Low-temperature Purification Research Articles

Monitoring the Fractional Distillation Purification of Inorganic Hydrides by Diode Laser Absorption Spectroscopy

We present our findings on the use of diode laser spectroscopy (DLS) for monitoring СО2, Н2О, СН4, C2H2, C2H4, NH3, and other gas impurities during low-temperature fractional distillation purification of gaseous hydrides. We demonstrate a lineup of instruments and techniques for continuously monitoring impurities during purification of hydrides: NH3, AsH3, РН3, and SiH4. The IR sources used are distributed feedback diode lasers (DLs) having a single mode output fiber pigtail and covering the near-IR spectral region, from 0.7 to 2.0 μm, where overtone and combination absorption bands of the impurities of interest are located. The systems offer high sensitivity and speed in impurity concentration measurements. Owing to their small size and low energy consumption, they can readily be integrated into a process equipment (components of fractionation columns) and enable prolonged continuous monitoring of the purity of hydrides. We describe gas concentration measurement techniques that use conventional high-resolution differential absorption spectroscopy and new, modulation correlation approaches for monitoring a weak molecular absorption by an impurity of interest against a strong selective absorption background of a matrix substance (hydride under study). We present results of technological experiments concerned with the low-temperature fractional distillation of hydrides and the degree of impurity removal from them as monitored by DLS.

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

Cresols are chemical contaminants derivative from phenol which can be found in sewage sludge. However, little attention has been given to monitoring these compounds in environmental matrices in the literature. Thus, the objective of this study was to develop a simple method based on solid-liquid extraction with low temperature purification for determining three cresol isomers in sludge. The quantification of these compounds was performed by gas chromatography coupled to mass spectrometry with a previous derivatization step. After a detailed study, the cresol recovery was higher than 91%, with relative standard deviation lower than 12% and a limit of quantification of 20 μg kg−1. Linearity was achieved between 10 and 90 μg L−1 (R2 > 0.98) with the standard solutions prepared in matrix extracts due to the trouble caused by the matrix effect. The proposed method was applied with success for monitoring cresols in sewage sludge samples coming from six different wastewater treatment plants. All samples showed contamination by cresols, mainly p-cresol with values between 32.3 and 516.9 μg kg−1. The majority of the analyzed samples showed a total sum of the isomers higher than the maximum residue limit established by Brazilian legislation (160 μg kg−1).

Optimisation, validation and application of the solid-liquid extraction with low-temperature purification followed by gas chromatography-mass spectrometry for determination of phthalates in sewage sludge

ABSTRACT Sewage sludge is a by-product obtained from sewage treatment plants (STP) that can be used to improve physical and chemical properties of the soil. However, xenobiotic compounds such as phthalates can be found in this material. Thus, the objective of this study was to optimise and validate the solid-liquid extraction with low-temperature purification (SLE-LTP) for the determination of five phthalates in sludge samples. Analyses were performed by gas chromatography coupled to the mass spectrometry (GC-MS). The SLE-LTP optimised parameters were water volume, extraction solvent, shaking mode and, freezing time. The most advantage of the proposed method is that it did not require additional clean up of the extracts with sorbents. In the best condition of extraction, recoveries of the five target analytes ranged from 76% to 119% and relative standard deviations were lower than 15%. Limits of quantification were 40 μg kg−1 for four phthalates and 80 μg kg−1 for dietylhexylphthalate (DEHP), which were about 6 to 12 times lower than maximum residue limits (MRL) established by Brazilian legislation. The validate method was applied to sewage sludge collected from six municipalities of Minas Gerais. Approximately 83% of the analyzed samples were contaminated by some phthalate, mainly DEHP with concentration ranging from 0.78 to 10.24 mg kg−1.

