Volatile aldehydes standards

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. 

A series of alcohols (C4 - Cll) were identified in the tail meat. Odor threshold concentrations were generally higher for alcohols than the aldehyde counterparts. Except for 1-pentanol, the remainder of alcohol peaks were very small and might not be significant in overall arctna of boiled crayfish tail meat. Josephson et al. (23-25) found l-octen-3-ol, an enzymatic reaction product derived from lipids, to be one of the volatile ccxnponents widely distributed in fresh and saltwater fish. The compound 2-butoxyethanol identified in crayfish tail meat (3) has been reported in beef products (26-27). GC aroma perception of standard 2-butoxyethanol gave a spicy and woody note, hence this compound could be an important flavor component of the boiled crayfish tail meat. 

Acidity (as acetic acid) Mix 38 mL of sample with an equal volume of carbon dioxide-free water, add 0.1 mL of phenol-phthalein TS, and titrate with 0.1 A sodium hydroxide. Not more than 0.1 mL is required to produce a pink color. Aldehydes (as formaldehyde) Prepare a Sample Solution by diluting 2.5 mL of sample with 7.5 mL of water. Prepare a Standard Solution containing 40 p,g of formaldehyde in 10 mL of water. Add 0.15 mL of a 5% solution of 5,5-dimethyl-1,3-cyclohexanedione in alcohol to each solution, and evaporate on a steam bath until the Acetone is volatilized. Dilute to 10 mL with water, and cool quickly in an ice bath while stirring vigorously. Any turbidity produced in the Sample Solution does not exceed that produced in the Standard Solution. 

Sarett and coworkers discovered that the complex (1) prepared by the addition of chromium(VI) oxide to pyridine (CAUTION—reverse order of addition may cause the mixture to inflame) is an efficient oxidizing agent for the preparation of ketones from secondary alcohols. The reagent, as prepared by Sarett, is moderately soluble in pyridine, but is only sparingly soluble in standard organic solvents. Thus the normal procedure is to add a solution of the dcohol in pyridine to three equivalents of the complex, also in pyrictoe. This procedure is also useful for the preparation of aromatic and a, -unsaturated aldehydes, but the use of pyridine as solvent prohibits the oxidation of volatile, saturated primary alcohols. ... 

Distillation techniques, commonly employed to measure total saturated aldehyde levels (free and bound), utilize elevated temperatures during the analysis which can result in aldehyde loss through volatilization or artifactual formation during the heat treatment (33). The standard titrimetric procedures measure aldehydes, following distillation, by titrating excess bisulfite that has not complexed with the aldehydes... 

This book provides standardized methods for measuring the major toxic organic contaminants found in air, inducting volatile organic compounds, aldehydes and ketones, phosgene, non-methane organic compounds, pofynudear aromatics hydrocarbons, and others. 

Fig. 3. Changes in total aldehyde content in cooked field peas as affected by type, cultivar, Icxntion and crop year. Results are from a two replicate analysis and expressed as mean + standard deviation. Relative peak area (%) = Peak area of total aldehydes/ Total peak area of volatile compounds x 100.

Dissolve 1-10 mg of ketone in 1 ml. of absolute methanol (free of carbonyl compounds) and treat with three times the excess of Girard s reagent. Carry out the condensation in a test tube with a standard joint, (for volatile ketones a sealed tube is more convenient). For non-volatile ketones, heat the reaction mixture for 2-8 hr under reflux. Heat the sealed tubes for the same period on a water-bath at 85°C. After completion of the reaction, distil off the methanol under reduced pressure at room temperature and dissolve the residue in 0 2-0-5 ml. of ketone- and aldehyde-free ethanol. Finally add an aliquot of this solution to a Britton-Robinson buffer (pH 7-8) containing 50 per cent ethanol, and record the... 

Product Characterization. The products of sunflower leaf hydroperoxide lyase are cw-3-hexenal and 12-oxo-c/.y-9-dodecenoic acid. Analysis of the methoxylamine derivative of the volatile C -aldehyde product by GC-MS showed that it had a mass spectrum and GC retention time identical to that of the methyloxime derivative of commercial c/>3-hexenal, with a small molecular ion at m/z 127 and a large M-29 peak at m/z 98. In contrast, the methyloxime derivative of commercial rra/ij-2-hexenal had a large molecular ion at m/z 127 and a smaller M-29 peak (m/z 98), and it eluted later on the chromatogram. The oxoacid product, 12-oxo-ci>9-dodecenoic acid, was characterized as its methyloxime, methyl ester derivative. The compound had a molecular ion at m/z 255, with a larger M-31 fragment at m/z 224. Its GC retention time was earlier than that of a methoxylamine, methyl ester derivative of 12-oxo-rra/2j-10-dodecenoic acid standard, which had an M-31 fragment (m/z 224) smaller than the molecular ion at m/z 255. 

Most solvent products, especially organic solvents and some additives, emitted from paints and varnishes are VOCs. The largest components of VOCs are solvents, e.g., aliphatic and aromatic hydrocarbons, alcohols, amines, acids, aldehydes, esters, ketones, ter-penes. The defrnition of the term VOC varies, a standard definition is published by CEN (European Committee for Standardization) VOCs are any organic liquids and/or sohds that evaporate spontaneously at the prevailing temperature and pressure of the atmosphere. VOCC (volatile organic compound content) is defined as follows Mass of the volatile organic compounds in a coating material, as determined under specified conditions. 

The volatile composition of roasted peanuts consists of aldehydes, alkylpyr-azines, furanones, and alcohols (22). Compounds identified by standards and retention times are shown in Figure 5. For the peanuts, the total volatile concentration is greater for the DTD method than for the P T method. The relatively larger chunks of the peanut sample prevent close packing and result in enhanced desorption efficiency from the sample in the DTD method. 

J. Lin, D. H. Welti, F. A. Vera, L. B. Fay, and I. Blank, Synthesis of deuterated volatile lipid degradation products to be used as internal standards in isotope dilution assays. 1. Aldehydes, J. Agiic. Food Chem. 47 2813 (1999). 

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