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The identification and quantification of volatile organic compounds (VOC's) which are responsible for the fragrance qualities in colognes are of significant importance to the perfume industry. Compounds, as the musks and pheromones are used by perfume manufacturers to enhance sexual attractiveness from one sex to another. Analytical techniques are needed to identify and quantitate VOC's present in colognes, so these techniques can be incorporated into troubleshooting problems that may arise as well as be used in a quality control program to ensure product purity. Previous methods for the extraction and analysis of these compounds used techniques as solvent extraction, headspace analysis and microdistillation followed by capillary gas chromatography. These methods either require large sample sizes, require the use of solvents or require considerable time and effort to achieve the analysis. In this study, a new technique entitled Direct Thermal Extraction using a thermal desorption apparatus attached to the injection port of a GC/MS system permits the direct thermal extraction of volatile and semi-volatile organics directly from small samples sizes without the need for solvent extraction or other sample preparation. The samples are ballistically heated and together with the carrier gas flow through the samples the volatiles are outgassed into the injection port and onto the front of the GC column for subsequent analysis via the GC and /or GC/MS. The volatile organics present in the colognes were quantified using matrix spiked deuterated internal standards. This technique can be easily incorporated into a troubleshooting technique to detect problems in various commercial colognes, to compare competing manufacturers products, as well as implementation into a quality control program.
All experiments were conducted using a Scientific Instrument Services model TD-2 Short Path Thermal Desorption System accessory (Figure 1) as described elsewhere (1&2) connected to the injection port of an HP 5890 Series II GC interfaced to an HP 5971 Mass Selective Detector. The mass spectrometer was operated in the electron impact mode (EI) at 70eV and scanned from 35 to 400 daltons during the GC run for the total ion chromatogram.
A short 0.5 meter by 0.53 mm diameter fused silica precolumn was attached to the injection port end of a 60 meter x 0.25 mm i.d. DB-5MS capillary column containing a 0.25 µm film thickness. This precolumn acts as a cold trapping area for the desorbed materials and also protects the capillary column and extends its lifetime. The GC injection port was set to 250 degrees C and a direct splitless injection was used. The head of the column was maintained at -70 degrees C using an S.I.S. Cryo-Tap model 951 during the desorption and extraction process and then ballistically heated to 200 degrees C after which the GC oven was temperature programmed from 35 degrees (hold for 5 minutes) to 80 degrees at a rate of 10 degrees /min and to 280 degrees C at degrees/min.
Figure 1 - Short Path Thermal Desorption System
Ten brands of commercial colognes were analyzed to compare and quantify the volatile organics of different manufacturers brands. For quantification, an internal standard was spiked into the adsorbent traps after the sample had been injected into the Tenax® matrix and purged to remove the ethanol. No correction for extraction efficiency of recovery is achieved using this technique; however, it serves as a useful means of quantifying the levels of components present on the adsorbent traps (3).
Sample sizes of 2.5ul of commercial cologne were injected into a preconditioned 4.0 mm i.d. glass-lined stainless steel desorption tube packed with 25 mg of Tenax TA. Once the samples were injected into the Tenax matrix, they were purged at 20 ml/min for 5 minutes to remove the ethanol. Then, they were spiked with 300 ng of a d-8 naphthalene internal standard by injecting 3 ul of a 100 ng/ul of a d-8 naphthalene stock solution in methanol by syringe injection into the Tenax matrix.
The desorption tubes with sample and internal standard were then attached to the Short Path Thermal Desorption System and a syringe needle. The desorption tube was injected into the GC injection port at desorption block temperatures of 220 degrees C for 5 minutes.
