On-line collection/concentration of trace amounts of formaldehyde in air with chromatomembrane cell and its sensitive determination by flow injection technique coupled with spectrophotometric and fluorometric detection

A simple, rapid and highly sensitive method for the determination of trace amounts of formaldehyde in air by using flow injection analysis (FIA) system coupled with a three-hole chromatomembrane cell (CMC) was investigated by using a spectrophotometer and a fluorometer. The CMC was applied to on-line collection/concentration of trace amounts of formaldehyde in air into water as an absorbing solution; formaldehyde in the air was found to be quantitatively transferred into the absorbing solution in CMC. The solution, containing absorbed formaldehyde, was introduced into the carrier stream of the FIA system. The amount of formaldehyde in an absorbing solution was measured spectrophotometrically and fluorometrically after the reaction with a mixed reagent of acetylacetone and ammonium acetate at pH 5.6–5.8. The amount of formaldehyde in the absorbing solution, measured by the proposed system, could be converted to the concentration of formaldehyde in the air sample. A calibration graph prepared by a series of standard formaldehyde aqueous solutions was adopted. The formaldehyde in indoor air, determined as exampled by the proposed spectrophotometric FIA, was found to be 5.14 ± 0.08 ppbv for 20 ml of the air sample at the air flow rate of 6 ml min⁻¹, and the relative standard deviation (R.S.D.) was 1.56%. The limit of detections (LODs) of HCHO in an absorbing solution was 2 × 10⁻⁸ M (0.6 ppb) and 8 × 10⁻⁹ M (0.2 ppb), respectively, by the spectrophotometric and the fluorometric FIA, and the LODs of HCHO in air sample of 40 ml were 0.05 and 0.03 ppbv, respectively. The interferences from foreign species were examined; tolerable concentrations of other aldehydes were more than 50-fold of formaldehyde (1 × 10⁻⁶ M).     

Study of the electrochemical oxidation mechanism of formaldehyde on gold electrode in alkaline solution

The oxidation of formaldehyde in alkaline solution was studied by in situ rapid-scan time-resolved IR spectroelectrochemistry（RS-TR-FTIRS） method.In the potential range between -0.7 V and 0.2 V,the gem-diol anions were oxidized(according to the 2765 cm^-1 of-ν_H-O and 1034 cm^-1 ofν_co downward IR bands) and the formate ions appeared(according to the 1588,1357 cm^-1 of the asymmetric and symmetricν_oco and 1380 cm^-1 ofδ_C-H upward IR bands) in aqueous solution.It was also confirmed that gem-diol anion was oxidized(according to the 2026,1034 cm^-1 downward IR bands) to formate ions (according to the 1595,1357,1380 cm^-1 upward IR bands) and water(according to the 3427 cm^-1 ofν_{H- O} upward IR band) in heavy water solution.The results illustrated that formaldehyde formed gem-diol anion in alkaline solution and was absorbed on the electrode surface;then gem-diol anion was oxidized to formate ions and water.     

A new approach to the determination of the heat of phenolic resol synthesis

A new method has been developed for the determination of the heat of phenolic resol synthesis carried out in an aqueous solution. This heat is determined as the difference in the heats of syntheses of the resitol from the mixture of raw materials and from the resol studied. Heats of resitol syntheses were determined by DSC at constant heating rate using high-pressure crucibles, i.e. under isochoric conditions for the liquid–vapour sample.

The heat of synthesis of resols, obtained at formaldehyde-to-phenol molar ratio equal to 3.0 and using NaOH as catalyst, were determined. The relevant values were calculated on the basis of the chemical composition of the resols and the molar enthalpies of the aromatic ring substitution and methylene bridge formation reactions. The experimentally determined heats were consistent with the calculated ones, not when free formaldehyde (CH₂O) but its monohydrate, CH₂O·H₂O (methylene glycol, HO–CH₂–OH) was assumed to be the reactive form of formaldehyde in an aqueous medium (formalin).     

Toward the supramolecular structure of collagen: a molecular dynamics approach

The structure, stability, and conformational dynamics of an assembly of two pentameric bundles made of collagen-like triple helical segments are explored using 1.2 ns molecular dynamics simulations in three environments: 8.0% (v/v) formaldehyde/water solution, 1.4% (v/v) gallic acid/water solution, and pure water. Stable supramolecular arrangements, where the two collagen units are very close to each other at interacting distances, are identified via docking and energy minimization procedures. Analysis of the interaction with formaldehyde and gallic acid suggests that they perturb the protein in a similar way depending on hydrogen-bonding capability, hydrophobic association properties, and the size and concentration of the compound.     

