Low-temperature Purification Research Articles

Development of a Low-Temperature Purification Method for Gas Chromatography–Mass Spectrometry Quantification of Three Cresol Isomers in Smoked Bacon

Development of a Low-Temperature Purification Method for Gas Chromatography–Mass Spectrometry Quantification of Three Cresol Isomers in Smoked Bacon

Application of an inertial vacuum trap for separation of the solid phase of carbon dioxide from the flow of fuel combustion products of boiler units

The technological process of low-temperature purification of fuel combustion products of boiler units from carbon dioxide by freezing it in a turboexpander and separating from the fuel combustion products flow in a separator is considered.The issue of separation of solid carbon dioxide from the flow of fuel combustion products of boiler units using a bag filter, an electric precipitator, a cyclone separator and an inertia-type separator is considered. Based on the analysis, the use of an inertial vacuum separator for separating the solid phase of carbon dioxide from the flow of fuel combustion products is proposed.Solidworks and ANSYS CFX modules were used for numerical modeling. To solve, the equations of continuity, motion, energy, and the k-ε model equations are used. The closing equation is for the effective and turbulent viscosity. There is also a description of the forces affecting the movement of the dispersed phase. The stream is considered lightly dusty.Numerical studies of the dispersed flow in the channel of an inertial-vacuum separator and in the previously used cyclone TsN-11 were carried out. The initial data for the calculation were taken based on the known mass flow rate and particle concentration, as well as from the continuity equation. From the results obtained, we can draw conclusions about a directly proportional relationship between the growth of the flow rate characteristics of the flow, the speeds along the flow path of the apparatus at the inlet and the resistance of the apparatus.Besides, based on the obtained calculation results, it was concluded that it is necessary to additionally install a rotary industrial air blower in order to create the necessary pressure drop in the inertial vacuum separator. The economic and environmental feasibility of installing a rotary air blower is consideredThe range of consumption of fuel combustion products has been determined at which the most effective purification of fuel combustion products from carbon dioxide in an inertial vacuum separator is possible within the technical characteristics of the refrigeration capacity of turborefrigeration machines.

A validated UPLC-MS/MS method for the quantification of immunosuppressive drugs in peripheral blood mononuclear cells using liquid-liquid extraction with low temperature purification without complex pretreatment steps

Immunosuppressive drugs (ISDs) are given to avoid the allograft rejection after transplantation. The concentrations of ISDs should be closely monitored owing to their wide inter-individual variability in its pharmacokinetics and narrow therapeutic window. Currently, the whole blood concentration measurement is the major approach of therapeutic drug monitoring of clinical ISDs in organ transplantation. Its correlation with the efficacy of ISDs remains elusive. While the acute rejection after transplantation may occur even when whole-blood ISDs concentrations are within the target range. Since the site of action of ISDs are within the lymphocyte, direct measurement of drug exposure in target cells may more accurately reflect the clinical efficacy of ISDs. Although several methods have been developed for the peripheral blood mononuclear cells (PBMCs) extraction and drug concentration measurement, the complex pre-processing has limited the study of the relationship between intracellular ISDs concentrations and the occurrence of rejection. In this study, the extraction of ISDs in PBMCs was carried out by the liquid-liquid extraction with low temperature purification, without centrifugation. The lower limit of quantitation were 0.2 ng/mL for cyclosporine A, tacrolimus and sirolimus, 1.0 ng/mL for mycophenolic acid, and the within-run and between-run coefficient of variations were both less than 12.4 %. The calibration curves of mycophenolic acid had a linear range (ng/mL): 1.0–128.0 (r2 = 0.9992). The calibration curves of other three ISDs had a linear range (ng/mL): 0.2–20.48 (r2 > 0.9956). A total of 157 clinical samples were analyzed by the UPLC-MS/MS for ISDs concentration in blood or plasma ([ISD]blood or plasma) and the concentration within PBMCs ([ISD]PBMC). Although there was strong association between [ISD]PBMC and [ISD]blood or plasma, the large discrepancies between concentration within [ISD]blood or plasma and [ISD]PBMC were observed in a small proportion of clinical samples. The developed method with short analysis time and little amounts of blood sample can be successfully applied to therapeutic drug monitoring of ISDs in PBMCs for analysis of large numbers of clinical samples and is helpful to explore the clinical value of ISDs concentration in PBMCs.

