Keywords: PTV Injection, Multicolumn Switching, Multidimensional GC, Cryotrapping, Capillary GC/MS, industrial Applications
The separation and analysis of low concentrations of organic compounds in complex sample matrices, such as petroleum products, waste and drinking water, food, beverages and pharmaceutical products is a rather complex analytical problem. Current methods are hampered by insufficient resolution obtained by single capillary columns even if they have rather high plate numbers. In this paper the potential of a combination of programmed temperature sample introduction and mass flow controlled multicolumn dual oven capillary gas chromatography and on-line mass spectrometry will be discussed and illustrated. The effect of cold trapping in between the columns for components with a moderate volatility will be demonstrated for different applications dealing with the determination of trace impurities in various main products such as gasoline, aromatics, steroids and aniline.
Keywords: Impurities, Industrial Products, Capillary GC/MS, PTV Injection, Multicolumn Switching, Multidimensional GC
The separation and identification of trace components in industrial products is a well known analytical problem, particularly if they elute in low concentrations close to the major component. Current methods fail due to insufficient resolution and or the detection limits of existing systems. In this paper the potential of a combination of programmed temperature sample introduction and dual oven multicolumn switching for the determination of trace impurities in industrial intermediates, is discussed and demonstrated on three examples. It will be shown that a reliable identification of trace amounts of impurities in these industrial products is possible, with a fully optimized multidimensional system, without interference of the major components.
Keywords: Capillary Gas Chromatography, Mass Selective Detection, Multidimensional GC/MSD System, Furan Fatty Acids, Fish Oil
The separation and analysis of very low concentrated furan fatty acids and other minor component fatty acids in complex sample matrices, such as fish oil or lipids derived from liver and testes, require several pre-analytical separation steps in order to obtain sufficient resolution in single column gas chromatography: after extraction and transesterification hydrogenation, urea complex precipitation and Ag+-TLC were applied prior to GC-analysis of furan fatty acids. By using a multidimensional GC/MSD-System with cooled injection and flow controlled column switching with cold trapping in between, it is now possible to identify directly the methyl esters of furan fatty acids without any further pre-analytical separations. The most common of the furan fatty acids can be subdivided into two groups, bearing either a propyl or a pentyl side chain in the 5-position of the furan ring. In addition to the known eight furan fatty acids in fish oil, six new ones were identified, four with a propyl and two with a pentyl side chain. Four of them were reported earlier to be found in the hepatopancreas of crayfish and in fish tissue, whereas the propyl group 16,19-epoxy-17,18-dimethyldocosa-16,18-dienoic acid and the pentyl group furan fatty acid 6,9-epoxy-7-methyltetradeca-6,8-dienoic acid are hitherto unknown ones.
Keywords: Capillary Gas Chromatography, Mass Selective Detection, Multidimensional GC/MSD, Blood Lipids, Human Milk, Furan Fatty Acids
The fatty acid composition of plasma, red blood cells and platelets were investigated. Human milk was analyzed and the fatty acid composition compared to cow’s milk. After lipid extraction and transesterification the methyl esters were analyzed without any further pre-analytical separation steps involved. Using a multidimensional GC/MSD System with cooled injection (CIS/PTV) and flow controlled column switching with cold trapping in between, the methyl esters of furan fatty acids were directly identified by means of their mass spectra. From the ten samples of human milk analyzed only one contained the furan fatty acid 12,15- epoxy-13,14-dimethyleicosa-12,14-dienoic acid (F-acid 10, Figure 1), which was also present in the cow’s milk sample. Furan fatty acids were found in all blood samples in differing relative amounts. F-acids 5,8 and 10 were detected in red blood cells, F-acids 8 and 10 in plasma and in platelets only F-acid 10 was found so far.
Keywords: Capillary Gas Chromatography, Mass Selective Detection, Multidimensional GC/MS, Nutritional Oils and Fats, Fish Oil, Furan Fatty Acids
ABSTRACT Identification of furan fatty acids as minor components in oils and fats require several pre-analytical separation steps in order to obtain sufficient resolution and sensitivity in single column gas chromatography. After extraction and transesterification hydrogenation, urea complex precipitation and silica gel column chromatography or Ag+-TLC were applied prior to GC analysis. By using a multidimensional GC/MS System with cooled injection and flow controlled column switching with cold trapping in between, the methyl esters of furan fatty acids can be identified directly without any further pre-analytical separations. Butter, milk and ten nutritional oils were investigated. Different transesterification methods were used for the characterization of the oils and compared with each other. Electron impact and chemical ionization were applied to identify the fatty acid methyl esters by GC/MS. Fourteen furan fatty acids were identified in fish oil, two in butter and one in milk. The same furan fatty acid were found in peanut, thistle, sunflower, hazelnut and olive oil, whereas none were detected so far in sesame, corn, walnut or grape seed oil.
Keywords: Multidimensional GC, Polymer, Headspace, Malodors
Analysts often encounter complex real-world sample types such as petroleum fractions or volatile polymer components. Resolving all individual compounds using a single chromatographic separation can be quite challenging. Coupling columns with different polarities (multidimensional GC) can significantly improve the resolution of complex samples. We coupled two low thermal mass (LTM) GC column modules with dissimilar column phases using a valveless, software controlled column switching device to perform heartcutting 2D GC on polymer headspace samples. Headspace sampling with Twister stir bars was used to introduce sufficient analyte mass on column to identify odor causing compounds. The LTM GC uses resistive heating rather than a convection oven, allowing for rapid heating and cooling rates. Column modules can be independently programmed to achieve optimal separation and short analysis times on a single GC.
