Stream Of Nitrogen Gas Research Articles

Optimizing refuse-derived fuel production from scheduled wastes through Aspen plus simulation

This study aims to improve the quality of fuel with high calorific value namely Sfuel – a commercial high-quality refuse-derived fuel (RDF) from hazardous waste via modifying the process design and operating parameters of thermal conversion process. The study analyses key parameters of RDF quality, such as calorific value and heavy metal content, before and after process modifications based on the combination of experimental and simulation using Aspen Plus. In this study, the temperature and pressure of the simulation system are varied from 100 to 700 °C and from 1 to 5 bar, respectively. Findings indicate that there are a total of eleven heavy metals and 179 volatile compounds in the “Sfuels”. The quality of the targeted product is greatly improved by the metal evaporation at high temperatures and pressures. However, the calorific value of RDF significantly decreases at 700 °C due to a large amount of the carbon content being evaporated. Although the carbon content at high temperatures is significantly lost, the heat from the vapour stream reactor outlet, which is reused to preheat the nitrogen gas stream supplied to the system, reduces energy consumption while improving the thermal conversion efficiency of the system. Besides, low pressure along with high temperature are not the optimal conditions for quality Sfuels improvement by thermal conversion. Results also indicate that electric heating is more economically efficient than natural gas heating.

Determination of eight cannabinoids in foods with enhanced matrix removal-lipid adsorbent by ultra performance liquid chromatography-tandem mass spectrometry

A novel method was developed for the simultaneous determination of eight cannabinoids in six types of food matrices, including chocolate, fondant, biscuit, beverage, cookie and baijiu, using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample extraction and cleanup steps were optimized, and various purification methods were investigated to remove the oil matrix and glue in chocolate and fudge, respectively. Enhanced matrix removal-lipid adsorbent (EMR-Lipid) provided efficient, selective cleanup of the evaluated matrices. The sample was extracted using acetonitrile, followed by EMR-Lipid cleanup, and then dried using anhydrous sodium sulfate. The acetonitrile layer was concentrated by nitrogen to near-dry after 100 μL 10% glycerol in methanol was added to improve the recovery by reducing loss during concentration under the stream of nitrogen gas. Eight cannabinoids were separated using a Waters ACQUITY UPLC BEH Shield RP18 column (100 mm×3.0 mm, 1.7 μm). The responses of the cannabinoids in the positive and negative ionization modes were investigated and optimized, and the responses were superior in the negative ion mode compared to those in the positive ion mode. MS detection was performed in the multi-reaction monitoring (MRM) mode using an electrospray source in the negative ion mode. The cannabinoids were quantified using an external standard with matrix calibration curves to reduce the influences of the matrix effects on the quantitative results. The developed method was verified, and the conditions of sample pretreatment were also optimized. The calibration curves of tetrahydrocannabinol, cannabidivarin, tetrahydrocannabivarin, and cannabigerol and those of cannabidiol, cannabinol, cannabidiolic acid, and tetrahydrocannabinolic acid exhibited good linearities, with r>0.995, in the ranges of 2-200 and 0.4-40 ng/mL, respectively. The respective limits of detection (LODs, S/N=3) and quantification (LOQs, S/N=10) of tetrahydrocannabinol, cannabidivarin, tetrahydrocannabivarin, and cannabigerol were 4 and 10 μg/kg, and those of cannabidiol, cannabinol, cannabidiolic acid, and tetrahydrocannabinolic acid were 0.8 and 2 μg/kg. The average recoveries of the cannabinoids were 82.0%-114.9% under three spiked levels with corresponding relative standard deviations (RSDs) of <15% (n=6). EMR-Lipid provided efficient, selective cleanups of food matrices with good accuracy. The method is sensitive, rapid, accurate, simple to execute, and it is suitable for the determination of cannabinol compounds in typical food matrices.

