Determination of propranolol by capillary electrophoresis with end-column amperometric detection

A capillary electrophoresis-amperometric detection system was developed for the determination of propranolol (PRO) at a 33 mu m carbon fiber microdisk electrode (CFE). The cyclic voltammogram, the hydrodynamic voltammograms and the effect of pH were studied. Under the optimum conditions: separation Voltage 15 kV; injection 3 s at 15 kV; 10 mM pH 7.5 phosphate buffer, 1.15 V (vs. Ag/AgCl) detection potential, the detection limit (LOD) for PRO was 0.05 mu M (S/N = 3). The response for PRO was linear over two orders of magnitude with a linear correlation coefficient of 0.994. The feasibility of this method was demonstrated by the detection of PRO in urine sample.

End-column electrochemical detection for aromatic amines with high performance capillary electrophoresis

Electrochemical detection of five species of aromatic amines at a carbon fiber microdisk electrode after separation by capillary electrophoresis is described. Under the optimum conditions, the detection limit for 3,4-dihydroxybenzylamine, N,N-dimethylaniline, p-phenylenediamine, p-aminophenol and aniline sulfate was 0.9, 0.03, 0.075, 1.2 and 0.15 mu M (S/N = 3), respectively. The linear response range was 5-1000, 0.1-500, 0.5-500, 5-500 and 1-200 mu M, respectively The effect of the electrode position and buffer pH on the detection was also studied. This method is very simple, sensitive and stable for the detection of these compounds.

Quantitative analysis of pethidine using liquid secondary ion and tandem mass spectrometry

A method for the quantatitive determination of pethidine in human urine by liquid secondary ion and tandem mass spectrometry is presented. Quantification was carried out by using ketamine as internal standard. It was found that the collision-induced dissociation (CID) spectrum of the [M + H](+) ion of pethidine exhibited a prominent daughter ion at mit 220 and ketamine also yielded the same daughter ion at nit 220, For ((quadrupole)) quantitative analysis, the first quadrupole mass filter was set to transmit mit 220 and a narrow-range magnet scan yielded a spectrum of parents, including mit 238 and 248, corresponding to ketamine and pethidine, respectively. Copyright (C) 1999 John Wiley & Sons, Ltd.

催化裂解色谱法及其应用

六十年代后期,人们提出了催化裂解色谱法(Catalytic Pyrolysis-Gas Chromatography,简称CPGC),并应用于某些高分子物质的分析和研究。这种方法是将高分子物质或其他非挥发性有机物同一定量的催化剂均匀混合或接触,裂解时在后者的催化作用下,改变产物的组成和分布,从而有效地对这类物质进行定性定量分析、链结构表征、催化裂解机

ASYMMETRIC ALKYLATION MEDIATED BY CHIRAL PHASE-TRANSFER CATALYSTS

Seven chiral phase-transfer catalysts, among which three have not been reported so far, have been prepared and applied to the asymmetric alkylation of alpha-isopropyl benzyl cyanide and alpha-isopropyl-p-chlorobenzyl cyanide. The result showed that short reaction time, low temperature, high catalyst concentration and non-polar solvent would improve the optical yield. The influence of structure of the catalyst on the asymmetric reaction was preliminarily studied. The optical purity of the products were evaluated by gas chromatography with a chiral column.

裂解气相色谱法讲座Ⅰ——裂解气相色谱法概述

裂解气相色谱法(Pyrolysis Gas Chromatography,简称PGC)是在热裂解和气相色谱两种技术的基础上发展起来的。自1954年W.H.T.Davison等人首先对高聚物的裂解产物进行气相色谱分离记出谱图而加以鉴别以来,经过S.B.Martin,R.S.Lehrle等人把高聚物的裂解技术直接同气相色谱仪连结在一起,由此建立了裂解气相色谱法。三十多年来,通过对裂解装置的不断改进和完善,以及采用毛细管分离、程序升温和微处理机系统,这一方法不仅广泛应用于高分子领域,并且也在微生物、生物、医学、药物、司法检验、地质、矿物燃料等方面得到了日益增长的应用。而方法本身,也从一种经验式的技术,发展为一门相对独立的分枝学科,成为同红外光谱法和核磁共振法相辅相成的分析和研究高分子及非挥发性有机化合物的不可缺少的有效的方法。

Antioxidant capacity and lipophilic content of seaweeds collected from the Qingdao coastline

