Sensitive Solid Reagent For Formaldehyde, And A New Formaldehyde Generator

The properties of formaldehyde in the environment, approaches to the valuation of its content in the air, measuring techniques, and the main sources of its releases to the environment are discussed. An overview of the measured concentrations of formaldehyde in the air in the cities of Belarus and other CIS countries, Europe and the USA. It is shown that the average concentration of formaldehyde in ambient air of cities of the CIS as a whole are close to the average annual levels of content in the cities of Europe and somewhat lower than in the U.S.

Room temperature thermocatalytic removal of formaldehyde in air using a copper manganite spinel-supported palladium catalyst with ultralow noble metal content

This paper describes a fluorescence technique for the detection of sub-ppm-concentrations of formaldehyde in air at atmospheric pressure. The aldehyde is excited by a frequency doubled tunable dye laser covering the 320-345-nm wavelength range. The fluorescence intensity, measured at right angles through a 400-nm cutoff filter, is proportional to the formaldehyde concentration in air. Interferences by NO(2) and SO(2) are negligible. The detection limit of the system is 5 pphm at present, in good agreement with an estimate of the fluorescence yield in 1 atm of air. A considerable increase of the sensitivity is possible, and the use of this technique for measuring formaldehyde in ambient air in the ppb concentration range is projected.

Three methods for measuring formaldehyde (HCHO) in indoor air were evaluated under field and laboratory conditions using different sources and concentrations of formaldehyde in air. Two impinger methods (the chromotropic acid method and modified pararosaniline method) and the Draeger short-term detector tube method (with and without activation tubes) were compared when sampling for formaldehyde from a particleboard box, formalin solution, and a conventional home. Concentrations of formaldehyde ranged from 0.05–0.5 ppm in air. All samples were collected independently using personal sampling pumps and a Draeger bellows pump. The results indicate that the Draeger tube method using an activation tube gives lower results than either of the impinger methods. Without using an activation tube (concentrations >0.5 ppm), the Draeger tube method was comparable to the tow impinger methods. In addition, there are indications that the chromotropic acid method gives different results than the modified pararosaniline method, depending on the source of formaldehyde. The modified pararosaniline method indicated higher results than the chromotropic acid method when sampling from a particleboard box but not from a formalin source. Overall analytical precision for each method of analysis was good.

Determination of ultra-trace formaldehyde in air using ammonium sulfate as derivatization reagent and capillary electrophoresis coupled with on-line electrochemiluminescence detection

A novel method is described for the determination of formaldehyde, with sensitivity enhancement based on the Hantzsch reaction, which involves the cyclization of ammonium, formaldehyde, and 2,4‐pentanedione (PD) in Nash's reagent to form the yellow compound 3,5‐diacetyl‐1,4‐dihydrolutidine (DDL) at pH 6. Silica‐gel beads are added into solution, and the reaction completes within 55 min at room temperature without heating. The silica‐gel beads not only catalyze the reaction process but also increase the sensitivity of the analysis. The proposed method is simple and convenient. The absorbance at 412 nm is proportional to the concentration of formaldehyde over the range of 0.1–2.0 g · mL−1. The detection limit is 0.1 g · mL−1. This method has been applied to the determination of formaldehyde in air with satisfactory results. This paper was invited as a contribution to a special issue of the journal concerning Chemical Spectroscopy in China. It was presented at Sichuan University, Chengdu China, October 17–24, 2003; the 6th International Symposium on Green Chemistry in China.

Improvement of stability and recovery time in porous-silicon-based NO 2 sensor

A highly sensitive gas sensor based on thermal desorption coupled with cataluminescence (TD/CTL) using TiO 2 -Y 2 O 3 (mass ratio 1:3) as a probe was firstly proposed for the determination of formaldehyde in air. Quantitative analysis was performed at an optimal adsorbent of active carbon, thermal desorption temperature of 140 °C, catalytic temperature of 195 °C, a wavelength of 490 nm and a flow rate of 280 mL/min. The linear range of CTL intensity versus concentration of formaldehyde was 0.026–1.30 mg/m 3 ( r = 0.9990, n = 7), and the detection limit (3 σ ) was 0.01 mg/m 3 . There was no or weak response to foreign substances, such as benzene, ethanol, chloroform, carbon tetrachloride, toluene, dimethylbenzene and n -hexane. This proposed formaldehyde gas sensor showed the high sensitivity, rapid response, good stability, and allowed on-line monitoring of formaldehyde in air.

