Gas Chromatography In Combination With Mass Spectrometry Research Articles

Application of magnetic sorbents modified with molecular imprinted polymers for screening of phenolic xenoestrogens

A new method for the determining phenolic xenoestrogens, chemicals that destroy the endocrine system (EDC), i.e., 4-octylphenol (OP), 4-nonylphenol (NLP) and bisphenol A (BPA), in sediments and river waters with preliminary concentration on magnetic sorbents functionalized by polymers based on molecular imprints is proposed. were determined In the concentrates EDC were converted to derivatives by reaction with acetic anhydride and then determined by gas chromatography in combination with mass spectrometry (GC-MS). The accuracy of the determination was evaluated by the "added–found" method. Use of the molecular imprinted polymers allows determining up to 5 ng/l NLP and 6 ng/l OP and BFA in wastewaters. In bottom sediments, the limit of determination was 100 ng/kg for NLP and 150 ng/kg for OP or BPA. The decrease in sensitivity was due to the high contamination of bottom sediments and increased matrix effects. Products of degradation of humic acid, surfactants and petroleum products have the greatest interfering effect. The method was tested on EDC screening in waters and bottom sediments of the Voronezh reservoir. Sites near the unorganized discharge of wastewaters and near the discharge of municipal wastewater treatment plants were selected as sampling points. The maximum concentrations of OP, NLP and BPA found in the river waters were 335, 1138 and 144 ng/l, respectively, and in the bottom sediments were 6.9, 10.7 and 5.9 μg/kg, respectively.

Profiling of essential oil chemical composition of some Lamiaceae species extracted using conventional and microwave‐assisted hydrodistillation extraction methods via chemometrics tools

AbstractThis study investigated the potential use of microwave energy as an effective technique for the extraction of essential oil (EO) from some plant species belonging to Lamiaceae family growing in Egypt, involving Origanum majorana L., Mentha pipereta L., Mentha longifolia L., Origanum syriacum L., Lavandula angustifolia L., Rosmarinus officinalis L., and Thymus vulgaris L., in comparison with conventional extraction using hydrodistillation (HD) approach, in terms of extraction time, oil yields, and chemical composition. The results showed that the use of microwave in a relevant technique, namely microwave‐assisted hydrodistillation (MAHD) required an extraction of 60 minutes, while HD required 180 minutes. In general, EO yield being extracted by MAHD was higher than those extracted by HD. Gas chromatography in combination with mass spectrometry (GC/MS) analysis indicated noticeable quantitative changes in EOs composition extracted by MAHD and HD extraction methods. Except for O majorana L., GC/MS analysis of extracted oils using MAHD showed higher amounts of oxygenated constituents compared to HD extraction. The results of this study introduced MAHD as rapid, economical and environmental friendly extraction method. A comparative analysis was stated here between the EOs of all plant species under study on chemometric tools such as principal components analysis (PCA) and agglomerative hierarchical clustering (AHC). In general, the PCA results showed that there is significant variation between species in the quality and quantity of EO composition. However, no significant difference is observed based on the extraction method used (HD and MAHD).

Chemical Composition, Antimicrobial andAntioxidant Activity of Birch (Betula pendula Roth.) Buds Essential Oil

:The essential oil from birch (Betula pendula Roth.) buds was obtained by Clevenger-type hydrodistillation. Its qualitative and quantitative composition was determined by gas chromatography in combination with mass spectrometry (GC/MS) and flame ionization detection (GC/FID), respectively. Twenty-seven compounds, mainly sesquiterpene hydrocarbons (78.7%) and oxygenated sesquiterpenes (14.8%), were identified comprising 93.5% of total identified components in the essential oil. The most abundant compounds were germacrene D (21.7%) and δ-cadinene (17.0%). Antimicrobial activity of isolated essential oil against Gram-positive and Gram-negative bacteria as well as fungus Candida albicans was determined using the disc-diffusion method. The isolated essential oil has shown antimicrobial activity against the following microorganisms: Proteus vulgaris, Bacillus luteus and Klebsiella pneumoniae. Antioxidative activity of the essential oil was determined using the DPPH assay, after adding DPPH radical and after 20 min, 30 min and 60 min incubation with radical. Essential oil showed antioxidant activity.

