In this work, a miniaturized version of the QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was optimized, validated, and applied for extracting eight pesticide residues in anuran liver tissue samples. The extracts were quantified by high-performance liquid chromatography with diode array detection, and the detected residues in liver tissue samples were identified by tandem mass spectrometry-liquid chromatography. The optimized extraction method entailed the scale reduction of the QuEChERS method twenty times using 500 mg of liver tissue sample, 200 mg Mg2SO4, 50 mg NaCl, 1.5 mL of acetonitrile, and a mixture of 25 mg C18 + 25 mg PSA (primary-secondary amine) as dispersive solid-phase extraction sorbent. The method was validated using liver tissue samples spiked at two levels of pesticide concentrations according to the SANTE/11312/2021 document. Recoveries ranged from 91-110% with a relative standard deviation < 20%. The method robustness assessed by the Steiner and Youden test resulted in recovery rate variations of less than 2% for all pesticides after deliberated changes in seven variables. The validated method was applied to 72 liver tissue samples from two anuran species, registering residues of some pesticides in 31 samples. The proposed method proved to be efficient, precise, and robust for determining pesticide residues in anuran liver tissues. work quick, quick (quick easy cheap effective rugged safe highperformance high performance detection spectrometryliquid spectrometry sample 20 Mg2SO4 MgSO Mg SO 5 NaCl 15 1 1. acetonitrile 2 C C1 primarysecondary primary secondary amine solidphase solid phase sorbent SANTE113122021 SANTE 11312 2021 SANTE/11312/202 document 91110% 91110 91 110% 110 91-110 20% variables 7 species 3 efficient precise tissues Mg2SO SANTE11312202 1131 202 SANTE/11312/20 9111 9 11 91-11 SANTE1131220 113 SANTE/11312/2 911 91-1 SANTE113122 SANTE/11312/ 91- SANTE11312 SANTE/11312 SANTE1131 SANTE/1131 SANTE113 SANTE/113 SANTE11 SANTE/11 SANTE1 SANTE/1 SANTE/

The physical adsorption of a polymer, poly(3,3,3-trifluoropropylmethylsiloxane), on aluminized silica particles, without any additional procedure for polymer immobilization, was studied for 180 days to evaluate the new chromatographic support. Morphological, structural, and chromatographic evaluations of the stationary phase were assessed. After the 15th day of adsorption, a sufficient polymer amount adsorbs onto the aluminized silica particles to separate mixtures of compounds in reversed-phase mode. However, after the 60th day, the polymer layer adhesion occurs more strongly, self-coating the aluminized silica particles. The self-coated stationary phases after 60 days showed similar chromatographic profiles with low hydrophobicity and more interactions with polar compounds, characteristics arising from the fluorinated polymer. The aluminized silica support firmly adhered to the polymer layer, resulting in a separation material chemically stable at alkaline conditions, suggesting a surface reactivity like other well-established supports without asymmetrical peaks for polar compounds. poly3,3,3trifluoropropylmethylsiloxane, poly333trifluoropropylmethylsiloxane polytrifluoropropylmethylsiloxane poly 3,3,3 trifluoropropylmethylsiloxane , 3 poly(3,3,3-trifluoropropylmethylsiloxane) immobilization 18 Morphological structural assessed th reversedphase reversed mode However strongly selfcoating self coating selfcoated coated 6 conditions wellestablished well established poly3 3trifluoropropylmethylsiloxane poly3,3,3trifluoropropylmethylsiloxane 333 3,3, poly(3,3,3-trifluoropropylmethylsiloxane 1 33 3,3 3,

Poly(ethylene oxide-co-dimethylsiloxane) was thermally immobilized on silica particles-Si(PEO)-to separate small polar compounds with water-rich mobile phases. Poly(ethylene oxide-co-dimethylsiloxane) content on Si(PEO) stationary phase was optimized using a central composite design. Infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis morphologically and structurally characterized the optimized material. Separation of standard test mixtures showed that the Si(PEO) phase had a typical reversed-phase elution order. However, the Si(PEO) phase retained polar compounds better than C18 or aqueous C18 phases under water-rich mobile phases. Under this condition, small changes in the acetonitrile fraction resulted in a marked increase in the retention of some polar drugs on the Si(PEO) phase. A typical condition observed in per aqueous liquid chromatography separations, a more environmentally friendly liquid chromatography approach. On the other hand, hydrophobic compounds showed lower mass transfer rates due to their low solubility in the aqueous mobile phase. Thus, the Si(PEO) phase was more suitable and efficient for separating polar or hydrophilic compounds.

Biodiesel purification by water washing has been proved to be an unattractive process from an economic and environmental point of view. In this work, we propose the use of regenerated cellulose membranes from peanut shell as an alternative in the biodiesel purification. The preparation of the membranes was optimized from a central composite design, resulting in dense and non-porous membranes. However, in contact with biodiesel, the membranes undergo expansion due to the retention of methanol, water, and glycerol molecules, allowing the permeation of fatty acid methyl esters. The filtered biodiesel presents quality parameters, such as total ester content of 98.3 ± 1.4% and free glycerol content < 0.02%, in agreement with the main regulatory agencies. The regenerated cellulose membranes from peanut shell are easily prepared, with high repeatability (relative standard deviation (RSD) < 1.8%) and are presented as an economical and environmental solution for the biodiesel purification.

Buffered solutions, additives, and column temperature are widely used in high-performance liquid chromatography to promote adequate retention of compounds and to improve the chromatographic separation. However, these factors can dramatically reduce the column lifetime. In this work, the effect of column temperature, pH and the salt type and concentration in buffered mobile phases were evaluated on the stability of a typical commercial C18 stationary phase. A method for rapid evaluation of stationary phase degradation caused by these variables was employed to avoid the generation of large volumes of organic waste. By monitoring the performance of stationary phase in the separation of a standard test mixture, it was possible to verify that the pH of the mobile phase is the most drastic condition to reduce the column lifetime. Buffer solutions of inorganic salts as well as the use of temperatures above 40 °C also significantly reduce the column lifetime. However, a column can have its use extended working with low concentrations of organic additives in the mobile phase, under moderated temperature, and adjusting the pH to the safety range of silica-based materials.

This study describes the use of uncured polydimethylsiloxane (PDMS) as a binder agent to prepare carbon paste electrodes (CPEs). A comparative study between the properties of CPEs prepared with PDMS and mineral oil Nujol®, the most common binder agent for CPEs, was carried out. Cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry showed that PDMS-CPEs presented higher electrical conductivity, active electrochemical area, and wider useful potential window compared with Nujol®-CPEs. Moreover, PDMS-CPEs were more stable in aqueous mixtures containing 50% (v/v) of ethanol or methanol than Nujol®-CPEs. PDMS-CPEs have also provided higher sensitivity and lower limit of detection to propranolol than Nujol®-CPE. Therefore, this study demonstrated that PDMS is a promising alternative binder agent able to produce CPEs with superior chemical/electrochemical stability and improved analytical performance.