Formaldehyde In Aqueous Solution Research Articles

Selective oxidation of arabinose to arabinonic acid over Pd–Au catalysts supported on alumina and ceria

Selective oxidation of arabinose to arabinonic acid was carried out isothermally in a shaker reactor at moderate conditions of 60°C and pH 8 on Pd–Au catalysts supported on nanosized alumina and ceria. The gold (4wt.%) was supported by deposition–precipitation (DP) using HAuCl4 and urea with subsequent chemisorption of palladium (1wt.%) using PdCl2. Before catalytic tests, samples were treated in hydrogen or oxygen at 300°C, or by aqueous solution of formaldehyde at room temperature. Synthesized bimetallic Pd–Au catalysts are characterized with higher activity in the selective aqueous phase oxidation of arabinose to arabinonic acid by molecular oxygen in comparison with monometallic ones. Activity and selectivity of catalysts depend on the sample treatment and the nature of the support used. Pd–Au/CeO2 catalyst reduced by formaldehyde manifests the highest activity and selectivity. The synthesized bimetallic catalysts have been characterized by TEM, XPS and UV–vis techniques under different stages of sample activation. Mutual interactions of supported gold and palladium species depending on the support nature and sample treatment were observed. A more pronounced interaction between gold and palladium species was observed for Pd–Au/Al2O3 catalyst, while interactions of Au and Pd with reducible ceria coexist with the mutual interaction between these metals. Gold metallic species seem to be responsible for activation of arabinose while an easy redox transformation of Pd species can provoke oxygen activation. Thus, gold species or Au–Pd alloy covered with thin PdO film manifest a synergetic effect in the selective arabinose oxidation by molecular oxygen.

Terbium (III) chelate complexes as fluorescence energy transfer donor in the determination of formaldehyde in aqueous solutions

The sensitized fluorescence intensity of the terbium (III) ion can be notably enhanced in the presence of sodium hexametaphosphate (SHMP). Based on this, water-soluble Tb-SHMP chelate complexes were synthesized in aqueous solutions, and characterized by spectrofluorometry. 6-Mercapto-5-triazole[4,3-b]-S-tetrazine was generated by the quantitative reaction of HCHO with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole under alkaline conditions at room temperature. The spectral overlap between the emission of Tb-SHMP chelate complexes and absorption of 6-mercapto-5-triazole[4,3-b]-S-tetrazine meets the prerequisite for fluorescence energy transfer. Based on this, a novel efficient fluorescence energy transfer system between Tb-SHMP chelate complexes as donor and 6-mercapto-5-triazole[4,3-b]-S-tetrazine as acceptor was developed for the determination of HCHO in aqueous solutions. Under the optimal experimental conditions, this method is capable of detecting HCHO concentrations from 2.06 × 10 −5 to 6.18 × 10 −3 mg mL −1 and the limit of detection was 7.11 × 10 −6 mg mL −1. Compared with other general methods for the determination of HCHO, the proposed method improved the sensitivity and selectivity. Moreover, the proposed method was successfully applied to the determination of HCHO in water samples.

Spectroscopic Properties of Formaldehyde in Aqueous Solution: Insights from Car-Parrinello and TDDFT/CASPT2 Calculations.

We present Car-Parrinello and Car-Parrinello/molecular mechanics simulations of the structural, vibrational, and electronic properties of formaldehyde in water. The calculated properties of the molecule reproduce experimental values and previous calculations. The n → π* excitation energy, calculated with TDDFT and CASPT2, agrees with experimental data. In particular, it shows a blue shift on going from the gas phase to aqueous solution. Temperature and wave function polarization contributions have been disentangled.

System for dosing formaldehyde vapor at the ppb level

Formaldehyde is one of the most relevant compounds for indoor air pollution. It is toxic, allergenic and carcinogenic and acts already at the ppb level. State-of-the-art detection methods are based on the wet chemical analysis of formaldehyde derivates. This is a complex and time-consuming approach and hinders the collection of real-time data. However, the use of wet chemistry allows for the simple calibration based on formalin solutions. By using gas sensors, online monitoring of indoor air quality is, in principle, possible. To find out whether their performance is good enough, calibration is the first issue to be resolved. Formaldehyde vapor at low concentrations has to be used, and temperature, humidity and flow rate have to be kept constant. This paper discusses the different possibilities of dosing formaldehyde and how to better meet the gas sensor calibration demands. The authors favor the use of an aqueous formaldehyde solution obtained by the depolymerization of paraformaldehyde in combination with a permeation tube used as external reference. Moreover, in the paper it is demonstrated that metal oxide sensors are appropriate detectors to calibrate the system for concentrations even down to 20 ppb. Consequently, the presented system is able to characterize gas sensors and can be used for the development of new devices which monitor indoor air quality.

Indoors lead corrosion: Reassessing the role of formaldehyde

The present work is focused on the role of formaldehyde in indoors Pb corrosion, that is still a controversial issue. Pb coupons were exposed to the atmosphere produced by formaldehyde aqueous solutions (1% and 4% in volume) and corrosion was followed by Raman Microscopy. The compounds formed in both experiments were the same, but were not in agreement with previously reported results in the literature, that identified plumbonacrite, hidrocerussite and Pb oxide. The experiments here reported have clearly shown that formates are produced on Pb surfaces exposed to formaldehyde and that oxidants, such as H 2O 2, are not necessary. Formaldehyde oxidation also occurs with powdered PbO in a controlled environment. The Raman spectra of the Pb formates are much more complex than the Pb(HCO 2) 2 spectrum and change when exposed to room conditions, by a slow reaction with CO 2, forming Pb carbonates (hidrocerussite and plumbonacrite mostly) and Pb(HCO 2) 2. Such spectral change may be responsible for the differences in terms of chemical composition of the corrosion layer when the data here reported is compared with the literature. Other factors that must be considered are the storage conditions (particularly relative humidity and CO 2 concentration) and time; the effect of metal composition cannot be discarded as it is well known that the presence of other metals can change significantly the Pb resistance to oxidation.

