Determination of three cresol isomers in sewage sludge by solid-liquid extraction with low temperature purification and gas chromatography-mass spectrometry

Liquid-liquid and solid-liquid extractions with low-temperature partitioning - A review

The paper represents the first review of solvent extraction techniques utilizing the low-temperature partitioning/purification (LTP) approach. Initially conceived in the 1960s to purify extracts from fatty matrices, it wasn't until the 2000s that this approach received increasing attention for its efficacy in extracting organic compounds from diverse samples, often without additional cleanup steps. This review covers a brief history and proposes a mechanism for LTP-based solvent extraction. Furthermore, the principal practical issues of the technique are spotlighted, elucidating the factors influencing extraction efficiency. The advantages, limitations, and potential combinations with other extraction techniques of the LTP-based solvent extractions are analyzed. The versatility of the LTP approach is demonstrated by its applications in extracting various compounds from food, environmental, and biological samples, emphasizing its potential for rapid sample preparation with minimal steps, few chemicals, and minimal analyst intervention.

Development of methods based on low-temperature partitioning (LTP) for monitoring cresols and chlorophenols in sewage sludge, soil, and water in column leaching

Cresols and chlorophenols are chemical contaminants that are potentially toxic to humans and can be found in sewage sludge. These chemical contaminants can migrate into the sludge-soil-water system when sludge is used as a conditioner for agricultural soils. Thus, the objective of this study was to develop methodologies based on extraction with low-temperature partitioning (LTP) to determine cresols and chlorophenols in sewage sludge, soil, and water. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The validated methods were applied to monitor cresols and chlorophenols in a column-leaching study of a sludge-soil-water system. Satisfactory results were achieved for selectivity, limit of quantification (LOQ), linearity, accuracy, and precision. In the column leaching study, only 2,4,6-trichlorophenol was quantified in sludge samples after 20 days of the experiment. None of the studied compounds were quantified in soil and leached water samples, due to the degradation promoted by the microorganisms present in the sewage sludge. Finally, validated methods were suitable for monitoring cresols and chlorophenols in the sludge-soil-water system.

Determination of p-cresol levels in smoked meat products using QuEChERS method and gas chromatography-mass spectrometry

p-Cresol is known as an environmental chemical contaminant that has toxic effects on humans. However, the presence of p-cresol in smoked foods has been seen as a flavor constituent. The present study had as objective to optimize and validate the QuEChERS method for the determination of p-cresol in beef hamburger, which was chosen as a representative matrix for six smoked meat products. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The method showed limit of quantification (LOQ) of 40 µg kg^-1, linearity between 40 and 200 µg kg^-1, recovery higher than 70% and relative standard deviation lower than 14%. The proposed method was applied to six different smoked foods and the p-cresol concentration ranged from 148 to 872 µg kg^-1 and only the turkey breast pate showed a concentration lower than the LOQ. The descending order of p-cresol level in smoked samples was: sausage > shredded tuna > salami > turkey breast > hamburger > turkey breast pate. In three analyzed samples, the results showed that the p-cresol migrates from the surface to the food inner. Finally, the proposed method was simple and efficient to quantify high levels of this contaminant in smoked foods and it could be a useful tool for the monitoring food safety and quality.

Characterization of organic compounds and drugs in sewage sludge aiming for agricultural recycling

The application of sewage sludge in soils can bring benefits to agricultural productivity, however, the risks arising from this application must be measured and carefully evaluated. Persistent organics compounds and drugs can be present in the sewage sludge and if applied to the soil, they can cause severe risks to the soil biota and contamination of groundwater. This work determined 174 persistent organic compounds and drugs in sludge samples from a wastewater treatment plant using chromatographic methods. The drugs ciprofloxacin, enrofloxacin and diclofenac were quantified, and values varied according to sampling period. For persistent organic compounds, cresols were the most abundant compounds in sewage sludge. With the analyses made of both the elutriate and the filtrate, it was possible to verify the potential for soil retention or leaching that each compound can present with the application of sewage sludge in the agriculture.

Determination of DDT in honey samples by liquid-liquid extraction with low-temperature purification (LLE-LTP) combined to HPLC-DAD

Honey is widely consumed worldwide, however, this food can be contaminated by chemical contaminants, such as the insecticide dichlorodiphenyltrichloroethane (DDT). Despite legal restrictions on DDT use, this organochlorine pesticide has been detected in honey collected in several developed and developing countries, representing risks to human health, animals, and the environment due to its high environmental persistence, potential carcinogenicity, and ecotoxicological effects. Thus, the development of an analytical method for DDT monitoring in this matrix is important to ensure food security. Therefore, this study aimed to optimize and validate a simple, low-cost, and efficient method using the liquid-liquid extraction with low-temperature purification (LLE-LTP) to determine DDT in honey samples by high-performance liquid chromatography with diode array detector (HPLC-DAD). The proposed method was validated according to SANTE guidelines, being considered selective, precise, accurate, and linear in the range of 8.0-160 μg kg^-1. The limits of detection (LOD) and quantification (LOQ) achieved were 4.0 and 8.0 μg kg^-1, respectively. This LOQ value is lower than the maximum residue limit established by the Brazilian and European Union legislation. Therefore, the LLE-LTP combined to HPLC-DAD allows the routine analysis of DDT in honey samples and can be widely applied in studies to monitor this pesticide, especially in developing countries, where DDT use is still allowed.

p-Cresol in cheese: Is it a flavouring compound or chemical contaminant?

p-Cresol has been identified as a flavouring compound in cheeses; however, scientific studies have already identified p-cresol as a potential chemical contaminant in environmental matrices. Thus, the objective of this study was to evaluate four traditional methods for extracting p-cresol from cheese samples in order to validate the best method, and finally to apply it to five cheese samples with different origins, processing and ripeness times. The analyses were performed by gas chromatography-mass spectrometry after derivatisation of p-cresol with anhydride acetic and pyridine. Better results were achieved by the QuEChERS method, which showed recovery higher than 80%, relative standard deviation lower than 16%, limit of quantification of 5 μg kg^-1 and linearity between 5 and 400 μg kg^-1 with R² 0.99. p-Cresol was quantified in almost all of the samples analysed at different concentration levels, which were in an increasing order at μg kg^-1: Cheddar (< LOQ), Parmesan (8 ± 0.7), Gorgonzola (103 ± 14), smoked Provolone (365 ± 28) and barbecue cheese (1001 ± 187). Although no maximum residue limit has been established for p-cresol in food, the results suggest that cheeses exposed to charcoal combustion notably increase the p-cresol levels and may represent a hazard to human health, especially in risk groups such as patients with chronic kidney disease who have serious problems with p-cresol.