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

Tailoring the structural and optical properties of Makrofol/CdS nanocomposite by gamma radiation

We synthesized nanocomposite (NCP) from Makrofol polycarbonate (PC) and Cadmium Sulfide (CdS) nanoparticles (NPs) by means of ex-situ casting procedure. We used thermalizes procedure to prepare the NPs in the presence of nitrogen gas stream. Rietveld refinement of x-rays records illustrated that the CdS has cubic and hexagonal constitutions. Samples from the PC-CdS NCP were exposed to γ dosages ranging from 20 to 250 kGy. The changes in structure and optical properties of the NCP films were investigated based on the γ dosage. The optical bandgap, refractive index, Urbach energy, optical dielectric parameters, chromaticity coordinates, tristimulus values, color intensity and color intercepts have been calculated and interpreted based on γ dosages. The bandgap decreased from 4.20 to 4.11 eV with increasing the γ dosage due to the domination of crosslinking, which damage the crystalline phase as indicated from X-ray diffraction (XRD). Further, the non irradiated PC-CdS NCP film displayed significant color difference by γ irradiation.

Quantitative determination of trace amounts of Diethylhexyl phthalate content in Dextrose injection proficiently by a simplistic Gas Chromatography Technique

The objective of present study was to analyze Diethylhexyl phthalate content in 5% Dextrose injection and other reconstituting diluents for pharmaceutical injectable formulations. Reconstituting diluents for pharmaceutical injectable formulations are mainly stored and supplied in polyvinyl chloride bags. This may lead to leaching of Diethylhexyl phthalate, a toxic content from polyvinyl chloride bags into reconstituting formulations. In the current study, a proficient and simple method by using a Gas Chromatograph was developed and validated for the quantitation of trace amounts of Diethylhexyl phthalate in 5% Dextrose injection. The method was optimized by using silica fused short capillary column (DB-1; USP G2 phase) with dimensions 5 m length x 0.53 mm inner diameter and 2.65µm film thickness. The method involves a simple extraction procedure for sample preparation by means of extraction with n-Hexane solvent and evaporation with a stream of nitrogen gas. An Internal standard (1-Phenydodecane) was added to standard and sample preparations by using n-Hexane as diluent. The method was validated as per the current regulatory guidance for analytical method validation.The projected methodology was found to be selective, accurate, precise, and linear in the test concentration range from 0.004 µg/mL to 5.065µg/mL for Diethylhexyl phthalate. The method was effectively used to analyze the Diethylhexyl phthalate content in 5% Dextrose Injection and other reconstituting diluents for pharmaceutical injectable formulations.

Thermally Induced Reversible Metal-to-Metal Charge Transfer in Mixed-Valence {Fe III 4 Fe II 4 } Cubes

Thermally Induced Reversible Metal-to-Metal Charge Transfer in Mixed-Valence {Fe ^III ₄ Fe ^II ₄ } Cubes

Development of a method based on dispersive liquid–liquid microextraction followed by partial vaporization of the extract for ultra–preconcentration of some pesticide residues in fruit juices

A new simple and efficient method has been developed for the ultra–preconcentration of multiclass pesticide residues including penconazole, chlorpyrifos, ametryn, clodinafop-propargyl, diniconazole, oxadiazon, and fenpropathrin from some fruit juice samples based on evaporation of the sedimented organic phase obtained from dispersive liquid–liquid microextraction. The enriched target analytes were analyzed by gas chromatography–flame ionization detection. In the microextraction procedure, a mixture of iso-propanol as a disperser and 1,2-dibromoethane as an extraction solvent is quickly injected into an aqueous phase containing the analytes and centrifuged. Afterward, the sedimented phase is transferred into a special shaped vaporization vessel and vaporized with nitrogen gas stream until remaining about 2 µL of it. Eventually, 1 µL of the remained sedimented phase is removed and analyzed by separation system. The optimum extraction and disperser solvents were found to be 1,2-dibromoethane and iso-propanol, respectively. In addition, the optimum pH range was 6-8, and nitrogen gas stream at a flow rate of 90 mL min−1 in a downward oriented vessel was applied. Eventually, the limits of detection and quantification were obtained in the ranges of 45-78 and 149-261 ng L−1, respectively. Relative standard deviations at the concentrations of 300, 500 and 1000 ng L−1 of each analyte were ranged between 2.2% and 5.8% for intra-day (n = 6) precision. Inter-day (n = 3) precision at a concentration of 500 ng L−1 of each analyte was obtained in the range of 4.9-7.1%. In addition, enrichment factors and extraction recoveries were ranged from 1382-2246 and 55-89%, respectively. Finally, the method was successfully utilized in analysis of the target pesticides in the selected juices.

