Keywords: Twister, SBSE, Solvent Back extraction, pH Adjustment
Strategies are shown that provide additional control of the partitioning of analytes into the PDMS phase during SBSE. Parameters such as sample pH, salt content and the presence of solvents during extraction can be used to enhance the extraction efficiency of a range of analytes including polar compounds. The very high capacity of the SBSE phase allows the use of solvent back extraction prior to thermal desorption to selectively reduce the background interference from complex sample matrices.
Keywords: Twister, SBSE, Fragrance, Acetic acid, Ethanol, Glycol, Detergent, Emulsion
Analysis of samples containing polar matrix components such as water, glycols, sugars or surfactants by gas chromatography has usually required extensive cleanup such as liquid/liquid extraction, solid phase extraction or distillation.Some polar matrix components like acetic acid or ethanol are highly volatile and difficult to eliminate using traditional sample preparation techniques. Stir bar sorptive extraction using a polydimethylsiloxane (PDMS) phase on the stir bar prior to GC analysis can eliminate major interference from these polar matrix components. The PDMS selectively extracts non-polar analytes, discriminating against the polar matrix components present in the sample at even percent levels or higher. Samples that contain high levels of interfering compounds like surfactants and emulsifiers that usually form emulsions when attempting organic solvent extractions can be analyzed directly by SBSE. Examples include separation of flavor and fragrance components in balsamic vinegar and alcoholic beverages, and analysis of fragrances and other additives in consumer products like soaps and detergents. Trace additive analysis in new and used antifreeze further demonstrates the versatility of SBSE for sample preparation prior to GC analysis.
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: Dynamic Headspace, Gas Chromatography, Replaceable Traps
In this study we describe the use of an automated dynamic headspace sampler for determination of volatiles in aqueous samples. This sampler uses a two-needle design to flush the headspace of standard headspace vials onto replaceable adsorbent traps that can be thermostatted to optimize analyte recovery and control interference from water vapor. Following analyte transfer, the adsorbent traps can be automatically dry purged to further eliminate water before introduction into the integrated thermal desorber. This design enables automated optimization of trapping conditions including choice of adsorbent, and has the potential for automated internal standard addition and automated calibration. To illustrate the versatility of the DHS system, examples of the determination of trace levels of volatile organic compounds (VOCs) in aqueous samples are shown. Detection limits and linearity are discussed in the following.
Keywords: Static Headspace, Multiple Headspace Extraction, MHE, Matrix Effects, Method Validation
A novel purge tool for the GERSTEL MultiPurpose autosampler (MPS) under MAESTRO software control allows the headspace of a sample vial to be purged with inert gas between injections. This new feature enables the syringe based MPS to perform MHE quantitation. The tool also allows automated purging of headspace samples prior to extraction. A brief explanation of MHE methodology along with specific examples will be given.
Keywords: Thermal Desorption, Gas Chromatography, Mass Spectrometry, Stir Bar Sorptive Extraction, SBSE, GERSTEL Twister, Pyrolysis
This study shows the analysis of a commercially available personal care product using the GERSTEL MultiPurpose autosampler (MPS) configured with Thermal Desorption Unit (TDU), Cooled Injection System (CIS) PTV-type inlet, Dynamic Headspace (DHS) and pyrolysis (PYRO) modules in combination with a GC/MS system. Information regarding product composition can be obtained from the chromatographic profiles obtained from one analysis system using a variety of sample introduction techniques.
Keywords: Full Evaporation Dynamic Headspace, Fragrance, Quality Control
The ability to perform accurate qualitative and quantitative analysis of perfumes or flavored products is essential to the flavor and fragrance industry. Especially when unknown samples need to be analyzed, traditional methods of GC analysis often lead to only qualitative results and often rely on time consuming and cumbersome sample preparation techniques such as solvent extraction (liquid/liquid, Soxhlet, Likens-Nickerson). In this work, the analysis of neat perfume oil is compared with that of consumer products containing the same oil, applying different traditional analytical techniques like static headspace, SPME, SDE, and comparing the results with those of a dynamic headspace approach. It will be shown that the technique of dynamic headspace requires minimal sample preparation and significantly reduces overall analysis time while delivering improved data quality.
Keywords: GC/MS, Lab Automation, Sample Preparation, Polymers and Plastics, Toys, Toy Safety, Child Care Articles
The US Consumer Product Safety Commission’s (CPSC) Test Method CPSC-CH-C1001-09.3 , is used by testing laboratories for the determination of phthalate content in children’s toys and child care articles covered by the standard set forth in the Consumer Product Safety Improvement Act Section 108. The CPSC determined that an appropriate combination of methods of extraction and analysis is sufficient to determine the concentration of the six regulated phthalates in most consumer products. The general manual approach is to dissolve the sample completely in tetrahydrofuran, precipitate any PVC polymer with hexane, filter and then dilute the solution with cyclohexane, and analyze by Gas Chromatography-Mass Spectrometry (GC/MS). A combined autosampler and sample preparation robot commonly used for sample introduction in GC or HPLC can be used to perform a wide variety of sample preparation techniques using a single instrument set-up and associated control software. Among the autosampler capabilities controlled by MAESTRO software are filtration and centrifugation, both of which can be used to clean up polymer extracts for further analysis. The autosampler can be configured as part of a GC or LC system or can be used independently as bench top workstation. In this work, we demonstrate automated extraction of phthalates in consumer products based on CPSC method CPSC-CH-C1001-09.3 directly combined with GC/MS analysis of the extract. The entire extraction and analysis process is streamlined and helps reduce or eliminate exposure of laboratory personnel to potentially hazardous materials.