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Philip J. Marriott - One of the best experts on this subject based on the ideXlab platform.
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quantitative Preparative Gas Chromatography of caffeine with nuclear magnetic resonance spectroscopy
Journal of Separation Science, 2013Co-Authors: Leesun Kim, Blagoj Mitrevski, Kellie L Tuck, Philip J. MarriottAbstract:Caffeine test solute was employed in combination with an internal standard (IS), 1,4-dimethoxybenzene, in Preparative-Gas Chromatography (prep-GC), with nuclear magnetic resonance (NMR) experiments. The IS served to: (i) quantify the trapping efficiency of an external trapping assembly, consisting of a capillary column cryotrap at the end of the analytical column; (ii) quantify the solute response in different NMR samples; and (iii) permit correlation of expected level of response of a compound in the NMR experiment, based on relative responses of the IS and solute in the GC result. The recovery rate of caffeine from multiple injections of sample (1×, 2×, 5× and 10×) was 69.6 ± 1.3%, which correlated well (R(2) = 0.999) with the number of injections of compound. The (1)H-NMR spectrum was sufficient to enable structural characterisation of the reference caffeine compound, and was achieved with recovery of amounts of ≤10 μg from a single aliquot. Less than 400 μg of collected caffeine (40 replicate injections) was sufficient for structural characterisation by (13)C-NMR spectral analysis. The method allows development of approaches to separate unknown compounds in complex samples, and to separately use MS and NMR for their characterisation.
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Preparative Gas Chromatography prep gc
2013Co-Authors: Leesun Kim, Kellie L Tuck, Philip J. MarriottAbstract:Differentiating structural isomers using Gas Chromatography (GC) and mass spectrometry (MS) can be difficult and often further structural elucidation is required. This is also the case when new or unknown compounds need to be identified in complex organic mixtures. Once sufficient amounts of the desired compound are obtained, structural elucidation can be determined by using additional analytic techniques, such as nuclear magnetic resonance, Fourier transform infrared spectroscopy, x-ray crystallography, and accelerator mass spectrometry. In these cases, Preparative-GC (prep) or Preparative multidimensional Gas Chromatography, suitably designed with necessary trapping and heart-cutting devices in a conventional GC, can be used to isolate a single compound. This is achieved by the use of either a single collector or multiple collectors with flow switching that allows multiple component isolation. The amount of analyte collected can be increased with multiple injections, thus ensuring that the analyte obtained is of sufficient purity and collected in a quantity that allows for structural characterization. This article outlines approaches to the Preparative technique and provides selected illustrative applications.
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simple Preparative Gas chromatographic method for isolation of menthol and menthone from peppermint oil with quantitative gc ms and 1h nmr assay
Journal of Separation Science, 2012Co-Authors: Hae Eun Park, Seungok Yang, Sunhee Hyun, Shin Jung Park, Hyungkyoon Choi, Philip J. MarriottAbstract:The quantitative performance of a simple home-built Preparative Gas Chromatography (prep-GC) arrangement was tested, incorporating a micro-fluidic Deans switch, with collection of the target compound in a deactivated uncoated capillary tube. Repeat injections of a standard solution and peppermint sample were made into the prep-GC instrument. Individual compounds were eluted from the trapping capillary, and made up to constant volume. Chloronaphthalene internal standard was added in some cases. Recovered samples were quantitatively assayed by using GC-MS. Calibration linearity of GC-MS for menthol standard area response against number of injections (2–20 repeat injections) was excellent, giving R2 of 0.996. For peppermint, menthol correlation over 2–20 repeated injections was 0.998 for menthol area ratio (versus IS) data. Menthone calibration for peppermint gave an R2 of 0.972. 1H NMR spectroscopy was conducted on both menthol and menthone. Good correspondence with reference spectra was obtained. About 80 μg of isolated menthol and menthone solute was collected over a sequence of 80 repeat injections from the peppermint sample, as assayed by 600 MHz 1H NMR analysis (∼100% recovery for menthol from peppermint). A procedure is proposed for prediction of number of injections required to acquire sufficient material for NMR detection.
