Efficient trihalomethane quantification in drinking water for minimally-equipped water treatment plants labs.

Chlorine is a common disinfectant used in water treatment. However, its reaction with organic matter can lead to the formation of harmful byproducts, such as trihalomethanes (THMs), which are potentially carcinogenic. To address this issue, the aim of this work was to enhance a colorimetric method capable of quantifying THMs in drinking water through UV/Vis Spectrophotometry, using cost-effective equipment, and validate this methodology for the first time according to established validation protocols. The method's innovation involved replacing the solvent pentane with the more common hexane, along with adjusting the heating ramp, elucidating the mechanisms involved in the process. This method involves the reaction between THMs, pyridine, and NaOH to produce a colored compound, which is then monitored through molecular absorption spectroscopy in the visible region. The method was thoroughly validated, achieving a limit of detection of 13.41 µg L-1 and a limit of quantification of 40.65 µg L-1. Recovery assays ranged from 86.1 % to 90.7 %, demonstrating high accuracy. The quality of the linear fit for the analytical curve exceeded R2 > 0.98. The method was applied to real samples, revealing concentrations ranging from 13.58 to 55.46 µg L-1, all way below the legal limit in Brazil (Maximum Contaminant Levels (MCL) = 100 µg L-1). This cost-effective and straightforward method is suitable for integration into water treatment plant laboratories.

Evaluation of imazalil dissipation/migration in postharvest papaya using low-temperature partition extraction and GC-MS analysis.

Methods involving solid-liquid extraction with low-temperature partition and analysis by gas chromatography coupled to mass spectrometry (GC-MS) were validated to investigate the dissipation/migration of residues of the postharvest fungicide imazalil in papaya skin, pulp, and seeds. The fruits were stored for 23 days (14 °C). Every two days, fruits from the control group and those treated with imazalil had their skin, outer pulp, inner pulp, and seeds separated and then analyzed by GC-MS. After the 23rd day, about 70% of the imazalil had dissipated. Most of the remaining residue was found in the skin; however, the small amount migrating into the pulp was above the maximum residue levels allowed by the regulatory agencies. Imazalil residue was also detected in seeds at concentrations lower than the LOQ (0.025 mg kg-1). Mass loss was the only quality parameter that showed a significant difference between the fruits of the control and study groups.

Microextraction technique associated with gas chromatography-mass spectrometry for determining pesticide residues in urine.

Urine is one of the biological matrices most used for detecting human contamination, as it is representative and easily obtained via noninvasive sampling. This study proposes a fast, accurate, and ecological method based on liquid-liquid microextraction with low-temperature partition (µLLE/LTP). It was validated to determine nine pesticides (lindane, alachlor, aldrin, chlorpyrifos, dieldrin, endrin, DDT, bifenthrin, and permethrin) in human urine, in association with gas chromatography coupled with mass spectrometry (GC-MS). The technique was optimized through a factorial design. The best conditions for the simultaneous extraction of the analytes comprised the addition of 600 µL of water and 600 µL of acetonitrile (extracting solvent) to a 500-µL urine sample, followed by vortexing for 60 s. By freezing the samples for 4 h, it was possible to extract the pesticides and perform the extract clean-up simultaneously. The parameters selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy were used to appraise the performance of the method. Good values of selectivity and linearity (R2 > 0.990), LOQ (0.39-1.02 µg L-1), accuracy (88-119% recovery), and precision (%CV ≤ 15%) were obtained. The µLLE/LTP-GC-MS method was applied to authentic urine samples collected from volunteers in Southeast Brazil.

Determination of quinclorac by adsorptive stripping voltammetry in rice samples without sample pretreatment.

A novel voltammetric method with practically no sample pretreatment was developed for determination of Quinclorac (QNC) in rice samples by using a working Carbon Paste Electrode (CPE) modified with ionic liquid, with deposition potential (ED) of -1.43 V for 30 s in NaOH 0.01 mol L-1. The systematic influence of cations and anions of imidazole ionic liquids on the composition of CPE has evaluated. The best electrode composition was 65% (w/w) of graphite powder, 30% (w/w) of mineral oil and 5.0% (w/w) of C4min+BF4- ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate). The matrices analyzed were deionized water and extracts of upland rice: white, brown, peel and seed. The limits of quantification ranged between 0.954 mg kg-1 and 3.61 mg kg-1. The recovery percentages of QNC in rice samples ranged between 90% and 121%. The simplicity and good analytical frequency enable the proposed method to be used to obtain preliminary information on the presence of QNC, prior to the implementation of more detailed, costly and elaborate quantitative analyses. The technique can be applied in the study and evaluation of sorption mechanisms, metabolization of the herbicide in plants and its persistence and degradation in the environment.

The efficacy of washing strategies in the elimination of fungicide residues and the alterations on the quality of bell peppers.

Food safety problems caused by pesticide residues in vegetables have become a top issue to raise public concern. In this study, bell peppers were grown in an experimental field and sprayed with two systemic (azoxystrobin and difenoconazole) and one contact (chlorothalonil) fungicides. Ozone (ozonated water and water continuously bubble with ozone) or conventional domestic (washing with distilled water, detergent, acetic acid, sodium bicarbonate, and sodium hypochlorite solutions) procedures were investigated to identify the most effective way to remove fungicide residues in bell peppers. The residues in the fruits and the washing solutions were determined by solid-liquid extraction with a low-temperature partition (SLE/LTP) and liquid-liquid extraction with a low-temperature partition (LLE/LTP), respectively, and analyzed by gas chromatography. Water continuously bubbled with ozone a concentration of 3 mg L-1 was the most efficient treatment with removal of fungicides residues ranging from 67% to 87%. However, similar treatment at a lower concentration (1 mg L-1) did not only efficiently removed fungicide residues (between 53% and 75%) but also preserving the quality of the fruit along a storage time of 13 days. Among the conventional solutions, sodium bicarbonate at 5% showed good efficiency removing between 60% and 81% of the fungicide residues from bell peppers, affecting the color quality of the fruit. Overall, the most affected physicochemical parameters in bell peppers after the treatments were weight loss, color, and vitamin C content.

