Use of lyophilization as analytical strategy for chromatographic characterization of aqueous phase of bio-oil produced by rice husk pyrolysis

Development of an ultra-high-performance supercritical fluid chromatography method for the analysis of phenols in the pyrolysis aqueous fraction

The pyrolysis process consists of the thermal decomposition of biomass in an inert atmosphere, which produces a liquid (bio-oil) composed of a complex mixture of organic compounds, including an oil and water phase. The aqueous fraction can reach up to 45% w/w, and understanding its composition is of utmost importance in determining its intended destination, whether for the reuse of compounds in industrial applications or for treating the effluent for disposal. In this study, a fast, direct, and efficient method using ultra-high-performance supercritical fluid chromatography (UHPSFC) was developed and optimized for monitoring phenols in aqueous samples obtained from the pyrolysis processing of six different biomass sources. The following parameters were evaluated for method optimization: stationary phase type, mobile phase flow, organic modifier, sample diluent, temperature, pressure, and modifier gradient time. With a total analysis time of 26 min, out of the fourteen (14) investigated phenolic compounds, eleven (11) were successfully separated after method optimization, and among them, five (5) were quantified in all six aqueous fractions. The aqueous fractions of residue from cowpea pod (1.89 mg.mL-1), sugar apple (3.09 mg.mL-1), and acerola (4.79 mg.mL-1) presented lower concentrations compared to grape (8.16 mg.mL-1), pine nuts (6.68 mg.mL-1), and guava (6.05 mg.mL-1) fractions. However, even at lower concentrations, all biomasses showed promising results regarding the phenolic compound content, analytes that have high added value for the chemical industry.

Research of Pesticide Metabolites in Human Brain Tumor Tissues by Chemometrics-Based Gas Chromatography-Mass Spectrometry Analysis for a Hypothetical Correlation between Pesticide Exposure and Risk Factor of Central Nervous System Tumors

Pesticides are widely used, resulting in continuing human exposure with potential health impacts. Some exposures related to agricultural works have been associated with neurological disorders. Since the 2000s, the hypothesis of the role of pesticides in the occurrence of central nervous system (CNS) tumors has been better documented in the literature. However, the etiology of childhood brain cancers still remains largely unknown. The major objective of this work was to assess the potential role of pesticide exposure as a risk factor for CNS tumors based on questionnaires and statistical analysis of information collected from patients hospitalized in the Neurosurgery Department of the Habib Bourguiba Hospital Medium in Sfax, Tunisia, during the period from January 1, 2022, to May 31, 2023. It also aimed to develop a simple and rapid analytical method by the gas chromatography-mass spectrometry technique for the research traces of pesticide metabolites in some collected human brain tumor tissues in order to more emphasize our hypothesis for such a correlation between pesticide exposure and brain tumor development. Patients with a history of high-risk exposure were selected to conduct further analysis. Chemometric methods were adapted to discern intrinsic variation between pathological and control groups and ascertain effective separation with the identification of differentially expressed metabolites accountable for such variations. Three samples revealed traces of pesticide metabolites that were mostly detected at an early age. The histopathological diagnosis was medulloblastoma for a 10-year-old child and high-grade gliomas for 27- and 35-year-old adults. The bivariate analyses (odds ratio >1 and P value <5%) confirmed the great probability of developing cancer by an exposure case. The Cox proportional hazards model revealed the risk of carcinogenicity beyond the age of 50 as a long-term effect of pesticide toxicity. Our study supports the correlation between pesticide exposure and the risk of development of human brain tumors, suggesting that preconception pesticide exposure, and possibly exposure during pregnancy, is associated with an increased childhood brain tumor risk. This hypothesis was enhanced in identifying traces of metabolites from the carbamate insecticide class known for their neurotoxicity and others from pyridazinone, organochlorines (OCs), triazole fungicide, and N-nitroso compounds known for their carcinogenicity. The 2D-OXYBLOT analysis confirmed the neurotoxicity effect of insecticides to induce oxidative damage in CNS cells. Aldicarb was implicated in brain carcinogenicity confirmed by the identification of oxime metabolites in a stress degradation study. Revealing "aziridine" metabolites from the OC class may better emphasize the theory of detecting traces of pesticide metabolites at an early age. Overall, our findings lead to the recommendation of limiting the residential use of pesticides and the support of public health policies serving this objective that we need to be vigilant in the postmarketing surveillance of human health impacts.

Silica extraction from rice hull ash through the sol-gel process under ultrasound

Rice is among the main foods produced in the world and is part of the daily diet of most families. The main waste from rice processing is rice husk (RH), which has been used as biomass for energy generation through combustion. In this process, rice husk ash (RHA) is generated as a residue, and its silica (SiO₂) content varies from 85 to 98%. The present work describes the study of the extraction of silica from RHA by the ultrasound-assisted sol-gel method. An experimental design based on the response surface methodology (RSM) with the symmetrical, second-order rotational central composite design (RCCD) was applied to determine the best extraction conditions considering extraction time and molar ratio (n) as variables = n_NaOH/n_Silica). These optimal conditions were then applied to three ash samples, two obtained by the combustion process in a boiler furnace, with a mobile grate system (RHAC₁ and RHAC₂), and one obtained by the pyrolysis process (RHAP) carried out in a fixed bed reactor. Results showed that a molar ratio of 4.4, and an extraction time of 107 min were the best extraction conditions, leading to a yield of 73.3% for RHAP, 43.9% for RHAC₁, and 31.1% for RHAC₂. It was found that the extraction yield and textural properties of the silica obtained depend on the characteristics of the ash used. The silica extracted from RHAC₁ presented a surface area of 465 m².g^-1, mesopores of 4.69 nm, purity greater than 95%, and an ultra-fine granulometric distribution, reaching nanoparticle dimensions, characteristics comparable to commercially available silicas.