Keywords: Multidimensional GC, Flavor, Fragrance, Polymer
Coupling columns having different polarities can significantly enhance the resolution of complex samples. This approach is commonly known as multidimensional gas chromatography. In this study, we coupled two low thermal mass (LTM) GC column modules with dissimilar column phases using a valveless, software-controlled column switching device for heartcutting GC-GC.The LTM has a resistive heating system rather than a convection oven which allows for rapid heating and cooling rates. In addition, the column modules can be independently programmed for optimal separation and minimum analysis time. This system was used to identify trace components responsible for off-odors in headspace samples from polymers by coupling an olfactometry detector to the powerful heartcutting technique. Two main advantages of the instrumental configuration used were the simple, robust design and short analysis times.
Keywords: Drugs, Urine, Blood, Dean‘s Switch, Multidimensional GC, Low Thermal Mass, LTM, Fast GC/MS
Reduction in analysis time is an important goal for easing the burden of large sample sets associated with routine screening of blood samples and sample sets produced from drug metabolism studies. This study focuses on reduction in analysis time for simultaneous detection of delta-9-THC, 11-OH-THC, and THC-COOH in whole blood and urine extracts. This was achieved using the GERSTEL fast GC system combined with an Agilent GC-MSD. Addition of the fast GC system allows three independently heated temperature zones for multidimensional chromatography using Agilent Capillary Flow Technology Dean’s Switches along with fast heating/cooling rates. A novel pre-column approach protects the analytical columns in independent temperature zones and adds a high level of robustness. The Agilent Capillary Flow Technology Dean’s Switch allows a combination of heartcutting multidimensional GC and back flushing to reduce the amount of unwanted background components. Standard analysis time was reduced from 15 minutes to less than 11 minutes for blood samples and from 15 to less than 8 minutes for urine samples. Two Agilent Capillary Flow Technology Deans Switches in tandem were used for this analysis. Three independently programmed pressure zones were used in conjunction with three independent heated zones. The MS was operated in the EI mode.
Keywords: Selectable 1D/2D GC/MS, SBSE, Food, Flavor, Fragrance
Identification of important trace components in complex samples like fragrances, natural products, petroleum fractions or polymers can be challenging. Achieving the mass on column and resolution necessary to locate and identify trace components using a single chromatographic separation can be difficult if not impossible. A selectable 1D/2D GC/MS configuration using Agilent capillary flow technology (CFT) and low thermal mass (LTM) GC column modules with dissimilar column phases was used to perform heartcutting 2D GC on two sample types. Stir Bar Sorptive Extraction was used as a solventless means to introduce sufficient mass of sample extract onto the pre-column of the multidimensional system. When additional mass is necessary to detect the analyte of interest in the second dimension separation, a selectable cryotrap after the pre-column can function as a fraction collector to accumulate fractions from many replicate chromatographic separations of the sample extract. Separation and identification of selected trace components from beverages and consumer products were used to demonstrate the effectiveness of this system. The main advantages of this configuration were the simple selection of one or two dimensional operation and the ability to collect multiple fractions to maximize signal from trace components in the second dimension.
Keywords: 2-Methyl Isoborneol, Geosmin, Haloanisole, Drinking Water, Dynamic Headspace, Selectable 1D/2D, GC/MS, Olfactometry
A method for the determination of trace amounts of off-flavor compounds such as 2-methyl isoborneol (MIB), geosmin and 2,4,6-trichloroanisole (TCA) in drinking water is described based on dynamic headspace coupled to selectable one dimensional or two-dimensional gas chromatography - mass spectrometry with simultaneous olfactory detection(DHS-1D/2D-GC-O/MS).
Keywords: Selectable 1D/2D GC/MS, SPME, Food, Flavor, Fragrance
Identification of important trace components in complex samples like fragrances, natural products, polymers or food products can be challenging. Achieving the mass on column and resolution necessary to locate peaks and identify trace components using a single column chromatographic separation can be difficult, if not impossible. A selectable 1D/2D GC/MS configuration based on Agilent® Technologies capillary flow technology (CFT) and low thermal mass (LTM) GC column modules with dissimilar column phases was used to perform two-dimensional GC analysis of different foodstuffs. Heartcutting was used to transfer analytes from the first to the second column. Mass spectrometry and olfactory detection were performed in parallel. Solid Phase Microextraction was used as a solventless means to introduce sufficient mass of sample onto the pre-column of the multidimensional system. SPME offers the added benefit of enabling "tuning" of the selectivity of the extraction through the choice of coating on the fiber. Separation and identification of selected flavor compounds from food products were used to demonstrate the effectiveness of the system. The main advantages of this configuration were the simple selection of one or two dimensional operation in combination with the ability to use mass spectrometry and olfactory detection in both dimensions for the analysis of odor active compounds.
Keywords: Ethyl Carbamate, Distilled Spirits, Capillary GC/MS, LVI, Solvent Vent, multidimensional column switching
A procedure is presented for quantification of ethyl carbamate at low ug/L levels in distilled spirits. A 100 uL large volume injection was used followed by orthogonal 2-dimensional GC/MS with heartcutting. The direct large volume injection ensured sufficient availability of analyte without an initial sample preparation step, and the 2D step allowed clean elution of ethyl carbamate and it’s labelled internal standard and compensated for the difficult detection of low mass non-specific ions in a complex matrix. The 2D separation was achieved using the new GERSTEL uFlow Manager based on metal ferrules for simple connection of the orthogonal columns. The principle and apparatus required for both large volume injection and 2D separation will be described together with results from actual samples.