Alkali-modified copper manganite spinel for room temperature catalytic oxidation of formaldehyde in air

Waterfowl are potential long‐distance dispersal vectors for aquatic microbes such as diatoms, but supporting empirical data are scarce, especially concerning external transport on feathers. We conducted an experiment designed to partially emulate diatom dispersal via adherence to waterfowl, and to evaluate the effects of relative humidity (RH) and exposure time on viability. We dipped individual breast feathers from mallards ( Anas platyrhynchos ) in a pure culture of the freshwater diatom Nitzschia pusilla Grunow, then, at room temperature (22.7°C), subjected them to one of four contrasting levels of RH ( c . 8%, 35%, 70%, 88%) crossed with one of four exposure times (10, 60, 120, 240 min) within a chamber through which air was passed continuously, mimicking light wind that might be experienced by diatoms adhered to subsurface feathers. We then gently placed the feather on sterile growth medium. After 2 weeks, we used spectrofluorometry to detect diatom growth and thus diatom viability. We found that exposure time and RH interacted significantly to affect diatom viability: the negative effect of exposure time was strongest under low RH conditions, but under high RH (88%) the probability of being viable was 0.84 for a 10‐min exposure (95% confidence interval: 0.64–0.94), and 0.45 for 4 hr of exposure (95% confidence interval: 0.18–0.75). We combined our experimental findings with geospatial data to predict the probability of potential dispersal via adherence to mallards throughout Nebraska, South Dakota, and North Dakota, which are situated within the central waterfowl migration flyway in North America, and host important mallard breeding grounds. Using published data about: (1) mallard flight speeds; (2) the geographic distribution of surface waters and of N. pusilla ; and (3) vapour pressure deficit (calculated using RH and air temperature) during the months of April and May, our geospatial model predicted high probabilities of potential dispersal, over tens to hundreds of kilometres, among water bodies of the central migration flyway. Taken together, the results of our experiment and geospatial models provide novel insights into ectozoochory of freshwater diatoms, specifically that long‐distance dispersal of diatoms via adherence to waterfowl feathers is highly plausible, particularly during the near‐dawn hours when waterfowl flight activity peaks and vapour pressure deficit is low. Considered alongside previous evidence suggesting successful internal transport by waterfowl, we conclude that, for freshwater diatoms, ectozoochory is likely to be commonplace among waterbodies frequented by waterfowl.

Arc/Arg3.1 is an immediate early gene whose expression is necessary for the late-phase of long-term potentiation (LTP) and memory consolidation. Whereas pathways regulating Arc transcription have been extensively investigated, less is known about the role of post-transcriptional mechanisms in Arc expression. Fluorescence microscopy experiments in cultured hippocampal neurons revealed that Arc protein level was dramatically increased by activation of the cAMP-dependent protein kinase (PKA) pathway, which is implicated in long-term memory. A PKA-dependent increase in Arc protein level was observed after pharmacological or synaptic activation of N-methyl-D-aspartate (NMDA) receptors, which play a critical role in both LTP induction and learning. Arc protein was also up-regulated by activation of PKA through G(s)-coupled dopamine and beta-adrenergic receptors, which regulate the late-phase of LTP and memory. When agonists for the NMDA and G(s)-coupled receptors were co-applied, they had an additive effect on Arc protein expression. Interestingly, G(s)-coupled receptor stimulation was ineffective in the presence of an NMDA receptor antagonist, suggesting calcium influx through the NMDA receptor plays a gating role in this pathway. Stimulation of the cAMP/PKA pathway did not affect Arc mRNA level or protein stability, identifying translational efficacy as the main determinant of Arc protein expression level. It is concluded that efficient Arc translation requires NMDA receptor activity, whereas a further enhancement can be achieved with activation of G(s)-coupled receptors. These experiments have, therefore, revealed remarkable similarities in the signaling pathways that control Arc expression and those that regulate LTP, learning, and memory.

