Comparison of four quantification methods for the determination of PCB in transformer oils

The analysis of PCB in transformer oils has been achieved with three HRGC/ECD based methods, proposed by the International Electrotechnical Commission (IEC/TC 10), by the Comité Européen de Normalisation (CEN/TC 19/WG 22) and by the Deutsches Institut für Normung (DIN 51 527). The same clean-up, described in the CEN/TC 19/WG 22, has been used for all the samples, allowing a comparison of the quantification procedure only. The total chlorine content has also been determined with X-ray fluorescence. These different methods of quantification are compared and their application for legislative purposes is discussed.Dedicated to Professor Dr Dieter Klockow on the occasion of his 60th birthday     

Dechlorination of contaminated sediments of Ionian Sea

Natural dredged sediments contaminated by PCBs from the heavy industrialized harbor of Taranto (S. Italy) on the Ionian Sea, previously dechlorinated by mechanical activation in different ball mills (SPEX and AGO-2), together with synthetic mixtures emulating the contaminated sediments, were submitted to thermogravimetric and calorimetric measurements as well as to X-ray powder diffraction in order to clarify the dechlorination reaction mechanism. Both major sediment components, i.e., carbonates and clay minerals, were found to be affected by the mechanical activation. As trace pollutants like PCBs are concentrated in clays, the mechanical activation of sediments increases the release of pollutants yielding a more active decontamination. DSC results were less informative as calorimetric peaks from different thermal events were found to overlap.     

A combination of solid-phase extraction on hypercrosslinked polystyrene with HPLC determination of furan derivatives in transformer oils

A chromatographic method for determining electric insulation degradation products in transformer oil (5-hydroxymethylfurfurol, furfurol, 2-acetylfurane, and 5-methylfurfurol) based on concentrating analytes by means of solid-phase extraction on hypercrosslinked polystyrene was developed. The main advantages of this method are high rapidity, reproducibility, and sensitivity. The detectability limit for each furan derivative was not above 30 μg/l, a characteristic that makes it possible to control the concentrations of analytes to an accuracy of 1% of their maximum permissible levels. The degrees of extraction for furfurol, 2-acetylfuran, and 5-methylfurfurol were above 95%, while that for hydroxymethylfurfurol ranged within 75–80%.     

Speciation of arsenic in a contaminated soil by solvent extraction

Soil collected from a disused cattle dip in northern New South Wales was studied with the aim of developing an inexpensive, yet effective method for quantitative determination of arsenic(III), arsenic(V) and total organic arsenic in a contaminated soil. Hydrochloric acid extractions were used as a method for removal of the arsenic from the soil in a form suitable for speciation. It was found that the extraction efficiency varied with the ratio of soil to acid, and the concentration of the acid. Arsenic(III), as arsenic trichloride, was selectively extracted into chloroform from a solution highly concentrated in hydrochloric acid. This was followed by back-extraction of the arsenic into water. Total inorganic arsenic was determined in a similar manner after the reduction of arsenic(V) to the trivalent state with potassium iodide. Arsenic(V) was determined by the difference between the results for arsenic(III) and total inorganic arsenic. All analyses for the various arsenic species were performed by hydride generation-atomic absorption spectroscopy; concentrations of total arsenic in the soil were confirmed using X-ray fluorescence spectrometry. It was found that all the arsenic in the soil was present as inorganic arsenic in the pentavalent state. This reflects the ability of arsenic to interchange between species, since the original species in cattle dipping solution is arsenic(III).     