Quantification of cresols in liquid smoke samples employing liquid–liquid extraction with low-temperature purification and analysis by gas chromatography–mass spectrometry

Liquid smoke is a food additive and cresols are among its chemical constituents, potentially toxic to human health. Thus, the objective of this study was to develop a method to quantify cresols in liquid smoke. First, the liquid-liquid extraction with low temperature purification (LLE-LTP) was validated for cresols in water, as there are no cresol-free liquid smoke samples. Analyzes were performed by gas chromatography coupled to mass spectrometry in full scan mode. LLE-LTP was subsequently applied in five commercial samples of liquid smoke. Validation results showed that the proposed extraction method was selective for cresols, linear in the range of 0.5 to 35 mg L−1, limit of quantification of 0.5 mg L−1, recovery rate between 90% and 104% and relative standard deviation lower than 10%. The quantification of cresols in liquid smoke samples ranged from 3.0 to 38.3 mg L−1 and the concentration of these chemical contaminants in liquid smoke remained constant for at least 21 days at 25 °C.

One-Pot construction of highly active hetero-interface over porous non-stoichiometric perovskite with gel combustion strategy to enhance toluene purification activity

Constructing active perovskite nanostructures by a simple method is of great value and significance to the practical application of non-precious metal oxide-based catalysts. Herein, a surfactant-assisted gel combustion approach was adopted to fabricate a state-of-the-art LaMnO3 perovskite catalyst with a rich porous structure and hetero-interface, which can be active for low-temperature purification of toluene. Due to the large amount of gas produced during the decomposition of surfactant, the obtained catalysts own a rich porous structure, which results in a higher specific surface area and exposes more active sites. Significantly, the highly active Mn2O3-LaMnO3 hetero-interface can be generated over the non-stoichiometric perovskite successfully through adjusting the proportion of B-site element. The introduction of hetero-interfaces alters the surface structure of the material with more oxygen vacancies, leading to a significant promoting effect. It is found that the T90 of toluene (1000 ppm in air) conversion over the sample with 30 % excess manganese (La: Mn = 1: 1.3) is only 289 °C at a relatively high weight hourly space velocity (WHSV = 120,000 mL•g−1•h−1), which is 87 °C lower than that of stoichiometric LaMnO3 perovskite. This work presents a versatile strategy for preparing highly active non-precious metal catalysts for industrial applications.

Determining pyroxasulfone herbicide in honey samples using liquid-liquid extraction with low temperature purification (LLE-LTP)

Pyroxasulfone is a selective, systemic, pre-emergence herbicide which acts to inhibit weeds in potato, coffee, sugar cane, eucalyptus, and soybean plantations, among others. This active ingredient was classified by Brazilian legislation as a very dangerous product for the environment, and to date there are no studies involving the development of extraction methods for monitoring this compound in environmental matrices. Therefore, the objective of this study was to optimize and validate liquid-liquid extraction with low temperature purification followed by a gas chromatography coupled to mass spectrometry analysis to determine this herbicide in honey samples. The results showed that the best extractor phase was acetonitrile and ethyl acetate (6.5 mL:1.5 mL), with recovery rates close to 100% and relative standard deviations below 11%. The validation proved that the extraction method was selective, precise, accurate and linear in the range of 3–225 μg kg−1, reaching a limit of quantification of 3 μg kg−1, with a −25.95% matrix effect. Monitoring on real samples did not reveal episodes of environmental contamination with pyroxasulfone residue.

Determining Tolfenpyrad in Water Samples Using Liquid-Liquid Extraction with Low Temperature Purification (LLE-LTP)

Tolfenpyrad is an insecticide and acaricide of the pyrazole class, which has been used to control pests in cereal, legume and vegetable crops. Despite its high efficiency, this insecticide is considered highly toxic to humans by Brazilian legislation. Therefore, this study aims to optimize and validate liquid-liquid extraction with low temperature purification followed by analysis by high-performance liquid chromatography with diode array detection to determine tolfenpyrad in water. The results showed that the optimal extraction conditions were achieved using only acetonitrile as extracting phase and 60 min as freezing time. Under these conditions, the extraction method was selective, accurate, and precise, with a recovery of 102.41% and a relative standard deviation of 11.29%. The method was linear from 2.0 to 150.0 µg L-1, with a limit of quantification of 2.0 µg L-1, and the matrix effect was –7.67%. The half-life was 23 days (with sunlight) and 30 days (no sunlight).