Simultaneous determination of eight additives in polyethylene food contact materials by ultrahigh-performance liquid chromatography

食品接触材料中添加剂残留量的测定为食品接触材料从源头进行安全监管具有重要意义。然而目前的大多数研究只针对食品接触材料中有害物迁移量的测定,对于食品接触材料中有害物含量的测定方法仅局限于残留单体、低聚体、重金属,以及邻苯二甲酸酯类、双酚类化合物等环境污染物,对食品接触材料中添加剂残留量的测定较少。该研究系统地优化了样品前处理过程及仪器分析中影响8种添加剂分析准确度与响应灵敏度的各主要因素,建立了超高效液相色谱同时测定聚乙烯材料中8种添加剂的定量分析方法。聚乙烯样品冷冻研磨后,取2.0 g样品采用甲苯作为萃取溶剂,80 ℃, 10.34~11.72 MPa (1500~1700 psi)下对其进行加速溶剂萃取,取10 mL上清液,氮气吹干后用10 mL初始流动相(甲醇-水,7∶3, v/v)定容。采用ACQUITY UPLC BEH C8色谱柱(100 mm×2.1 mm, 1.7 μm)进行分离,柱温30 ℃,进样量5 μL,以乙腈和水作为流动相进行梯度洗脱,流速0.3 mL/min,二极管阵列检测器(DAD)在210~400 nm范围内扫描,230、250、280、330 nm监测,外标法定量。8种目标物在0.2~10 μg/mL质量浓度范围内线性关系良好,相关系数(R 2)>0.999。空白聚乙烯样品添加含量为0.05%时,加标回收率在83.8%~103.4%之间,RSD在0.14%~7.86%之间。对于含量为0.2%~0.9%之间的质控样品,8种目标物的平均回收率在63.5%~118.5%之间,RSD在4.61%~15.6%之间。8种目标物的定量限为0.02%。应用该方法测定10份市售聚乙烯食品包装袋和手套,其中6份样品均检测出含有亚磷酸三(2,4-二叔丁苯基)酯(抗氧剂168),含量为0.02%~0.07%,均小于GB 9685-2016规定的聚乙烯类食品接触材料中抗氧剂168的最大使用量(0.2%)。该方法能够满足聚乙烯类产品中8种添加剂的分析要求,可用于食品接触材料风险监测。

Moisturizing mechanism of glycerol and diglycerol on human stratum corneum studied by synchrotron X-ray diffraction.

Polyols are moisturizers used in cosmetics. Using X-ray diffraction, we studied the moisturizingmechanism of polyol solutions in the stratum corneum (SC). We examined whether glycerol disrupts the ordered hydrocarbon chain packing structure in isolated SC, as previously proposed in an SC lipid model. The SC samples were prepared by treatment with water and aqueous solutions of glycerol, diglycerol and glycerol/diglycerol. To examine the differences in the water-retention efficiency of polyols, using a solution cell, we performed dynamic X-ray diffraction to analyse the structural changes that occurred during water removal from the hydrated samples by a stream of dry nitrogen gas. We focused on two structures, the orthorhombic hydrocarbon chain packing structure in the intercellular lipids and the soft keratin in the corneocytes where most of the water is stored. The spacing formed by the soft keratin in the corneocytes immersed in a solution of water and diglycerol solution decreased rapidly by water removal. In contrast, it decreased gradually in the corneocytes immersed in a solution of glycerol and glycerol/diglycerol, indicating that the glycerol-containing solutions maintained the hydrated state of the corneocytes for longer. Furthermore, the characteristic change of the spacing in the orthorhombic hydrocarbon chain packing structure over time was observed during the drying process. The hydrated state was maintained longer, in water, followed by glycerol, diglycerol and glycerol/diglycerol, in increasing order. This is the first study to report such characteristic properties that could be indicators of the capacity of the SC to regulate water. The dynamic X-ray diffraction experiment on the structure of the soft keratin and the orthorhombic hydrocarbon chain packing structure during the drying of the hydrated SC provides an insight into the moisturizing mechanism of the polyol solutions in the SC. The results show that the glycerol/diglycerol solution functions as an effective SC moisturizer at the molecular level. Further, it was confirmed that the behaviour of glycerol in the isolated SC varies from that proposed in the SC lipid model, wherein glycerol was proposed to prevent the formation of a regular hydrocarbon chain packing structure.