Ultra‐trace analysis of furanic compounds in transformer/rectifier oils with water extraction and high‐performance liquid chromatography

A novel approach for the determination of parts‐per‐billion level of 5‐hydroxymethyl‐2‐furaldehyde, furfuryl alcohol, furfural, 2‐furyl methyl ketone, and 5‐methylfurfural in transformer or rectifier oils has been successfully innovated and implemented. Various extraction methods including solid‐phase extraction, liquid–liquid extraction using methanol, acetonitrile, and water were studied. Water was by far the most efficient solvent for use as an extraction medium. Separation of the analytes was conducted using a 4.6 mm × 250 mm × 3.5 μm Agilent Zorbax column while detection and quantitation were conducted with a variable wavelength UV detector. Detection limits of all furans were at 1 ppb v/v with linear ranges range from 5 to 1000 ppb v/v with correlation coefficients of 0.997 or better. A relative standard deviation of at most 2.4% at 1000 ppb v/v and 7.3% at 5 ppb v/v and a recovery from 43% to 90% depending on the analyte monitored were obtained. The method was purposely designed to be environmental friendly with water as an extraction medium. Also, the method uses 80% water and 20% acetonitrile with a mere 0.2 mL/min of acetonitrile in an acetonitrile/water mixture as mobile phase. The analytical technique has been demonstrated to be highly reliable with low cost of ownership, suitable for deployment in quality control labs or in regions where available analytical resources and solvents are difficult to procure.     

Comparative properties of Amazonian oils obtained by different extraction methods

Pequi (Caryocar brasiliense Camb.), baba?u (Orbignya phalerata Mart.), buriti (Mauritia flexuosa), and passion fruit (Passiflora edulis) oils were studied to determine their antibacterial, antioxidant and cytotoxic activities, as well as their total phenol and carotenoid contents. The fatty acid contents were determined by GC-MS. The three types of passion fruit oils studied were refined, cold pressed or extracted from seeds in a Soxhlet apparatus. The oils thus obtained showed differences in antioxidant activity and carotenoid content, but were similar in regard to total phenols. Buriti and pequi had the highest carotenoid contents, while refined and cold pressed passion fruit oil displayed the highest antioxidant activity. Pequi oil was the only oil to display antibacterial and cytotoxic activity.     

Neutron activation analysis of rhenium in rocks after preliminary extraction with acetone

A preconcentrating neutron activation method for determination of rhenium in rocks is described. The preconcentration is based on a preliminary extraction separation with acetone. The chemical recovery is determined by an isotope tracer technique using¹⁸⁶Re. The method has been applied to the determination of rhenium in rock samples and extended to more complex systems. Rhenium content is in the range of 110 ppb.     

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.     

Quantitative moisture measurements in lubricating oils by FTIR spectroscopy combined with solvent extraction approach

Quantitative measurements of moisture in mineral and synthetic polyol ester based lubricating oils using FTIR spectroscopy combined with solvent extraction approach are described. The samples are prepared by mixing dry dimethyl sulfoxide (DMSO) and lubricating oils, and after phase separation, the extracted bottom DMSO layers are analyzed with FTIR. The results from the solvent extraction show that the DMSO is an excellent aprotic solvent for water removal from lubricating oils. The spectroscopic data reveal that near IR region (5400–4800 cm^{− 1}, molecular water) gives the best results for water determination in both mineral and synthetic lubricants, followed by mid-IR region (3800–3200 cm^{− 1}, O―H stretching). However, the water content estimated from the IR region (1800–1550 cm^{− 1}, O―H bending) has the lowest accuracy due to the interference from aminic, phenolic additives and other oxidation products present in the lubricants. The accuracy of the FTIR spectroscopy combined with solvent extraction approach is exemplified by monitoring the water content in mineral oil during oxidation process at 150 °C for 30 days. The quantitative determination of the moisture in the fresh and oxidized oils by the developed approach is shown to be an alternative technique to Karl Fischer titration.     

Solid‐phase extraction of explosive nitramines on macroreticular polymers modified by freezing with water or acetone

A novel approach is proposed to modify the porous structure and surface properties of the polymers used in solid‐phase extraction. The approach involves soaking in water or acetone, followed by freezing in liquid nitrogen (77.4 K) and was employed for two polymeric materials: Amberlite XAD‐7 and Amberlite XAD‐16. Variations in the surface properties of the adsorbents were justified by the action of acetone and water as solvents affecting the textural and other characteristic of the materials. The initial and treated adsorbents were used in extraction of explosive nitramines from aqueous samples. The performed modifications of the polymer texture allow us to increase the recovery rate as compared with the initial adsorbents. The results were justified by the swelling of fragments of the polymers and by the additional process of sorption of nitramines. The results indicate that polymeric adsorbents can be easily modified by the soaking/freezing process and the materials can be achieved that prove usefulness for the effective separation of explosive nitramines from aqueous samples.     

