Keywords: Capillary Gas Chromatography, Mass Selective Detection, Large Volume Injection, Cooled Injection System CIS, PTV, Wine Aroma
A combination of sensory testing and analysis of individual chemical species is now regarded as necessary, both for evaluation of wine character and quality as well as for a definite determination of off-flavors. In this regard advances in methodology for rapid determination of aroma compounds is an important developmental area.
In this paper a simple and fast method for enrichment and quantification of volatile compounds in wine using a solvent venting technique is described. 10 mL of wine and only 100 μL of extractant are necessary. The aroma extracts can directly be used for GC/MS analysis, without any further sample preparation.
Keywords: Online LC-GC Coupling, PTV, Large Volume Injection, Alkylphenolethoxylates, Nonylphenol, Estrogenic Effect
This paper describes an online LC-GC coupling system that allows fractions from an LC eluant stream to be transferred to a standard GC system. A large volume sampler equipped with a flow-cell takes a fraction of the eluant and introduces it into a PTV using the solvent venting/stop-flow technique. Sample volumes between 10 and 1000 μL can be injected. It will be demonstrated that this system permits the determination of alkylphenolethoxylates (APEOs) and their degradation products, at ultra-trace levels in water, sludge and biological matrices.
Keywords: Large Volume Injection, PTV, Distilled Spirits, Water Removal, Solvent Venting
It is the purpose of this paper to demonstrate how injection volumes up to 50 μl of distilled spirits can be automatically and routinely injected with PTV matrix removal and subsequent splitless transfer of compounds of interest. Injection volumes can be suited to the detection limits required for different classes of compounds. In addition to complete instrumental automation an on-line software calculator for optimum venting of solvents of interest is available.
Keywords: Beverage, Food & Flavor, PTV, Large Volume Injection, Headspace, Thermal Desorption
The sources of compounds that produce desired flavors and undesired off-flavors in alcoholic and non-alcoholic beverages are the raw materials used in their production and the production process itself. There are typically hundreds of compounds present in a beverage, and the concentrations of these compounds varies enormously. This means that analytical techniques not only have to be suited to these concentration levels, but they also must be able to handle the complexity of the matrix.
This note will outline some strategies for beverage analysis resulting from recent technology advances in sample introduction techniques such as large volume injection, thermal desorption, thermal extraction and large volume (dynamic) headspace. These techniques offer significant advantages in establishing improved product authenticity fingerprints and lower detection limits. They are also useful for determining production related problems, such as off-flavors deriving from packaging materials.
Keywords: Membrane Extraction, Triazines, VOCs, Large Volume Injection, LVI
Typically membrane-assisted solvent extraction (MASE) is carried out off-line in a vial, from which the organic extract is transferred to a sample vial followed by large-volume injection (LVI). In this study the extraction device for the membrane-assisted solvent extraction was modified for use with a conventional 20 mL headspace vial. For this purpose a tube of nonporous polypropylene membrane was sealed at one end to produce a membrane pouch, which could be inserted into the vial with the aid of a stainless steel adapter. 15 mL of the aqueous sample and 500 μL of solvent was used for the extraction procedure. A GERSTEL MultiPurpose autosampler (MPS) was used to place the solvent in the membrane pouch, followed by extraction in a heated agitator. After extraction, the MPS performed LVI directly from the extraction vial.
Keywords: Blood Alcohol, Headspace Analysis, Ethanol
Forensic laboratories face the need to analyze many samples of human blood and body fluids for alcohol content. The large number of samples that require quantification of ethanol in these facilities creates a challenge for the methodology employed. Factors that need to be considered are sample throughput, resolution, and carryover. A successful method for these analyses should be fast, precise, and accurate. Current methods used in these analyses use a gas chromatograph coupled to a static headspace sampler and flame ionization detector (FID). The x, y, z robotic autosampler used in this study has a capacity of up to 128 headspace samples, which is a distinct advantage compared to other samplers commercially available. Results obtained with the instrument and methodology described in this report meet the specifications set by the California Department of Justice Blood Alcohol Operating Procedures (Title 17). A dual-column, dual-FID blood alcohol analysis system that can be used for confirmation of ethanol peaks was also tested and produced results with good precision (below 5 % RSD).