CHROMATOGRAPHIC METHODS IN ANALYSIS OF HOUSEHOLD CHEMICALS AND COSMETICS FOR THE PRESENCE OF SURFACE ACTIVE SUBSTANCES

Classification of the surfactants being a part of detergents by dissociation of their functional charged group in an aqueous medium is considered. Surfactants are complex multicomponent mixtures consisting of homologues of surfactants and impurities of starting materials. An exploratory analysis of this type of raw material, which is a laborious analytical task, is carried out mainly by chromatographic methods. Gas chromatography (GC), high performance liquid chromatography (HPLC), gas chromatography in combination with mass spectrometry (GC-MS), high performance liquid chromatography in combination with mass spectrometry (HPLC-MS) and thin layer chromatography (TLC) are used depending on the structure and specificity of the analyte. A review of the research data in this field over the past 10 years is presented. HPLC is the most common method for studying surfactants. This method allows quantitative and qualitative determination of non-volatile analytes with both small and large molecular weights without preliminary derivatization. When using the GC method, the analyte must be converted to volatile compounds, which considerably complicates the stage of sample preparation. However, this method makes it possible to obtain a complete separation of the homologs and isomers of many surfactants. In combination with MS, it is possible to obtain specific structural fragments of the surfactant molecules. TLC method is widely used for qualitative determination and separation of surfactants. This method is mainly used for group identification of surfactants. The studies thus cponsidered were aimed at developing new and modifying existing methods; search for optimal chromatographic conditions, derivatizing agents, separation columns, etc.

Characterization of the Composition of Paraffin Waxes on Industrial Applications

The use of industrial paraffin depends upon the properties that are strongly influenced by the composition but also affected by the oil content. Because paraffin is a byproduct of lubricant oils in the petrochemical industry, there is inherently a certain amount of oil that is difficult to remove completely. The determination of the oil content in paraffin is described by the ASTM method, which involves the oil extraction with methyl ethyl ketone (MEK) at a very low temperature (−32 °C). However, this method is slow and scarcely precise. In this work, we characterized the main components of industrial paraffin (de-oiled paraffin and extracted oil) by gas chromatography in combination with mass spectrometry (GC/MS) and nuclear magnetic resonance (NMR) spectroscopy. Also, we developed two methods for the determination of the oil content in paraffin. The first method measures total isoparaffin content by GC. The second method uses near-infrared (NIR) spectroscopy to quantify the content of MEK-removable oil. The results obtained with the NIR-based method were quite consistent with those of the official, extraction-based method. NIR spectroscopy therefore provides an effective alternative to the ASTM method with the added advantage of substantially greater expeditiousness and reproducibility.

Investigation of cultivated lavender (Lavandula officinalis L.) extraction and its extracts

In this study essential oil content was determined in lavender flowers and leaves by hydrodistillation. Physical and chemical characteristics of the isolated oils were determined. By using CO2 in supercritical state the extraction of lavender flowers was performed with a selected solvent flow under isothermal and isobaric conditions. By the usage of gas chromatography in combination with mass spectrometry (GC/MS) and gas chromatography with flame ionisation detector (GC/FID) the qualitative and quantitative analysis of the obtained essential oil and supercritical extracts (SFE) was carried out. Also, the analysis of individual SFE extracts obtained during different extraction times was performed. It turned out that the main components of the analysed samples were linalool, linalool acetate, lavandulol, caryophyllene oxide, lavandulyl acetate, terpinen-4-ol and others. Two proposed models were used for modelling the extraction system lavender flower - supercritical CO2 on the basis of experimental results obtained by examining the extraction kinetics of this system. The applied models fitted well with the experimental results.

Identification of Muscadine Wine Sulfur Volatiles: Pectinase versus Skin-Contact Maceration

Muscadine grapes ( Vitis rotundifolia ) are widely grown in the southern United States, as the more common Vitis vinifera cannot be cultivated due to Pierce's disease. There is interest to determine if certain cultivars can be used for good-quality wine production. This study compared the effect of pectolytic enzyme pretreatment with conventional skin-contact fermentation on Muscadine (Noble, Vitis rotundifolia ) wine major volatiles, aroma active volatiles, and volatile sulfur compounds (VSCs). Volatile composition, aroma activity, and VSCs in the initial juice and wine samples after 3 years were determined by gas chromatography in combination with mass spectrometry (GC-MS), olfactory detection (GC-O), and pulsed flame photometric detection (GC-PFPD). Forty-three nonethanol MS volatiles were common to all samples. Total ion chromatogram (TIC) MS peak area increased 91% in the skin-contact wines from the initial juice but only 24% in the enzyme-treated wine. Thirty-one VSCs were detected. Twenty-four sulfur volatiles were identified by matching their retention characteristics on polar and nonpolar columns with those of standards or MS spectrum matches. Six of these (sulfur dioxide, 1-propanethiol, 3-mercapto-2-pentanone, 3-mercapto-2-butanone, 2,8-epithio-cis-p-menthane, and 1-p-menthene-8-thiol) were reported for the first time in muscadine wine. Five additional VSCs were tentatively identified by matching standardized retention values with literature values, and two remain unidentified. Total sulfur peak areas increased 400% in the skin-contact wine and 560% in the enzyme-treated wine compared to the initial juice. There were 42 aroma-active volatiles in the initial juice, 48 in the skin-contact wine, and 66 in the enzyme-treated wine. Eleven aroma-active volatiles in the skin-contact wine and 16 aroma volatiles in the enzyme-treated wine appear to be due to sulfur volatiles. Pectolytic enzyme-treated wines contained less total volatiles but more sulfur and aroma-active volatiles than the traditional skin-contact wine.

