A Comparison Of Measurement of Homovanillic Acid in Brain Tissue by Gas Chromatography Mass Spectrometry and Liquid Chromatography with Electrochemical Detection

Abstract

A comparison of liquid chromatography with electrochemical detection (LCEC) and gas chromatography mass spectrometry (GCMS) has been made for analysis of homovanillic acid (HVA) in rat brain tissue. The LCEC procedure gave slightly higher average values of HVA in the samples measured; however, the HVA content determined by both methods related significantly. Rat brain meostriatum was used as representative samples for comparison of the two analytical procedures.     

Phenols in whisky

Summary Twelve volatile phenols were identified in whisky by combined gas chromatography-mass spectrometry. Of these phenols 2,4-dimethylphenol was found for the first time in the aroma of whisky. The content of phenol, o-, m-, and p-cresol, guaiacol, p-ethylphenol, p-ethylguaiacol and eugenol in whiskies originating from different countries was determined by gas chromatography as their 2,4-dinitrophenyl ethers using electron capture detection. The results show that Scotch whiskies differ from others in the content of o-, m-, and p-cresol. The odour threshold values of phenols studied were determined in a 10% (v/v) ethanol-water mixture and in some cases also in the whiskies. Cresols have been found to make contribution to the aroma of Scotch whisky.Presented at the 14th International Symposium on Chromatography London, September, 1982     

四元共聚物的热裂解色谱-质谱分析

报道了2－丁烯、甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸辛酯四元共聚物在不同裂解温度下的热裂解行为。用热裂解色谱－质谱分析方法，研究了裂解温度对裂解产物的影响，并讨论了四元共聚物的热裂解规律。     

Determination of Volatile Organic Compounds as Impurities in Polystyrene Food Containers and Polystyrene Cups

Abstract

Volatile organic compounds in polystyrene food containers and polystyrene cups were determined using direct headspace sampling with gas chromatographic and gas chromatographic/mass spectrometric analysis. Compounds which were detected in polystyrene food containers and cups included 2-methy 1-2-propen-1-ol, ethylbenzene, styrene, β-methylstyrene, and trimethy 1- and tetramethylbenzenes. Individual concentrations of these impurities in the polymeric materials were estimated as 5 to 270 μg/g. Several impurities including styrene were extracted into water at 88 to 93°C within 2 to 3 minutes upon contact. VAriations in aqueous concentrations of styrene as a function of time in contact with polystyrene cups are reported here. Maximum concentrations of styrene in hot water were 35 μg/L after 15 to 20 minutes of contact of water with cups.     

Analysis of carboxylic acids by gas chromatography of acetonyl esters. Application to aromatic,dicarboxylic and higher fatty acids

Summary The gas chromatographic analysis of the acetonyl esters of aromatic, dicarboxylic and higher fatty acids is reported and discussed together with their electron impact and chemical ionisation mass spectra. An improved method for the preparation of acetonyl esters is discussed.     

Analysis of 3-Methoxy-4-Hydroxyphenylglycol in Human Cerebrospinal Fluid by Gas Chromatography Mass Spectrometry and Electrochemical Detection Liquid Chromatography

Abstract

Gas chromatography mass spectrometry [GCMS] and liquid chromatography with electrochemical detection [LCEC] have been compared in simultaneous determination of 3-methoxy-4-hydroxy-phenylglycol [MHPG] in human cerebrospinal fluid [CSF]. Both free and sulphate conjugated MHPG have been measured in these samples. By Spearman Rank Correlation non-parametric analysis both instrumental techniques related significantly for all quantitated samples.     

韭菜挥发油主要成份的气相色谱／质谱分析

韭菜是我国最常见的蔬菜之一，有特别的嗅味和很高的药用价值，本文用气相色谱和质谱联用的方法分析了韭菜挥发油中的主要成份，检出了二甲基二硫醚，甲基丙烯基二硫醚和二丙烯基三硫醚等２３种化合物。     

Spectroscopic Characterization of the Geminal Isomer of Lewisite

Abstract

Lewisite is generally a mixture of several components with the trans isomer of lewisite being the predominant compound. A geminal isomer has not been previously reported as one of the components of the mixture. In the lewisite samples we examined, the geminal isomer, dichloro(l-chlorovinyl)arsine, comprised 2.7 per cent of the total material compared to 95.2 and less than 1 per cent, respectively, for the trans and cis isomers. The remaining fraction was not identified. The geminal isomer of lewisite has been characterized along with the trans and cis isomers using several spectroscopic techniques. Proton NMR of the geminal isomer produced a coupling constant consistent with vinylic protons in a geminal configuration. Mass spectrometry and infrared spectroscopy characterizations were based on an ethanedithiol derivative of the lewisite isomers with gas chromatography used to first separate the derivatized isomers. The electron ionization massspectra of the trans and cis derivatives were very similar, but significant differences were observed in the mass spectrum of the geminal form. Infrared absorption spectra were obtained for the trans and geminal derivatives with significant differences observed between the two, but the method was not sensitive enough to detect the cis isomer.

