Determination of oxidation products in transformer oils using FT-IR spectroscopy

Transformer oils are subject to a lot of control checks in the process of their exploitation, because the presence of oxidized products causes damages in the electrical equipment. In the process of exploitation of transformer oils anti-oxidation additives get exhausted and products of oxidation are formed. This paper describes the development method for study of oxidation transformer oils by Fourier transform infrared (FT-IR) spectroscopy. The aim of this paper is to determine the main products of oxidation of transformer oils and to increase the sensitivity of FT-IR analysis by the extraction method. The method which we suggest to register all oxidized products is of great interest. The problem is the detection limit of routine apparatus. For this reason we have developed an extraction method, which can identify precisely all oxidized products qualitatively and quantitatively in the region 1800-1650 cm⁻¹. Thus a manifold increase of the FT-IR analysis is achieved, combined with increased sensitivity, precision and the possibilities for registering micro-amounts otherwise beyond the routine technique. FT-IR spectroscopy is a powerful method with great practical significance for investigation of carbonyl- and carboxylic degradation products from transformer oils.     

Materials chemistry and the futurist eco-friendly applications of nanocellulose: Status and prospect

Cellulose, a linear biopolymer, is present naturally in all plants. Apart from being the planet’s predominant natural polymer, it also offers a variety of features including excellent biocompatibility, lower density, substantial strength and the most beneficial mechanical characteristics, inexpensive in cost. Applying the mechanical or chemical techniques, cellulosic materials are transformed into cellulose nanofibres (CNFs) and even cellulose nanocrystals (CNCs). These CNFs and CNCs exhibit excellent capabilities in comparison with native cellulose fibre. Nowadays, nanocellulose is being used in a variety of practical applications such as product packaging, papers as well as paperboard, food sector, healthcare, hygiene products, paints, skin care products and sensors. The current review article summarizes the cellulose, processing methods for nanocellulose, techniques used for chemical modification of cellulose surface and consequently its application as reinforcement in polymeric materials. This article also provides a comprehensive discussion of the historical development in the area of nanocellulose.     

Synthesis and characterization of xylan-graft-poly(L-lactide)

In this study, xylan extracted from chestnut sawdust was used to synthesize the copolymers of xylan-graft-poly(L-lactide) (xylan-g-PLLA) by grafting L-lactide monomer onto xylan and using 4-dimethylaminopyridine as a catalyst at 80°C. Depending on the synthesis conditions and parameters, synthesized xylan-g-PLLAs were either water-soluble which form homogeneous plastic films after drying at room temperature or water-insoluble ones which do not form films at all. A Graeco-Latin design of experiments was used to determine the effects of three factors (reaction time, amount of L-lactide, and amount of the catalyst) on the results of the grafting reaction: the degree of substitution (DS) and the degree of polymerization (DP) of the copolymers. The DS and DP determined by ¹HNMR showed that they increase according to the amount of L-lactide and decrease according to the reaction time while the catalyst had no influence on the copolymerization reaction. Grafting of PLLA onto xylan was confirmed by Fourier transform infrared (FT-IR) and ¹HNMR analyzes. FT-IR spectra showed absorption bands at 1,784?cm^?1 characteristic of the ester functions (C?O) and ¹HNMR spectra revealed signals between 1 and 2.5?ppm corresponding to the protons of the aliphatic chains. Thermal properties show that the temperatures of start of degradation of copolymers are lower than those of PLLA and xylan. The N,N-dimethylacetamide results showed that the glass transition temperature of xylan-g-PLLA film was 147°C. We found that the Young’s modulus of this film is close to that of polypropylene.     

Effect of temperature on the extraction of Pd by liquid tin from molten borosilicate glass containing simulated radwaste

Separation of Pd from borosilicate glass-melt containing simulated high level radioactive waste (Pd, Mo, Cs, Sr, Zr, Nd, Ni, Fe) using Sn as the solvent metal was studied on lab scale. The separation of Pd was studied using varying amounts of Sn, and the percentage of extraction of Pd and other elements was investigated by varying the process temperature and the starting material for Pd. The process temperature was observed to have a profound influence on the separation of Pd from the glass melt to the metallic tin phase. The % extraction of Pd was found to be less for the batches heat-treated at temperatures below 900 °C. The decrease in the % extraction was due to the entrainment of Pd in the glass phase for the samples heat-treated at low temperatures. The entrainment of Pd leads to the formation of Pd-rose like structures in the glass phase as observed by SEM and EDAX. Similarly, Mo, Fe and Na also formed separate phases inside glass matrix when the samples were heated below 900 °C. However, entrainment was not seen when the samples were heat-treated above 1050 °C in Ar. At 1200 °C, a recovery of about 99% of Pd was obtained. The formation of a PdSn₄ type intermetallic phase was noticed in tin metallic phase. The extraction behavior of Pd in borosilicate glass melt was also studied by using Pd(NO₃)₂ instead of Pd powder as staring material, and the results showed that the process temperature is the key determinant of the extraction behavior of Pd.     