Investigation of Organic Acids in Saffron Stigmas (Crocus sativus L.) Extract by Derivatization Method and Determination by GC/MS

The beneficial health properties of organic acids make them target compounds in multiple studies. This is the reason why developing a simple and sensitive determination and investigation method of organic acids is a priority. In this study, an effective method has been established for the determination of organic (lactic, glycolic, and malic) acids in saffron stigmas. N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) was used as a derivatization reagent in gas chromatography combined with mass spectrometric detection (GC/MS). The saffron stigmas extract was evaporated to dryness with a stream of nitrogen gas. The derivatization procedure: 0.1 g of dried extract was diluted into 0.1 mL of tetrahydrofuran, then 0.1 mL MTBSTFA was orderly and successively added into a vial. Two different techniques were used to obtain the highest amount of organic acid derivatives from saffron stigmas. To the best of our knowledge, this is the first report of the quantitative and qualitative GC/MS detection of organic acids in saffron stigmas using MTBSTFA reagent, also comparing different derivatization conditions, such as time, temperature and the effect of reagent amount on derivatization process. The identification of these derivatives was performed via GC-electron impact ionization mass spectrometry in positive-ion detection mode. Under optimal conditions, excellent linearity for all organic acids was obtained with determination coefficients of R2 > 0.9955. The detection limits (LODs) and quantitation limits (LOQs) ranged from 0.317 to 0.410 µg/mL and 0.085 to 1.53 µg/mL, respectively. The results showed that the highest yield of organic acids was conducted by using 0.1 mL of MTBSTFA and derivatization method with a conventional heating process at 130 °C for 90 min. This method has been successfully applied to the quantitative analysis of organic acids in saffron stigmas.

Liquid chromatography-high resolution mass spectrometry for the determination of three cannabinoids, two (−)-trans-Δ9-tetrahydrocannabinol metabolites, and six amphetamine-type stimulants in human hair

Since cannabis and amphetamine-type stimulants (ATS) are drugs of abuse used alone and concurrently worldwide, it is important to analyze them simultaneously. However, there are no reports of analytical method for the simultaneous extraction of these compounds and metabolites in hair samples of suspected drug abusers, due to the different chemical properties of acidic and lipophilic cannabinoids, and basic and hydrophilic ATS. We developed a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method for the quantification of cannabidiol (CBD), cannabinol (CBN), (−)-trans-Δ9-tetrahydrocannabinol (THC), THC metabolites such as 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) and THC-COOH-glucuronide (THC-COOH-glu), and six ATS of amphetamine, methamphetamine, phentermine, methylenedioxyamphetamine, methylenedioxymethamphetamine, and methylenedioxyethylamphetamine in the least amounts of human hair samples. The pulverized hair samples (10 mg) were extracted with 1 mL of 0.5% formic acid in methanol three times, and the supernatants were evaporated in a stream of nitrogen gas. The residue was dissolved and the aliquot was analyzed by LC-HRMS using positive electrospray ionization and the parallel reaction monitoring mode. The lower limits of quantitation were 0.1 pg mg−1 for THC-COOH and THC-COOH-glu, 4 pg mg−1 for CBD, CBN, and THC, and 10 pg mg−1 for the six ATS. Linearity, accuracy, precision, matrix effect, recovery, and post-preparation stability for the 11 analytes were fully validated. The present method was successfully applied to the determination of 11 analytes in hair samples of 10 suspected drug abusers.