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Preparative Gas Chromatography
Gas Chromatography, 2012Co-Authors: Leesun Kim, Philip J. MarriottAbstract:Preparative Gas Chromatography (prep-GC) is an important tool for separation and purification of components of a mixture for further uses such as structure elucidation or for recovery of bulk materials in a pure form for commercial applications. Prep-GC increases the mass of a single compound, or zones of compounds isolated from a sample after GC separation. Sample collection includes Preparative fraction collection (PFC) into vials, trapping onto a capillary wall, or using sorbent materials attached to the end of the column or transfer line in order to collect the isolated compound(s). Analytically, chemical structure elucidation using techniques not readily hyphenated with the GC method includes some mass spectrometry (MS) methods, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), X-ray analysis, or other spectroscopic techniques. Implementation of prep-GC includes packed-column GC method which allows larger sample mass to be applied to the column, capillary column GC for greater component separation, or multidimensional methods where two capillary columns of different phases are coupled.
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Preparative Gas Chromatography as a sample preparation approach
Reference Module in Chemistry Molecular Sciences and Chemical Engineering#R##N#Comprehensive Sampling and Sample Preparation#R##N#Analytical Technique, 2012Co-Authors: Philip J. MarriottAbstract:Preparative Gas Chromatography (prep-GC) has been a valuable tool for sample preparation, primarily to increase the mass of an individual compound, or zones of compounds isolated from a sample, for the purposes of further chemical analysis. A Preparative step involving large and repetitive injected amounts of sample can precede improved or precise spectroscopic analysis of a single compound, usually where the spectroscopic step is either insufficiently sensitive or cannot be hyphenated with the GC instrument. The Preparative step is also useful when compounds cannot be readily concentrated before the GC analysis, to allow a greater mass to be introduced to a subsequent analytical GC measurement step. Both approaches provide considerable opportunity either for discovery of the identity of trace compounds that were previously below instrument detection limits or identification of molecular structure that requires more powerful spectroscopic characterization procedures.
Luigi Mondello - One of the best experts on this subject based on the ideXlab platform.
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evolution and status of Preparative Gas Chromatography as a green sample preparation technique
Trends in Analytical Chemistry, 2015Co-Authors: Danilo Sciarrone, Sebastiano Panto, Paola Dugo, Luigi Mondello, Carla RagoneseAbstract:Abstract The present paper reviews recent approaches to Preparative capillary Gas Chromatography (PCGC) covering the period 2010–14. The “green” character of this approach is discussed in relation to the capability to collect chemicals from complex samples, avoiding the consumption of organic solvents that represent a great environmental issue. A discussion is presented regarding critical points in PCGC, mainly related to sample injection, sample capacity, collection system, conditions and sample flushing issues. Following the increasing trend related to the use of multi-dimensional (MD) techniques in recent decades, a section is devoted to the benefits when such an approach is applied in PCGC. One-dimensional and MD applications covering different fields that have appeared in literature since 2010 are described, mainly followed by elucidation steps often performed by nuclear magnetic resonance (NMR), vapour-phase Fourier-transform infrared (FTIR) spectroscopy and mass spectrometric (MS) analyses.
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rapid collection and identification of a novel component from clausena lansium skeels leaves by means of three dimensional Preparative Gas Chromatography and nuclear magnetic resonance infrared mass spectrometric analysis
Analytica Chimica Acta, 2013Co-Authors: Danilo Sciarrone, Sebastiano Panto, Archimede Rotondo, Laura Tedone, Peter Quinto Tranchida, Paola Dugo, Luigi MondelloAbstract:Abstract The present research reports the use of a three-dimensional Preparative Gas Chromatography (prep GC) system, equipped with three Deans-switch devices and 5%diphenyl/wax/mid-polarity ionic liquid stationary phases, for the isolation of volatile components from a complex natural source, namely wampee essential oil (derived from Clausena lansium Skeels leaves). Collection was performed by using a simple and effective lab-constructed trapping device. Initially, an unknown (and abundant) wampee oil constituent was erroneously identified as α-sinensal, through an MS database search (a low similarity match was attained), performed after a GC-quadMS experiment., The unknown compound was then the isolated by using the novel prep GC system, in a highly pure form (at the mg level), and was correctly identified by using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS). Both FTIR and MS data were used to confirm the NMR information. The name given to the molecule was (2E,6E)-2-methyl-6-(4-methylcyclohex-3-enylidene)hept-2-enal. The results herein described will demonstrate the need for a high-resolution GC step, prior to analyte collection, in the prep GC analysis of complex samples.
Dennis M Bier - One of the best experts on this subject based on the ideXlab platform.
