Introduction
In the course of our daily lives as homeowners, taking out the garbage probably ranks in the top five of least favorite chores. To make this task less onerous, manufacturers have taken to adding fragrances to garbage bags to help mask any potential malodors present.
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Scented Products: Quality and Safety Concerns
The level of fragrances in or on a product needs to be quantified to ensure product quality and safety. Too high a level may cause an allergic response for the consumer. Too low a level may cause the product to not function as advertised. The level of fragrance compounds is also important as some compounds can emit a pleasant or unpleasant odor depending on the level in the product. An example is 3-methylindole, which at low concentrations has a flowery smell. At higher concentrations, it emits a fecal odor.
Direct Thermal Extraction
A simple and reliable technique for fragrance determination is direct thermal extraction (DTE). DTE is a technique where a solid or liquid sample (in a suitable holder) is heated with inert gas flow and the analytes evolved are trapped. In an on-line system, the thermal desorber is used to heat and provide inert gas flow and the analytes are trapped in the GERSTEL CIS 4 inlet liner. The analytes can be trapped cryogenically or on a sorbent. After analyte trapping is complete, the trap is rapidly heated to transfer the analytes onto the head of the GC column as a narrow band to provide optimum chromatographic performance. A sample size of 10-50 mg is typically used for this technique. The experimental variables which need to be optimized are extraction temperature, extraction time and flow rate across the sample. Since there is very little dilution (split) of the analytes before entering the GC column this technique can provide very low detection limits, even with the relatively low sample size used.
4 Benefits of DTE
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Minimal sample preparation
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Sensitive technique
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Easy method development
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Simple quantification using external standards spiked on sorbent tubes
Case Study on DTE for Scented Garbage Bags
In a recent study, GERSTEL scientists analyzed two scented garbage bags to identify fragrance compounds with DTE. The samples were prepared by using an 8 mm punch to sample the bags, which were then placed into empty TDU tubes for analysis. No further sample preparation was needed.
The results obtained from the DTE analysis revealed the presence of various fragrance compounds in the scented garbage bags, such as floral, citrus, musk, and sweet scents, along with solvents and hydrocarbons possibly from machinery oil.
First Trash Bag:
Light Floral Scent
 The chromatogram shows several fragrance compounds which contribute to the scent of the bag. These include α-isomethyl ionone (floral), lilial (floral, lilies), amyl salicylate (floral), methyl dihydrojasminate and (floral, jasmin). Limonene (citrus) and galaxolide (musk, sweet) are also present. A large benzyl benzoate peak is present. It is commonly used as a solvent for fragrances. Isopropyl myristate, also a solvent, is present. Several hydrocarbons, possibly from machinery oil, are present.
Second Trash Bag:
Strong Floral Scent
The chromatogram shows several fragrance compounds which contribute to the scent of the bag. These include methyl anthranilate (grape), Lilial (floral, lilies), α-amylcinnamaldehyde (sweet, floral), α-hexylcinnamaldehyde (floral, jasmine), benzyl salicylate (balsamic, floral) and ethylene brassylate (musk, floral, woody). Limonene (citrus) was also present. Isopropyl myristate, a solvent, is present in the chromatogram. Several hydrocarbons, possibly from machinery oil, are present, similar to the first sample.
Conclusion
As this study demonstrates, DTE is a sensitive and effective technique for evaluating fragrance compounds in solid samples. It requires little to no sample preparation and is easy to optimize. Because of these advantages, DTE is a valuable tool for quality control and product development in industries where fragrance plays a significant role.
Discover more applications of Direct Thermal Extraction in the following AppNotes:
