Formaldehyde quantitative estimation

The concentration of open-chain polymers, similar to what was observed in the homopolymerization, reached a steady state and could be ascertained easily. However, the concentration of CH20 increased rapidly as the polymerization progressed, reaching a maximum immediately before precipitation of the polymers. An attempt to measure the maximum formaldehyde concentration was made by integrating the spectra immediately before solidification. This was somewhat difficult since the polymer precipitates from solution rapidly. Therefore, quantitative estimates may not represent the maximum concentrations of CH20 but are a close approximation. 

Eikmann T, Prajsnar D, Einbrodt HJ. 1987. Quantitative estimation of formaldehyd exposure in normal population collectives on the basis of the formic acid excretion in urine [Abstract]. Zentralbl Bakteriol Mikrobiol Hyg [B] 183 483-484. 

Detection and Determination of Aldehyde. The amount of formaldehyde in methanolic reaction mixture was estimated quantitatively according to the procedure by Kolthoff (16). A series of solutions containing varying amounts (5 X 10" to 5 X lO M) of formaldehyde as well as the unknown sample, with pH adjusted to 3 by phosphate-citric acid buffer, was treated with 1.5 X lO M Schiff s reagent (3i). Thirty minutes later, the optical density at 5500 A. was determined by a Coleman Junior spectrometer. The unknown concentration of formaldehyde was estimated by interpolating the known values. This procedure was reproducible for autoxidation of ferrous chloride in methanol. However, in the presence of a reactive cosubstrate, such as benzoin, the color became unstable, and the analysis was only semiquantitative. It was possible to determine acetaldehyde quantitatively in ethanolic reaction mixtures by vapor chromatography using a decylphthalate column at 66°-68°C. 

Noth. The above method can be successfully applied only to dilute solutions of formaldehyde which are free in particular from other alfphatic aldehydes, since the latter, if present, would undergo a similar oxidation. Formaldehyde, if mixed with other aldehydes, should be estimated by quantitative addition of potassium cyanide for details, see advanced text-books of quantitative organic analysis. 

Their main results may be summarized as follows. The periodic acid oxidation of polyols afforded a method for quantitative determination of these compounds, and it was demonstrated that the first reaction products are carbonyl compounds, themselves in turn degraded from their reducing end. After complete oxidation, it is possible to make an estimate of the consumption of oxidant, as well as of the formic acid and formaldehyde that are produced. The monosaccharides are attacked preferentially at the neigh-... 

A third method relies on the precipitation of proanthocyanidins with formaldehyde. First, the total phenolic content is measured using the Folin-Ciocalteu reagent as described before. A 0.5 mole equivalent of phloroglucinol (1.3) is added for every gallic acid equivalent in the extract. To 2 mL of this plant extract and phloroglucinol is added 1 mL of a 2 5 HC1 /H20 solution and 1 mL of an aqueous solution of formaldehyde (13 mL of 37% formaldehyde diluted to 100 mL in water). After an overnight incubation at room temperature, the unprecipitated phenols are estimated in the supematent by the Folin-Ciocalteu method. The precipitate contains the proanthocyanidins and the known amount of phloroglucinol, which is always quantitatively precipitated. 

Most recently, work by Barber et al.10 has thrown considerable doubt on reaction (23). They photolyzed methyl iodide in the presence of oxygen at room temperature by a quantitative method which they have developed for estimation of normal pressure reactions by the mass spectrograph. Working to 0.25 or 0.5% conversion with 10 mm. methyl iodide and a total pressure of 50 mm., they were able to agree with previous workers that equal quantities of methanol and formaldehyde were produced by the oxidation of methyl radicals. However, when a little hydrogen iodide was added to the system, the amounts of methyl hydroperoxide, previously found to be small, were greatly increased (Fig. 14) and the amounts of methanol and formaldehyde decreased. Its seems significant that the methanol was decreased more than the formaldehyde. 

Stanfill, S.B. and D.L. Ashley Quantitation of flavor-related aUcenylbenzenes in tobacco smoke particulate by selected ion monitoring gas chromatography-mass spectrometry J Agr. Food Chem. 48 (2000) 1298-1306. Starr, T.B. and J.E. Gibson The mechanistic toxicology of formaldehyde and its implications for quantitative risk estimation Ann. Rev. Pharmacol. Toxicol. 25 (1985)745-767. 

In the previous chapter, we ha ne reviewed those methods which are best suited for the detection and estimation of formaldehyde in compositions in which it is a minor constituent. Such methods require a maximum of selectivity and sensitivity. We shall now consider methods of quantitative analysis which are best adapted to the accurate determination of formaldehyde in commercial solutions, pol mers and other compositions in which formaldehyde is present in quantity and in which impurities such as ketones, higher aldehydes, etc., which mterfere with the determination of formaldehyde, are either completely- absent or present in minor amounts. These methods possess a good d ee of accuracy but do not require the extreme sensitivity demanded by the procedures previously discussed. 

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