Hierarchical ZSM-5 based on fly ash for the low-temperature purification of odorous volatile organic compound in cooking fumes

Hierarchical ZSM-5 (HZ) zeolites with different SiO2/Al2O3 ratios (SiO2/Al2O3 = 50, 100, 150, 200, 250 and 300) were synthesized using a two-step hydrothermal treatment method, and the Al and Si were obtained from fly ash by the alkali melting and acid leaching method. On this basis, the 10 wt% LaMnO3/HZ catalysts were prepared by impregnation. The all the synthesized catalysts were investigated for the low-temperature (200 °C) catalytic oxidation of pentanal, which was selected as a typical odorous volatile organic compound (VOC) in cooking fumes. In addition, the physicochemical properties of HZ zeolites were characterized by several techniques (XRD, N2 physical adsorption–desorption, ICP-OES, SEM,TEM,NH3-TPD and 27Al MAS-NMR). The results showed that the HZ zeolite, which was micro-mesoporous material and had high specific surface area, provided a higher diffuser efficiency for long-chain VOC gas. The catalytic performance of HZ zeolite was better than that of the traditional ZSM-5 zeolite. Compared with the dry atmosphere, HZ-100 zeolite, which possessed more proper medium strong acid sites and the appropriate amount of acid sites, had the higher pentanal catalytic combustion conversion of above 92% and the relatively superior stability with 2 V% water steam in air, indicating that the suitable acid sites can form the best synergistic catalytic effect with water molecules for purifying long-chainVOC gas. In addition, the catalytic conversion of pentanal on 10 wt% LaMnO3/HZ-100 was 100% with no deactivation, and compared with HZ under a dry atmosphere, the average CO2 yields of 10 wt% LaMnO3/HZ catalysts in the steady catalytic oxidation stage under a dry atmosphere and 2 V% water steam in air were improved by 6–18% and 13–20%.

An LC–ESI–MS/MS method for residues of fluoroquinolones, sulfonamides, tetracyclines and trimethoprim in feedingstuffs: validation and surveillance

ABSTRACTAn increasing concern about food safety has been observed over the years. The presence of drugs residues in food is one of the major subjects of research in food safety. Feedingstuffs can be responsible for carryover into the food chain of residues of several drugs. This paper describes the development, validation and application of a fast and simple method for analysis of 24 antibiotic residues in feedingstuffs for cattle, pigs and poultry. Analytes include compounds from different antimicrobials classes, such as sulfonamides (sulfadiazine, sulfamethazine, sulfamethoxazole, sulfaquinoxaline, sulfachlorpyridazine, sulfadoxine, sulfadimethoxine, sulfizoxazole, sulfamerazine and sulfathiazole), fluoroquinolones (ciprofloxacin, enrofloxacin, norfloxacin, danofloxacin, difloxacin, sarafloxacin, flumequine, nalidixic acid and oxolinic acid), tetracyclines (tetracycline, doxycycline, oxytetracycline and chlortetracycline) and trimethoprim. Samples were extracted with methanol:water (70:30) 0.1% formic acid, followed by clean-up steps using centrifugation, low-temperature purification (LTP) and ultracentrifugation. Instrumental analysis was performed using liquid chromatography coupled to tandem mass spectrometry. Chromatographic separation was achieved using a C18 column and a mobile phase composed of acetonitrile and water, both with 0.1% formic acid. Validation parameters such as limit of detection (LOD), limit of quantification (LOQ), selectivity, linearity, accuracy, precision, decision limit (CCα) and detection capability (CCβ) were determined and meet the adopted criteria. LOD and LOQ were set to 30 and 75 µg kg−1, respectively. Inter-day precision were in the range from 4.0 to 11.1%, and linearity provides values of r2 above 0.95 for all analytes. The optimised method was applied to the analysis of more than 1500 real samples within the period 2012–2017. Non-compliant results were discussed and classified in terms of analytes, feed types and target species. Multivariate analysis of the data was performed using principal component analysis.