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measurement of muscle protein fractional synthetic rate by capillary Gas Chromatography combustion isotope ratio mass spectrometry
Journal of Mass Spectrometry, 1992Co-Authors: Kevin E Yarasheski, M J Rennie, Kenneth Smith, Dennis M BierAbstract:The measurement of skeletal muscle protein fractional synthetic rate using an infusion of (1-13C)leucine and measuring the isotopic abundance of the tracer in skeletal muscle protein by Preparative Gas Chromatography (GC)/ninhydrin isotope ratio mass spectrometry (IRMS) is laborious and subject to errors owing to contamination by 12C. The purpose of this study was to compare muscle (13C)leucine enrichment measured with the conventional Preparative GC/ninhydrin IRMS approach to a new, continuous-flow technique using capillary GC/combustion IRMS. Quadriceps muscles were removed from four Sprague–Dawley rats after each was infused at a different rate with (1-13C)leucine for 6–8 h. Muscle leucine enrichment (at.% excess) measured by both methods differed by less than 4%, except at low (13C)leucine enrichments (<0.03 at.% excess). In addition, capillary GC/combustion IRMS was used to assess muscle (13C)leucine enrichment and fractional muscle protein synthesis rate in ten normal young men and women infused with (1,2-13C2)leucine for 12–14 h. This approach reduced the variability of the isotope abundance measure and gave estimates of muscle protein synthesis rate (0.050 ± 0.011% h−1 (mean ± SEM); range = 0.023–0.147% h−1) that agree with published values determined using the standard analytical approach. The measurement of (13C)leucine enrichment from skeletal muscle protein by capillary GC/combustion IRMS provides a simple, acceptable and practical alternative to Preparative GC/ninhydrin IRMS.
Christian P G Ruhle - One of the best experts on this subject based on the ideXlab platform.
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liquid Chromatography fractionation with Gas Chromatography mass spectrometry and Preparative Gas Chromatography nuclear magnetic resonance analysis of selected nonylphenol polyethoxylates
Journal of Chromatography A, 2011Co-Authors: Christian P G Ruhle, Philip J. MarriottAbstract:Commercial nonylphenol polyethoxylates, designated as NPnEOs, where n is the number of ethoxy groups, comprise a range of ethoxylate groups. According to the starting material nonylphenol, they may also be composed of a complex mix of isomeric nonyl substituents. In order to study more fully the heterogeneity arising from both the ethoxylate and nonyl groups, a mixture of NPnEOs is first fractionated by normal phase liquid Chromatography (NPLC) into separate fractions comprising individual ethoxymers, n. Preparative collection of each early elution ethoxymer fraction allows further separation of different isomeric nonyl group components by using analytical Gas Chromatography/mass spectrometry (GC/MS). The nonyl isomers are not resolved in the NPLC method. The distribution of the isomeric nonyl side chain of different ethoxymers bears close resemblance with each other, and also with the original nonylphenol starting material, although separation efficiency of the nonyl isomers for each ethoxymer decreases with increasing ethoxymer number. Mass spectrometry of the separated isomers display close similarity for presumed equivalent isomers in each fraction, based on elution order of the nonyl isomers. This suggests that each corresponding peak has the same isomer structure. Mass spectra are interpreted based on branching within the nonyl side chain. Preparative GC coupled with MS and nuclear magnetic resonance spectroscopy elucidated the molecular structure of one of the resolved isomers as 4-(1,3-dimethyl-1-propyl-butyl)-phenol diethoxylate.
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characterization of tetra aryl benzene isomers by using Preparative Gas Chromatography with mass spectrometry nuclear magnetic resonance spectroscopy and x ray crystallographic methods
Analytical Chemistry, 2010Co-Authors: Christian P G Ruhle, Julie O Niere, Paul D Morrison, Roderick C Jones, Tom T Caradocdavies, Allan J Canty, Michael G Gardiner, Vickianne Tolhurst, Philip J. MarriottAbstract:The present study describes a Preparative Gas chromatographic (GC) approach employed to study a series of products arising from reaction of phenylacetylene with para-substituted aryl-iodides under SonoGashira catalysis conditions. GC analysis resolves the isomers from each reaction; however, it cannot provide structural details (their MS data are virtually identical). Since classical liquid Chromatography cannot resolve the isomers, Preparative-scale GC is the only practical approach to provide further spectroscopic characterization of the isomers. The products are well separated by GC so a single thick-film capillary column is adequate for this case, with operation up to ∼+300 °C. By collection of 50+ repeat injections, sufficient material could be isolated for 1H NMR spectral analysis of the isomers, and for one isomer (isomer I) of a number of analogous related catalytic reaction mixtures, X-ray crystal structure determination enabled complete structural elucidation (absolute configuration) of the subs...