Isolation of essential oils from tobacco by gas co-distillation/solvent extraction

Summary The essential oils have been isolated from tobacco leaves using a simple gas co-distillation apparatus. The method involves co-distillation with water under the continuous stream of an inert gas with subsequent single solvent extraction of the distillate. The extract is analysed on GC and GC/MS in splitless injection mode without further concentration. The method was evaluated for reproducibility using n-octadecane as an internal standard. The distillation-extraction procedure was reporducible with an average deviation of ±3% for the major constituents. The present method was applied to the analyses of the essential oils of other agricultural products.Dedicated to Dr. L. S. Ettre on the occasion of his 60th birthday.     

丙酮双水相萃取预富集荧光法测定痕量1-萘胺

基于丙酮水溶液在适当电解质作用下能形成双水相及1-萘胺能发射荧光的特点,建立了一种丙酮-电解质-水体系双水相萃取、蠕动泵进样荧光法测定1-萘胺的新方法.研究了电解质的种类和用量、丙酮体积、1-萘胺浓度、温度、酸度和共存物等的影响.发现在最佳萃取体系丙酮-K3PO4-H2O中,1-萘胺的一次性萃取率82.7%～89.9%,测定1-萘胺的线性范围7.2×10-8～6.0×10-1 mol/L,检出限2.6×10-9 mol/L.方法用于强化水样和豆芽样品中痕量1-萘胺的测定,回收率96%～106%,相对标准偏差2.8%～5.8%.     

Dechlorination of chlorophenols by magnesium-silver bimetallic system

More than 85% of 10 mg L(-1) of pentachlorophenol (PCP) was removed by magnesium/silver (206/1.47 mM) bimetal system in the presence of acetic acid. Dechlorination was found to be sequential and phenol was identified as the ultimate hydrocarbon skeleton along with some accumulation of tetra-, tri-, and dichlorophenols. The dechlorination reaction was found to follow second-order kinetics. Lower PCP removal efficiency (35%) was observed when the reaction was carried out in the absence of acid using Mg(0)/Ag system. When the reaction was conducted using Mg(0) alone in the presence of acid, substantial sorption of PCP occurred with very low efficiency of PCP dechlorination. Dechlorination studies on 10 mg L(-1) initial concentrations of 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and 2,4,5-trichlorophenol (2,4,5-TCP), under identical conditions as to PCP, revealed that dechlorination efficiency and reaction rate constants decrease with decreasing number of chlorine atoms on the target compound. A correlation (R(2)>0.9) between the dechlorination rate constants and E(LUMO) for chlorophenols was obtained.     

Absorption spectroscopic study of synergistic extraction of praseodymium with benzoyl acetone in presence of crown ether

The extraction behaviour of Pr(III) from aqueous nitric acid medium employing benzoylacetone has been studied in presence of two crown ethers, viz., 15-crown-5 and benzo-15-crown-5 in chloroform medium using UV-vis absorption spectroscopy. The binary equilibrium constant (logk(ex)) for the complex [Pr(benzoylacetonate)(NO3(-))2(H(2)O)] in organic phase was found to be 1.170. The overall equilibrium constants (logK) for the ternary species [Pr(benzoylacetonate)(crown ether)(NO3(-))(2)] were estimated to be 4.01 and 4.41 for 15-crown-5 and benzo-15-crown-5, respectively. The trend in the equilibrium constant values were very much in accordance with the nature of substitution of the donor moiety. The extraction of Pr(III) by the benzoylacetone-crown ether combination was maximum at pH 3.0 and extraction decreases with increase in pH. It has been found that the extent of extraction of Pr(III) in organic phase as the binary as well as ternary complex [Pr(benzoylacetonate)(NO3(-))(2)(H(2)O)] and [Pr(benzoylacetonate)(crown ether)(NO3(-))(2)] increases with increase in concentration of the ligand. Similar trend is observed in the extraction by only donors. Enthalpies and entropies of formation for the ternary extraction process have been estimated. In addition, the effect of NaNO(3) as foreign salt was also studied and it was observed that with increase in ionic strength, percentage extraction increases.     