Dynamic propagation of ice-water phase front in a supercooled water droplet

A three-dimensional (3-D) theoretical model is proposed to take the crystallization kinetics into the consideration of heat transfer, which allows for the description of the entire freezing process of a supercooled water droplet with the inclusion of the description of recalescence. The temporal evolution of the temperature and solid mass fraction at various stages during freezing are numerically studied, which shows a good agreement with the experimental results of the water droplet frozen in cold nitrogen gas stream. In particular, the ice-water phase front dynamics initiated from a single ice nucleation site is numerically investigated in recalescence stage, which shows that the ice-water phase front spreads over the entire water droplet with a diameter of 1.4 or 2.0 mm within about 16.0 or 23.0 ms governed by crystallization kinetics, leading to the drastic increase of the temperature and solid mass fraction of the droplet under the effect of thermodynamics. The present theoretical model can be useful to describe the dynamic behavior of ice crystallization in many other relevant cases.

The macromolecular neutron diffractometer at the spallation neutron source.

The Macromolecular Neutron Diffractometer known as MaNDi is located on beamline 11B of the Spallation Neutron Source at Oak Ridge National Laboratory. Neutrons are produced in discrete pulses at the Spallation Neutron Source, which enables Laue diffraction data through measuring the time-of-flight and thus wavelength of each diffracted neutron. The MaNDi diffractometer is optimized to collect diffraction data from protein crystals with unit cell axes between 30 and 300Å. The instrument is designed to provide flexibility in several instrumental parameters such as wavelength bandwidth and beam divergence to allow data collection from a range systems. Data collection is possible at room temperature or 100K using a standard nitrogen gas stream cooler combined with standard X-ray style mounting pins and loops.

Determination of pendimethalin in water, sediment, and Procambarus clarkii by high performance liquid chromatography-triple quadrupole mass spectrometry.

We established a high-performance liquid chromatography-triple quadrupole mass spectrometry method for the analysis of pendimethalin residues in water, sediments, and Procambarus clarkii (Louisiana crayfish) tissues. Water samples were concentrated on a HLB solid-phase extraction column and eluted with dichloromethane and acetone (1:1). After drying under a stream of nitrogen gas, the sample volume was adjusted to 1 mL with the mobile phase solvent methanol/water/acetic acid (8:20:0.1). Pendimethalin was extracted with ethyl acetate containing 0.1% acetic acid, after rotary evaporation to dryness at 35 °C, the residue was dissolved in mobile phase solvent, purified by a neutral alumina column and graphitized carbon black powder (0.1 g). The mass characterization was conducted in positive ion mode, and the corresponding ions were detected in multi-reaction monitoring mode. The linear equations were y = 1 × 106x + 14275, at pendimethalin levels of 0.05-20 μg L-1 and y = 691029 × - 414368 for 20-200 μg L-1. The detection limits of pendimethalin in water, sediments, and P. clarkii tissues were 1.0 × 10-4μg L-1, 5.0 × 10-3μg kg -1and 5.0 × 10-3 μg kg -1, respectively. The spiked recoveries ranged from 81.6 to 106.3%, and the relative standard deviations ranged from 4.58 to 13.6% (n = 6). The method provided an efficient and low-cost extraction and purification procedure that enabled a sensitive determination of pendimethalin in water as well as complex matrices.

The Effect of Parameter Combinations (Carbonization Temperature - Chemical Activator) on Degree of Graphitization, Aromaticity, and Fungsional Group of Rose Petal (Rosa sp) Based-Activated Carbon

Activated carbon is a porous material which is produced from the carbonization of organic compounds by involving the activation process. Activated carbon can be used as an absorbent of heavy metal cations, anions, and organic compounds. Quality of activated carbon is determined by the crystal structure, aromaticity, and its surface functional group. Activated carbon consists of amorphous and graphite structures. The graphite structure in activated carbon is important because it determines its thermal stability. Content of graphite structure in the activated carbon is stated as degree of graphitization (DOG). Aromaticity (fa) is related to amount of carbon atoms which form graphene layers in the activated carbon. The oxygenated functional groups of the activated carbon determines its hydrophilic / hydrophobic nature. Purpose of this research is to learn effect of carbonization temperature - chemical activator (ZnCl2) combination on degree of graphitization, aromaticity, and functional group on activated carbon. This research was conducted by using a pink rose flower precursor, at activator/precursor mass ratio of 0.1 at carbonization temperature of 400, 600 and 800°C for two hours under nitrogen gas stream. Characterization was carried out with FTIR spectrophotometry and X-ray diffraction. The DOG and aromaticity were calculated based on intensity of the difractograms. The characterization with FTIR spectra related to –OH and aromatics C=C bond vibrations. The highest DOG was obtained by the activated carbon resulted at 400°C, i.e. 92.31%. However, no significant different of the aromaticity, about 0.42 to 0.50.