Lipophilic extracts from 16 species of seaweeds collected along the Qingdao coastline were screened and evaluated for their antioxidant activities (AA) using the beta-carotene-linoleate assay system. The diethyl ether soluble extracts of all selected seaweeds exhibited various degrees of antioxidative efficacy in each screen. The highest antioxidant capacities among the tested samples were observed for Rhodomela confervoides and Symphyocladia latiuscula and were comparable with that of the well-known antioxidant butylated hydroxytoluene and greater than that of propyl gallate. The lipophilic content of all 16 samples and the chemical composition of 4 selected seaweeds, R. confervoides and S. latiuscula, which had higher AA, Laminaria japonica, which had intermediate AA, and Plocamium telfairiae, which had lower AA, were analyzed by gas chromatography and gas chromatography-mass spectrometry, respectively. Fatty acids and alkanes were found. The present data indicated an increase in antioxidative property with increasing content of unsaturated fatty acid. The result of this study suggests that seaweeds can be considered as a potential source for the extraction of lipophilic antioxidants, which might be used as dietary supplements or in production in the food industry. This is the first report on the antioxidant activities of lipophilic extracts from seaweeds.

Concentrations and distribution of organochlorine pesticides in shellfish from Changjiang estuary

To analyze and evaluate the status of organochlorine pollutants in the Changjiang (Yangtze River) estuary and adjacent waters, the concentrations of hexachlorocyclohexane (HCHs) and dichlorodiphenyltrichloroethane (DDTs) in shellfish collected in study area from 2006 to 2007 were determined with gas chromatography (GC). The concentration range of HCHs was (ND-12.13)x10(-3) mg/kg wet weight and averaged at 0.54x10(-3) mg/kg while the concentration of DDTs was in the range of (4.06-281.73) x10(-3) mg/kg with a mean of 57.52x10(-3) mg/kg in the survey areas. The concentrations of DDTs in the shellfish were higher than HCHs', so that DDTs could be considered as typical organochlorine pollutants in the areas. The concentrations of DDTs in the shellfish were higher than HCHs', so that DDTs could be considered as typical organochlorines pollutants. The HCHs in all the shellfish conformed to the first level of criterion (0.02 mg/kg) of the Marion Biology Quality (GB 18421-2001), and that of DDTs in most samples were beyond the first level (0.01 mg/kg) but conformed to the second level (0.10 mg/kg). On average, alpha-HCH and delta-HCH occupied the most part of HCHs, while O,P'-DDT and P,P'-DDT occupied the most part of DDTs. The concentrations of organocholorine pesticides in shellfish samples varied in site and in species. The highest level occurred at the Shengsi (SS), followed by Yangkougang (YKG), Lvsi (LS), Dongyuan (DY) and Beibayao (BBY), low concentrations were observed at Changsha (CS), Beidaodi (BDD), and Gouqi (GQ). The concentration of HCHs and DDTs in most sites decreased clearly from 2006 to 2007 except for YKG, DY, BDD, LYS, and SS. All of above results suggested that the study area was slightly affected by organochlorine pesticide, special by DDTs.

Study on the fatty acid composition of jellyfish Rhopilema esculentum

The fatty acids composition in different parts of full-grown Rhopilema esculentum jellyfish from Yellow Sea was investigated. The lipids, extracted from the umbrella and oral arms and gonads of R. eculentum jellyfish, respectively were analysed by combined capillary gas chromatography/mass spectrometry. The results show that there are more than thirty kinds of fatty acids in jellyfish, and the fatty acid compositions of three parts of R. esculentum are almost the same. In the three parts, percentages of polyunsaturated fatty acids (PUFA) are high, and range from 36.23% to 38.74%. Docosahexaenoic acid (DHA), eicosatetraenoic acid (AA) and eicosapentaenoic acid (EPA) are three major PUFA.

