Percorrer por autor "Ahmad, Samir M."
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- Application of bar adsorptive microextraction for the determination of levels of tricyclic antidepressants in urine samplesPublication . Oliveira, Mariana N.; Gonçalves, Oriana C.; Ahmad, Samir M.; Schneider, Jaderson K.; Krause, Laiza C.; Neng, Nuno R.; Caramão, Elina B.; Nogueira, José M. F.This work entailed the development, optimization, validation, and application of a novel analytical approach, using the bar adsorptive microextraction technique (BAμE), for the determination of the six most common tricyclic antidepressants (TCAs; amitriptyline, mianserin, trimipramine, imipramine, mirtazapine and dosulepin) in urine matrices. To achieve this goal, we employed, for the first time, new generation microextraction devices coated with convenient sorbent phases, polymers and novel activated carbons prepared from biomaterial waste, in combination with large-volume-injection gas chromatography-mass spectrometry operating in selected-ion monitoring mode (LVI-GC-MS(SIM)). Preliminary assays on sorbent coatings, showed that the polymeric phases present a much more effective performance, as the tested biosorbents exhibited low efficiency for application in microextraction techniques. By using BAμE coated with C18 polymer, under optimized experimental conditions, the detection limits achieved for the six TCAs ranged from 0.2 to 1.6 μg L−1 and, weighted linear regressions resulted in remarkable linearity (r2 > 0.9960) between 10.0 and 1000.0 μg L−1. The developed analytical methodology (BAμE(C18)/LVI-GC-MS(SIM)) provided suitable matrix effects (90.2–112.9%, RSD ≤ 13.9%), high recovery yields (92.3–111.5%, RSD ≤ 12.3%) and a remarkable overall process efficiency (ranging from 84.9% to 124.3%, RSD ≤ 13.9%). The developed and validated methodology was successfully applied for screening the six TCAs in real urine matrices. The proposed analytical methodology proved to be an eco-user-friendly approach to monitor trace levels of TCAs in complex urine matrices and an outstanding analytical alternative in comparison with other microextraction-based techniques.
- Bar adsorptive microextraction approach for trace determination of local anesthetics in urine matricesPublication . Pereira, Joana R. P.; Rocha, Daniela C.; Neng, Nuno R.; Maurício, Paulo; Torres, M. Edite; Ahmad, Samir M.; Quintas, AlexandreThe present work reports the development, optimization, and validation, of a methodology to determine lidocaine, procaine, tetracaine, and benzocaine in urine matrices. Two extractive preconcentration techniques, solid-phase microextraction (SPME) LC Tips and bar adsorptive microextraction (BAμE), were studied and applied to the four target anesthetics, followed by gas chromatography-mass spectrometry (GC-MS) analysis. Several parameters that could affect microextraction and back-extraction were optimized using two different designs of experiments (Box–Behnken and full-factorial) to maximize extraction efficiency from aqueous media. Under optimized experimental conditions, the BAμE technique showed better performance than SPME LC Tips and was chosen for validation assays and urine sample analysis. In blank urine, the BAµE/GC-MS methodology revealed suitable sensitivity (LOD between 2 and 18 ng/mL), good linearity (r2 ≥ 0.9945) between 0.5 and 30.0 µg/mL and recovery yields of 30.3–97.9%. Good precision (%RSD ≤ 8.8%) and accuracy (bias % between −15.9 and 15.0%) values were achieved. The developed methodology was successfully applied to the target anesthetics analysis of volunteers’ urine matrices and proved to be an environmentally friendly alternative to monitor trace levels of local anesthetics in complex matrices compared to other extraction techniques.