Validation of the Biofish-300 SUL Enzymatic Biosensor for the Detection of Sulfite in Crustacean.

Background: Sulfites are some of the oldest and most widespread preservatives in our food supply. They are food additives that have antioxidant properties, but they are also recorded as allergens by the main international regulatory bodies on food safety because of their adverse health effect. Hence, sulfites maximum concentration in foodstuff is regulated and they must be ensured by the agro-food processing industries. The most widely used technique for the quantification of sulfites is the Modified Monier-Williams (AOAC Official Method 990.28). Objective: In this method, SO₂ is released from sulfites and some bound compounds when the sample is mixed with an acid (normally hydrochloric acid, but sometimes phosphoric acid) and heated. The SO₂ is distilled using a stream of nitrogen gas, which carries the gaseous SO₂ into an absorbing solution of hydrogen peroxide (H₂O₂) where it is oxidised to sulphuric acid. The amount of SO₂ distilled into the H₂O₂ is determined by titration with 0.1M sodium hydroxide. Apart from being time consuming (at least 2 h) and the usage of toxic solvents, the method presents some other disadvantages that make it inappropriate as a routine-control technique for the agro-food industry. Hence, the industry demands simple, fast and accurate methods for sulfite level monitoring. Methods: BIOLAN is a SME that develops and commercializes biosensors for quantitative analysis of food quality and safety parameters, based on its proprietary enzyme-based electrochemical biosensor technology platform. This technology enables high accurate and robust analysis with a compact device that help the users to control the quality in an easy and safety manner. Biofish-300 SUL method is a highly specific enzimatic biosensor for the rapid quantification of sulfite, measured as SO₂ content, in crustaceans. It consists on the extraction of sulfite in an aqueous based solution, by the aid of an Ultra-turrax or similar, and its subsequent quantification by the biosensor after previous calibration (3 min). Results: Sulfite in raw shrimp head-on, raw shrimp head-off, and boiled shrimp was analyzed, and performance was examined using naturally contaminated and spiked samples by comparisons with AOAC Official Methods of AnalysisSM (OMA) 990.28. Linearity, selectivity, matrix, consistency, and robustness were evaluated. All results were within acceptable ranges except robustness, which reflected deviation in the sample volume and ultraturrax time compared with the standard assay procedures described in the Biofish 300 SUL Instruction Manual. Accuracy, assessed as a comparison of the Biofish results with the OMA results, ranged from 82 to 115% in all samples except for fortified raw shrimp head-on, in which the low level yielded an accuracy of 138%. The method bias was in general negative in both incurred and fortified high levels, and slightly positive in incurred low levels. Repeatability was very good as shown by the low RSDr values, demonstrating acceptable repeatability precision with results <10% in most of the evaluated values. Regression analyses showed a good correlation between the Biofish and OMA methods with R² = 0.99 in all cases. Conclusions: As a whole, accuracy, recovery and bias within range results indicate that the kit provides accurate and precise sulfite quantification for all the evaluated matrices, confirming that sample preparation and assay procedures produce acceptable results. Biofish 300 SUL has proved to be a suitable tool for monitoring sulfite levels in quality control routines due to its high accuracy, precision, rapid response and ease of use. Highlights: With a simple sample preparation, results are obtained in approximately 3 min, making a big difference with other technologies that require specific skills or tedious sample pretreatments and analysis procedures.