Polysaccharides from Ulva pertusa (Chlorophyta) and preliminary studies on their antihyperlipidemia activity

Polysaccharides from Ulva pertusa were isolated and prepared by extraction in hot water and precipitation by ethanol. The water-soluble polysaccharides were chemically well defined, containing 47.0% total carbohydrate, 23.2% uronic acids, 17.1% sulfate groups, 1.0% N and 29.9% ash. Gas chromatography analysis demonstrated that the neutral sugars were mainly composed of rhamnose, xylose and glucose and smaller amounts of mannose, galactose and arabinose. The FTIR and C-13-NMR spectra indicated that basic repeating units of the polysaccharides were (beta-D-GlcpA-(1->4)-alpha-L-Rhap 3S) and (alpha-L-IdopA-(1->4)-alpha-L-Rhap 3S). Fifty ICR mice were used to study the effect of water-soluble polysaccharides from Ulva pertusa on the level of plasma lipids, with inositol niacinate as positive control. The results indicated that the polysaccharides significantly lowered the contents of plasma total cholesterol, low-density lipoprotein cholesterol, triglyceride and markedly increased the contents of serum high-density lipoprotein cholesterol, compared with the hyperlipidemia control group (p<0.01). Moreover, administration of polysaccharides significantly decreased the atherogenic index. The present results suggest that the polysaccharides from Ulva pertusa have great potential for preventing ischemic cardiovascular and cerebrovascular diseases.

Fatty acids of some algae from the Bohai Sea

The fatty acid compositions of 22 species of marine macrophytes, belonging to the Ceramiales, Cryptonemiales, Nemalionales, Laminariales, Chordariales, Scytosiphonales, Desmarestiales, Dictyosiphonales, Fucales, Dictyotales and Ulvales and collected from the Bohai Sea, were determined by capillary gas chromatography. The contents of polyunsaturated fatty acids (FAs) in the Bohai Sea algae, in comparison with the same species from the Yellow Sea were found to be lower. Red algae had relatively high levels of the acids 16:0, 18:1(n-7), 18:1(n-9), 20:5(n-3) and 20:4(n-6), and those examined were rich in C-20 PUFAs, these chiefly being arachidonic and eicosapentaenoic acids. The major FAs encountered in the Phaeophyta were 14:0, 16:0, 18:1(n-9), 18:2(n-6), 18:3(n-3), 18:4(n-3), 20:4(n-6) and 20:5(n-3). C18PUFAs are of greater abundance in the brown algae than in the red algae examined. All three green algae from the Ulvales had similar fatty acid patterns with major components, 16:0, 16:4(n-3), 18:1(n-7), 18:2(n-6), 18:3(n-3), and 18:4(n-3). They contained 16:3(n-3) and more 16:4(n-3), were rich in C18PUFAs, chiefly 18:3(n-3) and 18:4(n-3) and had 18:1(n-7)/18:1 (n-9) ratios higher than 1. (C) 2002 Elsevier Science Ltd. All rights reserved.

Growing season ecosystem respirations and associated component fluxes in two alpine meadows on the Tibetan Plateau

From 30 June to 24 September in 2003 ecosystem respiration (Re) in two alpine meadows on the Tibetan Plateau were measured using static chamber- and gas chromatography- (GC) based techniques. Simultaneously, plant removal treatments were set to partition Re into plant autotrophic respiration (Ra) and microbial heterotrophic respiration (Rh). Results indicated that Re had clear diurnal and seasonal variation patterns in both of the meadows. The seasonal variability of Re at both meadow sites was caused mainly by changes in Ra, rather than Rh. Moreover, at the Kobresia humilis meadow site (K_site), Ra and Rh accounted for 54% and 46% of Re, respectively. While at the Potentilla fruticosa scrub meadow (P_site), the counterparts accounted for 61% and 39%, respectively. T test showed that there was significant difference in Re rates between the two meadows (t = 2.387, P = 0.022). However, no significant difference was found in Rh rates, whereas a significant difference was observed in Ra rates between the two meadows. Thus, the difference in Re rate between the two meadows was mainly attributed to plant autotrophic respirations. During the growing season, the two meadows showed relatively low Q(10) values, suggesting that Re, especially Rh was not sensitive to temperature variation in the growing season. Additionally, Re and Rh at the K_site, as well as Rh at the P_site was negatively correlated with soil moisture, indicating that soil moisture would also play an important role in respirations.

