 3) were in the range of 96.4-101.6%, 2.2-3.0, and 3.7-4.7 for AMP as well as 94.2-98.6%, 2.2-3.8, and 3.5-4.6 for CLI, respectively. The preconcentration factor of 20 was achieved for both analytes. From these results, it can be concluded that the validated method is a simple, cost-effective and repeatable method for analysis of AMP and CLI in water samples and provide a new platform for antibiotics decontamination.

Two-step dispersive-solid phase extraction strategy for pesticide multiresidue analysis in a chlorophyll-containing matrix by gas chromatography-tandem mass spectrometry

Two-step dispersive-solid phase extraction strategy for the cleanup of QuEChERS extracts in multiresidue analysis of current-use pesticides in a chlorophyll-containing matrix was evaluated and is reported for the first time. The proposed approach combines two sequential steps of dispersive-solid phase extraction (d-SPE) to reduce matrix co-extractives. In the first step, primary secondary amine (PSA) together with a new type of sorbent, known as ChloroFiltr, was employed. This was followed by a second step of d-SPE using octadecyl (C18) and graphitized carbon black (GCB). Also, new zirconium dioxide-based sorbents (Z-Sep+ and Z-Sep/C18) were evaluated but the use of GCB/C18 provided the highest pesticide coverage with recoveries in the range of 70-120% from spiked green soybean samples. The final extracts were analyzed by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). The overall recoveries at three spiking levels of 0.01, 0.05 and 0.2 mg kg(-1) were 96±15%, 93±13% and 92±13% with relative standard deviations of 10±7%, 9±5%, and 11±5%, respectively. The proposed method provided matrix effect <20% for 77% of the target compounds, which may be considered as negligible because such variability is closed to the accepted repeatability. For the rest of 8 and 15% of the compounds, the matrix effect was 20-30% and >30%, respectively. The developed method was successfully applied to study dissipation patterns of pesticides applied to soybean in experimental plot trials, thus contributing to establish safe and proper use of pesticides by extension of authorization on minor crops in Poland.