Analysis of volatiles in dehydrated carrot samples by solid-phase microextraction followed by GC-MS

A solid-phase microextraction (SPME)-based method for the GC-MS analysis of volatiles in dehydrated carrot root samples has been developed and the effect of the most important factors (fibre coating, extraction temperature, equilibrium time and extraction time) on the fractionation of different volatiles has been studied. GC-MS chromatograms showed terpenoids relevant to carrot aroma such as alpha-pinene, sabinene, beta-myrcene, limonene, gamma-terpinene, terpinolene, trans-caryophyllene and beta-bisabolene, and several furan derivatives whose origin is discussed in this paper. As an example of application, this methodology has been used for the characterization of volatile composition of industrially dehydrated carrots. SPME followed by GC-MS is shown as an affordable, fast and solvent-free technique which can be performed with low sample amounts and be easily implemented at an industry for quality control purposes.     

红霉素与水杨基荧光酮胶束增敏荷移反应光度分析

本文提出了一种基于胶束增敏荷移反应测定红霉素的光度分析法.研究了在阴离子表面活性剂十二烷基硫酸钠(SDS)胶束体系中红霉素作为电荷供体与电荷受体水杨基荧光酮(SAF)之间的荷移络合物的光谱性质.发现SDS对该体系有增敏作用(ε=3.95×104 L·mol-1·cm-1提高近3倍),红霉素浓度在0.73mg/L～51.4mg/L范围内符合比尔定律,r=0.9999.本方法用于片剂中红霉素含量的测定,回收率为99.7%,9次测定的相对标准偏差为0.24%.     

A Fluorescence Quenching Method for the Determination of Iodide Ion with Salicylfluorone and Hydrogen Peroxide

Abstract

A highly sensitive and selective fluorescence quenching method has been developed for rapid determination of iodide ion with salicylfluorone (SAF) as fluorogenic reagent (λ_ex = 495 nm, λ_em = 520 nm) at pH 2.5-3.0. The calibration graph is linear over the range 0.05-300 μg/25 ml. The detection limit is 0.05 μ/25 ml iodide. Other halide ions do not interfere with the determination even when present in large excess. The method is rapid and was successfully applied for the determination of iodide ion in sodium chloride, table salt and low sodium salt.     

Study of ionic catalytic systems by the electrodialysis method

A special method of electrodialysis has been developed for investigation of the kinetics and mechanism of polymerization reactions involving ions. The ionic composition of homogeneous systems such as Cp₂TiRClAlRCl₂, RTiCl₃ + AlRCl₂, Ti(OR)₄ + AlR₃, and (RLi)_n has been studied. The composition of catalytically active ions has been determined. Using the regularities of “open” systems, the methods of determining the carbocation reactivity under electrodialysis conditions havebeen worked out. The impulse electrodialysis method has been suggested for studying ionic polymerization kinetics and evaluating the rate constants ofion reactions with the monomer and gegenion.     

Gravimetric determination of carbon fibre in composites on the centigram scale

Summary A gravimetric method for determining the fibre content of carbon fibre/epoxy resin composites has been adapted for samples of about 20 to 50 mg. The epoxy resin was decomposed with sulphuric acid and hydrogen peroxide; the fibres were collected and weighed on a glass-fibre filter. Means of results from the small-scale and standard methods were not significantly different. Although developed for small samples of very thin composites, the method has possible applications in investigating the homogeneity of larger composite pieces.     

Quantitation of verapamil and norverapamil in postmortem and clinical samples using liquid-liquid extraction, solid phase extraction, and HPLC

Summary A sensitive micellar electrokinetic chromatography method for the determination of impurities in SB-209247, a novel LTB₄ antagonist, has been developed. Selectivity was optimised by systematic examination of the effects of the acetonitrile content in the separation buffer. Sensitivity and resolution was enhanced by focusing effects for both charged and neutral analytes achieved by a special sample buffer composition. Minor impurities well below 0.1% peak area ratio can be readily and reliably detected. The validity of the method has been successfully demonstrated with respect to reproducibility of peak area ratios and the linearity of a key impurity. A comparison with HPLC has shown the method has complementary selectivity and competitive sensitivity.     