Leesun Kim - One of the best experts on this subject based on the ideXlab platform.
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absolute molecular configuration strategies using Preparative Gas Chromatography and multidimensional Gas Chromatography with spectroscopy
2017Co-Authors: Leesun KimAbstract:This thesis is about method development for the structural elucidation of selected known and unknown organic compounds using prep-GC and prep-MDGC combined with NMR spectroscopic analysis. Quantification of a model compound using prep-GC combined with NMR spectroscopy, and the introduction of two novel prep-MDGC approaches for complex samples with NMR spectroscopy, were successfully achieved. Prep-GC techniques have been introduced especially for structural characterisation of unknown or trace compounds which cannot be absolutely identified using MS data alone, or in the absence of appropriate reference compounds. For example, differentiating structural isomers using GC-MS can lead to uncertainty in assignment and often further structural elucidation is also required. Therefore prep-GC techniques make it possible to isolate individual pure compounds of interest out of complex matrices that can then be subjected to other spectroscopic studies such as NMR, FTIR and Raman spectroscopy, AMS and X-ray crystallography in a wide range of research applications. Method development was initiated with the quantitative determination of caffeine using a prep-GC system combined with off-line 1H and 13C NMR spectroscopic analysis to demonstrate the efficiency of a purpose-designed xTA. This study was also designed to understand how prep-GC and prep-MDGC techniques could be readily applied to routine analysis. Therefore, caffeine as a model compound was collected with the different number of GC injections, and with an internal standard added to the collected material; these solutions were analysed by both GC and 600 MHz NMR spectroscopy. Both techniques demonstrated good correlation between the number of collected injections and caffeine-to-IS response areas obtained by each technique. This quantitative study provides basic understanding to inform the performance of prep-GC and prep-MDGC studies. For it is important to recognise the minimum amount of analyte that must be collected - which increases with multiple injections - and to ensure that the analyte obtained was of sufficient purity and collected in a quantity that allowed for structural characterisation. In the next phase of the investigation, two new prep-MDGC systems were developed to achieve better resolution – ideally to generate completely resolved compounds – and study the possibility for absolute characterisation of target compounds out of complex mixtures. MDGC systems and in particular those based on capillary GC formats, have not been commonly used as a Preparative isolation approach. For validation of these two systems the Preparative-scale isolation of DMN isomers (from a standard mixture) was achieved. Using prep-H/C-GC×GC system retrofitted with a Deans switch (DS) and xTA, two out of the most abundant peaks were separately successfully collected into the xTA. The NMR data obtained for the most abundant peak (using 50 replicate injections) showed that the peak was in fact an unresolved peak that contained approximately the same amount of two isomers, 1,3-DMN and 1,6-DMN. The NMR data obtained from the least abundant peak out of 3 major peaks (again from 50 injections) demonstrated that the isomer was 1,7-DMN. A further innovation involved prep-H/C MDGC but now with dual DSs, and was set up with the best column set (BPX90 as 1D and VF-200ms as 2D) as selected for the DMN isomers separation. The NMR data obtained from one out of three major peaks (38 replicate injections) collected demonstrated that the two isomers, 2,6-DMN and 2,7-DMN, were unresolved. One of the methods developed in the previous study (prep-H/C MDGC-MS) was validated for profiling of crude oil samples. To characterise some target compounds (i.e. biomarkers) out of complex samples using prep-GC, enhanced resolution is a prerequisite. Therefore the “total” sample analysis of a crude oil as a model sample was performed using a technique for which the term ‘incremented sequential H/C analysis’ has been coined. This approach demonstrated substantially increased resolution for structural identification of biomarkers, and an interesting grouping of different chemical classes for this complex crude oil sample. Even though this method required relatively long analysis time, the enhanced resolution that was accomplished served to support additional compound identification. As a model compound, one of the most important biomarkers in crude oil samples, pristane (2,6,10,14-tetramethylpentadecane), was separated from a C17 linear hydrocarbon (heptadecane) compound with which it often co-elutes in a conventional single column GC system. This method will allow Preparative-scale isolation of other biomarkers, permitting both GC-MS and NMR analysis identification, depending on the total mass of sample that can be collected. Subsequent to the quantitative determination of caffeine, some illicit drugs, known as legal highs provided by Racing Analytical Services Ltd (RASL) and a synthesised legal high were used to develop the prep-GC method combined with 1H NMR spectroscopy. The aim of this research was to validate the prep-GC system for the identification of pharmacologically active compounds from the complex mixture using the system. Legal highs require authorities to quickly act to identify the occurrence of new substances, and to support this with adequate characterisation of compounds. It was found to be deleterious to health, and then steps for prevention of proliferation may be required since they have recently caused serious social issues. The NMR data obtained from one of the legal highs collected after derivatisation showed that the methyl groups severely decomposed. One of the legal highs, 4-methylcathinone was synthesised to confirm the stability of these drugs. The NMR spectrum obtained from the synthesised compound, collected following the prep-GC procedure, showed that the methyl groups decomposed as well.
