Analysis of volatile aldehydes

GC analysis of volatile aldehyde standards. A mixture of formaldehyde, acetaldehyde, propionaldehyde, isobutyl aldehyde, isovaleraldehyde, methyl glyoxal, and furfural (0.1 mg each) were added to 20 ml of cysteamine solution (6g/1 liter of deionized water). The pH of the solution was adjusted to 8 with 6 N NaOH solution. The reaction proceeded promptly to formm thiazolidine derivatives. The reaction mixture was then extracted with 2 ml of dichloromethane, and an aliquot of the extract was injected in the GC. A gas chromatoram of the extract is shown in Figure 2. 

Yasuhara A, Shibamoto T. 1995. Quantitative analysis of volatile aldehydes formed from various kinds of fish flesh during heat treatment. J Agric Food Chem 43 94-97. 

The technique of static headspace gas chromatography (Chapter 5.F.1) proved to be useful in our laboratory for the quantitative analysis of volatile aldehydes in oxidized human LDL. This method was used to distinguish volatile oxidation products of n-6 polyunsaturated fatty acids (pentane and... 

Saito, Y., Ueta, I., Ogawa, M., Jinno, K. Simultaneous derivatization/preconcentration of volatile aldehydes with a miniaturized fiber-packed sample preparation device designed for gas chromatographic analysis. Anal. Bioanal. Chem. 386, 725-732 (2006)... 

HPLC solvents (PDMS-coated fibres are incompatible with hexane). PDMS fibres are more selective towards nonpolar compounds and polyacrylate fibres towards polar compounds such as acids, alcohols, phenols and aldehydes. Another feature of SPME fibre selectivity is discrimination towards high-MW volatiles. SPME has successfully been applied to the analysis of both polar and nonpolar analytes from solid, liquid or gas phases. Li and Weber [533] have addressed the issue of selectivity in SPME. 

For those aldehydes and ketones which are volatile enough, gas chromatography of the headspace gases can be used, and this has been used to measure acetone, butyraldehyde, and 2-butanone in oceanic waters. In a gas chromatography-mass spectrometry analysis of a single sample of volatile materials concentrated from inshore waters onto Tenax GC, MacKinnon [ 139] reported tentative identification of methyl isopropyl ketone, bromoform, 4-methyl-2-pentanone, 2-hexanone, and 2-hexanal. 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

XAD-2 macroreticular resin columns. This situation implied that the XAD-2 column was not effective in retaining completely all the solutes present in the water samples. [NOTE The XAD-2 resin column contained about 25% more packing, and the rate of percolation was about the same as that normally used for processing 200 L of tap water (21).] In addition, a variety of volatiles that appeared immediately following the solvent peak were also present. Subsequent analysis of these concentrates by GC-MS indicated the presence of 6-chloro-2,4-diamino-1,3,5-triazine (tentative), 2,5-diphenylisoxazole (tentative), tributoxyethyl phosphate (confirmed), bis(2-ethylhexyl) phthalate (confirmed), and dimethylbenzoic acid (confirmed) from site 1. The concentrate from site 2, however, showed the presence of 2,4,5-trichlorophenol (confirmed), BHC (confirmed), 2,5-diphenylisoxazole (tentative), bis(2-ethyl-hexyl) phthalate (confirmed), trimethylbenzene (confirmed), ethylbenz-aldehyde (confirmed), ethylacetophenone (confirmed), hexanoic acid (confirmed), and 4-cyano-3,7,ll-tridecatriene (tentative). 

It becomes clear that analytical methods based on the evaluation of the end products of deteriorative reactions will not be satisfactory. Therefore in our own experiments amino acid analysis of Amadori compounds and gas chromatography of volatile Strecker aldehydes were applied to detect the onset of the Maillard reaction well before detrimental sensory changes occurred. 

The volatile oil components in cardamom are summarized by Guenther (1975). The first detailed analysis of the oil was reported by Nigam et al. (1965). The oil has little mono- or sesquiterpenic hydrocarbons and is dominated by oxygenated compounds, all of which are potential aroma compounds. While many of the identified compounds (alcohols, esters and aldehydes) are commonly found in many spice oils (or even volatiles of many different foods), the dominance of the ether, 1,8-cineole and the esters, a-terpinyl and linalyl acetates in the composition make the cardamom volatiles a unique combination (Lewis et al., 1966 Salzer, 1975 Korikanthimath et al., 1997). 

Behera et al. (2004) concluded that the optimum conditions for the conventional roasting method were 125°C for 10 min and, in the microwave processing method, the best conditions were 730 W for 10min. The yields and physico-chemical properties of the volatile oils were similar in both cases. Changes were observed in the optical rotation values, which indicated differences in the chemical compositions. GC and GC-MS analysis of optimized condition samples showed that microwave-heated samples could better retain the characteristic flavour compounds of cumin (i.e. total aldehydes) than conventionally roasted samples (Table 11.5). Earlier GC reports showed cuminaldehyde as the only major aldehyde present in Indian cumin oil, but this study revealed the... 

Chemical Reactions of Aldehydes in Grapes and Wines. The short chain, volatile aldehydes are quite reactive making accurate analysis and quantitation difficult. In addition, many of these reactions are equilibrium reactions with the concentration of unreacted and reacted aldehydes being lughly dependent on the analysis conditions. 

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