In this work, organic–inorganic hybrids based on nanocrystalline indium oxide and ruthenium (II) heteroleptic complexes were used as sensitive materials for room temperature light-activated NO2 detection. In2O3 was obtained by chemical precipitation method and then annealed at three different temperatures (T = 300, 500, 700 °C) in order to investigate the influence of the microstructure of indium oxide on sensor characteristics of hybrid materials and on kinetics of the rise and fall of photoconductivity. The results of the X-ray phase analysis demonstrated that the obtained materials are single-phase with a cubic bixbyite structure. The Ru (II) heteroleptic complex, which was used as a photosensitizer, made it possible to shift the optical sensitivity range of the hybrids to the low energy region of the spectrum and to use a low-power LED (λmax = 470 nm) source for the photoactivation process. The sensor properties were investigated toward NO2 at sub-ppm range at room temperature. It was found that for pure oxides, the sensor signal correlates with a specific surface area, while for hybrid materials, both the sensor signal and photoresponse increase with increasing the matrix crystallinity. In this case, the main role is played by traps of nonequilibrium charge carriers, which are structural defects in the matrix.

Efficacy of heat against the vaccinia virus, variola virus and monkeypox virus

Background and Aim:The selection and proper application of disinfectants are crucial to the prevention of many diseases, so disinfectants must be evaluated before being used for the prevention of African swine fever (ASF). Three disinfectant products belonging to the group of potassium hydrogen peroxymonosulfates, product A and product B, and a quaternary ammonium compound called product C, were examined in vitro for host cell cytotoxicity and the efficacy of ASF virus inactivation. The study parameters included various concentrations, exposure times, temperatures, and degrees of cytotoxicity.Materials and Methods:Three disinfectant products were evaluated for cytotoxicity using primary porcine alveolar macrophage (PAM) cells at dilutions from 1:200 to 1:51,200. Disinfectants in concentrations of 1:200, 1:400, and 1:800 were prepared, the pH and the virucidal activity were tested. An equal volume of each dilution was mixed with the ASF virus and incubated at room temperature (20°C) or on ice (4°C) for 1 min, 5 min, or 30 min. Hemadsorption (HAD) or rosette formation was observed using an inverted microscope for 5 days after inoculation, and the virus titer was calculated as HAD50/mL. Each treatment and virus control were tested in triplicate, and the titers were reported as means and standard deviations. The reduction factor was used to measure inactivation.Results:Products A, B, and C at 1:400, 1:800, and 1:25,600 of dilution, respectively, did not show significant cytotoxic effects on PAM cells. Products A and B could inactivate ASF virus at 1:200 dilution within 5 min after exposure at 4°C. However, at 20°C, the exposure time had to be extended to 30 min to inactivate the virus. Product C could inactivate the virus at 1:400 dilution within 5 min under both temperature conditions, whereas at 1:800 dilution, the exposure time had to be extended to 30 min to completely inactivate the virus at 20°C.Conclusion:All disinfectants could inactivate ASF virus in various concentrations, under appropriate exposure times and reaction temperatures, and there was no evidence of host cell cytotoxicity. For the control of ASF in pig farms, the appropriate concentration, ambient temperature, and contact time of these disinfectants should be taken into account.

Fabry-Perot interferometers (FPIs), comprising foundry-compatible dielectric thin films on sapphire wafer substrates, were investigated for possible use in chemical sensing. Specifically, structures comprising two vertically stacked distributed Bragg reflectors (DBRs), with the lower DBR between a sapphire substrate and a silicon-oxide (SiO2) resonator layer and the other DBR on top of this resonator layer, were investigated for operation in the near-ultraviolet (near-UV) range. The DBRs are composed of a stack of nitride-rich silicon-nitride (SiNx) layers for the higher index and SiO2 layers for the lower index. An exemplary application would be formaldehyde detection at sub-ppm concentrations in air, using UV absorption spectroscopy in the 300-360 nm band, while providing spectral selectivity against the main interfering gases, notably NO2 and O3. Although SiNx thin films are conventionally used only for visible and near-infrared optical wavelengths (above 450 nm) because of high absorbance at lower wavelengths, this work shows that nitride-rich SiNx is suitable for near-UV wavelengths. The interplay between spectral absorbance, transmittance and reflectance in a FPI is presented in a comparative study between one FPI design using stoichiometric material (Si3N4) and two designs based on N-rich compositions, SiN1.39 and SiN1.49. Spectral measurements confirm that if the design accounts for phase penetration depth, sufficient performance can be achieved with the SiN1.49-based FPI design for gas absorption spectroscopy in near-UV, with peak transmission at 330 nm of 64%, a free spectral range (FSR) of 20 nm and a full-width half-magnitude spectral resolution (FWHM) of 2 nm.