Determination of ten cephalosporins in bee products by solid phase extraction-ultra-performance liquid chromatography-tandem mass spectrometry

An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantitative determination of ten cephalosporins in bee products, including honey, royal jelly, and lyophilized royal jelly powder, has been established. The samples were extracted with an acetonitrile-water (80:20, v/v) solution. After purification by solid phase extraction using an Oasis PRIME HLB cartridge, the extract was blown to dryness under a stream of nitrogen gas and then re-dissolved in 1 mL 0.1% (v/v) formic acid solution and methanol (95:5, v/v). The samples were separated on an Acquity UPLC BEH C18 column, using a mixture of 0.1% (v/v) formic acid solution and methanol as the mobile phase under gradient elution. The analysis was carried out using a positive electrospray ion source in the multiple reaction monitoring mode. The matrix-matched external standard method was applied to quantitative analysis. Good linear relationships were obtained for the ten cephalosporins in certain concentration ranges, and the correlation coefficients were more than 0.999. The limits of detection and limits of quantification for the ten cephalosporins were in the ranges 0.15-1.5 μg/kg and 0.5-5 μg/kg, respectively. The recoveries for the analytes in the bee products were in the range of 75.0%to 89.8%, with relative standard deviations of 1.4% to 4.6%. This method is characterized by a short analysis time and is suitable for the determination of cephalosporins in different bee products by virtue of its simplicity and reliability.

Dynamic Study of VSA and TSA Processes for VOCs Removal from Air

Volatile organic compounds are air pollutants that necessitate to be eliminated for health and environment concerns. In the present paper, two VOCs, that is, dichloromethane and acetone are recovered by adsorption on activated carbon from a nitrogen gas stream. Experimental adsorption isotherms of the two VOCs are determined at three different temperatures 298, 313, and 323 K by the dynamic column breakthrough method. The dynamic mathematical model succeeds to predict satisfactorily the experimental breakthrough curves for pure VOCs and different binary mixtures for various conditions. Thus, the validated dynamic mathematical model has been used as a simulation tool for optimization purposes of VSA and TSA processes in order to achieve the highest performances under the given constraints. The effects of the adsorption step duration, the vacuum pressure, and the desorption temperature on the recovery of dichloromethane and acetone have been studied. A recovery of 100% of the two VOCs could be attained. However, the adsorption step duration should be determined precisely so as not to affect the recovery and alter the quality of air being purified due to the breakthrough of VOCs. The vacuum pressure and the desorption temperature should be carefully chosen in order to both reduce the energy consumption and shorten the purge step duration. Regeneration by hot nitrogen stream seems to be more efficient than regeneration by reducing pressure.

Synthesis of zirconium nitride from zircon sand by transferred arc plasma assisted carbothermal reduction and nitridation process

This paper reports the experimental results on synthesis of zirconium nitride from zircon sand through transferred arc plasma processing via carbothermal reduction and nitridation reaction. A mixture of zircon sand and carbon was processed in a transferred arc set-up in a stream of nitrogen gas. The influence of the amount of carbon and processing parameters such as input power and processing time on zirconium nitride phase formation and product morphologies were investigated by means of XRD and SEM-EDS respectively. Thermodynamic calculations were performed using free energy minimization technique to predict the conditions under which zirconium nitride is formed when zircon is processed in nitrogen atmosphere. Conversion diagrams were constructed for the ZrSiO4-C-N2 system with different mole ratios of carbon. The experimental results show that the optimum mole ratio of carbon to zircon to convert zircon to zirconium nitride by this process is 1:4. Further, the results show that the plasma input power has a greater influence on the formation of zirconium nitride rather than the processing time. Experimental observations show that the optimum processing parameters for effective formation of zirconium nitride from zircon are 10 kW of plasma input power and 5 min of processing time under nitrogen environment.

Design and Control of a Novel Plant-Wide Process for Epichlorohydrin Synthesis by Reacting Allyl Chloride with Hydrogen Peroxide

A novel plant-wide process is designed for epichlorohydrin synthesis by the epoxidation of allyl chloride with hydrogen peroxide in the presence of titanium silicate 1 catalyst and methanol solvent. The design targets are to satisfy the requirements of product purities and address gas-phase safety concerns caused by the exothermic and violent decomposition potential (to oxygen and water) of hydrogen peroxide. There is a risk of oxygen/allyl chloride and oxygen/methanol systems exploding in the gas phase. A plant-wide process that includes one packed bed reactor, one distillation column, one decanter, and two strippers is proposed to meet the design targets and is optimized with minimum total annual cost. The strategies of feeding excess allyl chloride into the packed bed reactor and feeding two nitrogen gas streams into the column top and gas vent of a partial condenser in the distillation column, respectively, are used to prevent explosion in the gas phase. High-purity epichlorohydrin and water can be pr...