Extraction Method for Determining Dinotefuran Insecticide in Soil Samples

Dinotefuran is a third-generation neonicotinoid insecticide that has a broad action spectrum in agriculture pests. Dinotefuran was authorized in Brazil in 2019, being classified as a very dangerous product for the environment. Therefore, this study aimed to optimize and validate the solid-liquid extraction with low temperature purification to determine dinotefuran in soil samples using high-performance liquid chromatography coupled diode array detection. The results showed that the best extracting phase was acetonitrile:water (8:2 v/v), followed by the clean-up with 50 mg of primary-secondary amine. The method under these conditions has a linear range of 15.0 to 140 µg kg-1 and reached limits of detection and quantification of 10.0 and 15.0 µg kg-1, respectively. The validation revealed that the method was selective, precise, accurate, and presented a matrix effect of 15%. Although dinotefuran was not detected in real soil samples, the proposed method proved to be an efficient alternative for monitoring dinotefuran in soil samples.

Development and validation of a sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry method for quantitative analysis of bambermycin in livestock and aquatic products: Implications for food safety control and regulatory enforcement.

A sensitive and accurate analytical method was developed and validated to detect bambermycin, a commonly used antibiotic in animal feed and livestock. The presence of bambermycin residues in food products can pose health risks to consumers, emphasizing the need for a sensitive and accurate analytical method. A reversed-phase analytical column was utilized with a mobile phase comprising 0.005 mol/L ammonium acetate in 5% acetonitrile (A) and 0.005 mol/L ammonium acetate in 95% acetonitrile (B) to achieve effective chromatographic separation. Quantitative determination of bambermycin in various samples, including beef, pork, chicken, milk, eggs, flatfish, eel, and shrimp, was performed using ultra-high-performance liquid chromatography-tandem mass spectrometry. Sample extraction involved a mixture of methanol and a 25% ammonium hydroxide solution, followed by low-temperature purification and phospholipid removal utilizing a Phree cartridge. The method exhibited a satisfactory recovery rate ranging from 69% to 100%. Validation results demonstrated the reliability, robustness, and accuracy of the method, exhibiting good linearity, precision, and recovery. This validated method can be applied for routine analysis of bambermycin residues, assisting in the development of effective monitoring and control measures to ensure the safety of livestock and aquatic products.

Extraction method for determining dinotefuran insecticide in water samples

Dinotefuran is a compound belonging to the third generation of nicotinoid insecticides, and has been effective in combating pests that are resistant to conventional insecticides, such as organophosphates, carbamates, and pyrethroids. This molecule presents high-water solubility (39,830 mg L−1 at 25 °C) compared to other pesticides, which facilitates its drag and leaching to lower soil layers. Therefore, the present study aimed to optimize and validate liquid–liquid extraction with low temperature purification (LLE–LTP) to determine dinotefuran residues in water by high performance liquid chromatography with diode array detection (HPLC–DAD). The results revealed that the analyte recovery ranged from 85.44 to 89.72% with a relative standard deviation <5.8. LLE–LTP was selective, precise, accurate, and linear in the range from 10.0 to 210 µg L−1, and presented limits of detection and quantification of 5.00 and 10.00 µg L−1, respectively. The matrix effect was <14%. The stability study of dinotefuran in water revealed significant stability of this molecule in water in the absence of light (>130 days), and a half-life of 7 days in water with sunlight. LLE–LTP coupled to HPLC–DAD was a simple, easy, and efficient method for extracting and analyzing dinotefuran in water samples.

Optimization and Validation of the Miniaturized Solid-Liquid Extraction with Low Temperature Purification (SLE-LTP) Method for Determining Fluopyram in Sandy, Clayey and Medium-Textured Soil

Fluopyram is a fungicide which can also be used as a nematicide in agricultural areas. The Brazilian Ministry of Agriculture authorized the commercialization and use of this molecule in Brazilian agriculture in 2019, but studies involving the development of an extraction and quantification method of this compound in environmental matrices such as soil are still scarce. Therefore, the present study aimed to optimize and validate the miniaturized version of the solid-liquid extraction with low temperature purification (SLE-LTP) method for determining this compound in sandy, clayey and medium-textured soil samples. All analyzes in this study were performed by gas chromatography coupled to mass spectrometry (GC-MS). The results revealed that the analyte recovery percentages in the three soil types ranged from 86 to 114% with a relative standard deviation of less than 15%. In addition to employing smaller amounts of reagents and sample, the miniaturized SLE-LTP method was selective, precise, exact, and linear in the range from 3 to 210 μg kg-1, and reached a limit of quantification lower than 3.00 μg kg-1 for the three soil types. The extraction method was applied to 30 real samples collected in coffee growing regions, but no residue of this compound was detected in these samples.