木质素对木质素-脲醛共聚树脂的影响及反应机理

通过调控甲醛与尿素摩尔比, 降低脲醛树脂胶黏剂中游离甲醛的含量, 以生物质玉米芯为原材料, 用碱液提取得到的碱木质素溶液与甲醛和尿素进行三元逐步共聚, 弥补降低醛脲比带来的胶合强度的快速下降问题. 以降低游离甲醛含量同时兼顾胶合强度为原则进行探索, 得到最佳实验条件为甲醛与尿素摩尔比(F/U)为0.91∶1, 木质素添加量为20%(质量分数), 在此条件下木质素-尿素-甲醛共聚树脂(LUF)胶合强度为0.99 MPa, 游离甲醛含量为0.26%. 对共聚树脂进行了结构表征, 表明木质素参与到反应中, 并能提高树脂的热稳定性和耐水性, 同时对反应的机理进行了讨论.     

可视化测定痕量甲醛的研究

摘 要：共振光散射(RLS)法是近年发展起来的新的分析测试技术,它具有简便快速,灵敏度高的特点,已用于痕量元素或物质的分析。本文基于一定条件下,在碱性溶液中甲醛能还原Ag+ 得到黄色银胶,使体系的RLS增强,从而建立起测量环境中痕量甲醛的RLS新方法。结果表明,新建方法测定甲醛的浓度线性范围为1.0?10-6?2.0?10-5 mol/L,检出限为1.0?10-7 mol/L,样品加标测定的回收率为96.26%? 103.32%。并且不同浓度的甲醛还原Ag+ 得到黄色银纳米粒子的颜色明显不同,基于此建立了一种可视化半定量测定痕量甲醛的新方法,新建方法简便快速,灵敏度高。用于环境水样、室内空气中甲醛的测定,结果满意。     

基于银纳米粒子的生成测定痕量甲醛

在碱性溶液中甲醛能还原Ag~+得到黄色银纳米粒子,使体系的共振光散射(RLS)强度增强,从而建立起测量环境中痕量甲醛的RLS新方法. 结果表明,新建方法测定甲醛的浓度线性范围为1.0×10~(-6)～2.0×10~(-5) mol/L,检出限为1.0×10~(-7) mol/L,样品加标测定的回收率为96.26%～103.32%. 并且不同浓度的甲醛还原Ag~+得到黄色银纳米粒子的颜色明显不同,基于此建立了一种可视化半定量测定痕量甲醛的新方法,此方法简便快速、灵敏度高. 用于环境水样、室内空气中甲醛的测定,结果满意.     

The analysis of combustion products : The estimation of traces of methanol in the presence of formaldehyde

In the analysis of combustion products, the estimation of traces of methanol can be rendered difficult by the presence of excess formaldehyde. A method is described for separating the formaldehyde from methanol by treating the solution with sodium bisulphite, and then carrying out a Chromatographie separation on filter paper. Ether carries the methanol to the end of the strip, leaving behind formaldehyde and hydrogen peroxide. The paper is cut into pieces, which are separately extracted with water, and the solution oxidised. The formaldehyde so formed ib estimated in the usual way with chromotropic acid.     

The Electro‐Oxidation of Formaldehyde at a Boron‐Doped Diamond Electrode

Abstract

The characteristics of the boron‐doped diamond (BDD) electrode in this work were studied by atomic force microscope (AFM), scanning electron microscopy, and Raman spectroscopy. The electro‐oxidation of formaldehyde at the BDD electrode in 0.5 M K₂SO₄ with different pH was studied by cyclic voltammetry and amperometry. There is no significant oxidation peak of formaldehyde in acidic solution because the oxidation of formaldehyde is at the potential range of water discharge. However, in neutral solution, there is a well‐defined oxidation peak at about +2.2 V vs. Ag/AgCl. The relation between the response current and formaldehyde concentration is linear behavior at the concentration range from 50 to 600 µM. Besides, in neutral solution, the oxidation of formaldehyde is dominated by indirect oxidation at lower formaldehyde concentration, and it is dominated by direct oxidation at higher concentration. Finally, in alkaline solution, the oxidation of formaldehyde is dominated by indirect oxidation caused by a powerful oxidant and is related to the ratio of the amounts of formaldehyde and OH molecules at the BDD electrode surface.     

Indirect amplification method for determining formaldehyde and chloralhydrate by differential pulse polarography

An indirect differential pulse polarographic method for the determination of formaldehyde and chloralhydrate is described; it is based on the oxidation of the alkaline sample solutions of formaldehyde and chloralhydrate with a chloroform solution of iodine and removal of its excess. The resulting iodide is oxidized with bromine water and measured polarographically as iodate (at pH 9.3) with sixfold amplification.     