Proposal of a controlled release of citrate by solubility equilibrium.

Some substances at high concentrations in both the body and the environment can be toxic. The remediation of contaminated environments, for example by metals in toxic concentrations is a fairly current problem. In this way, organic acids of low molecular weight, because they are biodegradable, constitute an alternative potentially for their use in phytoremediation processes. Among these acids, citric acid was chosen to be used in this work due to its suitable binder behaviour, with high stability constants. The purpose of this work was to develop a controlled release of citrate that allows its release to the soil solution to pre-defined concentrations by the system and that this concentration is maintained even if the binder is consumed in the complexation of metals, diluted or percolated. In this way, the system has an additional feature, compared to the conventional controlled release system. The presence of calcium citrate allowed for a slower release of citrate compared to citrate soluble salts or even with calcium citrate directly in solution. The Noyes-Whitney model allowed to explain the effects of pellet sizes and percentages of agar-agar. The pH of the receptor solution and the calcium concentrations used in the preparation of the gels influenced the equilibrium concentration of the citrate, demonstrating the independence of the controlled release process in relation to other variables in the solution. The controlled release system proposed in this work is a promising and very useful system for phytoextraction processes.

Building robust models for identification of adulteration in olive oil using FT-NIR, PLS-DA and variable selection.

Being a product with a high market value, olive oil undergoes adulterations. Therefore, studies that make the verification of the authenticity of olive oil more efficient are necessary. The aim of this study was to develop a robust model using FT-NIR and PLS-DA to discriminate extra virgin olive oil samples and build individual models to differentiate adulterated extra virgin olive oil samples. The best PLS-DA-OPS classification model for olive oils showed specificity (Spe) and accuracy (Acc) values higher than 99.7% and 99.9%. For the classification of adulterants, PLS-DA-OPS models presented values of Spe at 96.0% and Acc above 95.5% for varieties. For the blend, the best PLS-DA-GA model presented Acc and Spe values greater than 98.2% and 98.8%. Reliable and robust models have been built, allowing differentiation from seven adulterants to genuine extra virgin olive oils.

Environmental remediation processes by zero valence copper: reaction mechanisms.

Recent studies have shown Cu(0) as a promising material for the removal of organic and inorganic pollutants. However, there is no review addressing the studies performed. This fact may be related to the toxicity of the particles and the copper released in solution that has not motivated researchers, which entails in a reduced number of publications. However, studies point out how to solve the problem of Cu deposition in support materials. In this work, a detailed review of Cu(0) applications was performed. The specific focus was the reaction mechanisms related to adsorption, oxidation, and reduction processes. Initially, the resources that allow the understanding of the reaction mechanism, such as characterization techniques and the experimental conditions for investigation of the species involved in the process, were presented. The studies were evaluated separately, showing the mechanisms involved only with the application of Cu(0) in pure and isolated form and in association with oxidizing or reductive agents, combined with irradiation sources and ultrasonic waves and in the form supported in polymer matrices. It was verified that by the proposed reaction mechanisms, the exclusive participation of Cu(0), being the removal process, explained only by the redox behavior of copper. Therefore, the review showed the need for future research regarding the redox behavior of the contaminants.

Pesticide residue removal in classic domestic processing of tomato and its effects on product quality.

This study was undertaken to evaluate the effectiveness of several household practices (washing with water or acidic, alkaline, and oxidizing solutions, and peeling) in minimizing pesticide residue contamination of tomatoes, as well as the impact on the quality of the treated fruit. Tests were performed using two systemic fungicides (azoxystrobin and difenoconazole) and one contact fungicide (chlorothalonil). Solid-liquid extraction with low temperature partition (SLE/LTP) and liquid-liquid extraction with low temperature partition (LLE/LTP) were used to prepare the samples for pesticides determination by gas chromatography. Washing the tomatoes with water removed approximately 44% of chlorothalonil, 26% of difenoconazole, and 17% of azoxystrobin. Sodium bicarbonate (5%) and acetic acid (5%) solutions were more efficient, removing between 32 and 83% of the residues, while peeling removed from 68 to 88% of the pesticides. The washing solutions altered some fruit quality parameters, including acidity and chroma, and also caused weight loss. Acetic acid (0.15 and 5%) and hypochlorite (1%) solutions had the greatest effect on these parameters.

Effects of ozone fumigation treatment on the removal of residual difenoconazole from strawberries and on their quality.

The effect of ozone fumigation on the reduction of difenoconazole residue on strawberries was studied. Strawberries were immersed in 1.0 L of aqueous solution containing 400 µL of the commercial product (250 g L(-1) of difenoconazole) for 1 min. Then, they were dried and exposed to ozone gas (O3) at concentrations of 0.3, 0.6 and 0.8 mg L(-1) for 1 h. The ozone fumigation treatments reduced the difenoconazole residue on strawberries to concentrations below 0.5 mg kg(-1), which corresponds to a 95% reduction. The strawberries treated with ozone and the control group, which was not treated with ozone, were stored at 4°C for 10 days. Some characteristics of the fruit were monitored throughout this period. Among these, pH, weight loss and total color difference did not change significantly (P > 0.05). The fumigation with ozone significantly affected the soluble solids, titratable acidity and ascorbic acid content (vitamin C) of the strawberries preventing a sharp reduction of these parameters during storage.