Results and Discussion
Ten brands of commercial colognes were analyzed to identify, compare and quantify the volatile and semi-volatile organics present. The results of the total terpenoid content of all ten colognes are summarized in Table I. The colognes were found to contain numerous aroma additives such as mono- and sesquiterpenoid compounds, straight and branched chain aldehydes and alcohols, benzene derivatives and phthalates as well as several musk compounds. Although they possessed many common compounds, each cologne had its own distinct fingerprint chromatograph. High concentrations of the monoterpene linalool (3,7-dimethyl-, 1,6-octadien-3-ol) were detected in Brands A, B, C, G, H and I (Figures 2-4, 8-10). When linalool, which is the chief constituent of linaloe oil and other essential oils, is used in perfumery it commonly replaces bergamot or French lavender because of a similar odor to these oils. This was evident in Brand D (Figure 5) where linalool was not detected and linalyl acetate, a constituent of bergamot and lavender oil, was present. Beta-citronellol, which is a constituent of rose and geranium oils, and isocaryophyllen found in many essential oils, especially clove oil, were among other aroma additives detected in Brand A (Figure 2) . 2-hydroxy-, benzoic acid butyl ester used in the manufacturing of artificial perfumes was also identified in Brand A. Alpha-ionone which has an odor reminiscent of cedar wood was identified in Brand B (Figure 3). Vanillin which exhibits a pleasant aromatic odor was detected in Brands C and I (Figures 4 & 10). Brand D (Figure 5) was found to contain a very high concentration of limonene which is derived from various ethereal oils, especially in the oil of lemon, orange, caraway, dill and bergamot. Nerol, a cis-isomer of geraniol in many essential oils, and several nitro-containing compounds were identified in Brand E (Figure 6). Brands F and J (Figures 7 & 11) contained beta-myrcene, an intermediate in the manufacturing of perfume chemicals, as well as several phenolic compounds. Benzenemethanol and benzeneethanol were detected in Brand I (Figure 10) and Brands G and I (Figures 8 & 10), respectively. Benzenemethanol is a constituent of jasmine, hyacinth and ylang-ylang oils, whereas benzeneethanol is found in a number of natural essential oils such as rose, carnation, hyacinth and orange blossom. Farnesene, a constituent of various essential oils and an alarm pheromone of several aphid species, was detected in Brand H (Figure 9). Brand J (Figure 11) also contained 4-hydroxybenzoic acid which occurs in the form of esters in several plants such as in wintergreen leaves and in the bark of sweet birch.
Figure 2 Brand A
Figure 3 Brand B
In addition to the synthetic musk compound 7-AC-6-ET-1144-ME4-Tetralin found in Brands A, B, D and J (Figures 2, 3, 5 & 11), musk ketone and musk xylene were identified in Brands B and H (Figures 3 & 9) and C (Figure 4), respectively. These musks may be obtained from plant and animal sources or by chemical synthesis. Natural musks are macrocyclic ketones or lactones having approximately fifteen carbons in their ring structure. Synthetic musks are of greater industrial importance and include nitro and non-nitro benzenes, indans and tetralins; derivatives of hydrindacene, isochroman, naphthindan and coumarin. Coumarin, a precursor of tetralin, was detected in Brands D, G and H (Figures 5, 8 & 9). Coumarin is present in tonka beans, lavender oil and sweet clover and has a pleasant fragrant odor resembling that of vanilla beans.
Figure 4 Brand C
Figure 5 Brand D
Figure 6 Brand E
Figure 7 Brand F
Figure 8 Brand G
Figure 9 Brand H
Direct Thermal Extraction using the Short Path Thermal Desorption System attached to the injection port of a GC/MS system permits the direct thermal extraction of volatile and semi-volatile organics directly from small sample sizes without the need for solvent extraction or other sample preparation. This technique offers several unique advantages over other techniques such as solvent extraction, headspace sampling and microdistillation. It presents a tremendous improvement over the time consuming solvent extraction techniques routinely used in the laboratory. New methods which reduce or eliminate the solvents required for sample purification provides many advantages to the laboratory. The exposure of laboratory personnel to these solvents has become of major concern to both employees and health officials. The disposal of used solvents has become a serious problem and is rapidly becoming quite expensive. The thermal extraction of volatiles and semi-volatiles using the Direct Thermal Extraction technique is thorough and complete with no trace of foreign contaminates from the extraction technique, solvents or other memory effects contributing to the chromatogram. The Direct Thermal Extraction technique makes it possible to identify all the volatiles and semi-volatiles accurately and quantitatively. This technique has also been applied to other applications such as quantification of benzene and toluene in food products (3), and flavors and fragrances in food products (4&5), commercial products (6) and plant material (7). This technique can be easily incorporated into a troubleshooting technique to detect problems in various commercial colognes, to compare competing manufacturers products, as well as implementation into a quality control program.
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