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quantitative Preparative Gas Chromatography of caffeine with nuclear magnetic resonance spectroscopy
Journal of Separation Science, 2013Co-Authors: Leesun Kim, Blagoj Mitrevski, Kellie L Tuck, Philip J. MarriottAbstract:Caffeine test solute was employed in combination with an internal standard (IS), 1,4-dimethoxybenzene, in Preparative-Gas Chromatography (prep-GC), with nuclear magnetic resonance (NMR) experiments. The IS served to: (i) quantify the trapping efficiency of an external trapping assembly, consisting of a capillary column cryotrap at the end of the analytical column; (ii) quantify the solute response in different NMR samples; and (iii) permit correlation of expected level of response of a compound in the NMR experiment, based on relative responses of the IS and solute in the GC result. The recovery rate of caffeine from multiple injections of sample (1×, 2×, 5× and 10×) was 69.6 ± 1.3%, which correlated well (R(2) = 0.999) with the number of injections of compound. The (1)H-NMR spectrum was sufficient to enable structural characterisation of the reference caffeine compound, and was achieved with recovery of amounts of ≤10 μg from a single aliquot. Less than 400 μg of collected caffeine (40 replicate injections) was sufficient for structural characterisation by (13)C-NMR spectral analysis. The method allows development of approaches to separate unknown compounds in complex samples, and to separately use MS and NMR for their characterisation.
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Preparative Gas Chromatography prep gc
2013Co-Authors: Leesun Kim, Kellie L Tuck, Philip J. MarriottAbstract:Differentiating structural isomers using Gas Chromatography (GC) and mass spectrometry (MS) can be difficult and often further structural elucidation is required. This is also the case when new or unknown compounds need to be identified in complex organic mixtures. Once sufficient amounts of the desired compound are obtained, structural elucidation can be determined by using additional analytic techniques, such as nuclear magnetic resonance, Fourier transform infrared spectroscopy, x-ray crystallography, and accelerator mass spectrometry. In these cases, Preparative-GC (prep) or Preparative multidimensional Gas Chromatography, suitably designed with necessary trapping and heart-cutting devices in a conventional GC, can be used to isolate a single compound. This is achieved by the use of either a single collector or multiple collectors with flow switching that allows multiple component isolation. The amount of analyte collected can be increased with multiple injections, thus ensuring that the analyte obtained is of sufficient purity and collected in a quantity that allows for structural characterization. This article outlines approaches to the Preparative technique and provides selected illustrative applications.
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Preparative Gas Chromatography
Gas Chromatography, 2012Co-Authors: Leesun Kim, Philip J. MarriottAbstract:Preparative Gas Chromatography (prep-GC) is an important tool for separation and purification of components of a mixture for further uses such as structure elucidation or for recovery of bulk materials in a pure form for commercial applications. Prep-GC increases the mass of a single compound, or zones of compounds isolated from a sample after GC separation. Sample collection includes Preparative fraction collection (PFC) into vials, trapping onto a capillary wall, or using sorbent materials attached to the end of the column or transfer line in order to collect the isolated compound(s). Analytically, chemical structure elucidation using techniques not readily hyphenated with the GC method includes some mass spectrometry (MS) methods, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), X-ray analysis, or other spectroscopic techniques. Implementation of prep-GC includes packed-column GC method which allows larger sample mass to be applied to the column, capillary column GC for greater component separation, or multidimensional methods where two capillary columns of different phases are coupled.