Fluorimetric flow injection analysis of trace amount of formaldehyde in environmental atmosphere with 5,5-dimethylcyclohexane-1,3-dione

A simple and sensitive flow injection method with fluorimetry and 5,5-dimethylcyclohexane-1,3-dione (dimedone) was developed for the determination of formaldehyde. Formaldehyde reacted with dimedone in the presence of ammonium acetate to form a fluorescence compound, which has an excitation wavelength at 395 nm and an emission wavelength at 463 nm. A two-channel flow system was assembled. Distilled water and 0.3% dimedone buffered at pH 5.5 were delivered at 0.7 ml min⁻¹ and 100 μl of sample was injected into the carrier stream. The reaction was done in the reaction system designed newly, which consists of heating and cooling devices. The chemical reactivity with formaldehyde was excellent in the reaction system and selective. The calibration graphs were linear in the range of 25–100 and 5–10 ppb. RSDs (n=10) for 50 and 10 ppb formaldehyde were 0.6 and 3.4% and the LOD (S/N=3) was 0.9 ppb. The sample throughput was 20 h⁻¹. The method was applied to the determination of formaldehyde in gas sample evolved from adhesive agents and in living environmental indoor. The sensitive and selective method is useful for monitoring trace of formaldehyde in the environmental atmosphere.     

Sensitive Solid Reagent For Formaldehyde,And A New Formaldehyde Generator

Abstract

A solid reagent of Purpald®-acetone aminal on sodium or potassium bicarbonate responds to formaldehyde in the sub-ppm concentration range. A purple color (λ=560 nm) is developed proportional to concentration of formaldehyde and time of exposure after wetting with a 90% acetone-10% water solution. The reagent should be of value as a semi-quantitative warning device for the presence of formaldehyde. A device is described which generates formaldehyde in air in the sub-ppm concentration range at room temperature with desired relative humidity. This generator could be used in the same manner to generate low concentrations of other substances of low volatility.     

Application of wet effluent diffusion denuder for measurement of uptake coefficient of gaseous pollutants

The comparison of theoretical approaches describing the collection of analyte in the cylindrical wet effluent diffusion denuder (CWEDD) with experimental data is presented. Various absorption liquids were tested for the collection of formaldehyde (distilled-deionized water, H₂SO₄ solution), acetaldehyde (distilled-deionized water) and nitrous acid (distilled-deionized water, sodium carbonate and sodium bicarbonate solutions of various concentrations and sodium phosphate pH 6-8) in CWEDD. pH of absorption liquids significantly influences the collection of formaldehyde as well as nitrous acid. The collection efficiency of formaldehyde for 0.05 M H₂SO₄ as absorption liquid was generally higher than for distilled-deionized water. Absorption liquid pH markedly affected the collection efficiency of HONO too (with increasing pH the collection efficiency increase). Data derived by Gormley-Kennedy equation for all investigated compounds were overestimated especially for higher flow rates of air, data calculated with respect to Henry constant are not in good agreement with experimental data and are considerably depended on a determination of the Henry constant value. The CWEDD can be alternative tool for the determination of uptake coefficient. Obtained uptake coefficients were in good agreement with data found in other literature.     

Assembled Organoruthenium(II) for Formaldehyde Decomposition and Hydrogen Production

Formaldehyde decomposition is not only an attractive method for hydrogen production, but also a potential approach for gaseous formaldehyde removal. In this research, we prepare some assembled organoruthenium through coordination reaction between Ru(p-Cymene)Cl₂ and bridge-linking ligands. It is a creative approach for Ru(p-Cymene)Cl₂ conversion into heterogeneous particles. The rigidity of bridge-linking ligand enables assembled organoruthenium to have highly ordered crystalline structure, even show clear crystal lattice with spacing of 0.19 nm. XPS shows the N−Ru bond are formed between bridge-linking ligand and Ru(p-Cymene)Cl₂. The assembled organoruthenium has high abundant active sites for formaldehyde decomposition at low temperature. The reaction rate could increase linearly with temperature and formaldehyde concentration, with a TOF of 2420 h⁻¹ at 90 °C. It is promising for gaseous formaldehyde decomposition in wet air or nitrogen. Formaldehyde conversion is up to 95 % over Ru-DAPM is 4,4′-diaminodiphenylmethane at 90 °C in air. Gaseous formaldehyde decomposition is a two-steps process under oxygen-free condition. Firstly, formaldehyde dissolve in water, and be converted into hydrogen and formic acid through formaldehyde-water shift reaction. Then intermediate formic acid will further decompose into hydrogen and carbon dioxide. We also find formaldehyde decomposition is a synergetic catalysis process of oxygen and water in moist air. Oxygen is conducive to formic acid desorption and decomposition on the active sites, so assembled organoruthenium exhibit slightly higher conversion for formaldehyde decomposition in moist air. This work proposes a distinctive method for gaseous formaldehyde decomposition in the air, which is entirely different from formaldehyde photocatalysis or thermocatalysis oxidation.     

