Formaldehyde, quantitative determination

Similarly, the m/z = 60 ion current signal was converted into the partial current for methanol oxidation to formic acid in a four-electron reaction (dash-dotted line in Fig. 13.3c for calibration, see Section 13.2). The resulting partial current of methanol oxidation to formic acid does not exceed about 10% of the methanol oxidation current. Obviously, the sum of both partial currents of methanol oxidation to CO2 and formic acid also does not reach the measured faradaic current. Their difference is plotted in Fig. 13.3c as a dotted line, after the PtO formation/reduction currents and pseudoca-pacitive contributions, as evident in the base CV of a Pt/Vulcan electrode (dotted line in Fig. 13.1a), were subtracted as well. Apparently, a signihcant fraction of the faradaic current is used for the formation of another methanol oxidation product, other than CO2 and formic acid. Since formaldehyde formation has been shown in methanol oxidation at ambient temperatures as well, parallel to CO2 and formic acid formation [Ota et al., 1984 Iwasita and Vielstich, 1986 Korzeniewski and ChUders, 1998 ChUders et al., 1999], we attribute this current difference to the partial current of methanol oxidation to formaldehyde. (Note that direct detection of formaldehyde by DBMS is not possible under these conditions, owing to its low volatility and interference with methanol-related mass peaks, as discussed previously [Jusys et al., 2003]). Assuming that formaldehyde is the only other methanol oxidation product in addition to CO2 and formic acid, we can quantitatively determine the partial currents of all three major products during methanol oxidation, which are otherwise not accessible. Similarly, subtraction of the partial current for formaldehyde oxidation to CO2 from the measured faradaic current for formaldehyde oxidation yields an additional current, which corresponds to the partial oxidation of formaldehyde to formic acid. The characteristics of the different Ci oxidation reactions are presented in more detail in the following sections. 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

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-... 

Dillon HK, Gao P. 1994. Laboratory evaluation of a novel reactive passive sampler for the quantitative determination of formaldehyde in air. Am Ind Hyg Assoc J 55 1061-1068. 

Lyles, G. Dowling, F. Blanchard, V. "Quantitative Determination of Formaldehyde in the Parts Per Hundred Million Concentration Level" J. Air Pollution Control Association,... 

Dyno has contributed to the development of a method, named the Bell method, for the quantitative determination of the formaldehyde emission from a panel surface ( 5). A glass flask or bell having a plane flange is placed on the surface to be measured. A tight sealing between the flange of the bell and the panel surface is very important. The air can be kept in circulation by means of a membrane pump, pumping about 2 liters per minute in a closed loop, which also contains a gas burette. After a predetermined time the formaldehyde concentration of the air in the gas burette is determined by a sensitive analytical method. 

The cyanogen halides can be detected at trace levels using gas chromatography with electron-capture detection. Thiocyanate can be quantitatively determined in the presence of cyanide by the addition of an excess of formaldehyde which converts the cyanide ion to the unreactive cyanohydrin. 

This reaction fails with higher aldehydes and can thus be used for quantitative determination of formaldehyde in the presence of other aldehydes (sensitivity 3.4 10-6 g of CH20 per ml). 

Kiefer, J.E. and R.E. Leonard A new method for quantitatively determining formaldehyde and other carbonyl compounds in cigarette smoke Seminar, Tennessee Eastman Personnel to R. J. Reynolds Tobacco Company R D Personnel, Winston-Salem, NC, 1964, see www. ijrtdocs.com 501013036 -3054. 

Taylor, M.J. and J.F. Graham Simultaneous quantitative determination of formaldehyde and hydrogen cyanide in cigarette smoke using a simple solid trapping system CORESTA 1986 Symp., Taormina, Italy, CORESTA Inf. Bull., Spec. Edition 1986 Paper ST09, 104-105. 

Seileb and Wiechmann [35] separate mescaline and other phenyl-ethylamines on silica gel 6 layers with isopropanol-chloroform-concen-trated ammonium hydroxide (80 + 5 + 15). Through condensation with formaldehyde in the presence of concentrated ammonium hydroxide and subsequent heating with hydrochloric acid or with the Proch4zka reagent (No. 123), derivatives are obtained which show intense green fluorescence, adaptable to fluorometric quantitative determination or to further separation with ethyl acetate-methanol-formic acid (60 + 35 + 5 or 80 + 10 + 10) (limit of detection for mescaline = 0.01 (xg). 

TLC was used for both qualitative (26-28) and quantitative analysis (29-31) of flavins in different matrices. The separation and quantitative determination by fluorescence quenching of the B-complex vitamins in some pharmaceutical products was performed using a newly synthesised carbamide formaldehyde polymer aminoplast with solvent systems 1-butanol/water/acetone (25 9 5, v/v) and 1-butanol/methanol/benzene/water (20 10 10 8, v/v) (29). 

The amounts of periodate consumed and the amount of formic acid and formaldehyde can be quantitatively determined. Thus, for methyl-a- (or )-D-glu-copyranoside, 2 moles of periodate were consumed and 1 mole of formic acid was formed per mole of glucopyranoside. The wavy line indicates the site of periodate carbon bond cleavage. 

Formation of formaldehyde by the dehA drogenation of methanol aa Us studied in 1910 by" Sabatier and Mailhe , who showed it to be a reversible reaction. Mom recently, Newton and Dodge " quantitatively determined the equilibrium relations for this reaction and found that... 

The aldehyde R"CHO liberated can be determined quantitatively by means of dinitrophenylhydrazine. In the case of formaldehyde (R" = H) being split in an alcoholic-acid medium, it has been found that the formation of a dinitrophenylhydrazone is a relatively slow process. This seems to suggest that formaldehyde is originally split off in the form of an acetal which gradually yields formaldehyde under action of dinitrophenylhydrazine. 

In order to systematically remedy the previous drawbacks, we recently proposed to perform a perturbation treatment, not on a wavefunction built iteratively, but on a wavefunction that already contains every components needed to properly account for the the chemistry of the problem under investigation [34], In that point of view, we mean that this zeroth-order wavefunction has to be at least qualitatively correct the quantitative aspects of the problem are expected to be recovered at the perturbation level that will include the remaining correlation effects that were not taken into account in the variational process any unbalanced error compensations or non-compensations between the correlation recovered for different states is thus avoided contrary to what might happen when using any truncated CIs. In this contribution, we will report the strategy developed along these lines for the determination of accurate electronic spectra and illustrate this process on the formaldehyde molecule H2CO taken as a benchmark. 

The hexitols may be determined quantitatively by periodate oxidation. Either the amount of oxidant consumed or the amount of acid or formaldehyde liberated may be determined. This method will not... 

Quantitative tests for formaldehyde in fabrics There are two types of test for formaldehyde content of fabric. The first type is designed to imitate dry skin contact with the fabric and especially for the release of formaldehyde during storage and transportation in closed containers. During the test the fabric sample is held above water in a sealed jar. Free and easily released formaldehyde dissolves in the water dnring the test and can be determined by specific analytical methods. 

---