Measurement methods formaldehyde

Researchers had noted the release of formaldehyde by chemically treated fabric under prolonged hot, humid conditions (85,86). The American Association of Textile Chemists and Colorists (AATCC) Test Method 112 (87), or the sealed-jar test, developed in the United States and used extensively for 25 years, measures the formaldehyde release as a vapor from fabric stored over water in a sealed jar for 20 hours at 49°C. The method can also be carried out for 4 hours at 65°C. Results from this test have been used to eliminate less stable finishes. 

Lawson, D. R., H. W. Biermann, E. C. Tuazon, A. M. Winer, G. I. Mackay, H. I. Schiff, G. L. Kok, P. K. Dasgupta, and K. Fung, Formaldehyde Measurement Methods Evaluation and Ambient Concentrations during the Carbonaceous Species Methods Comparison Study, Aerosol Sci. Technol., 12, 6A-16 (1990). 

The measurement of formaldehyde release from wood products Involves the collection of formaldehyde vapor in the test chamber using a suitable absorbing solution and then analyzing the formaldehyde collected. For many years, formaldehyde emission measurements were carried out using the desiccator test sampling method due to... 

The enzymatic methods described in this paper are not only more specific but also more sensitive than the chromotropic acid method. These methods can be used for the measurement of formaldehyde emission from wood products as well as formaldehyde exposure in the workplace and in indoor environments. 

Formaldehyde Measurement Methods For Chamber Field Concentrations... 

Limiting formaldehyde levels should not be set by regulation unless adequate measurement methods are available, except in case of acute health risk. 

However, it appears that limiting values are being proposed in several European countries, even though we know that it is still difficult to measure and enforce the proposed standard levels and even though the proposed measurement methods have been challenged. In France we want to be certain that we can enforce a standard before we finalize methods and set specific values. Therefore, we still continue to work towards a better understanding and definition of the formaldehyde emission process. 

This area is still in flux. One major problem is that one needs to develop better measurement methods for formaldehyde at low levels, and one needs to have a better field measuring protocol for measuring meaningful formaldehyde levels that are dependent on age of the product, temperature, humidity, and ventilation rate as well as the activities of occupants. All these problems could be reduced, if formaldehyde emission would be effectively controlled at the source. 

Full experimental details for the measurement of periodate uptake and the production of formic acid, formaldehyde, and carbon dioxide are given in many of the publications referred to in this Section. A spectrophoto-metric method for periodate determination, modified for oligosaccharides, is suitable for small-scale oxidations it may replace the classical arsenite-iodometric method. Good micromethods for measurement of formaldehyde are also now available. ... 

Glycerol can be determined by measuring the formaldehyde or formic acid produced or the periodate consumed. In this method the formic acid is measured. The weight of glycerol present must not exceed 0.4 g. 

A method suitable for analysis of sulfur dioxide in ambient air and sensitive to 0.003—5 ppm involves aspirating a measured air sample through a solution of potassium or sodium tetrachloromercurate, with the resultant formation of a dichlorosulfitomercurate. Ethylenediaminetetraacetic acid (EDTA) disodium salt is added to this solution to complex heavy metals which can interfere by oxidation of the sulfur dioxide. The sample is also treated with 0.6 wt % sulfamic acid to destroy any nitrite anions. Then the sample is treated with formaldehyde and specially purified acid-bleached rosaniline containing phosphoric acid to control pH. This reacts with the dichlorosulfitomercurate to form an intensely colored rosaniline—methanesulfonic acid. The pH of the solution is adjusted to 1.6 0.1 with phosphoric acid, and the absorbance is read spectrophotometricaHy at 548 nm (273). 

Various polymers and latexes ai e used in manufacturing different articles for medical use. Safety measures in using such articles require strict control measures which provide for detecting toxic substances on hygienic standard levels or on the permissible migration level (PML) (mg/dm ). Chromatographic reaction methods ai e used to reveal formaldehyde, phenol, and epichlorhydrin. 

A method for the determination of formaldehyde in the presence of acetaldehyde was developed by Nicolet and Shinn.88,100 103 After the excess periodate had been destroyed, these workers swept the acetaldehyde (from the neutral reaction mixture) into a sodium bisulfite solution by means of a stream of carbon dioxide. The acetaldehyde was measured by conventional, bisulfite methods, and the residual formaldehyde was precipitated with Dimedon. This procedure was applied to protein hydroly-zates and to terminal deoxy structures of carbohydrates.88,280 ... 

Another spectrophotometric method measuring both simple and combined sugars was described in papers by Johnson and Sieburth [158] and Burney and Sieburth [159]. The basic method comprised reduction of sugars to alditols with sodium borohydride, and oxidation of the alditols to form free formaldehyde. The formaldehyde was then determined spectrophotometrically with 3-methyl-2-benzothiazolinone hydrazone hydrochloride. 

In principle the velocity of dehydration could be measured if a physical rather than a chemical method were available for removing the unhydrated carbonyl compound at a rate comparable to its hydration. It was claimed by Bieber and Triimpler (1947a) that this could be achieved by the removal of formaldehyde in a rapid gas stream, the rate of which appeared to be dependent on the pH of the solution. However, attempts to repeat their experiments have proved unsuccessful moreover, although they give no experimental details, calculation in terms of known kinetic and equilibrium constants shows that for a 1-ml liquid sample a gas flow of at least 30 litres/min would be required to produce an appreciable perturbation of equilibrium conditions (Bell and Evans, 1966). It is thus clear that this method has no practical application, at least to formaldehyde solutions. 

This release of formaldehyde can also be quantified by using formaldehyde dehydrogenase, as described above. An alternative way to determine demethylase activity by measuring the amounts of released formaldehyde is the use of the Nash reaction [68, 69]. This method is based on the formation of the colored 3,5-diacetyl-1,4-dihydropyridine by condensation of formaldehyde and acetylacetone in the... 

Calibration. Most aldehydes, except formaldehyde, form two geometrical isomers of the derivatives and appear as two peaks in the chromatogram. The sum of these two peak areas was used in the calibration measurements. A six-point calibration curve for nine carbonyl compounds was measured. The calibration range was 0.1-50 ppb, except for (E)-2-nonenal, where the calibration range was 0.01-5 ppb. The matrix used for calibration solutions was 5% ethanol solution, pH 4.5. Correlation coefficient (Rh values indicate that this method can be used for analysis of aldehydes in a wide range of concentrations (Table 1). 

There are some methods that are specific to HCHO. For example, the Hantzsch reaction of HCHO, collected with a diffusion scrubber, with ammonium acetate, acetic acid, and acetylacetone to form diacetyldihydrolutidine, which is measured using its fluorescence at 470 nm, has been applied to air measurements (Dasgupta et al., 1988, 1990 Kleindienst et al., 1988a,b Lawson et al., 1990 Khare et al., 1997). Reaction with 1,3-cyclohexanedione and ammonium acetate to form a dihydropyridine derivative that is measured by fluorescence has been used in conjunction with a diffusion scrubber (Fan and Dasgupta, 1994). Enzymatic methods have been used in which formaldehyde dehydrogenase catalyzes the oxidation of HCHO to HCOOH in the presence of -nicotinamide adenine dinucleotide, NAD+, which is reduced to NADH. The latter is measured by fluorescence at 450 nm (Lazrus et al., 1988 Ho and Richards, 1990). 

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