Liquid Chromatography-Tandem Mass Spectrometry Determination and Depletion Profile of Chlortetracycline, Doxycycline, and Oxytetracycline in Broiler Chicken Muscle After Oral Administration

A simple and fast method based on liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–ESI-MS/MS) was developed and validated for determination of tetracyclines in broiler chicken muscle. Sample preparation was performed using extraction with acetonitrile, followed by low-temperature purification (at − 20 °C) and further concentration. The chromatographic analysis was carried out using a Zorbax SB-C18 column with gradient elution using water and methanol both acidified with 0.025 M of formic acid. Mass spectrometry with electrospray ionization was operated in positive polarity using selected reaction monitoring (SRM) analysis mode, achieving the requirements of four identification points for each compound. Demeclocycline was used as internal standard. The method validation was done according to the criteria of Commission Decision 2002/657/EC. Parameters such as recovery, matrix effects, selectivity/specificity, linearity, precision (intra- and inter-day precision), accuracy, limits of detection (LOD) and quantification (LOQ), decision limit (CCα), detection capability (CCβ), and robustness were determined. Intra-day precision values were within the range 2.2–5.8% and inter-day precision was less than 10% for all analytes. Accuracy ranged from 98.2 to 103.2%. The method was successfully applied for depletion studies of chlortetracycline, doxycycline, and oxytetracycline in broiler chicken tissues after multiple oral administrations. After the depletion studies, the present study support more prudent use of CTC, DOX, and OTC for treatment of chickens and suggest a dose of 60 mg kg−1 body weight for CTC and OTC and 20 mg kg−1 body weight for DOX, orally administrated for five consecutive days.

Validation of a method for extraction of polycyclic aromatic hydrocarbons from sewage sludge and analysis by GC-MS

ABSTRACTIn the present study, the solid–liquid extraction with low temperature purification was validated for the determination of 16 polycyclic aromatic hydrocarbons from sewage sludge by gas chromatography-mass spectrometry. Recoveries ranged 70–114% for naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene and chrysene, while the compounds benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene showed recoveries of between 40 and 70%. The relative standard deviation was less than 13% for all of the compounds. Negative matrix effect was observed on the 10 compounds with less retention time in the chromatographic analysis and positive matrix effect noticed on the others. The limits of quantification were from 2 to 20 μg kg−1, about 30 times less than the maximum residue limit allowed in sludge by the European Union. The validated method produced quantification of 11 PAHs in one sludge sample at concentrations ranging 20–2000 μg kg−1.

Easy and fast extraction methods to determine organochlorine pesticides in sewage sludge, soil, and water samples based at low temperature

ABSTRACTOrganochlorine pesticides present in sewage sludge can contaminate soil and water when they are used as either fertilizer or agricultural soil conditioner. In this study, the technique solid–liquid extraction with low temperature purification was optimized and validated for determination of ten organochlorine pesticides in sewage sludge and soil samples. Liquid–liquid extraction with low temperature purification was also validated for the same compounds in water. Analyses were performed by gas chromatography-mass spectrometry operating in the selective ion monitoring mode. After optimization, the methods showed recoveries between 70% and 115% with relative standard deviation lower than 13% for all target analytes in the three matrices. The linearity was demonstrated in the range of 20 to 70 µg L−1, 0.5 to 60 µg L−1, and 3 to 13 µg L−1, for sludge, soil, and acetonitrile, respectively. The limit of quantification ranged between 2 and 40 µg kg−1, 1 and 6 µg kg−1, and 0.5 µg L−1 for sludge, soil, and water, respectively. The methods were used in the study of pesticide lixiviation carried out in a poly vinyl chlorine column filled with soil, which had its surface layer mixed with sludge. The results showed that pesticides are not leached into soil, part of them is adsorbed by the sewage sludge (4–40%), and most pesticides are lost by volatilization.