- Bar adsorptive microextraction coated with carbon-based phase mixtures for performance-enhancement to monitor selected benzotriazoles, benzothiazoles, and benzenesulfonamides in environmental water matricesPublication . Ahmad, Samir M.; Calado, Bruno B.C.; Oliveira, Mariana N.; Neng, Nuno R.; Nogueira, J.M.F.In the present work we propose, for the first time, bar adsorptive microextraction coated with carbon-based phase mixtures, followed by microliquid desorption and high performance liquid chromatography-diode array detection (BAμE-μLD/HPLC-DAD) analysis, to enhance the performance of the determination of traces of benzotriazoles (BTRs), benzothiazoles (BTs), and benzenesulfonamide derivatives (BSDs) in environmental water matrices. Assessing six carbon-based sorbents (CA1, CN1, B test EUR, SX PLUS, SX 1, and R) with different selectivity properties allowed us to tailor the best phase mixture (R, 12.5%/CN1, 87.5%) that has convenient porosity, texture, and surface chemistry (pHPZC,mix ~6.5) for trace analysis of benzenesulfonamide, 1-hydroxybenzotriazole, 1H-benzotriazole, 5-methyl-1H-benzotriazole, benzothiazole, and 1,3-benzothiazol-2-ol chemicals in aqueous media. Optimized experimental conditions provided average recoveries ranging from 37.9% to 59.2%, appropriate linear dynamic ranges (5.0 to 120.0 µg L−1; r2 ≥ 0.9964), limits of detection between 1.0 and 1.4 μg L−1, and good precisions (relative standard deviation (RSD) ≤ 9.3%). The proposed methodology (BAμE(R, 12.5%/CN1, 87.5%)-μLD/HPLC-DAD) also proved to be a suitable sorption-based static microextraction alternative to monitor traces of BTRs, BTs, and BSDs in rain, waste, tap, and estuarine water samples. From the data obtained, the proposed approach showed that the BAμE technique with the addition of lab-made devices allows users to adapt the technique to use sorbents or mixtures of sorbents with the best selectivity characteristics whenever distinct classes of target analytes occur simultaneously in the same application.
- Development of green approaches for preconcentration of local anesthetics in biological matricesPublication . Pereira, Joana; Rocha, Daniela C.; Neng, Nuno R.; Torres, M. Edite; Quintas, Alexandre; Ahmad, Samir M.Poster presented at the CQE Days - 5º encontro anual do Centro de Química Estrutural do Instituto Superior Técnico da Universidade de Lisboa. Lisboa, 25-26 may 2023
- Development of green methodologies for pre-concentration of local anaesthetics in biological matricesPublication . Pereira, Joana; Rocha, Daniela C.; Neng, Nuno R.; Torres, M. Edite; Quintas, Alexandre; Ahmad, Samir M.Poster presented at the 6th International Congress of CiiEM—Immediate and Future Challenges to Foster One Health. Monte de Caparica, 5-7 july 2023
- Drawing as a process of psychic mediation along the child´s developmental trajectoryPublication . Dias, Maria do Rosário; Ahmad, Samir M.; Evangelista, José Grillo; Carvalho, Maria do Rosário; Santos, Helcília Dias dos; Pires, Maria CalejoINTRODUCTION: The intrapsychic process of resorting to the symbolic is innate and prepares the child for the organization of his internal world. Throughout the child's developmental trajectory, its playful projective expression, allows us to assess the psychographically internalized stages of development. The present study aims to evaluate the mental representation of the concept of symbolism, size, and perspective of designed percepts along the developmental trajectory (age range from 4 to 12 years).
- Simple analytical strategy for screening three synthetic cathinones (α-PVT, α-PVP, and MDPV) in oral fluidsPublication . Segurado, André M.; Ahmad, Samir M.; Neng, Nuno R.; Maniés-Sequeira, Margarida M.; Gaspar, Helena; Nogueira, José Manuel F.Synthetic cathinones are analogue compounds of the plant based stimulant cathinone. Its use, abuse, and related consumption complications have steadily increased in the last years. For this reason, there is a need for innovative analytical approaches that enable its rapid screening in biological matrices (e.g., oral fluids). The present work proposes a new analytical methodology by combining bar adsorptive microextraction followed by microliquid desorption and gas chromatography coupled to mass spectrometry (BAµE-µLD/GC-MS) for screening three synthetic cathinones (α-PVP, α-PVT, and MDPV) in oral fluids. The optimization of the BAµE-µLD/GC-MS methodology was successfully applied for the analysis of the target compounds in oral fluids. The results show average recoveries between 43.1 and 52.3% for the three synthetic cathinones. Good selectivity was also noticed. The developed methodology presents itself as an alternative tool to screen these compounds in oral fluids. To the best of our knowledge, this is the first work that combines a microextraction sorption-based technique followed by GC-MS analysis for the screening of synthetic cathinones in oral fluids.