Volatile detection

GC/FID has been used for quantifying sulfur volatiles such as hydrogen sulfide in human saliva (Solis and Volpe 1973). This method included microcoulometric titrations and a procedure for incubation of saliva and sampling of headspace sulfur volatile components. The amount of total sulfur volatiles detected in control samples of saliva incubated at 37°C for 24 hours ranged from 4.55 to 13.13 ppm. 

Of the 400 volatiles detected in the tomato, only 17 have a positive impact on the flavor profile. Two of the most important ones are also key players in the aroma of roses p-ionone and p-damascenone. Another player is methyl salicylate, a compound we previously encountered in oil of wintergreen. Some of the most important flavor elements are present in very small concentrations but can be perceived by us at these extremely small concentrations. 

Hansson, B. S., Larsson, M.D. and Leal, W. S. (1999). Green leaf volatile-detecting olfactory receptor neurones display very high sensitivity and specificity in a scarab beetle. Physiological Entomology 24 121-126. 

Paperboard. Vaccaro identified several volatiles released from PET coated paperboard during heating (37.)- When the paperboard and PET films were analyzed separately to establish the origin of the released volatiles, no volatiles were detected from the PET film used for the coating during analysis. All of the volatiles detected were released from the paperboard. Seven compounds were identified acetone, 2,3-butanedione, chloroform, furan, furfural,... 

One such study comparing headspace purge and trap GC-MS, odour tests and an electronic nose showed that the electronic nose could differentiate between unprinted boards and printed and lacquered boards by analysing the vapour phase of the heated boards (Heinio and Ahvenainen, 2002). Optimum differentiation of materials was achieved when test materials were heated at 60 °C for 20 minutes before sampling. Twenty board samples were studied including one unprinted board. Volatiles detected by headspace GC-MS included hexanal, hexane, heptane, toluene and branched hydrocarbons. The board samples were equilibrated overnight at room temperature in sealed headspace vials. 

Oil and Asphaltene Bases. The compositional data for the volatile nitrogen- and nitrogen-plus-oxygen-containing compounds in the oil- and asphaltene-base fractions on a total liquid basis are summarized in Tables VIII and IX, respectively. The compound types in these tables represent the major contributors to the composition of the volatiles from these base fractions. Table X lists minor compound types present in these volatiles. Detection of many of these minor compound types in the Exxon but not in the OSU analysis is attributable to the enhanced sensitivity and resolution of the MS-50 compared with the 21-110B. 

Table 16.2.3. Percentage of volatiles detected in the pyrograms of three model carbohydrates and of lignin [47],...

Benzene has a short half-life in surface water because it is so volatile. Detection of benzene in natural waters would therefore only be seen in areas adjacent to grossly contaminated waste sites. It would also tend not to bioaccumulate into fish tissue or biomagnify up the food chain. 

Since toxins are not volatile, detection of toxins is limited to analysis of liquid or solid agents, residue, or by employing air samplers that collect and concentrate aerosol particles into a liquid sample. Portable immunoassay kits have been developed for a limited number of toxins. While the kits are capable of identifying toxins within 30 minutes, the overall sampling procedure (i.e., air-sampling in conjunction with the immunoassay analysis) can take several hours to produce a result. In addition, clinical immunoassays (ELISA), as well as laboratory analytical methods for detection and identification of toxins are available. These methods can take from 2 to 4 hours to identify individual toxins even under ideal conditions. 

TABLE 5.2. Wine Volatiles Detectable by HS-SPME Using a CAR-PDMS-DVB Fiber and Their Principal m/z Signals"... 

We are interested in trace volatile sampling and measurement with emphasis on odour measurement. Commercially about 11 SPME fibre types are available such as those from Supelco , but in the case of odour (trace volatile) detection in air, we have found that three fibre types are most applicable. These comprise 100 pm polydimethylsiloxane (PDMS), 65 pm polydimethylsiloxane/divinylbenzene (PDMS/DVB) and 75 pm carboxen/polydimethylsiloxane (CAR/PDMS) types. Our previous work has investigated the use of both 100 pm PDMS and 65 pm PDMS/DVB fibre types, and we have adopted the latter after initial screening studies. 

Derivatization is a technique modifjhng a chemical compound into a product with properties suitable for GC or high-performance liquid chromatography (HPLC). It permits analysis of compounds not directly or sufficiently detectable or volatile. It enhances volatility, detectability, stability, and sensitivity and also improves chromatography behavior. 

The results obtained for freshly roasted Arabica coffee are illustrated in Fig. 5 (17). From more than 1000 volatiles detected in the original aroma extract by FID, only about 60 odor-active regions were selected by GC-O. AEDA revealed 38 odorants with FD factors of 16 or higher. Odorants 5, 14, 19, 26, 30, and 32 have been newly identified in coffee aroma. Their identification stemmed from the high FD factors. They would most likely have been overlooked without using GC-O as a screening method for odor-active compounds. Odorants with FD factors of 128 or higher are shown in Fig. 6. 

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