The intact muscle lipid composition of bulls: an investigation by MALDI-TOF MS and 31P NMR

The analysis of beef lipids is normally based on chromatographic techniques and/or gas chromatography in combination with mass spectrometry (GC/MS). Modern techniques of soft-ionization MS were so far scarcely used to investigate the intact lipids in muscle tissues of beef. The objective of the study was to investigate whether matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) mass spectrometry and (31)P nuclear magnetic resonance (NMR) spectroscopy are useful tools to study the intact lipid composition of beef. For the MALDI-TOF MS and (31)P NMR investigations muscle samples were selected from a feeding experiment with German Simmental bulls fed different diets. Beside the triacylglycerols (TAGs), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylinositol (PI) species the MALDI-TOF mass spectra of total muscle lipids gave also intense signals of cardiolipin (CL) species. The application of different matrix compounds, 2,5-dihydroxybenzoic acid (DHB) and 9-aminoacridine (9-AA), leads to completely different mass spectra: 9-AA is particularly useful for the detection of (polar) phospholipids, whereas apolar lipids, such as cholesterol and triacylglycerols, are exclusively detected if DHB is used. Finally, the quality of the negative ion mass spectra is much higher if 9-AA is used.

Advances in the use of mass spectral libraries for forensic toxicology.

Gas chromatography in combination with mass spectrometry (GC-MS) plays an important role in the field of analytical toxicology. The identification of unknown compounds is very frequently undertaken with GC-MS and utilizing mass spectral libraries. Currently available libraries for analytical toxicology were compared for overlapping and uniqueness of their entries. Furthermore, the widely known Pfleger-Maurer-Weber-Drugs-and-Pesticides-Library for toxicology (PMW_tox2) was used to compare the search algorithms PBM (Probability Based Matching, Agilent Technologies), INCOS (Finnigan/Thermoquest), and MassLib (Max Planck Institute). To our knowledge, direct comparisons of mass spectral libraries and search programs for analytical toxicology have not been published previously. The capabilities and necessities of modern MS technology in the field of general unknown analysis are revealed, and some of the potential pitfalls are described.

Simultaneous Determination of Methadone, Heroin and Their Metabolites in Hair By Gc-Ms

ABSTRACT A method for the simultaneous identification and quantitation of methadone, codeine, morphine, monoacetylmorphine and heroin in hair by use of gas chromatography in combination with mass spectrometry (GC-MS) is proposed. Hair samples are incubated with dithiothreitol and subsequently subjected to enzymatic hydrolysis with Pronase E. Following addition of their deuterated internal standards, samples are subjected to liquid-liquid extraction in ToxiTubes A 8. The residue thus obtained is derivatized with N, O-bis(trimethylsilyl)trifluoroacetamide/trimethylchlorosilane (BSTFA/TMCS) and directly injected into a GC-MS in the single ion mode (SIM). The calibration curve is linear over the range 0.5-50 ng/mg for all the analytes. The method was reproducible with limits of detection between 0.06 ng/mg (methadone) and 0.29 ng/mg (codeine). This method was applied in a 5-years-old child suspected to be victim of a coercive drug administration.

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Application of glass capillary-column gas chromatography-mass spectrometry to the studies of human diseases

Open-tubular glass capillary columns have been used in gas chromatography in combination with mass spectrometry (GC-MS) and computer methods to study human diseases. Patients with maple syrup urine disease excrete not only α-keto and α-hydroxy acids but also six other metabolites which hitherto have been overlooked. The GC-MS methods demonstrated that a group of patients suffering from hereditary progressive loss of hearing have an impaired metabolism of leucine, leading to the accumulation of 3-hydroxyisovaleric acid and 3-methylcrotonylglycine. GC using the capillary columns proved suitable for mapping of the carbohydrate profile of human seminal fluid and for the analyses of organic compounds accumulating in human adipose tissue. The high resolving power and long life of the glass capillary columns suggest that they will be valuable in the diagnosis and studies of human disorders.