Detection of formaldehyde

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. 

Several color reactions were reported for heterocycbc nitramines RDX and HMX [43, 44, 53, 58]. These nitramines release formaldehyde when treated with concentrated sulfuric acid. Therefore, the use of 1,8-dihhydroxynaphthalene-3,6-disulfonic acid (chromotropic acid) in concentrated sulfuric acid — a known reagent for the detection of formaldehyde [4] — produced the expected violet-pink color. The reaction is hardly specific other compounds that release formaldehyde under similar conditions will react in the same way. 

As well as these major application fields, biosensors and analytical techniques should also benefit from the technology. Some examples have already been described. The detection of formaldehyde by a formaldehyde dehydrogenase coated onto a piezoelectric crystal has been performed at the ppm level. Detection of pesticides and organophosphorus compounds at the ppb level has been rendered... 

The use of protein-coated acoustic wave devices for detection of gas-phase species has also been reported with claims of good sensitivity and selectivity. Guilbault et al. reported TSM sensors for the reversible gas-phase detection of formaldehyde [227], and organophosphorous pesticides [228,229]. More recent studies have cast some doubt as to whether the gas-phase sensitivity was the result of selective immunochemical binding, or simply due to nonspecific adsorption. In work reported by Thompson et al. [230], sensors coated with parathion antibody exhibited sensitivities to the pesticides parathion, malathion, and disul-foton that were remarkably similar to sensors coated with nonspecific proteins (valproic acid antiserum, human immunoglobulin G, and bovine serum albumin). The fact that the previous study [228] reported significantly larger sensitivity at... 

Detection of formaldehyde-induced crosslinking in soft elastic gelatin capsules using near-infrared spectrophotometry. Pharm. Dev. Technol. 1998, 5 (2), 209-214. 60. 

Methods for the determination of fonnaldehyde in drinking water are available and they utilize the same detection methods as those utilized for the analysis of formaldehyde in air, with LODs reported to be 20 ppb (Tomkins et al. 1989) and 8.1 ppb (EPA 1992b). The MRL for chronic oral exposure to formaldehyde is 0.2 mg/kg/day. If a 70-kg person is assumed, the maximum intake is 14 mg/day. If a daily intake of 2 L of water or 2 kg/day of food per day is assumed, then any analytical method must have an LOD of less than 7 mg/L for water or 7 mg/kg (ppm) for food. The cited methods for detecting formaldehyde in water have LODs far below the needed value and are sensitive enough to measure background levels in the environment no additional methods for formaldehyde detection in water are required. Other than for milk (Kaminski et al. 1993b, LOD=9 ppb), no methods for formaldehyde detection in food were found. Additional methods for detection of formaldehyde in foods are needed. Methods for the detection of formaldehyde in soil are not adequately described in the available literature. 

Glaze WH, Koga M, Cancilla D. 1989. Ozonation byproducts 2. Improvement of an aqueous phase derivatization method for detection of formaldehyde and other carbonyl compounds formed by the ozonation of drinking water. Environ Sci Technol 23 838-847. 

G4. Gallop, P. M., Fliickiger, R., Hanneken, A., Mininsohn, M. M., and Gabbay, K. H., Chemical quantitation of hemoglobin glycosylation fluorometric detection of formaldehyde released upon periodate oxidation of glycoglobin. Anal. Biochem. 117, 427-432 (1981). 

As well as macralstonine71" and others, a new alkaloid,716 alstonisidine, has been isolated from Alstonia muelleriana. The structure (80) suggested for this dimer rests on spectral measurements, principally the presence of several ions in its mass spectrum which have the same mass numbers as characteristic fragment ions of authentic macroline and ajmaline alkaloids, the formation of a mono-0-acetate, of a triol with lithium aluminium hydride (fission of N—C—O), and the detection of formaldehyde after acid treatment. Formaldehyde was also detected after a model acid treatment of quebrachidine (81) and it is suggested that this rather surprising result can be explained, for both the dimer, believed to contain a quebrachidine unit, and for quebrachidine itself as shown [arrows in (81) and (82)]. 

Dahlquist I, Fregert S (1978) Formaldehyde releasers. Contact Dermatitis 4 173 Dahlquist I, Fregert S, Gruvberger B (1980) Detection of formaldehyde in corticoid creams. Contact Dermatitis 6 494... 

Fregert S, D lquist I, Gruvberger B (1984) A simple method for the detection of formaldehyde. Contact Dermatitis 10 ... 

Stonecipher MR, Sherertz EF (1993) Office detection of formaldehyde in fabric Assessment of methods and update on frequency. Am J Contact Dermat 4 172-174... 

Tests often cited in the medical literature for the detection of formaldehyde in various products are the chromotropic acid and acetylacetone tests. Flyvholm et al. (1996 and 1997) describe both tests and present the results of a study in which both of these tests were used to detect formaldehyde. The majority (63%) of the 1134 products tested with the methods were cosmetics and toiletries and another 18% were household products. Some resin-finished fabrics were included. For 81% of the products, the two tests gave the same results. 

