Keywords: Determination of Flavor and Off Flavor Compounds in Dairy Products using Stir Bar Sorptive Extraction (SBSE) and Thermal Desorption GC/MSD/PFPD
The analysis of flavor compounds in dairy products such as milk, cream, yogurt and cheese as well as their blends with several ingredients usually requires cumbersome sample preparation steps such as liquid/liquid extraction, solid phase extraction or distillation techniques, often with the drawback of organic solvent use. Headspace and purge & trap methods do not use organic solvents, but their analyte range is restricted to volatile compounds and therefore characterize compounds that contribute to the aroma/smell of a sample, not flavor/taste. In addition heating of the sample should be avoided since this would lead to reaction products which dramatically modify the flavor and taste of any dairy product. The sensitivity of solid phase microextraction (SPME) is limited by the small amount of sorptive material that can be coated on the fibers. A new extraction technique, Stir Bar Sorptive Extraction (SBSE), that overcomes the major problems with classical extraction techniques is applied in this paper. With this technique, a small stir bar is coated with polydimethylsiloxane, placed directly in the sample, and stirred for about 1 hour. During this time, analytes are extracted into the PDMS phase, which acts as an immobilized liquid phase. The stir bar is removed, rinsed with distilled water, and placed into a thermal desorption unit. Due to the hydrophobic character of PDMS, a drying step is not necessary. Heating the stir bar releases the extracted compounds into a GC/MS system for sub sequent analysis with very low detection limits (parts per trillion).
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, 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: Sample Preparation, Water, Stir Bar Sorptive Extraction, SBSE, Thermal Desorption, GC/MS
This paper applies SBSE coupled to thermal desorption (TD)-GC/MS to determine ultra-trace levels (sub-ng/L to ng/L) of compounds in aqueous samples.
Keywords: Aldehydes, Ketones, Food, Fish, Dynamic Headspace
In this paper we report on the use of a novel dynamic headspace system (DHS) to determine several aldehydes, ketones and other fatty acid degradation markers in oily samples. Samples were kept in standard 20 mL screw cap vials. During dynamic headspace sampling inert gas (nitrogen) was purged through the headspace of the vial. Analytes were purged from vial and concentrated on adsorbent packed tubes placed in the gas exit. Adsorbent tubes can be filled individually and are exchangeable, making it possible to use a new tube for every sample. After sampling a defined volume, the tubes were transferred to a thermal desorption system where they were desorbed, transferring the analytes to the GC/MS system. The entire process was automated using an industry standard GERSTEL MultiPurpose autosampler (MPS).
Keywords: fragrance Extraction, Stability Testing, Quality Control
Accurate qualitative and quantitative analysis of perfumed 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 vague results and often require time consuming and cumbersome sample preparation techniques such as solvent extraction (liquid/liquid, Soxhlet, Likens-Nickerson). The technique of dynamic headspace requires minimal sample preparation, and significantly reduces overall analysis time while also improving data quality. In this work, the dynamic headspace technique is applied to different types of consumer products. The analysis of neat perfume oil is compared with that of consumer products containing the same oil.
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: Stri Bar Sorptive Extraction, SBSE,GC/MS, Phenols, Off-flavor, Water
16 phenolic compounds along with typical drinking water off-flavor compounds like geosmin, 2-methylisoborneol(MIB), and 2,4,6-trichloroanisole (TCA) were determined using two different approaches: 1) In-situ derivatization with acetic anhydride followed by SBSE using the PDMS Twister and Thermal Desorption (TD)-GC/MS; 2) Direct SBSE without derivatization using the EG-Silicone Twister and subsequent TD-GC/MS. In the case of the EG-Silicone twister, derivatization is not required due to its higher affinity for polar compounds. Both methods were evaluated for the extraction of 0.01 to 1 μg/L of phenols from water samples.
Keywords: Aroma Analysis, Off-flavor, Edible Oil, Direct Thermal Desorption, Thermal Extraction, Microvial, GC/MS
This application note describes the direct thermal desorption of desirable and undesirable aroma compounds from edible oils. The oil sample is placed in a microvial from where it is directly heated using a GERSTEL Thermal Desorption Unit (TDU). Volatile compounds are transferred to the GC/MS system while leaving non-volatile oil matrix behind, preventing contamination of the GC inlet and column. Different microvial designs were evaluated and those with a slit positioned 1 cm from the bottom of the microvial were found to provide the best analyte transfer.
Keywords: Air sampling, thermal desorption, gas chromatography, mass spectrometry
Air fresheners contained in spray cans are commonly used in households to mask unpleasant odors. Many types of fragrances are commercially available. The fragrance can be a complex mix of many components. The effectiveness of the freshener to mask the off odors over time can be directly related to the concentration of the fragrance components in the air. Therefore, an important aspect in product development is to monitor the airborne concentration of the fragrance components.
This study describes the use of the Field Portable GERSTEL Gas Sampling System (GSS28) for the collection of fragrance compounds in air. The GSS28 is a 28 position sampling system designed to perform active i.e. pumped sampling of air onto sorbent tubes. The sampler can collect multiple samples on a pre-programmed schedule or on demand from the user interface.
Air fresheners were released into the air and dispersed across a room and air samples were collected using the GSS28. The sorbent tubes were subsequently analyzed by thermal desorption GC/MS. Several fragrance components contained in the dispersed products were monitored and quantified over time. The study also included validation of an air sampling method for the compounds.