Keywords: Ultra Fast GC, Environmental, Hydrocarbon Oil Index, HOI, ISO 9377-2, Low Thermal Mass Heating
Ultra-fast gas chromatographic methods for determination of the hydrocarbon oil index according to ISO 9377-2 were developed using a low thermal mass column heater (LTM). The column heater consists of a module that enables very fast and controlled heating of the capillary column. The speed of analysis for the hydrocarbon group eluting between C10 and C40 could in this way be increased by up to a factor 18 compared to the conventional method. Since the column can also be cooled very quickly, the total cycle time can be reduced to less than 2 minutes. In addition to ultra-fast screening and a fully compliant method, an analytical method was developed that allows the separation of groups of hydrocarbons eluting between n-C10 and n-C20, n-C20 and n-C30, and n-C30 and n-C40, respectively. The cycle time for this analysis was 4.5 min. The quantitative performance of chromatographic analysis, with respect to linearity and sensitivity, is comparable to the conventional method.
Keywords: Pesticide Analysis, Matrix Effects, QuEChERS, Automated Liner Exchange, ALEX, Cooled Injection System, CIS, PTV
Fruit and vegetable extracts that are produced following the well established QuEChERS method typically contain a significant amount of nonvolatile matrix material. After several injections of such extracts into the GC, sufficient matrix residue will be present in the GC inlet liner to lower or sometimes even increase the response of certain pesticide compounds affecting the accuracy of the analysis. The performance can be restored by exchanging the GC inlet liner. Normally this has to be done manually which means stopping the analysis sequence. The GERSTEL Automated Liner Exchange system (ALEX) provides an automated solution. As this study shows, automated liner exchange restores the original performance of the GC system and is therefore generally useful for the analysis of extracts that contain nonvolatile matrix residue.
Keywords: Phenols, Whiskey, Capillary GC/MS, LVI, Solvent Vent, TDU, SBSE, Deconvolution
In this study, a method was developed for quantitative determination of seven phenolic compounds in scotch whisky. Two different whisky brands were analyzed by Stir Bar Sorptive Extraction (SBSE), based on novel EG-Silicone Twisters, combined with thermal desorption gas chromatography-mass spectrometry (TD-GC-MS). Direct Large Volume Injection (LVI) GC/MS was used as reference method. Optimized methods for LVI-GC/MS and SBSE-TD-GC/MS analysis were used for quantitative determination of the target compounds: phenol, o-,m-, and p-cresol, guaiacol, 4-ethylguaiacol, and 4-ethylphenol. Both methods were evaluated regarding linearity of calibration, reproducibility, and limits of detection (LOD), or limits of quantification (LOQ), for the target compounds. These values were calculated for pure whisky (40 % v/v, ethanol/water).
Keywords: Extractables, Leachables, Food Packaging Materials, Medical Materials, Automated Sample Preparation, Liquid Injection, Thermal Desorption, Gas Chromatography
This application note describes two automated methods for screening of extractable compounds from materials for food packaging, medical or technical purposes. The first method is based on automated liquid extraction performed by the GERSTEL MultiPurpose autosampler (MPS), the second involves thermal desorption of the material in question in the GERSTEL Thermal Desorption Unit (TDU). Both methods are suitable for gaining an overview of the quality and emission potential of a material and therefore useful in the search for a suitable packaging material. The methods deliver comparable qualitative results.
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.
Keywords: Large Volume Injection, PTV, Water Analysis
This study shows the use of the GERSTEL Cooled Injection System (CIS) a programmable Temperature Vaporization (PTV) type inlet for large volume injection of water samples and consequent trace compound analysis. Emphasis is placed on developing method parameters in order to use the technique for routine trace analysis.
Keywords: Gas Chromatography, Injector, PTV, Automated Liner Exchange, Sample Preparation, Sample Clean-up, Large Volume Injection, LVI
Sample clean-up steps, which are needed in order to prepare for example environmental or food samples for pesticide analysis, are time-consuming and a potential source of errors. Simplification or elimination of such procedures is often the motivation behind the development of new analytical methods and new instrumentation. Unfortunately, analytical instruments normally do not tolerate introduction of “dirty” samples or even “dirty” extracts. For example, extracts containing suspended matter or high molecular weight compounds contaminate a GC inlet within a few injections, causing peak broadening or even loss of sensitive compounds. Reducing or eliminating clean-up steps will result in “dirty” extracts and daily – or even hourly - maintenance of the GC system.