Factorial Design Optimisation of Solid Phase Extraction for Preconcentration of Parabens in Wastewater Using Ultra-High Performance Liquid Chromatography Triple Quadrupole Mass Spectrometry

Levamisole incorporation in fish feed - Ensuring the medication dose and avoidance of leaching into the water

Levamisole, an anthelmintic and immunostimulant drug, has been studied as a promising alternative for aquaculture use. While oral administration through feeding is the main route of administration in fish farming, no studies evaluating methods of levamisole incorporation into the feed have been reported so far. Therefore, this study aimed to evaluate potential procedures for levamisole incorporation in extruded fish feed using ethyl cellulose, gelatin, or vegetable oil, to avoid drug leaching to the water during the animal's medication. A suitable LC-MS/MS method was optimized (full factorial design), validated, and applied to evaluate the efficiency of the process, the homogeneity of the drug concentration, and the leaching rate. The method has been demonstrated to be selective, precise (RSD < 4.9%), accurate (recovery > 98.4%), and linear (r > 0.99, 125-750 mg kg-1). The incorporation procedures using the three coating agents showed high incorporation efficiency (70%) and a homogeneous drug concentration among the extruded feed pellets. A low levamisole leaching rate was verified in the feed prepared using the ethyl cellulose coating procedure (4.3% after 15 min of immersion in the water). On the other hand, fish feed coated with gelatin and oil resulted in a high leaching rate (30-35% after 15 min). Thus, this study shows that coating ethyl cellulose may be a promising procedure for levamisole incorporation in fish feed and with the potential to enhance its use in animal production while reducing environmental contamination.

Hybrid porous material supported in a cellulose acetate polymeric membrane for the direct immersion thin-film microextraction of parabens in water

A simple and sensitive direct immersion thin-film microextraction (DI-TFME) method based on MIL-101(Cr) modified with carbon nanofibers supported in cellulose acetate (CA-MIL-101(Cr)@CNFs) polymeric membrane was developed for the extraction and preconcentration of parabens in environmental water samples. A high-performance liquid chromatography-diode array detector (HPLC-DAD) was used for the determination and quantification of methylparaben (MP) and propylparaben (PP). The factors affecting the DI-TFME performance were investigated using central composite design (CCD). The linearity of the DI-TFME/HPLC-DAD method obtained under optimal conditions was 0.04-0.04-500 µg/L with a correlation coefficient (R2) greater than 0.99, respectively. The limits of detection (LOD) and quantification (LOQ) for methylparaben were 11 ng/L and 37 ng/L; for propylparaben, they were 13 ng/L and 43 ng/L, respectively. The enrichment factors were 93.7 and 123 for methylparaben and propylparaben. The intraday (repeatability) and interday (reproducibility) precisions expressed as relative standard deviations (%RSD) were less than 5%. Furthermore, the DI-TFME/HPLC-DAD method was validated using real water samples spiked with known concentrations of the analytes. The recoveries ranged from 91.5 to 99.8%, and intraday and interday trueness values were less than ±15%. The DI-TFME/HPLC-DAD approach was effectively used for the preconcentration and quantification of parabens in river water and wastewater samples.

Optimization and validation of liquid-liquid extraction with low-temperature purification (LLE-LTP) for determining fluopyram fungicide in water samples using HPLC-DAD

Fluopyram is a fungicide and nematicide that belongs to the chemical group of benzamides, which act as succinate dehydrogenase inhibitors (SDHIs) on the mitochondrial respiratory chain of fungi. Despite being well known in several countries, there are few studies involving the optimization and validation of extraction methods for determining fluopyram in water samples. Therefore, this study aimed to optimize and validate liquid-liquid extraction with low-temperature purification (LLE-LTP) to determine fluopyram fungicide in water samples using high-performance liquid chromatography with diode array detection (HPLC-DAD). A two-level full factorial design was employed to optimize LLE-LTP which enabled achieving a recovery rate close to 100% and relative standard deviations (RSD) < 10.0%. The validation showed that the extraction method may be considered selective, precise, accurate, and linear in the range of 6.0 to 200 μg L^-1. The LOD and LOQ were 4.0 and 6.0 μg L^-1, respectively, proving the efficiency of this method for trace level determination of this fungicide in water samples. LLE-LTP coupled to HLPC-DAD analysis showed a matrix effect of less than 8% and it was applied in monitoring 20 environmental water samples, but no fluopyram residue was detected in the samples.