Studies on the voltammetric behaviour of salicyl fluorone and gallium-salicyl fluorone complex

In the NH₄Cl supporting electrolyte, within the pH range from 1 to 5, an irreversible adsorptive reducing wave of salicyl fluorone(SAF) was obtained. The electrode process was verified as follow: On the surface of mercury electrode, the adsorption of SAF obeys Frumkin isotherm.In 0.2 mol/l potassium hydrogen phthalate/HCl buffer solution, at pH 3.0, the sensitive adsorptive complex wave of Ga-SAF was obtained by linear sweep voltammetry. The composition of the electroactive complex was determined as Ga:SAF = 11. The peak height of the complex is proportional to the concentration of Ga(III) in the range of 1.5 × 10^–9 to 6.0 × 10^–7 mol/l, the detection limit is 1.0× 10^–9 mol/l. The proposed method has been applied to the determination of gallium content in aluminium alloys.     

The crystallinity of polyaryl ether ether ketone

Measurement of the degree of crystallinity of the polymer matrix in a composite is complicated by the presence of the reinforcing additive. This is particularly the case in APC-2 in which as much as 70% can be carbon fibre. A First Law procedure, developed for determining the degree of crystallinity of PEEK, which involves direct measurement of the enthalpy changes associated with melting, crystallization and heat capacity changes, has found to be an effective method for the determination of the crystallinity of the PEEK matrix. The procedure has been applied to carbon fibre and glass fibre PEEK composites.     

Trace metal analysis of coal fly ash collected plain and on a quartz fibre filter

A simple, uniform procedure has been developed for microwave-based digestion of fly ash samples collected from the hoppers of an electrostatic precipitator (ESP), or collected from flue gases on a heat-resistant quartz fibre filter and for subsequent atomic absorption spectrometric analysis of trace metals (Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, V and Zn). HNO(3), HCl, HF and mixtures have been tested as digestion acids. The combination of HNO(3) and HF has been found to be efficient for the digestion of fly ash samples with and without quartz fibre filter material. In spite of the complicated matrix, results with satisfactory accuracy and precision (relative standard deviation below 10% for most of the elements) have been obtained. In the case of analysis of fly ash together with a quartz fibre filter, the calibration curve has to be determined by standard addition to a blank solution containing a dissolved blank quartz fibre filter.     

十二烷基硫酸钠—水杨基荧光酮痕量锡的光度测定

提出一种高选择性、高灵敏度吸光光度测定痕量锡的方法。试验表明阴离子表面活性剂十二烷基硫酸钠具有特殊的选择性,在十二烷基硫酸钠的存在下,锡与水杨基荧光酮在强酸性介质中形成高灵敏度的三元配合物,常见干扰离子均不发生类似的显色反应,具有很高的选择性,不需分离可直接测定钢铁样品中的痕量锡。     

Preliminary studies of a fast screening method for cocaine and cocaine metabolites in urine using hollow fibre membrane solvent microextraction (HFMSME)

A simple and efficient screening method for cocaine and cocaine metabolites has been developed using an inexpensive, disposable hollow fibre membrane. Drug extraction was achieved using hollow fibre membrane solvent microextraction (HFMSME). Extraction and separation, using a gas chromatograph, was achieved in less than 7.5 min. Using HFMSME, concentrations below 0.050 microg mL(-1) were measurable. Good reproducibility was achieved when an internal standard was used, producing relative standard deviation values averaging 5.4%. The effects of various adulterants and interferents on the screening technique were studied and a direct comparison to drop solvent microextraction was made.     

Evidence for selectivity of absorption of volatile organic compounds by a polydimethylsiloxane solid-phase microextraction fibre

Solid-phase microextraction using a 30 microns polydimethylsiloxane fibre has been used to sample the volatile organic compounds from standard mixtures and from mixtures produced by the decomposition of organic compounds. This method of sampling has been compared with the direct injection of an aliquot of headspace gas and shows an enrichment factor of approximately 100 over a 1 ml gas injection for organosulphur gases such as dimethyldisulphide. The performance of the fibre has been evaluated with respect to accuracy and precision at several concentrations in representing the composition of multicomponent mixtures. It was found that the presence of a second component in a gas sample reduced the capacity of the fibre to absorb the primary component. The selectivity of the fibre for various volatile compounds with differing functionality was also studied. It was found that the non-polar polydimethylsiloxane fibre preferentially absorbed the non-polar components of a mixture, e.g. nonane and, correspondingly, under reported the more polar components, e.g. ethanol. Hence, the fibre discriminates in favour of non-polar and against polar components in a mixture in comparison with direct analysis of a headspace sample. Thus, quantitation of a component in a multi-component mixture is liable to error from competitive interference from other components. A major advantage of the technique, however, is that it does not absorb, and therefore introduce, water into the analytical system.     

