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Projeto de investigação
Institute of Molecular Sciences
Financiador
Autores
Publicações
Inter-equipment ongoing validation of microplastic identification by micro-FTIR using optimal resources
Publication . Fernandes, Rafaela; Miclea, Paul-Tiberiu; ROSSI, Andrea Mario; Giovannozzi, Andrea M.; Putzu, Mara; Morgado, Vanessa; Palma, Carla; Almeida, José Miguel; Pedro, Matilde São; Drago, Claudia; Quendera, Raquel Maria Pina Amaral; Pellegrino, Olivier; Bettencourt da Silva, Ricardo
ABSTRACT: FTIR is widely used for identifying microplastics due to its performance and affordable equipment. However, there is a need for a universal method for the automatic identification of microplastics by FTIR, robust to different spectra collection conditions, and capable of adapting to the diversity of particle spectra. This research presents a method for developing a reliable and simple algorithm for inter-instrumental microplastic identification using micro-FTIR. Spectra collected from different equipments and settings across various laboratories, from microparticles previously confirmed as PET (positive cases) and non-PET (negative cases), were compared with a PET reference using multiple algorithms (match methods) based on six weighted and unweighted correlation coefficients. After excluding low signal-to-noise spectra with a newly developed universal algorithm, the 5th percentile of the match values for positive cases, estimated using a robust bootstrap method, was used as a minimum match (P5 & raquo;P) to ensure a 95% true positive rate (TP). Assuming a normal distribution of the match values for negative cases, the false positive rate (FP) was calculated. The best method identified uses an unweighted correlation of differentiated signals, resulting in a P5 & raquo;P = 0.4140 and FP = 0.0005% for spectra with a minimum signal-to-noise ratio of three. This identification performance, estimated from 117 spectra, is statistically equivalent to that observed from the identification of 405 additional particles using the validated method, at a 99% confidence level set by the Clopper-Pearson method, thereby extending the method's applicability to 522 particles. The developed method for PET identification by FTIR is robust across various acquisition conditions and instruments, was implemented in a user-friendly MS Excel spreadsheet, and can be easily tested with more particles and different instrumental settings. The validity of the identification algorithm and the defined criteria cannot be extrapolated to a different reality with respect to spectral collection conditions and the diversity of negative cases without a prior performance assessment.
Highly selective valorisation of D-xylose from corncobs hydrolysates catalysed by C-scorpionate gold(III) complexes
Publication . Van-Dúnem, Vanmira; Duarte, Luís; Martins, Pedro L.; Lapa, Hugo; Martins, Luisa Margarida; Carvalheiro, Florbela
ABSTRACT: D-xylonic acid is a multifunctional, environmentally friendly, and versatile platform chemical, and one of the most promising conversion products of D-xylose for replacing several petrochemicals that is still not produced commercially. Although microbial conversion is the most widely studied process, the low efficiency and cost of these methods create opportunities for the development of chemical routes. In this work, we report for the first time the direct chemical conversion of real hemicellulose-derived pentose-rich hydrolysates into D-xylonic acid. Furthermore, a novel chemical oxidation route based on C-scorpionate gold(III) complexes was explored. Two specific complexes are used as model catalysts, the cationic [AuCl2(kappa 2-Tpm)]Cl (1, Tpm = hydrotris(pyrazol-1-yl)methane, HC(C3N2H3)(3)) or the neutral [AuCl2(kappa 2-Tpms)] complex (2, Tpms = tris(1H-pyrazol-1-yl)methane sulfonate, [SO3C(C3H3N2)(3)](-)). The catalytic operational conditions (i.e., reaction time, temperature, type and concentration of alkali and oxidant agent) were initially optimised for D-xylose solutions using cationic complex 1. Under the best conditions (100 degrees C, 2 mmol NaOH and 20 mmol H2O2) nearly 100% conversion of D-xylose and a 94% D-xylonic acid yield were achieved, with minimal formation of secondary products, when using 6 g/L D-xylose as sole carbon substrate. The direct catalytic conversion of real hemicellulosic hydrolysate, without any previous purification was possible and up to 36 g/L of D-xylose, regardless of the presence of other sugars, aliphatic acids, furans and phenolic compounds. Comparing similar catalytic conditions among model D-xylose solutions and real hydrolysates with similar titres, the later presented better performance, even though D-xylose conversion and D-xylonic acid yield decreased slightly for higher D-xylose concentrations. The catalysis was further improved by using the neutral gold(III) C-scorpionate complex 2, which further increased the D-xylose conversion and selectivity.
Unidades organizacionais
Descrição
Palavras-chave
Molecular-based Innovation,Chemical Sciences for Health,Energy & Environment: a molecular perspective,Advanced Materials and Chemical Processes, Exact and natural sciences
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia, I.P.
Programa de financiamento
Concurso para Atribuição do Estatuto e Financiamento de Laboratórios Associados (LA)
Número da atribuição
LA/P/0056/2020