     

Comparison of On-Column and Splitless Injections for the Capillary Gc Quantitation of Organics Extracted from Landfill Leachatesl

Abstract

An extensive study of the organic components of the leachate from the University of Connecticut landfill has been carried out. A modification of EPA Method 625 for base/neutral extractable organics was used to obtain both the gas chromatographic profiles and the mass spectrometric identification of the organics in groundwater samples from six test wells and several private wells in the vicinity of the landfill. A characteristic fingerprint representing a number of components was consistently found in the analysis of the landfill leachate but not in the drinking water of the private residences located on an adjoining road. Gas chromatographic parameters for optimum qualitative and quantitative analysis of field samples were determined using an acetone solution of the model leachate sample. It was confirmed that the on-column injection mode resulted in greater flame ionization detector (FID) response and more reproducible peak areas than the splitless mode. The major variable in obtaining reproducible data was the field sampling at the landfill, not the solvent reduction step or the injection mode used to introduce the sample into the gas chromatograph.     

High Performance Liquid Chromatographic Separation of Tropatepine in Biological Fluids. Application to a Healthy Volunteer

Abstract

A high performance liquid chromatographic method for the determination of tropatepine in human plasma and urines is described here. After addition of an internal standard (2 chloro-11-(4-methyl piprazine 1-yl) dibenzo (b-f)(1–4) thiazepine) to the biological fluid and extraction at pH 12.0 in hexane, the analysis was performed on a reversed phase column (C18 microBondapak) with UV detection at 231 nm. The compound was eluted by a perchlorate buffer-acetonitrile mixture with a flow rate of 1.7 ml/min. The detection limit was about 25 ng/ml; reproducibility was around 7.5% for plasma concentrations below 50 ng/ml. Mass spectrometry by direct insertion probe had validated the chromatographic results. The method was successfully applied to plasma specimen collected from a healthy human volunteer following a single intravenous administration of 20 mg of tropatepine.     

Leaching of Pesticides from Fields with Recorded Pesticide Applications

During two winter seasons, 1998/99 and 1999/2000, drainage water was sampled each fortnight from four fields with recorded pesticide application. Water was analysed for a range of pesticides used on the fields. Two of the four fields were equipped with three vertical stainless steel tubes with screens at 1-1.3 m depths. Two other fields were equipped with traditional tile drains, which solely drained the specific fields. Isoproturon, which was banned from use after 1999, was the most frequently found pesticide in the drainage water. Pendimethalin was another compound frequently found, however in low concentrations. In drainage water from a field at Silstrup the active ingredients bentazone and propyzamide appeared in the drainage water at the first sampling following treatment and during the following months. The highest concentration levels were 1.3 and 2.8 µg/L, respectively. Phenoxyacid herbicides, which had been detected at concentration levels up to 0.34 µg/L in an earlier study 10 years ago, no longer appeared in the drainage water.     

Accurate screening for synthetic preservatives in beverage using high performance liquid chromatography with time-of-flight mass spectrometry

In this study, liquid chromatography time-of-flight mass spectrometry (HPLC/TOF-MS) is applied to qualitation and quantitation of 18 synthetic preservatives in beverage. The identification by HPLC/TOF-MS is accomplished with the accurate mass (the subsequent generated empirical formula) of the protonated molecules [M + H]+ or the deprotonated molecules [M − H]−, along with the accurate mass of their main fragment ions. In order to obtain sufficient sensitivity for quantitation purposes (using the protonated or deprotonated molecule) and additional qualitative mass spectrum information provided by the fragments ions, segment program of fragmentor voltages is designed in positive and negative ion mode, respectively. Accurate mass measurements are highly useful in the complex sample analyses since they allow us to achieve a high degree of specificity, often needed when other interferents are present in the matrix. The mass accuracy typically obtained is routinely better than 3 ppm. The 18 compounds behave linearly in the 0.005-5.0 mg·kg⁻¹ concentration range, with correlation coefficient >0.996. The recoveries at the tested concentrations of 1.0 mg·kg⁻¹-100 mg·kg⁻¹ are 81-106%, with coefficients of variation <7.5%. Limits of detection (LODs) range from 0.0005 to 0.05 mg·kg⁻¹, which are far below the required maximum residue level (MRL) for these preservatives in foodstuff. The method is suitable for routine quantitative and qualitative analyses of synthetic preservatives in foodstuff.     

