Formaldehyde, determination

Formaldehyde, Determination of, in Biological Systems (Frisell and Mackenzie). 6 63... 

Ernes D A. An alternative method for formaldehyde determination in aqueous solutions . Textile Chemist and Colorist, 1985, 17, 17-20. 

Formaldehyde Determination of Significant Risk Advance Notice of Proposed Rulemaking and Notice, Fed. Register,... 

Automated Flow Injection Analysis System for Formaldehyde Determination... 

The need for an automated and reliable system for formaldehyde determination is now clearly recognized. In response to this need, an automated and microprocessor-controlled flow injection analysis (FIA) system was developed in our laboratory. This system is based on the use of the modified pararosaniline colorimetric method (j6). The simplicity, versatility, good precision, high sampling rate, complete automation and relatively low cost of the system make it attractive for the analysis of large numbers of formaldehyde samples. In this chapter, sufficient background in the principle of FIA will be presented to allow the readers to evaluate the technique and its potential application to the routine analysis of formaldehyde will be explored. 

These test chambers can be incorporated to the enzymatic methods for formaldehyde determination. Formaldehyde emissions of a product, or mix of products, to the ambient air can be collected in distilled water or 1% sodium bisulfite as the absorbing solution. After collection, formaldehyde samples are analyzed as described above. In the mobile home simulator test method (2J, double or triple impingers, which are placed in series, should be used in order to collect all of the formaldehyde vapor. The test conditions should simulate the actual environment. Several factors such as temperature and relative humidity of the system including the specimens and background of formaldehyde in the test chamber, affect the precision and accuracy of the results. It has been shown that a 7 C change in temperature doubles the emission level (L). The temperature of the test chamber should be... 

To stabilize temperature, relative humidity, and formaldehyde concentrations within the chamber, we have found it necessary to have an air deflector (Item 13) placed between the back wall and a floor fan (Item 14) in such a way that the air flow from the floor fan is directed counter-current to the air flow movement from the air cooler s blower. Formaldehyde recovery studies, smoke stick evaluations, and formaldehyde determinations performed in several locations within the chamber have substantiated the efficiency of this mixing technique. 

Ambient formaldehyde determinations taken during large scale test chamber studies and field investigations are based on two colorimetric analyses. The two methods are a modification of NIOSH P CAM 125 and the CEA 555 continuous formaldehyde monitor. 

The CEA 555 continuous monitor(17) is used for real-time monitoring of chamber and actual field survey formaldehyde determinations. The monitor is a useful instrument in field surveys because it is one method that provides real time formaldehyde measurements which is useful in tracing and iden tifying usually high formaldehyde sources. The monitor s analytical method is based on the modified Schiff procedure developed by Lyles, Dowling and Blanchard (18). Formaldehyde is absorbed in a sodium tetrachloromercurate solution that contains a fixed quantity of sodium sulfite. Acid bleached pararosaniline is added, and the intensity of the resultant dye is measured at 500 nm. Both formaldehyde in air and liquid standards can be analyzed. 

Report of the Consensus Workshop on Formaldehyde," Environmental Health Perspectives, 1984, 58, 323-381. "Formaldehyde Determination of Significant Risk," U.S. 

Methyl Esters In Pectin. A titration method has been reported twT in which methyl ester levels are calculated from the number of equivalents of standard sodium hydroxide required to neuturalize the pectin sample before and after saponification. The copper titration procedure described earlier for determination of galac-turonic acid residues in pectin (15), is also used to determine methyl ester levels from the increase in copper-binding after hydrolysis of the esters. An accurate and sensitive colorimetric method (M) is rather time-consuming, but several samples can be run in parallel. Samples are saponified, the released methanol oxidized to formaldehyde, and the formaldehyde determined by spectrophometric assay (4l2nm) of its condensation product with pentane-2,4-dione. 