SIMS Profiling and TEM of CVD Films on Multi-Filament Samples

 A suitable fibre coating is essential to obtain optimal fibre-matrix interaction in fibre-strengthened composite materials. Thin films (∼100 nm) of silicon carbide, turbostratic carbon, and boron nitride were deposited by CVD as single or double layers on commercial multi-filament fibres in a continuous process. The fibre material itself may be carbon, alumina, silicon carbide, or a quaternary ceramic of SiCBN. The application of MCs⁺-SIMS enables one to determine the composition (including impurities of H and O) of various fibre coating materials with an accuracy of at least 20% relative. Due to the special geometry of the multi-filament samples the depth resolution of the SIMS depth profiles is limited, nevertheless, layered structures and some details of the interface between coating and fibre can be studied. The depth calibration of the SIMS depth profiles is derived from sputter rates established on flat samples with a composition similar to that of the fibre coating material. However, the obtained film thicknesses are not extremely different from the values derived from TEM on cross sections of coated fibres.     

Volatile flavour constituent patterns of Terras Madeirenses red wines extracted by dynamic headspace solid-phase microextraction

A suitable analytical procedure based on static headspace solid-phase microextraction (SPME) followed by thermal desorption gas chromatography-ion trap mass spectrometry detection (GC-(ITD)MS), was developed and applied for the qualitative and semi-quantitative analysis of volatile components of Portuguese Terras Madeirenses red wines. The headspace SPME method was optimised in terms of fibre coating, extraction time, and extraction temperature. The performance of three commercially available SPME fibres, viz. 100 mum polydimethylsiloxane; 85 mum polyacrylate, PA; and 50/30 mum divinylbenzene/carboxen on polydimethylsiloxane, was evaluated and compared. The highest amounts extracted, in terms of the maximum signal recorded for the total volatile composition, were obtained with a PA coating fibre at 30 degrees C during an extraction time of 60 min with a constant stirring at 750 rpm, after saturation of the sample with NaCl (30%, w/v). More than sixty volatile compounds, belonging to different biosynthetic pathways, have been identified, including fatty acid ethyl esters, higher alcohols, fatty acids, higher alcohol acetates, isoamyl esters, carbonyl compounds, and monoterpenols/C(13)-norisoprenoids.     

Trace metal analysis of coal fly ash collected plain and on a quartz fibre filter

A simple, uniform procedure has been developed for microwave-based digestion of fly ash samples collected from the hoppers of an electrostatic precipitator (ESP), or collected from flue gases on a heat-resistant quartz fibre filter and for subsequent atomic absorption spectrometric analysis of trace metals (Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, V and Zn). HNO₃, HCl, HF and mixtures have been tested as digestion acids. The combination of HNO₃ and HF has been found to be efficient for the digestion of fly ash samples with and without quartz fibre filter material. In spite of the complicated matrix, results with satisfactory accuracy and precision (relative standard deviation below 10% for most of the elements) have been obtained. In the case of analysis of fly ash together with a quartz fibre filter, the calibration curve has to be determined by standard addition to a blank solution containing a dissolved blank quartz fibre filter.     