Biogas to liquefied biomethane via cryogenic upgrading technologies

Liquid biomethane (LBM), also referred to as liquid biogas (LBG), is a promising biofuel for transport that can be obtained from upgrading and liquefaction of biogas. With respect to fossil fuels, LBM is a renewable resource, it can be produced almost everywhere, and it is a carbon neutral fuel. LBM is 3 times more energy dense than compressed biomethane (CBM) and it allows longer vehicle autonomy. LBM has also a higher energy density than other transport biofuels, it is produced from wastes and recycled material without being in competition with food production, and it assures a high final energy/primary energy ratio. The low temperatures at which LBM is obtained strongly suggest the use of cryogenic/low-temperature technologies also for biogas upgrading. In this respect, since biogas can be considered as a “particular” natural gas with a high CO2 content, the results available in the literature on natural gas purification can be taken into account, which prove that cryogenic/low-temperature technologies and, in particular, low-temperature distillation are less energy consuming when compared with traditional technologies, such as amine washing, for CO2 removal from natural gas streams at high CO2 content. Low-temperature purification processes allow the direct production of a biomethane stream at high purity and at low temperature, suitable conditions for the direct synergistic integration with biogas cryogenic liquefaction processes, while CO2 is obtained in liquid phase and under pressure. In this way, it can be easily pumped for transportation, avoiding significant compression costs as for classical CO2 capture units (where carbon dioxide is discharged in gas phase and at atmospheric pressure). In this paper, three natural gas low-temperature purification technologies have been modelled and their performances have been evaluated through an energy consumption analysis and a comparison with the amine washing process in terms of the equivalent amount of methane required for the upgrading, proving the profitability of cryogenic/low-temperature technologies. Specifically, the Ryan-Holmes, the dual pressure low-temperature distillation process and the anti-sublimation process have been considered. It has been found that the dual pressure low-temperature distillation scheme reaches the highest thermodynamic performances, resulting in the lowest equivalent methane requirement with respect to the other configurations.

A New Distillation Process for the Upgrading of Acid Gas

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 183154, “The Potential of a New Distillation Process for the Upgrading of Acid Gas,” by L.A. Pellegrini, G. De Guido, S. Langé, and S. Moioli, Politecnico de Milano, and B. Picutti, P. Vergani, G. Franzoni, and F. Brignoli, Tecnimont, prepared for the 2016 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 7–10 November. The paper has not been peer reviewed. In this work, the potential of a new low-temperature distillation process for natural-gas sweetening has been investigated. The proposed technology consists of a dual pressure-distillation scheme designed to avoid the formation of a solid phase in all parts of the process while remaining able to fulfill the required natural-gas-purity specifications. The new process offers the competitive advantages of low-temperature technologies while avoiding carbon dioxide (CO2) solidification and solvent addition. Introduction The industry must find technologies that allow the profitable exploitation of low-quality and high-CO2-content gas reserves in order to meet increasing demand while still decreasing production costs. Low-temperature processes are preferred to traditional chemical or physical absorption for gas purification when the CO2 concentration in natural-gas streams is high. For this reason, attention on low-temperature processes for CO2 removal has increased in recent years. In this work, an analysis has been carried out to determine the trade-off between classical methyldiethanolamine (MDEA) gas-sweetening units, still representing the industry benchmark for acid- and sour-gas purification, and a low-temperature distillation process. The MDEA unit typically requires steam at the reboiler of the regeneration column, while the low-temperature distillation processes consume electric energy to drive the refrigeration cycle. In amine regeneration units, the steam consumption is a significant part of the total energy demand of the process and thus of the total operating costs. The complete paper defines a merit-index function to determine the trade-off between the two considered technologies. The Low-Temperature Process The new process for the low-temperature purification of natural gas is based on a dual-pressure (approximately 40/50 bar) low-temperature distillation operation, designed to bypass the solid/liquid/vapor (SLV) locus of the methane (CH4) and CO2 binary mixture through a proper thermodynamic pathway. In this work, an optimized process layout has been taken into account. The gas stream to be purified is fed to the high-pressure (HP) section at its dewpoint; in this first part of the distillation unit, the natural-gas feed is separated into two streams: a bottom one with a high CO2 content and a top product flow rich in CH4. The top product stream from the HP section is split into two streams: the first is heated and expanded to the low-pressure (LP) section; the second one is cooled so that after expansion it is at its bubblepoint at 40 bar. The superheated gas stream is fed at the bottom of the LP section, while the liquid feed enters the column a few theoretical trays above the bottom of the LP section. In the LP distillation section, a top product CH4 gas stream at commercial grade is obtained, while the bottom liquid stream rich in CH4 is pumped back to the HP section to provide the reflux. The condenser is a full-reflux condenser, and the top product stream is obtained as gas. The rationale of the process to avoid solid CO2 formation is the bypassing of the maximum of the SLV locus of the CH4-CO2 system.