Synthesis of novel water-soluble linear and heterocyclic phosphino amino acids from 2-phosphinophenols or 2-phosphinophenolethers, formaldehyde and amino acids

Acyclic and cyclic amino acid derivatives of 2-phosphinophenols have been synthesised by reaction of primary phosphinophenols (4-R-2-H₂PC₆H₃OH; R=H, Me, OMe) 1a–c with formaldehyde and amino acids (o- and p-aminobenzoic acid, -lysine) via in situ formed hydroxymethyl species 2a–c. Condensation reactions with glycine did not afford defined products except when the methoxymethyl and tetrahydropyranyl ethers of 1d,e were used instead of the hydroxy compounds. o-Aminobenzoic acid gives rise to linear bis(o-carboxyphenylaminomethyl)phosphines 3a–e. p-Aminobenzoic acid, dependent on the molar ratio, affords bis(p-carboxyphenylaminomethyl)phosphines 4a,d as well as eight-membered heterocyclic 1,5,3,7-diazadiphosphacyclooctanes 5a–e. The aliphatic amino acids glycine and -lysine form six-membered heterocyclic 1,3,5-diazaphosphorinanes 6d and 7a–e, respectively, in presence of excess formaldehyde. -lysine differs from glycine by reaction at the terminal amino group. The structures of the compounds have been elucidated by multinuclear NMR spectroscopy. The salts of the phosphino amino acids are soluble in water. Water solubility increases with the number of hydrophilic groups, i.e. free phenols are more soluble than their ethers. Ligand concentrations in water from 0.1 to 1 M were observed.     

Aminomethylation of substituted pyrroles and 4,5,6,7-tetrahydroindoles with biogenic cyclic amines

Aminomethylation of 2-methyl(aryl)-, 2-aryl-3-alkylpyrroles, 4,5,6,7-tetrahydroindole and its 1-vinyl- and 1-benzyl-substituted derivatives with a mixture of 5% water-ethanol solution of formaldehyde and cyclic amine (pyrrolidine, piperazine, and morpholine) without catalyst at room temperature leads to the formation of the corresponding 2-aminomethylpyrroles and 2-aminomethyl-4,5,6,7-tetrahydroindoles in up to 92% yields. In reaction of 1-vinyl-4,5,6,7-tetrahydroindole with formaldehyde water solution and piperazine in a 60% yield 1,4-bis(1-vinyl-4,5,6,7-tetrahydroindol-2-yl)piperazine was obtained, a promising bifunctional monomer and a building block for the synthesis of new indole derivatives, in particular, of biologically active polymers. In the reaction of 2-methylpyrrole and 4,5,6,7-tetrahydroindole with formaldehyde and morpholine along with the С²-aminomethylation the 1-hydroxymethylation of the pyrrole ring was observed.     

A simple spectrophotometric determination of endosulfan in river water and soil

Summary A simple spectrophotometric determination of endosulfan (Thiodan), a sulphur containing pesticide is described. The method is based on the liberation of sulphur dioxide from endosulfan which is subsequently absorbed into an absorbing reagent, malonyldihydrazide and estimated by using p-aminoazobenzene and formaldehyde to give a pink coloured dye which has an absorbance maxima at 505 nm. The Beer's law is obeyed in the range of 1–6 ppm for a standard solution of endosulfan. The method can be easily applied in river water and soil samples to determine endosulfan levels as low as 0.05 ppm and 0.25 ppm in river water and soil, respectively. The method is free from the interference of most of the commonly used pesticides and foreign ions.     

In situ FTIR Study of the Adsorption of Formaldehyde, Formic Acid, and Methyl Formiate at the Surface of TiO2 (Anatase)

The catalytic properties of TiO₂ (anatase) in the reactions of formaldehyde oxidation and formic acid decomposition are examined. At 100–150°C, formaldehyde is converted into methyl formate with high selectivity regardless of the presence of oxygen in the reaction mixture. Formic acid is decomposed to CO and water. Surface compounds formed in the reactions of formaldehyde, formic acid, and methyl formate with TiO₂ (anatase) are identified by in situ FTIR spectroscopy. In a flow of a formaldehyde-containing mixture at 100°C, H-bonded HCHO, dioxymethylene species, bidentate formate, and coordinatively bonded HCHO are observed on the TiO₂ surface. In the adsorption of formic acid, H-bonded HCOOH and two types of formates (bidentate and unsymmetrical formates) are formed. In the adsorption of methyl formate, H-bonded HCOOCH₃, HCOOCH₃ coordinatively bonded via the carbonyl oxygen, and bidentate formate are identified.     

Study on the production of formaldehyde-14C by direct reduction of14CO2 with LiAlH4

A vial technique was developed for the synthesis of formaldehyde-¹⁴C from¹⁴CO₂ in an ether solution of lithium aluminium hydride. The yield of formaldehyde (40–50%) was achieved by optimization of the reaction parameters.