An Analytical Technique for Identifying Tribromoanisole - Pharmaceutical Technology

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An Analytical Technique for Identifying Tribromoanisole
Combining olfactometry analysis with multidimensional gas chromatography–mass spectrometry provides an extremely useful analytical method for identifying aroma or odor notes from a sample.

Pharmaceutical Technology
pp. s10-s14

TBA contamination occurs upon direct contact with the source, including air, in an enclosed area. Because TBA is readily absorbed by solid materials, the contamination can be instantaneous and can quickly spread throughout a facility. Products can be contaminated simply by environmental exposure.

When a moldy, musty, off odor emanates from a product, it is crucial that the problem be identified as quickly as possible to minimize the financial consequences and damage to the brand's reputation. The source of the contamination must be determined, and the area isolated. An analysis of samples with the odor may identify the specific compounds that are responsible, which can suggest possible mechanisms for the contamination.

One caveat about this type of contamination is that the typical smell of various packaging materials, shipping containers, and warehouses may be musty or moldy. Thus, a musty or moldy off odor may not be a contamination problem.

The largest problem associated with the analysis of TBA is the extremely low odor-threshold concentration. A concentration of 30 parts per quadrillion is well below the detection limits of any analytical instrument. Consequently, an individual will be able to smell the odor of the compound long before an analytical instrument can identify and measure it.

As mentioned earlier, the wine industry encountered a similar odor problem that resulting from TCA contamination. Only after the instrumental sensitivity increased and the detection limits decreased were scientists able to identify the compounds responsible for cork taint. Much of the analytical methodology developed for the analysis of TCA can be applied directly to the analysis of TBA.

A method can be developed for routine testing of TBA in samples using gas chromatography–mass spectrometry (GC–MS) instrumentation. However, TBA may not be the only compound in the sample responsible for the offending odor. Other compounds present could also contribute to it.

Since many foul-smelling compounds have extremely low odor thresholds, GC with olfactory detection provides an excellent methodology to identify aroma notes from a sample. These concentrations are generally below the detection limits for a mass spectrometer. By identifying the retention times for crucial odor notes, the scientist can focus on these areas and use the mass spectrometer to confirm the compound identification.

Environmental samples can be collected using two methodologies. In the first method, air is drawn continuously through a thermal desorption cartridge packed with an appropriate adsorbant material for specific periods of time. In the second method, solid-phase microextraction (SPME) fibers can be located throughout the facility. These two types of samples can be directly inserted and desorbed in the GC inlet for separation and analysis.

Many other types of samples, such as corrugated containers, plastic containers, and pharmaceutical products, can be analyzed. The sample is enclosed in a sealed container, in the headspace of which the volatile and semivolatile compounds equilibrate, and SPME fibers are used to sample the headspace of the container. Depending on the strength of the off odor, the volatility, and the headspace concentration of the key odorants, the length of the collection time can vary.

One advantage of SPME fiber technology is its ease of operation. Following headspace collection, the fiber is inserted directly into the hot inlet of the GC system, and the adsorbed compounds are flash desorbed into the column for GC analysis.


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