Glyoxal, determination

Dinitrophenyl-hydrazine has been successfully employed in the analysis of simple aldehydes, substituted aldehydes, glyoxal and gluteraldehyde (43-45), all the isomers of the C3 to C7 aliphatic ketones (44,45) and in the determination of formaldehyde in tobacco smoke (46). 

The extent of oxidation, when determined by the reaction of the product with phenylhydrazine, is 85%. Hydrolysis of the oxidized xylan should produce approximately equimolar quantities of D-glyceraldehyde and glyoxal. Experimental determination of glyceraldehyde indicates 67 % of the theoretical when the oxidized xylan is distilled with sulfuric acid and the evolved methylglyoxal measured as the phenylosazone. Glyoxal is isolated in 63% yield, when separated as the phenylosazone or as the dioxime. Aldehyde groups in the oxidized xylan may be further... 

Peptides containing a tryptophan residue at the N-end can be determined by pre-column derivatization with glyoxal and RP-HPLC-FLD, as shown in reaction 9, giving single fluorescent peaks LOD 0.55-3.82 nM (SNR 3) for 100 pL injection volume221. 

Mirza, M. A., Kandhro, A. J., Memon, S. Q., Khuhawar, M. Y., and Arain, R. (2007). Determination of glyoxal and methylglyoxal in the serum of diabetic patients by MEKC using stilbenediamine as derivatizing agent. Electrophoresis 28, 3940-3947. 

Analysis. Ca gives a brick-red flame coloration, indicating that various optical spectroscopies will be effective in its determination. Ca is quantitatively determined by colorimetry down to 100 ppb using murexide or o-cresolphthalein, by atomic absorption spectroscopy (AAS) to 20 ppb, to 1 ppb by electrothermal absorption spectroscopy (ETAS), to 0.01 ppb by inductively-coupled plasma emission spectroscopy (ICPES), and to 10 ppb by inductively-coupled plasma mass spectroscopy (ICPMS). A spot test for Ca which extends to 3 ppm is provided by glyoxal bis(2-hydroxyanil). 

To enhance the shelf life of finished paper product, the step 1 product was applied below its critical micelle concentration (CMC). Materials additized above the CMC formed insoluble gels when aged for 8 days at 73°C. The CMC ranges was determined using glyoxalated poly(vinylamide-co-diallyldimethyl-ammonium chloride) containing 90 wt% vinylamide and are provided in Table 1. 

Nickerson, T. A., Moore, E. E. and Zimmer, A. A. 1964. Spectrophotometric determination of calcium in milk using 2,2 -(ethanediylidene-dinitrilo) diphenol (glyoxal bis (2-hydroxyanil). Anal. Chem. 36, 1676-1677. 

Table 58 gives the formation constants for silver(I) complexes of acetone thiosemicarbazone and glyoxal dithiosemicarbazone (55).443 In the latter case, the ligand was found to be suitable for the photometric determination of silver at pH 1 1, in the presence of EDTA. The effective molar absorptivity was 43 000 cm2 mmol-1 at 335 nm.443... 

Derivatives of Formaldehyde and Acetaldehyde.—According to Tafel and Pfeffermann,1 the phenylhydrazones of aldehydes are readily converted into amines by reduction in sulphuric-acid solution at a lead cathode. Thus ethylidene phenyl-hydrazine yields about 60% of the theoretical percentage of pure ethylamine salt. The decomposition of glyoxime is more complicated. Besides ammonia and glyoxal and a small quantity of an acid (glyoxylic acid ) there is formed as the principal product the crystalline sulphate of a base, C2H802N2, the nature of which could not be determined with certainty. Ethylenediamine is not formed. Nor was a diamine obtained from methylglyoxime. 

If oxylene exists only as structure A, ozonolysis would cause cleavage at the bonds indicated and would yield two equivalents of pyruvaldehyde and one equivalent of glyoxal for each equivalent of A consumed. If o-xylene exists only as structure B, ozonolysis would yield one equivalent of 2,3-butanedione and two equivalents of glyoxal. If o-xylene exists as a resonance hybrid of A and B, the ratio of ozonolysis products would be glyoxal pyruvaldehyde 2,3-butanedione = 3 2 1. Since this ratio is identical to the experimentally determined ratio, we know that A and B contribute equally to the structure of o-xylene. Note that these data don t distinguish between the resonance hybrid structure and the alternate possibility, equilibrium between two isomeric o-xylenes. 

Trace quantities of formaldehyde and methyl glyoxal in aqueous and food samples were determined by a newly developed method. Formaldehyde and methyl glyoxal were reacted with cysteamine in aqueous medium or food sample to give thiazolidine and 2-acetylthiazolidine, respectively, at pH 6 and 8. Thiazolidine derivatives formed from formaldehyde and methyl glyoxal were extracted with dichlorometh-ane or chloroform and subsequently analyzed by a gas chromatograph equipped with a fused silica capillary column and a thermionic detector. Seventeen commercial food items were analyzed for formaldehyde and methyl glyoxal. The quantities of formaldehyde and methyl glyoxal varied from 0 to 17 ppm and from 0 to 620 ppm, respectively. 

Certain volatile aldehydes such as formaldehyde and methyl glyoxal have always presented some difficulties in the determination of their levels in foods and beverages. Formaldehyde is difficult to extract from an aqueous solution with an organic solvent because it is very water soluble or exists as a polymer in an aqueous media. Methyl glyoxal is also hard to recover from food samples because it exists as a copolymer with some amines such as amino acids and proteins. 

Since direct analyses for formaldehyde and methyl glyoxal are difficult with gas chromatography (GC) or any other methods, we attempted to determine levels of formaldehyde and methyl glyoxal in various food samples using their derivatives thiazolidine and 2-acetylthiazolidine, respectively. The proposed mechanism of thiazolidine formation from cysteamine and corresponding aldehydes is shown in Figure 1. 

It would be ideal if 2-acetylthiazolidine was formed exclusively from methyl glyoxal. The optimum reaction condition for 2-acetylthiazolidine, therefore, was determined by the following experiments ... 

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