Determination of multi-mycotoxins in cereals and of total fumonisins in maize products using isotope labeled internal standard and liquid chromatography/tandem mass spectrometry with positive ionization

Mycotoxins are secondary fungi metabolites present in foods that cause adverse effects in humans and animals. The aims of this work were to develop and validate a multi-mycotoxin method to determine the presence of aflatoxins, citreoviridin, deoxynivalenol, fumonisins ochratoxin A, zearalenone and some metabolites/derivatives in rice, maize-based products and wheat-based products, and a method to determine total fumonisins (free and bound/hidden forms) in maize-based products. The validated multi-mycotoxin method was based on extraction with acidified acetonitrile and LC-ESI+-MS/MS analysis, with LOQs ranging from 0.5 to 121μg/kg, and proved to be suitable for the multi-mycotoxin analysis in wheat, maize and rice products. Bound/hidden fumonisins were determined after extraction of the free forms using the multi-mycotoxin method, followed by a basic hydrolysis of the unextracted bound/hidden and solid-liquid extraction with low temperature purification (SLE-LTP). The hydrolysis efficiency of the bound/hidden extraction procedure was investigated by analyzing a maize reference material and showed recoveries ranging from 75% (HFB2) to 108% (HFB1). The use of isotope internal standards was crucial for mycotoxins quantification in maize meal and wheat flour, while for rice, external calibration and matrix matched curves gave satisfactory results. All 55 samples of wheat-based products analyzed were contaminated with at least one mycotoxin and 16% of 44 rice samples were also contaminated. The most prevalent mycotoxins were DON and ZON in wheat-based products.

Fast extraction of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran in sewage sludge and soil samples

ABSTRACTThe current environmental legislations recommend monitoring chemical contaminants such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans before the use of sewage sludge on the agricultural land. In this study, a solid–liquid extraction with low-temperature purification (SLE-LTP) was optimized and validated to determine 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran in sewage sludge and soil samples. The analyses were performed by gas chromatography-mass spectrometry operating in the selective ion mode (GC-MS-SIM). Acetonitrile:ethyl acetate 6.5:1.5 (v/v) was the best extraction phase, and the recoveries percentages were close to 100%. The linearity was demonstrated in the range of 1.25–25 µg L−1 of 1.25–20 µg L−1 for sewage sludge and soil, respectively. Matrix effect was proved for the two compounds and in the two matrices studied. Extraction percentages were between 78 and 109% and relative standard deviations ≤ 19%. The proposed method is faster than methods described in the literature because showed a few steps. The quantification limits (LOQ) in sewage sludge were 6.4 and 32 ng TEQ kg−1 for 2,3,7,8-TCDF and 2,3,7,8-TCDD, respectively. In soil, LOQs were 0.8 and 8.0 ng TEQ kg−1 for 2,3,7,8-TCDF and 2,3,7,8-TCDD, respectively. These values are lower than the maximum residue limits established by European Legislation. The method was applied to 22 agricultural soil samples from different Brazilian cities and 2,3,7,8-TCDF was detected in one of these samples.