塔里木盆地塔中地区寒武-奥陶系烃源岩古地温及成烃演化史研究

The present maturity of Cambrian and Ordovician source rocks in Tazhong area, Tarim basin, is studied using several organic petrology methods and conodont CAI method. The highest palaeotemperature that the Cambrian-Ordovician undergone is revealed by Laser Roman Microprobe (LRM) analysis and by simulating experiment of the kerogen chemical kinetics. In according to all above study, the thermal history of Cambrian and Ordovician is reconstructed based on numerical simulating approaches. The characteristics of secondary hydrocarbon generating are studied by inclusions analysis. The reflectances of the samples in the drills located in Tazhong area show that the maturities of Cambrian source rocks are in the stages of condense oil-dry gas, and that of Ordovician source rocks range from peak of oil generating to wet gas stage. The palaeotemperature data of Cambrian-Orovician source rocks from well Tacan 1, based on LRM analysis, are in coincidence with that from other methods. Also are the palaeotemperature data of Cambrian-Orovician source rocks in well Tacan 1 based on the simulating experiments of kerogen pyrolysis, similar to the homogenization temperatures of inclusions in the source rocks. Aaccording to the vitrinite inflectance data of the TZ12 well and Tacan 1 well, the paleotemperature gradients are analysized and reconstructed. These data show that the paleotemperature gradient in Tazhong area was the highest during Cambrian-Ordovician period, it was up to 3.5°C/100m. Following, the temperature gradient descended gradually and it reached to the lowest at present (2.2°C/100m). The histories of maturation and hydrocarbon generation of Cambrian and Ordovician source rocks in Tazhong area are researched systematically and quantitatively, the results show that periods of oil generation from Cambrian and Ordovician source rocks lasted for a long time from Ordovician to Carbonferious periods because the central Cambrian stratum in the north slope of Tazhong area is buried differently in depth. The top of the Cambrian entered into the peak of oil generation in middle-late Ordovician, and most area of the north slope of Tazhong area entered into the peak of oil generation in Carbonferious period, and on the uplift belt some of source rocks entered into the peak of oil generation in Permian period. In early Devonian, the central of the Lower Ordovician source rocks near the Manjiaer depression reached the peak of oil generation and near the top of the Tazhong uplift did not reached the peak of oil generation until early Cretaceous. The middle-upper Ordovician entered into the peak of oil generation in early-middle Jurassic. The time of the middle-upper Ordovician in the top of the uplift belt entering into the peak of oil generation was delayed, because the source rock was buried shallowly, and it did not reached the peak of oil generation until middle Cretaceous. Middle-upper Ordovician in the top of the north slope has been in the peak of oil generation now, it is consistent with the maturity (1.0-1.2%Ro) of the source rocks. The characteristics of the inclusions formed by kerogens are different from that by crystal-enclosed organic matters(OM) during secondary hydrocarbon generation of Cambrian and Ordovician source rocks. The secondary hydrocarbon generation mainly occurred in Mesozoic-Cenozoic period, in an area of about 9000km2 in the north slope. The intensity of the secondary hydrocarbon generation of Cambrian and Ordovician is up to 21kg/torg and 36kg/torg) respectively. Using the staged gas chromatography, the high-over maturated carbonate source rocks are analysized to release the adsorbed OM, inclusions OM and crystal-enclosed OM, respectively, and to evaluate their relative contributions to secondary hydrocarbon generation. The three periods of oil and gas migration and petroleum pools formation in Tazhong area are determined according to organic inclusions and solid bitumen.

Peak identification for PCDD/Fs in environmental samples at different temperature programs

A method has been developed for peak recognition of 136 polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) at different temperature programs. Their retention behaviours are predicted on the basis of an identification database of retention values (A, B) of gas chromatography. By the retention times of C-13 labelled 2,3,7,8-substituted PCDD/F internal standards, the retentions of all PCDDs and PCDFs can be calculated. After comparison with the retentions of practical environmental samples, the predicted values have been proved to be very accurate. (C) 2000 Elsevier Science Ltd. All rights reserved.

Computer-assisted automatic peak recognition and result evaluation for analysis of chlorinated hydrocarbons in environmental samples

A data manipulation method has been developed for automatic peak recognition and result evaluation in the analysis of organic chlorinated hydrocarbons with dual-column gas chromatography. Based on the retention times of two internal standards, pentachlorotoluene and decachlorobiphenyl, the retention times of chlorinated hydrocarbons can be calibrated automatically and accurately. It is very convenient to identify the peaks by comparing the retention times of samples with the calibrated retention times calculated from the relative retention indices of standards. Meanwhile, with a suggested two-step evaluation method the evaluation coefficients and the suitable quantitative results of each component can be automatically achieved for practical samples in an analytical system using two columns with different polarities and two internal standards. (C) 2002 Elsevier Science B.V. All rights reserved.