Extraction Method for Determining Florpyrauxifen-benzyl Herbicide in Soil

Florpyrauxifen-benzyl is the new active ingredient authorized by Brazilian legislation, which acts as herbicide and may be used to control weeds in rice cultivation, but studies on toxicity to humans and the environment are still under review. Due to recent insertion in the world pesticide market, there are still few studies related to the extraction and detection methodologies of this compound. Therefore, this study aimed to optimize and validate solid-liquid extraction with low temperature purification (SLE-LTP) for determining florpyrauxifen-benzyl in soil using highperformance liquid chromatography coupled to a diode array detection (HPLC-DAD). The results showed that the best conditions were achieved using Poroshell column, a temperature of 30 °C, mobile phase composition of acetonitrile:water (85:15 v/v) acidified with formic acid 0.1% (v/v), a flow rate of 0.3 mL min-1, and 243 nm as the wavelength. The best extracting phase was acetonitrile acidified with formic acid 0.1% (v/v) which achieved a recovery rate ca. 100% and relative standard deviation (RSD) less than 3.9%. The methodology was precise, accurate, linear and selective, with a limit of quantification of 20 μg kg-1. The stability study of this compound in soil showed that approximately 17.5 days is the half-life of florpyrauxifen-benzyl in soil.

Optimization and validation of LLE-LTP to determine florpyrauxifen-benzyl herbicide in water samples by HPLC-DAD

Florpyrauxifen-benzyl is a systemic herbicide which acts on weeds of common occurrence in rice cultivation areas using flooded or rainfed systems. The Brazilian Health Regulatory Agency (ANVISA) authorized the commercialization of this pesticide, but did not establish guidelines with an extraction and quantification method of residues of this compound as a form of environmental monitoring. Therefore, the present study aimed to optimize and validate the liquid-liquid extraction with low temperature purification (LLE-LTP) to determine florpyrauxifen-benzyl content in water samples by high performance liquid chromatography with diode array detection (HPLC-DAD). The recovery ranged from 95.84 to 105.4% with a relative standard deviation less than 1.5. LLE-LTP was selective, precise, accurate, linear in the range from 4.00 to 150 µg L−1, and the limit of quantification was 4.00 µg L−1. The stability study of the compound in water revealed its degradation in 25 days and DT50 in approximately 5 days. LLE-LTP coupled to HPLC-DAD presented itself as a simple, easy and efficient method of extracting and analyzing it in water samples.

Multi-residue methodology for quantification of antiparasitics in hen eggs by LC-MS/MS: development, validation and application to 348 samples from Brazil

Analytical methodology for quantification of 15 antiparasitic drugs and their respective metabolites in laying hen eggs was optimized and validated. The method uses acetonitrile as solvent extraction, sodium chloride for salting-out, low-temperature purification and analysis by LC-MS/MS. A total of 348 egg samples were collected in 11 states of Brazil and 50% of the total samples presented antiparasitic residues, which were albendazole, fipronil, fenbendazole, ivermectin, oxibendazole and mebendazole. A total of 12.4% of the samples were considered non-compliant, and residues quantified in these samples were albendazole, fipronil, and mebendazole. Albendazole was always identified as albendazole sulfone. Only one sample presented fipronil and fipronil sulfone; all others exclusively the sulfone metabolite. Fenbendazole was characterized by the presence of both metabolites: sulfone and sulfoxide. Maximum limits adopted are based on the Normative Instruction 51/2019 of the Brazilian Health Regulatory Agency (ANVISA), but albendazole, fipronil, oxibendazole, ivermectin, and mebendazole do not have their maximum residue level established. In addition, metabolites of albendazole, fipronil and fenbendazole in eggs are not considered in this Instruction.

