Aldehydes determination

Acetone and Aldehydes. Determine the acetone and ethanol content in accordance with ASTM D1612. The sample is reacted with Nessler s reag and the turbidity that is produced is compared to a standard contg the equivalent of 0.003 weight % acet... 

Dinitrophenylhydrazones (DNP) aldehyde determination, 670 core aldehydes, 689 malondialdehyde determination, 669 ozonide reduction, 726... 

Particle emissions, diesel fuel additive, 624 Partition number, conjugated dienes, 671 Pasteurization, lactoperoxidase, 612, 631, 634 Paterno-Buchi triplet 1,4-diradical, 290-1 PCPO see Bis(pentachlorophenyl) oxalate Pentacoordinate silyl peroxides, 808-10 Pentacosane, thermal oxidation, 685 O -Pentafluorobenzylhydroxyamine, aldehyde determination, 670... 

Air pollutants, transport, 4 Air sampling—See Interstitial air sampling Aldehydes, determination in atmospheric samples, 299 Allegheny Mountain acid deposition and atmospheric chemistry, 28-36 deposition budgets for sulfate and nitrate, 33... 

Aldehydes Determine as directed in the Hydroxylamine/ Tert-Butyl Alcohol Method under Aldehydes and Ketones, Appendix VI, using about 5 mL of sample, accurately weighed, and 76.12 as the equivalence factor (e) in the calculation. Allow the mixture to stand at room temperature for 1 h before titrating. 

The Lessen reaction of peptide carboxylic acids has teen investigated in order to determine the carboxy terminal amino acid residue of peptides." The procedure first involves the formation of 0-pivaloylhydroxamic acids (187) by condensation of peptide carboxylic acids (184) with 0-pivaloylhy-droxylamine (185) using a water soluble carbodimide, l-ethyl-3-(3-dimethylaminopropyl)carbodiimide (186). The Lossen rearrangement of (187) occurs at pH 8.5 and 50 C to give a mixture of isocyanates (188) and their reaction products, which, on acidic hydrolysis, afford the aldehydes (189), ammonia and amino acids, as shown in Scheme 30." Identification of aldehydes determines the C-terminal amino acids of the original peptides. 

Oxidation of an aldehyde group to a carboxyl group has often been used for identification of the compounds. As far as can be judged from the results, such oxidations, using chromium trioxide/acetic acid, bromine-water, - peroxy acids, - or chlorite, have not been accompanied by any important side-reactions. Hypoiodite titration, using the iodine in sodium bicarbonate-sodium carbonate procedure, has sometimes been used, giving almost stoichiometric aldehyde determinations. - - Reduction by the Meerwein-Ponndorf reaction, with borohydride - - ... 

Aliphatic carbonyl compounds consist mainly of aldehydes and ketones. A large number of aliphatic aldehydes have been shown to be present in alcoholic beverages. Among the aldehydes determined quantitatively acetaldehyde is the major component, and generally constitutes more than 90% of the total aldehyde content of the beverage. For this reason it could be expected that acetaldehyde is of importance... 

While much of the aldehyde present in wines is bound to bisulfite, etc., some is free. Villforth (1940) outlined a procedure for its determination which has also been used by Koch and Bretthauer (1960-1951). It is based on treating ice-cold wine with calcium carbonate and calcium hydroxide, decarbonating with ice-cold barium chloride, and filtering. The filtrate is distilled with calcium carbonate and the aldehyde determined by the usual procedures. Probably more than the free aldehyde is determined. 

An aldehyde determination in the usual way, with 30 per cent, sodium bisulphite solution, gave 16 per cent, of aldehydes. The preparation of the non-aldehydic oil was carried out quantitatively to act as a check on the other determinations. Thirty grms. of oil gave 25 4 grms. of non-aldehydic constituents equal to 15 33 per cent, of aldehydes. 

The procedure for aldehyde determination is described above in the section on EO, PO, dioxane, and acetaldehyde. Generally, HPLC is preferred for determination of all aldehydes but acetaldehyde. Formic and acetic acid can be determined by a number of procedures, including gas chromatography and ion chromatography. A method for HPLC determination of these acids as their 2-nitrophenylhydrazone derivatives has been worked out specifically for ethoxylated esters of sorbitan (93). 

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