曲线拟合分光光度法测定微量钼的研究

在表面活性剂ＯＰ存在下，钼与ＳＡＦ形成灵敏度很高的三倍络合物，本文研究了测定微量钼的最佳显色条件和消除干成的方法，应用在多种干扰离子共存时进行分光光度法的一种新的数学解析方法－拟合曲线分光光度法，根据最逼近样品吸收曲线的拟合曲线，计算混合体系微量的钼的含量，该方法具有准确度高，抗干扰能力强的特点，比经典的单波分光光度法测定有更大的适应性。     

Studies on extraction of Cu(II), Ga(III), In(III) and Tl(III) with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one Separation and spectrophotometric determination of copper and gallium

The extraction of Cu(II), Ga(III), In(III) and Tl(III) with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HPMBzP) from aqueous solutions has been investigated. The mechanism of extraction and the composition of the species extracted has been determined. The effect of equilibration time, various organic solvents and salting-out agents on the extraction of copper and gallium has also been investigated. The green Cu(PMBzP)₂ chelate has absorption maxima at 298 and 670 nm, and PMBzP has maximum absorbance at 290 nm. A new and sensitive spectrophotometric method for copper has been devised, based on the absorbance at 670 nm. The presence of excess of reagent does not interfere and no special treatment is necessary to destroy it. The proposed method has some advantages and has been applied for the determination of copper in various soil samples. Gallium has been separated from indium, thallium, copper, iron and many other elements. The recovery of gallium and copper was 100 ± 0.2%.     

Comparison of a gas chromatography-optical fibre (GC-OF) detector with a gas chromatography-flame ionization detector (GC-FID) for determination of alcoholic compounds in industrial atmospheres

An analytical methodology based on an optical fibre detector coupled to gas chromatograph has been developed for the speciation of some volatile alcoholic compounds. This methodology combines the separation capability of gas chromatography with an optical fibre detector made of an optical fibre sensitized with a thin polymeric film of poly[methyl(3,3,3-trifluoropropyl)siloxane] (PMTFPS). The response of the detector has been characterized at 650 nm for nine different alcohols (allyl alcohol, n-propyl alcohol, sec-butyl alcohol, isobutyl alcohol, n-butyl alcohol, isoamyl alcohol, methyl isobutyl carbinol, cyclohexanol and diacetone alcohol). An alternative method based on gas chromatography-flame ionization detector (GC-FID) was also used in order to evaluated the performance and compare the analytical results with the proposed method. The time of analysis, the analytical error and the analytical performance were similar for both methods. However, the analytical apparatus based on the GC-OF detector is much less expensive than the GC-FID and show high accuracy and suitability for actual monitoring on indoor atmospheres.     

Calculation of composition heterogeneity of block and graft copolymers

The composition heterogeneity has been calculated for some block and graft copolymers. General relationships have been derived for a model of the poly(A-g-B) or poly-(A-b-B) type fulfilling the assumption of random grafting. Numerical results have been calculated for special cases of particular interest. These include a copolymer having independent molecular weight contributions from units of species A and B (a special case of which is a block copolymer) and a graft copolymer where the grafting is not accompanied by crosslinking or degradation side reactions and no homopolymer B is formed. Two other model systems represent the effects of the presence or absence of both homopolymers. For the above models, the dependence of the composition heterogeneity on the structure-determining parameters (average number of grafts in the molecule, polydispersity index of the molecular weight of the backbone and graft) is discussed. The heterogenities thus calculated are in many cases comparatively low. The composition heterogeneity of the system is in most cases increased by the presence of homopolymers.     

Determination of chlorophenols by solid-phase microextraction and liquid chromatography with electrochemical detection

A solid-phase microextraction method has been developed for the determination of 19 chlorophenols (CPs) in environmental samples. The analytical procedure involves direct sampling of CPs from water using solid-phase microextraction (SPME) and determination by liquid chromatography with electrochemical detection (LC-ED). Three kinds of fibre [50 microm carbowax-templated resin (CW-TPR), 60 microm polydimethylsiloxane-divinylbenzene (PDMS-DVB) and 85 microm polyacrylate (PA)] were evaluated for the analysis of CPs. Of these fibres, CW-TPR is the most suitable for the determination of CPs in water. Optimal conditions for both desorption and absorption SPME processes, such as composition of the desorption solvent (water-acetonitrile-methanol, 20:30:50) and desorption time (5 min), extraction time (50 min) and temperature (40 degrees C) as well as pH (3.5) and ionic strength (6 g NaCl) were established. The precision of the SPME-LC-ED method gave relative standard deviations (RSDs) of between 4 and 11%. The method was linear over three to four orders of magnitude and the detection limits, from 3 to 8 ng l(-1), were lower than the European Community legislation limits for drinking water. The method was applied to the analysis of CPs in drinking water and wood samples.