Superheated water extraction of essential oils of Origanum micranthum

Superheated water extraction is used to extract essential oil of leaves of Origanum micranthum. The effect of different temperatures on the essential oil profile and rate of extraction as a function of time is investigated. The components of essential oil of Origanum micranthum are removed from the aqueous extract by C18 solid-phase extraction. The identification of components is carried out using comprehensive gas chromatography-time of flight-mass spectrometry. The number of extracted components is almost the same; however, the concentrations change with changing temperature. The highest yield (0.64%) is found at a temperature of 150 degrees C, 2 mL/min and 60 bar for 30 min. The increasing temperature from 100 degrees C to 175 degrees C increased the rate of extraction of six selected components of essential oil of Origanum micranthum. cis-Sabinenehydrate exhibits the fastest rate of extraction at all temperatures studied. Some degradation products are observed at a temperature of 175 degrees C.     

Quantitation of volatile oils in ground cumin by supercritical fluid extraction and gas chromatography with flame ionization detection

Ground cumin is used as a flavoring agent in a number of ethnic cuisines. The chemical entities, which primarily establish its characteristically pungent flavor, are found in the volatile oil of cumin. Fixed oils and carbohydrates tend to round out the harshness of the volatile oil components. However, the quantity of volatile oil is commonly the measure of the quality of this spice. For several decades, the spice industry has used a classical distillation procedure for the determination of volatile oil in cumin and other spices. However, the method is cumbersome and requires nearly 8 h to complete. Supercritical fluid extraction with capillary gas chromatography-flame ionization detection is utilized in the formulation of a rapid, accurate, and specific method for the determination of volatile oil in ground cumin. Samples are extracted in a static-dynamic mode with CO2 at 550 bar and 100 degrees C. Toluene is used as a static modifier addition. The extracted volatile oil, collected in toluene, is analyzed directly using tetradecane as the internal standard. Integration is performed as grouped peaks to include all chemical entities found in cumin volatile oil recovered from the official distillation procedure. Results from this procedure compare favorably with those obtained by the official procedure (coefficient of correlation = 0.995, 24 samples).     

Thermal-spectroscopic characterization of acetone peroxide and acetone peroxide mixtures with nitrocompounds

Triacetone triperoxide (TATP), also known as acetone peroxide, is a powerful homemade energetic compound, highly unstable and not detectable by traditional detection technologies. The calorimetric profiles of TATP mixtures with TNT, ammonium nitrate, and nitroguanidine were evaluated and compared to pure materials. Raman spectroscopy was used to identify possible interactions between mixture components that may arise on contact. Typical results show a shift of the TATP decomposition temperature to higher temperatures, as well as decomposition of the nitrocompound initiated by TATP decomposition. The vibrational spectra were used as spectroscopic signatures for these mixtures, which can be used to understand detection challenges and for the development of desensitization approaches.     

植物油中邻苯二甲酸酯类化合物的一步萃取方法

为实现植物油中邻苯二甲酸酯（PAEs）的现场快速检测,建立了气液微萃取（GLME）技术并与GC-MS检测技术联用实现了植物油中PAEs的一步萃取检测。GLME方法在气流吹扫-微注射器萃取技术的基础上建立而成。此方法定量取0.1 g植物油样品,利用GLME在5 min内完成PAEs的萃取、净化和浓缩,结合内标法确保了结果的准确性。在大豆油、调和油、橄榄油、香油等4种样品中添加200 μg/kg的15种PAEs,基质加标回收率为60.0%~112.3%,相对标准偏差（RSD）为0.9%~28.4%。该法操作简单、方便,准确度高,重现性好,基质干扰少,适用于现场检测和快速检测,对于保障我国食品安全、构建完整的食品安全检测体系具有重大意义。