Stilbenoids and Phenols in Acanthopanax brachypus

Three new stilbenoids, including α‐(3′‐O‐β‐D ‐glucopyranosyl‐5′‐methoxyphenyl)‐2‐methoxy‐3‐methylbenzofuran ( 1 ), 4‐methyl‐(E)‐resveratrol 3‐(2″‐p‐hydroxybenzoyl)‐O‐β‐D ‐glucopyranoside ( 2 ), and 5‐O‐methyl‐(E)‐resveratrol 3‐(6″‐acetyl)‐O‐β‐D ‐glucopyranoside ( 3 ), together with six known stilbenoids and phenols, acetovanillone 1‐(6′‐vanilloyl)‐O‐β‐D ‐glucopyranoside, eugenyl‐O‐β‐D ‐glucopyranoside, α‐(3′‐hydroxy‐5′‐methoxy‐2′‐methylphenyl)‐2‐hydroxybenzofuran, α‐(3′‐hydroxy‐5′‐methoxyphenyl)‐2‐hydroxybenzofuran, pinosilvin 3‐O‐β‐D ‐glucopyranoside, and (E)‐resveratrol 3‐(6″‐galloyl)‐O‐β‐D ‐glucopyranoside were isolated from the EtOH extract of the stem bark of Acanthopanax brachypus. Their structures were determined by spectral analysis including extensive 2D‐NMR spectral analyses. Compounds 2 and 3 exhibited weak cytotoxicity against human tumor A549 cell line (IC₅₀ values of 4.87 and 5.63 μM , resp.).     

Development and evaluation of an interface for coupled capillary supercritical fluid chromatography/magnetic sector mass spectrometry. Application to thermally unstable and high molecular mass compounds

An interface for coupling supercritical fluid chromatography to a magnetic sector mass spectrometer was developed and evaluated. The interface is based on direct introduction of the mobile phase, carbon dioxide, into the ion-source of the mass spectrometer. The SFC-MS system was optimized with respect to the signal-to-noise ratio. Under optimized conditions, the estimated detection limit for n-pentadecane is approximately 30 ppm. Spectra obtained in the electron-impact ionization mode show a very good similarity with library spectra. The performance of the SFC-MS system was evaluated by the analysis of a number of test mixtures. A sample containing several low molecular mass, thermally unstable compounds, which could neither be analyzed by GC-MS nor by LC-MS, was analyzed. Also for the analysis of high molecular mass compounds, the coupled system showed a good performance.     

Measurement of the composition of gas desorbed from coal by gas chromatography

Summary Direct methods for the determination of the gas content of a coal seam are based upon extracting a coal sample, enclosing it in a sealed container and measuring the volume of the gas evolved. In our work we measured evolved gas as a function of time, type and quantity of low rank coal (lignite) at normal (atmospheric pressure and temperature) conditions. The evolved gas was, collected in gas sampling bags and analyzed by GC for its main components (carbon dioxide, methane and dimethyl sulfide). From the parameters obtained (gas volume, CH₄:CO₂ ratio, rate of gas desorption, time concentration profile and different lithotypes of lignite) a more detailed identification of hazardous areas in underground coal extraction could be ensured. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

Determination of Abnormal Hemoglobins by the Combined use of Reversed-Phase high Performance Liquid Chromatography and Fast Atom Bombardment Mass Spectrometry

Abstract

Separation by reversed-phase high performance liquid chromatography (RP-HPLC) of peptide mixtures obtained from tryptic digestion of abnormal human hemoglobins and subsequent analysis by fast atom bombardment mass spectrometry (FAB-MS) of selected peptides allow unambiguous, rapid identification of the hemoglobin variants. By this method two varied hemoglobins, Hb D Punjab and Hb J Sardegna, have been determined. The methodology described, which is simple and reliable, could be used for the detection and structural identification of known and unknown Hb variants, without amino acid (a.a.) or sequence analysis.     

载溴树脂溴化酚类的研究

用简便方法制备得载溴树脂并用于酚类的溴化,当采用不同摩尔比的载溴树脂时,有选择地得到一溴、二溴及三溴代物,并有较高的产率,同时该树脂具有良好的稳定性。     

Gas chromatographic-tandem mass spectrometric identification of phenolic compounds in Sicilian olive oils

Phenolic compounds in Sicilian olive oils were analyzed by GC-MS and GC-MS/MS after extraction with methanol:water 80:20 and derivatization with bis(trimethylsilyl)trifluoracetamide and trimethylchlorosilane (BSTFA:TMCS 99:1). Numerous compounds were detected and 23 were identified. Tyrosol, hydroxytyrosol and the decarbomethoxy ligstroside and oleuropein aglycons in the dialdehydic forms were the most abundant compounds. 4-(Acetoxyethyl)-1-hydroxybenzene, 3,4-dihydroxyphenylacetaldehyde, syringaldehyde and the cis form of ferulic acid were identified: these compounds were not found in olive oils before. The presence of the dialdehydic form of elenolic acid (without carbomethoxy group) linked to 3-methoxy-4-hydroxyphenylethanol was hypothesized. There were quantitative differences in oils from the varieties Nocellara del Belice, Santagatese and Cerasuola; these differences could depend on the olive varieties and ripeness.     

邻硝基氯苯异构体成分的GC/MS分析

本文采用GC／MS分析邻硝基氯苯异构体成分，对样品前处理、溶剂及色谱条件、质谱条件、组分定量作了探讨，分析结果满意。该法无需标样，具有准确、简便、快速的特点。