Abstract This work aims to develop analytical methods using high-performance liquid chromatography with a diode array detector (HPLC-DAD) for analysis and quantification of avermectins (AVMs) and milbemycins (MBMs) in bulk samples. First, the methods were optimized and some parameters such as temperature, flow rate, injection volume and mobile phase with different proportions of solvents were evaluated. The best chromatographic conditions were obtained using the Phenomenex® C18 (150 × 4.60 mm, 5 μm) column at a temperature of 20 °C, flow rate of 1.2 mL min-1, injection volume of 20 μL, and detection at 250 nm. Acetonitrile: ultrapure water (87: 13, v/v) was used as mobile phase for moxidectin and eprinomectin, and acetonitrile: methanol: ultrapure water (53: 35: 12, v/v/v) for abamectin and ivermectin. Under these conditions satisfactory results were obtained, with appropriate limits of detection and quantification, acceptable linearity, precision, accuracy, and robustness. These methods satisfy the need for analytical methods for the multi-determination of MBMs and the B1a and B1b forms of AVMs by HPLC-DAD, which can be considered simple, effective, innovative and should aid in the development of the field.

In this work, we have studied both experimentally and theoretically the oxybutynin chiral discrimination. According to the main results, the enantioseparation of oxybutynin was efficiently achieved by high performance liquid chromatography in normal phase using the Chiralpak® AD column, which has amylose tris (3,5‐dimethylphenylcarbamate) as a chiral selector. The energetic and structural parameters obtained via density functional theory calculations pointed out the chiral discrimination as well as the enantiomeric elution order of oxybutynin, thus explaining, at molecular level, the experimental data. Finally, the strength of the hydrogen bonds played a key role in the discrimination between the oxybutynin diastereomeric complexes formed.

ELECTROSPINNING APPLIED TO THE DEVELOPMENT OF ADSORBENT NANOFIBERS AIMING AT IMPROVING SOLID PHASE (MICRO)EXTRACTION TECHNIQUES. The limitations and challenges associated with the complex analyte-matrix-interfering interactions make the development of new sorbent materials an attractive line in several research areas, ranging from the synthesis and characterization to the application of these materials. Among the different strategies for manufacturing sorbent nanomaterials, the electrospinning of nanofibers based on polymeric solutions incorporated into Metal-Organic Frameworks (MOFs), Molecularly Imprinted Polymers (MIPs) and Nanoparticles (NPs) have represented in recent years, one of the methods more versatile and promising with regard to obtaining materials with large surface area and potential for functionalization and chemical modification. In this sense, the objective of this contribution is to highlight recent work aimed at the synthesis of electrospun nanofibers applied in adsorption and sample preparation processes, highlighting the synthetic nanofiber strategies based on MOFs, MIPs and NPs and the main challenges and perspectives of the applications, although little explored, of these materials in solid phase extraction and microextraction techniques.

This study shows that Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) can be used as supporting tools for the evaluation of the quality of antiparasitics. In addition, an analytical methodology was developed and validated to quantify simultaneously thiabendazole (TB), febantel (FB), toltrazuril (TZ), and fluazuron (FZ) in bulk and in their veterinary pharmaceutical formulations using reverse phase high performance liquid chromatography (RP-HPLC). In order to investigate stability, pharmaceuticals were submitted to degradation processes under different conditions, such as recommended by the International Conference on Harmonization. The chromatographic conditions were optimized and the validation parameters, such as selectivity, linearity, detection limit, quantification limit, precision, accuracy, and robustness showed results within acceptable standards. All analytes were stable in the stability assays in acid and basic media and thermal conditions, except in the oxidation process, which presented two degradation peaks. Physicochemical characterization by TGA, FTIR, and SEM of raw materials of TB, FB, TZ, and FZ provided information about the authenticity of the analytes, proving the wide applicability of the instrumental techniques. The RP-HPLC proposed method was found to be accurate, precise, and reproducible and can in addition be used for routine quality control analysis.

Piplartine (PPTN) is an alkaloid amide found in Piper species that presents different activities. PPTN determination in rat plasma is necessary to better understand its biological effects. The aim of this study was to develop a sensitive LC-MS/MS method for the determination of PPTN in rat plasma. The performance criteria for linearity, sensitivity, precision, accuracy, recovery, and stability have been assessed and were within the recommended guidelines. The validated method proved to be suitable in a pilot study of PPTN kinetic disposition in rat plasma after a single intraperitoneal dose, and represents an appropriate tool to further pharmacokinetic studies.

The enantioselective biotransformation of propranolol (Prop) by the endophytic fungi Phomopsis sp., Glomerella cingulata, Penicillium crustosum, Chaetomium globosum and Aspergillus fumigatus was investigated by studying the kinetics of the aromatic hydroxylation reaction with the formation of 4-hydroxypropranolol (4-OH-Prop). Both Prop enantiomers were consumed by the fungi in the biotransformation process, but the 4-hydroxylation reaction yielded preferentially (-)-(S)-4-OH-Prop. The quantity of metabolites biosynthesized varied slightly among the evaluated endophytic fungi. These results show that all investigated endophytic fungi could be used as biosynthetic tools in biotransformation processes to obtain the enantiomers of 4-OH-Prop.

Analysis of diazepam (DZP) and its active metabolite nordiazepam (NDZP) in plasma is commonly performed in clinical medicine to ensure proper therapeutic effects while minimizing the incidence of toxicity. This study aimed to optimize analytical parameters and compare two pre-treatment techniques, liquid-liquid (LLE) and solid phase extraction (SPE), as well as liquid chromatographic conditions to analyze simultaneously DZP and NDZP in plasma from 20 patients treated with a daily dose of 10 mg. Both techniques showed to be well in line with the international criteria for analytical validation, which permitted to quantify DZP (66.2 - 1148.6 ng mL-1) and NDZP (138.5 - 808.6 ng mL -1) in all samples. The correlation coefficients between SPE and LLE were respectively 0.9729 for DZP and 0.9643 for NDZP.