M. H. Ho, Automated Flow Injection Analysis System for Formaldehyde Determination. ACS Symp. Ser., 316 (1986) 107. 

Dahlquist I, Fregert S, Gruvberger B (1980) Reliability of the chromotropic acid method for qualitative formaldehyde determination. Contact Dermatitis 6 357-358... 

Resoles are usually mixtures of a number of methylol phenols, with small amounts of higher condensation products involving methylene and benzylic ether linkages. The kinetics of base-catalyzed phenol-formaldehyde reactions have been extensively researched. At high dilution and at a pH not exceeding 10, the rate equation can be expressed by Eq. (13), where [PhO ] denotes the concentration of phenoxide anion and [F] the concentration of unreacted formaldehyde, determined titrimetrically. " ... 

Strategy Draw the Lewis structure of formaldehyde, determine the hybridization of the C and O atoms, and describe the formation of the sigma and pi bonds in the molecule. 

As seen above, the mole ratio of phenol to formaldehyde determines the type of resin and degree of cross-linking obtained. This particularly affects the physical properties and resulting strength of the casting resins [32]. Using a basic catalyst, Sprung found that the rate of formaldehyde disappearance follows the relationship Eq. (2) [33],... 

Though the accuracy of hydroxylamine hydrochloride method of formaldehyde determination normally runs at about 94.4% of the theoretical value regardless of time and temperature (20 C-25°C) of determination", yet it is the most commonly used method by the U.S. wood adhesive industry to determine the content of free-formaldehyde in phenol formaldehyde resins. Therefore, the unreacted free formaldehyde content in each sample was determined by this method using a pH meter to detect the end point (pH = 4.00) of titration rather than using a bromophenol blue indicator. Two determinations were made for each sample and the average free formaldehyde content calculated. Then the results were converted into percentages of initially added formaldehyde for comparison. 

Formation of some unstable salts, through the reaction between urea and some of the initial formaldehyde, determines from the beginning an increased medium pH in the subsequent stages of the reaction, due to urea consumption, a reduction of medium pH takes place. This pH variation necessitates permanent control of reaction medium pH by the addition of buffers (sodium acetate, (H4N)2C03, citric acid, and sodium acetate mixture) or urotropine. The latter forms, with formic acid, medium-buffering compounds [21]. 

A specific test method has been developed for determining the VOC and odorant concentration of coated surfaces," "" as shown schematically in Figure 17.1.10. Similar to formaldehyde determination, sample testing is done using a test chamber approach. After some atmospheric conditioning, of the varnished furniture, the samples are stored in a test chamber (typically 1 m ) xmder the following conditions 23°C 0.5 45 3% relative... 

Marzuki NI, Abu Bakar F, Salleh AB, Heng LY, Yusof NA, Siddiquee S (2012) Development of electrochemical biosensor for formaldehyde determination based on immobilized enzyme. Int J Electrochem Sci 7(7) 6070-6083... 

Heat of Formation and Free Energy of Monomeric Gaseous Formaldehyde. Within the limits of experimental error, the most accurate value for the heat of formation of monomeric gaseous formaldehyde determinable from existent data is 28 kcal per mol at 18°C. 

The hydrogen evolved in the alkaline peroxide oxidation of formaldehyde has been used as a basis for a gas volumetric method of formaldehyde determination by Frankforter and West. ... 

Potassium Cyanide Method. Romijn also devised this method of formaldehyde determination which is considered by Mutschin to be as. accurate as the sodium sulfite, alkaline peroxide, and iodimetric methods for pure solutions of formaldehyde, and superior to them in the presence of acetoner acetaldehyde, benzaldehvde, higher aldehydes, and ketones. The procedure is based on the quantitative formation of cyanohi drin when formaldeh de is treated vith a solution containing a -known excess of potassium cyanide. 

Medidnal Soaps. Medicinal soaps containing formaldehyde may be analyzed by dissolving in four to five time.s their weight of water and precipitating the soap with barium chloride or sulfuric acid. After filtration, the filtrate is adjusted to a definite volume and the formaldehyde determined bv the iodimetric methods... 

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