Liquid Chromatography–Tandem Mass Spectrometry Multiclass Method for 46 Antibiotics Residues in Milk and Meat: Development and Validation

A screening method for analysis of 46 antibiotics residues, belonging to different classes, such as tetracyclines, sulfonamides, fluoroquinolones, β-lactams, cephalosporins, macrolides and other minority groups was developed and validated for application in bovine milk and bovine, swine, poultry, equine, fish and shrimp meat samples. Sample preparation consists in solvent extraction followed by clean up with C18 bulk and low temperature purification. Instrumental analysis was performed using liquid chromatography coupled to tandem mass spectrometry system. Chromatographic separation was achieved using a C18 column. Mobile phase was composed by methanol and water. The method was validated according to Commission Decision 2002/657/EC criteria. Validation parameters such as specificity and detection capability (CCβ) were determined and considered suitable to the established criteria. Values of CCβ ranged from 1.0 to 50.0 μg L−1 or μg Kg−1, depending on the compound and the matrix. The proposed method has been applied into Brazilian National Residue Control Plan since 2013 for the determination of antibiotic residues. A total of 3833 samples were analyzed until the current date and 13 samples showed positive results with concentrations above the permitted. The method is fast, easy and adequate for high throughput analysis in routine laboratories.

Low-temperature purification of the synthesis gas

In this paper, studies are made of the most economical method of low-temperature purification of synthesis gas, which is obtained during steam gasification of carbonizate. The analytical calculation is based on the cooling and phase transition of sulfur and carbon dioxide compounds and their separation. The paper presents the comparison of process energy costs depending on consumption characteristics and process parameters.

Salting-Out Assisted Liquid/Liquid Extraction Coupled with Low-Temperature Purification for Analysis of Endocrine-Disrupting Chemicals in Milk and Infant Formula by Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry

In this paper, salting-out assisted liquid–liquid extraction was coupled with low-temperature purification for the analysis of five kinds of endocrine-disrupting chemicals (EDCs) in milk and infant formula by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Acetonitrile and potassium hydrogen phosphate were used for the extraction of EDCs and the precipitation of protein. After the extract’s being frozen at −35 °C in the freezer for 2 h to remove fat, the remaining liquid phase was passed through a neutral alumina cartridge for further purification. Some important parameters, such as the extraction solvent and protein precipitant, the species and amount of salting-out reagent, the volume ratio between sample solution and acetonitrile, the freezing temperature and freezing time, as well as the amount of adsorbent, were carefully investigated and optimized to achieve the best extraction efficiency. Under the optimal conditions, good linearity was obtained with coefficient of determination ≥0.9995 except for 17β-estradiol (R 2 = 0.9950). Satisfactory recoveries were obtained for the five EDCs in the range of 73.5–119.2 %. Limits of detection were in the range of 0.03–0.23 ng mL−1. Relative standard deviations for intraday and interday precision were in the range of 4.5–9.0 and 2.7–6.0 %, respectively. The proposed method has been successfully applied to the analysis of seven kinds of market-purchased milk and two kinds of infant formula.

Low temperature techniques for natural gas purification and LNG production: An energy and exergy analysis

Due to the rapid increase of the World’s primary energy demand of the last decades, low-temperature processes for the purification of natural gas streams with high carbon dioxide content has gained interest, since they allow to make profitable exploitation of low-quality gas reserves. Low temperature purification processes allow the direct production of a methane stream at high purity and at low-temperature, suitable conditions for the direct synergistic integration with natural gas cryogenic liquefaction processes, while CO2 is obtained in liquid phase and under pressure. In this way, it can be pumped for transportation, avoiding significant compression costs as for classical CO2 capture units (where carbon dioxide is discharged in gas phase and at atmospheric pressure), and further uses such as Enhanced Oil Recovery (EOR) or underground storage.In this paper, the three most common natural gas low-temperature purification techniques have been modelled and their performances have been evaluated through energy and exergy analyses. Specifically, the dual pressure low-temperature distillation process, the anti-sublimation process and a hybrid configuration have been considered. It is found that the dual pressure low-temperature distillation scheme reach the highest thermodynamic performances, resulting in the best values of exergy efficiency and equivalent methane requirements with respect to the other configurations. This is mainly due to the distributed temperature profile along a distillation column, resulting in a less irreversible heat exchanging process.