Several methods are available for detection of formaldehyde in textiles. The main one is AATCC Test Method 112-1990, Formaldehyde Release from Fabric, Sealed Jar Method (American Association of Textile Chemists and Colorists, 1997 Pasad et al. 1989). This method is applicable to fabrics which may have been given a finish with a formaldehyde-containing resin. It provides accelerated storage conditions and an analyt-... 

The antimicrobial efficacy of the amine-formaldehyde reaction products essentially corresponds to the formaldehyde content of these compounds. Known exceptions are HTA, hexahydro-oxadiazines and octahydro-s-tetrazines, which derive from ammonia respectively certain alkylolhydrazines (Paulus, 1980) here the detection of formaldehyde by the Taimenbaum methods gives a negative result, which means that these substances have no significant antimicrobial effect at neutral to alkaline pH they release formaldehyde in acidic media only. This pH dependency is broken off, if, for example, HTA is quatemized (Jacobs et al., 1916). In contrast to HTA the quaternary hexaminium salts release formaldehyde widely independent of pH and therefore may be used as preservatives also for media of neutral to alkaline pH. They are not comparable with the surface active conventional quaternary ammonium compounds (QACs see Section 16.1)... 

Sun W, Sun G, Qin B, Xin Q (2007) A fuel-cell-type sensor for detection of formaldehyde in aqueous solution. Sens Actuators B Chem 128 193... 

Suzuki Y, Nakano N, Suzuki K. Portable sick house syndrome gas monitoring system based on novel colorimetric reagents for the highly selective detection of formaldehyde. Environ Sci Technol. 2003, 37, 5695-700. 

The detection of formaldehyde after ozonolysis of poly(vinyl chloride) is evidence for this type of unsaturated terminal. 

A color reaction of the methylenedioxy group is based on the well-known detection of formaldehyde (p. 215) with chromotropic and sulfuric acids (the mixture is heated over a boiling water bath for 30 min) (7, 8). 

For a specific detection of formaldehyde, chromotropic acid (1,8-di-hydroxynaphthalene-3,6—disulfonic acid III) is used. 

Detection of formaldehyde 1.2 ml of Concentrated sulfuric acid followed by 5 ml of Schiff s reagent are added to 5 ml of a dilute formaldehyde solution. A blue-violet color appears. 

Significantly, in order to improve the sensitivity and response and recovery speed of the prepared sensors, several methods are introduced to the design of resistance sensors (1) attaching nanoparticles which have catalytic function (e.g., Pd, Ag, Pt) onto the surface of nanoflbers [73, 81] and (2) choosing metal salts such as KCl, LiCl, NaCl, and MgCL as the dopant to add into the nanoflbers, especially in humidity sensors the influences of the nanoparticles or metal salts are illustrated in Fig. 11.4c, d [82, 84]. For example, Xu et al. [85] fabricated Ag nanoparticle-coated ZnO-Sn02 nanoflbers for the detection of formaldehyde. Due... 

Wang X, Si Y, Wang J, Ding B, Yu J, Al SS (2012) A facile and highly sensitive colorimetric sensor for the detection of formaldehyde based on electro-spiiming/netting nano-fiber/nets. Sens Actuator B Chem 163(1) 186-193. doi 10.1016/j.snb.2012.01.033... 

Achmann S, Hermann M, Hilbrig F, Jerome V, Hammerle M, Freitag R, Moos R (2008) Direct detection of formaldehyde in air by a novel NAD(-I-)- and glutathione-indep d t formaldehyde dehydrogenase-based biosensor. Talanta 75(3) 786-791. doi 10.1016/j.talanta. 

A wide range of color tests of -arying degrees of aensithity and specificily ha e been reported for the detection of formaldehyde in addition to the two authenticated methods already described. These tests involve the use of phenols, aromatic amine. , alkaloids, and other miscellaneous reagents. 

The characteristic reactions of formaldehyde with phenolic componnds and amines have also been adapted to the detection of the aldehyde in food-.stuffs. In such instances the material i generally steam-distilled and a qualitative analysis is then carried out on the distillate obtained. Cohn -shakes 2 ec of the distillate with an equal volume of 0.1 per cent resorcinol solution, then carefully adds 2 ce of concentrated sulfuric acid to produce a dense precipitate at the zone of contact between acid and solution with a dark violet-red zone immediate v below. Fomiic, ox alic, and tartaric acids are claimed not to interfere with this color reaction, which is sensitive to OjOO(K>5 mg foimaldehi de. Gallic acid reacts with like sensitivity to form an emerald green bandb The test devi.Sed by Pittarelli (page 247) is reported to be of value for the detection of formaldehyde in wine, milk. 

Detection of Formaldehyde in Products which have been Subjected to Formaldehvde Treatment... 

In 2007, Novoselov and co-workers first demonstrated the application of pristine graphene as a sensor for room-temperature detection of NH3, NO2, and CO. ° Subsequently, Kern and co-workers functionalized graphene with palladium nanoparticles to impart sensitivity towards hydrogen. Currently, there are not many reports in the literature for detectiOTi of VOCs by pristine graphene. However, graphene functionalized with ZnO ° and Sn02 nanoparticles and GO functionalized with polypyrene have been reported for rapid and sensitive detection of formaldehyde, propanal, and toluene, respectively (Table 14.3). 

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