Simultaneous Determination of Aldrin and Mirex in Honey by Liquid–Liquid Extraction with Low-Temperature Purification combined with GC–MS

Simultaneous Determination of Aldrin and Mirex in Honey by Liquid–Liquid Extraction with Low-Temperature Purification combined with GC–MS

Catalytic combustion of propane over Zr-modified Co3O4 catalysts: An experimental and theoretical study

As one of the domain volatile organic compounds (VOC), short chain alkane is an obstacle for low-temperature purification. Here, cobalt-zirconium oxides catalysts in a range of Co/Zr ratios were synthesized by sol-gel method for the catalytic combustion of propane. The result indicates that the catalyst with a ratio of Co to Zr of 4 (Co4Zr1) not only exhibits the superior catalytic performance with 90% conversion at 242 °C, but also maintains high thermal stability and water resistance. The synergistic effect between Co and Zr over cobalt-zirconium oxides catalysts contributes to the high increase of catalytic activity, which are relevant to the formation of ZrO2-Co3O4 solid solution. Additionally, the introduced Zr leads to more surface Co3+ species and surface-absorbed oxygen over Co4Zr1 catalyst. Moreover, high-resolution transmission electron microscopy (HRTEM) reveals Co4Zr1 catalyst exposes abundant (220) crystal face. Density functional theory (DFT) suggests that Co3O4 (220) shows lowest adsorption energy (−0.71 eV) and the formation of oxygen defects will reduce the adsorption energy (−1.03 eV). All these results confirm that the CoxZry catalysts are promising alternative for propane degradation and provide important guiding significance for the design of catalysts and catalytic combustion kinetics.

Optimization and validation of liquid–liquid extraction with low-temperature purification (LLE-LTP) for determining fluopyram fungicide in water samples using HPLC-DAD

Fluopyram is a fungicide and nematicide that belongs to the chemical group of benzamides, which act as succinate dehydrogenase inhibitors (SDHIs) on the mitochondrial respiratory chain of fungi. Despite being well known in several countries, there are few studies involving the optimization and validation of extraction methods for determining fluopyram in water samples. Therefore, this study aimed to optimize and validate liquid-liquid extraction with low-temperature purification (LLE-LTP) to determine fluopyram fungicide in water samples using high-performance liquid chromatography with diode array detection (HPLC-DAD). A two-level full factorial design was employed to optimize LLE-LTP which enabled achieving a recovery rate close to 100% and relative standard deviations (RSD) < 10.0%. The validation showed that the extraction method may be considered selective, precise, accurate, and linear in the range of 6.0 to 200 μg L-1. The LOD and LOQ were 4.0 and 6.0 μg L-1, respectively, proving the efficiency of this method for trace level determination of this fungicide in water samples. LLE-LTP coupled to HLPC-DAD analysis showed a matrix effect of less than 8% and it was applied in monitoring 20 environmental water samples, but no fluopyram residue was detected in the samples.

The enhancement of rice bran oil quality through a novel moderate biorefining process

Edible grade rice bran oil (RBO) rich in γ-oryzanol and phytosterol but without glycidyl esters (GEs) and monochloropropanediol esters (MCPDEs) was obtained from rice bran by moderate biorefining. High-acid RBO (acid value of 51.22 mg KOH/g) was firstly extracted from rice bran and was then moderately biorefined by combining improved enzymatic degumming, dewaxing, enzymatic deacidification, bleaching, and low-temperature purification (120 °C). Through monitoring the refining process, results showed that the improved enzymatic degumming by combining partial glyceride lipase SMG1-F278N and phospholipase A1 enabled the phosphorus content to quickly decrease to 4.56 mg/kg after optimization by response surface methodology. After biorefining, the final RBO with the acid and peroxide value of 0.10 mg KOH/g and 2.05 mmol/kg reached the grade-one standard of edible oil. Additionally, the final RBO contained 20.66 mg/kg γ-oryzanol and 20.63 mg/kg phytosterol with the retention rate of 71.67% and 59.2% but with undetectable GEs and MCPDEs. The environmental friendliness of the novel moderate biorefining process and superior product quality of the final product point toward a promising viable process for RBO refining in the further.

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.

Synthesis and properties of Pt/TiN catalyst for low-temperature air purification from carbon monoxide

Catalysts of carbon monoxide oxidation were synthesized by deposition of platinum on titanium nitride (TiN). Two substrates with an average particle size of 18 and 36 nm were obtained by hydrogen reduction of titanium tetrachloride in a stream of microwave plasma of nitrogen. The surface of the catalysts was studied by X-ray photoelectron spectroscopy (XPS). The data obtained by us in the present work indicate the presence of oxynitride as a transition layer between nitride and oxide. It was found that the CO oxidation rate on the 9–15 wt. % Pt loaded TiN catalysts is 120 times higher than that on the platinum black with a specific surface of 30 m2g–1. Increase in the reaction rate of CO oxidation on Pt/TiN catalysts as compared to platinum black can be associated with both an increase in the concentration of CO molecules adsorbed and a decrease in the activation energy of the reaction. Catalysts are promising for use in catalytic air purification systems.