Solid-Liquid Extraction with Low Temperature Purification Coupled with Gas Chromatography and Mass Spectrometry for Determination of Polychlorinated Biphenyls in Sewage Sludge

Sewage sludge is the residue produced by the wastewater treatment plants, which can be used as soil conditioner in agriculture. However, the current legislation recommends monitoring chemical contaminants such as polychlorinated biphenyls (PCBs). In this study, solid-liquid extraction with low temperature purification (SLE-LTP) was optimized and validated for monitoring six PCBs. The analyses were performed by gas chromatography and mass spectrometry. Sulfur interference was removed by 1.5 g of copper metal. The extraction was carried out using 6.50 mL isopropanol, 1.50 mL ethyl acetate, 0.1 g NaCl, 0.8 mL water and 15 min into ultrasound. Extraction percentages were between 82 and 94% and relative standard deviation ≤ 16% for low concentrations. Detection and quantification limits were 3.3 and 10 µg kg-1, respectively. The method was applied to sludge samples collected monthly in the wastewater treatment plant and PCB 52 was detected in six samples.

Вихревая технология стратификации газов для решения экологических вопросов в нефтегазовых и химических производствах (обзор)

One of the important tasks of the Russian economy and ecology is development and realization of energy-saving technologies, allowing the most efficient use of both primary and secondary energy resources. In oil, gas and chemical industries, there are processes, in which the potential energy of pressure of hydrocarbon or waste gases is either lost, either recycled with minimum efficiency. The energy lost should be used for low-temperature purification of waste and prepared gases, thus reducing environmental pollution. One way to solve this problem is to develop a vortex technology based on the Rank-Hilsch effect. By efficiency this method of purification exceeds standard throttling systems. This review presents an analysis of both theoretical and technological aspects of research of the vortex effect. different constructions of vortex tube are considered along with the one of the important conditions of its operation and realization in the industry - regulation of the incoming flow. It is shown that the realization of the regenerative scheme with vortex tubes will improve ecological and economic indicators of the core technology. A critical review of existing theories of the Ranque-Hilsch effect is provided. The article reviews the prospects of development of shock-wave mechanism that allows to explain the excessive cooling capacity of triple-flow vortex tubes used for associated petroleum gas treatment.

High-throughput method for the determination of residues of β-lactam antibiotics in bovine milk by LC-MS/MS

This study describes the development and validation procedures for scope extension of a method for the determination of β-lactam antibiotic residues (ampicillin, amoxicillin, penicillin G, penicillin V, oxacillin, cloxacillin, dicloxacillin, nafcillin, ceftiofur, cefquinome, cefoperazone, cephapirine, cefalexin and cephalonium) in bovine milk. Sample preparation was performed by liquid-liquid extraction (LLE) followed by two clean-up steps, including low temperature purification (LTP) and a solid phase dispersion clean-up. Extracts were analysed using a liquid chromatography-electrospray-tandem mass spectrometry system (LC-ESI-MS/MS). Chromatographic separation was performed in a C18 column, using methanol and water (both with 0.1% of formic acid) as mobile phase. Method validation was performed according to the criteria of Commission Decision 2002/657/EC. Main validation parameters such as linearity, limit of detection, decision limit (CCα), detection capability (CCβ), accuracy, and repeatability were determined and were shown to be adequate. The method was applied to real samples (more than 250) and two milk samples had levels above maximum residues limits (MRLs) for cloxacillin – CLX and cefapirin – CFAP.

Natural Clinoptilolite Based Solid-State Compositions for Low-Temperature Air Purification from Sulphur Dioxide

Natural clinoptilolite (N-CLI) and N-CLI based solid-state compositions containing copper(II) chloride and halide ions (X- = Cl-, Br- or I-) were investigated by X‑ray diffraction phase analysis, IR spectroscopy, thermogravimetry, water vapour adsorption, and pH‑metry. After that, they were tested in the reaction of low-temperature sulphur dioxide oxidation with air oxygen. It has been found that N-CLI has no protective properties in respect of sulphur dioxide whereas CuCl2‑KX/N-CLI compositions have the significant protective activity in the process of air purification from sulphur dioxide increasing in the order Cl- < Br- < I-.