TODGA/HNO_3萃取La~(3+)的界面性质

利用滴体积法研究了La~(3+)/HNO_3/N,N,N',N'-四辛基-3-氧戊二酰胺(TODGA)/稀释剂体系的界面性质,考察了TODGA浓度、液滴形成时间、稀释剂种类、La~(3+)浓度、体系温度、离子强度和溶液酸度等因素对体系界面性质的影响.实验结果表明,体系达到界面饱和吸附时间约为120 s,可认为体系达到萃取平衡;TODGA浓度不同时,界面张力也不同,进而判定界面饱和吸附物种亦不相同;极性较小的稀释剂体系的界面张力降低较大,按照正辛烷环己烷苯甲苯次序降低;HNO_3对TODGA的质子化作用使其表面活性显著增强,故硝酸浓度增大导致界面张力降低;Na NO_3的存在降低了界面上游离萃取剂分子的浓度,致使界面张力增大.     

Extraction of organophosphorus pesticides by carbon‐coated Fe3O4 nanoparticles through response surface experimental design

In this paper, carbon‐coated Fe₃O₄ nanoparticles were successfully synthesized and used as a magnetic solid‐phase extraction absorbent for the preconcentration and extraction of organophosphorus pesticides in environmental water samples. The carbon‐coated Fe₃O₄ nanoparticles were characterized by transmission electron microscopy, X‐ray powder diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The determination of organophosphorus pesticides in water samples with carbon‐coated Fe₃O₄ nanoparticles was investigated by high‐performance liquid chromatography with a diode array detector. Furthermore, the response surface model based on the central composite design was applied to quantitatively investigate the effect of some important variables influencing the extraction efficiency, such as pH, treatment time, amount of nanoparticle sorbents, and amount of salt and to find the optimized conditions providing the highest extraction efficiency. Under optimized conditions, the calibration curve was linear in the range of 0.5–15.0 ng/mL with a regression coefficient of 0.9948, 0.9958, and 0.9931 for fenitrothion, diazinon, and ethion, respectively. The obtained results showed that this analytical method would be useful for the analysis of fenitrothion, diazinon, and ethion in tap water with high precision and accuracy.     

Development of a stir bar sorptive extraction method for the determination of volatile compounds in orange juices

A stir bar sorptive extraction method for the determination of volatile compounds in orange juices was developed. The extraction variables were optimized using a reduced two‐level factorial screening design (2^5‐1), and the most suitable analytical conditions for the extraction of the studied compounds were: sample volume 10 mL, extraction time 60 min, stirring speed 1800 rpm, NaCl amount 30% (weight/volume), and twister length 10 mm. The optimized method was further validated, obtaining good linearity and detection and quantification limits low enough to correctly determine the studied compounds. As well, for most of the studied compounds precision and recovery values were good. Several orange juice samples (squeezed and commercial) were extracted following the optimized extraction method and analyzed by gas chromatography coupled to mass spectrometry detection. The method has proven to be suitable for the determination of the aroma of orange juice, of which limonene was the major volatile compound in all the studied samples.     

Toward a comprehensive microextraction/determination unit: A chip silicon rubber polyaniline‐based system and its direct coupling with gas chromatography and mass spectrometry

An inexpensive silicon rubber‐based chip was constructed by fabricating a triangle‐shaped microcanal with a 135 μm width and 234 μm depth by laser ablation technique. The fabricated groove was sealed by a thin glass cover while two pieces of stainless‐steel tubing were connected to each side of the canal. Then, a thin polyaniline film was synthesized on the walls of the canal by chemical oxidation using a syringe pump to deliver the relevant reagents. The microfluidic system was eventually connected to a gas chromatography‐mass spectrometry. To evaluate the capability of the constructed microfluidic system, it was implemented to the analysis of submilliliter volumes of environmental samples spiked with the trace amounts of some pesticide residues. To show the applicability of the hyphenated system, the extraction/determination of triazines was implemented while only 500 μL sample with the limits of detection ranged from 0.2 to 0.5 ng/mL could be easily achieved. In addition, the influential extraction parameters such as sample volume, flow rate, and sample pH were optimized. Under the optimized conditions, the relative standard deviation values for double‐distillated water sample spiked with the selected triazines at 250 ng/mL were 6.5–12.5% (n = 3).     

Interfacial reaction using particle-immobilized reagents in a fluidized reactor. Determination of glycerol in biodiesel

A novel fluidized beads strategy for utilization of particle-immobilized reagents in flow analysis was developed in this study. The performance of the suggested strategy was demonstrated by the determination of glycerol in biodiesel. This analytical task was used as a proof-of-concept example. The method is based on on-line extraction of glycerol from biodiesel into aqueous stationary phase of extraction-chromatographic column, followed by elution and spectrophotometric determination in the form of copper glycerate formed in a fluidized reactor of stepwise injection system. The floating of cation exchange resin Dowex^® 50WX4, saturated with Cu(II) ions in liquid phase, was accomplished by air-bubbling. The linear range was from 100 to 1000 mg kg⁻¹, and the limit of detection, calculated as 3s of a blank test (n = 5), was found to be 30 mg kg⁻¹. The method was successfully applied to the analysis of biodiesel and biodiesel-blend (B 20) samples.