Sistematização da origem, da distribuição e dos territórios da artéria cerebral caudal na superfície do encéfalo em gatos

Foram estudados 26 encéfalos de gatos, adultos, sem diferenciação de sexo, sem raça definida, corados com látex e fixados por solução aquosa de formaldeído. As artérias cerebrais caudais, direita e esquerda, apresentaram-se únicas em 96,1 e 88,4% dos casos, respectivamente. Em 69,2% dos casos no antímero direito e 80,8% no esquerdo, a artéria cerebral caudal originou-se pela anastomose entre o ramo caudal da artéria carótida interna, com maior contribuição, e o ramo terminal da artéria basilar. Em 88,4% dos casos no antímero direito e em 84,6% no esquerdo, a artéria cerebral caudal originou a artéria tectal rostral e um ramo caudal. O ramo caudal bifurcou-se e vascularizou os colículos rostrais e caudais dos corpos quadrigêmeos e em alguns casos contribuiu na formação do plexo coroide do terceiro ventrículo. A artéria tectal rostral seguiu ventralmente ao lobo piriforme e durante seu trajeto liberou ramos para o hipocampo e, no antímero esquerdo, supriu a superfície dorsal do tálamo, contribuindo para a formação do plexo coroide do terceiro ventrículo.

Origem e distribuição dos nervos isquiáticos do preá

O preá do semiárido nordestino (Galea spixii Wagler, 1831) é um roedor pertencente à família Caviidae. Pouca literatura é encontrada sobre essa espécie em relação a sua morfologia e seu comportamento ambiental e reprodutivo. Com o objetivo de entender a morfologia geral, em foco, na inervação do membro pélvico dessa espécie, neste trabalho, foi explorado o nervo isquiático, o qual é o maior de todos os nervos do organismo. Foram utilizados 10 preás (cinco machos e cinco fêmeas) que vieram a óbito por causas naturais, oriundos do Centro de Multiplicação de Animais Silvestres da Universidade Federal Rural do Semiárido (CEMAS/UFERSA). Os animais foram fixados após o óbito em solução aquosa de formaldeído 10% e, após 48 horas de imersão nessa solução, foram dissecados para exposição do nervo isquiático. Dessa forma, os dados obtidos foram compilados em tabelas e expressos em desenhos esquemáticos e fotografias. Os pares de nervos isquiáticos originaram-se de raízes ventrais de L6L7S1 (70%) e de L7S1S2 (30%) e distribuíram-se pelos músculos glúteo profundo, bíceps femural, semitendinoso e semimembranoso.

Microvirin, a Novel α(1,2)-Mannose-specific Lectin Isolated from Microcystis aeruginosa, Has Anti-HIV-1 Activity Comparable with That of Cyanovirin-N but a Much Higher Safety Profile

Microvirin (MVN), a recently isolated lectin from the cyanobacterium Microcystis aeruginosa PCC7806, shares 33% identity with the potent anti-human immunodeficiency virus (HIV) protein cyanovirin-N (CV-N) isolated from Nostoc ellipsosporum, and both lectins bind to similar carbohydrate structures. MVN is able to inhibit infection by a wide variety of HIV-1 laboratory-adapted strains and clinical isolates of different tropisms and subtypes in peripheral blood mononuclear cells. MVN also inhibits syncytium formation between persistently HIV-1-infected T cells and uninfected CD4(+) T cells and inhibits DC-SIGN-mediated HIV-1 binding and transmission to CD4(+) T cells. Long term passaging of HIV-1 exposed to dose-escalating concentrations of MVN resulted in the selection of a mutant virus with four deleted high mannose-type glycans in the envelope gp120. The MVN-resistant virus was still highly sensitive to various other carbohydrate binding lectins (e.g. CV-N, HHA, GNA, and UDA) but not anymore to the carbohydrate-specific 2G12 monoclonal antibody. Importantly, MVN is more than 50-fold less cytotoxic than CV-N. Also in sharp contrast to CV-N, MVN did not increase the level of the activation markers CD25, CD69, and HLA-DR in CD4(+) T lymphocytes, and subsequently, MVN did not enhance viral replication in pretreated peripheral blood mononuclear cells. Therefore, MVN may qualify as a useful lectin for potential microbicidal use based on its broad and potent antiviral activity and virtual lack of any stimulatory properties and cellular toxicity.

Determination of formaldehyde in formaldehyde‐releaser patch test preparations

Positive patch test reactions to formaldehyde-releasers in patients co-reacting to formaldehyde are often ascribed to formaldehyde allergy. However, the formaldehyde content of patch test materials has not been investigated. To demonstrate and quantify free formaldehyde in commercial patch test materials and in prepared aqueous solutions of formaldehyde releasers. Free formaldehyde was measured by (13)C NMR Spectroscopy in (i) all formaldehyde-releasers in water available from Chemotechnique and Brial, (ii) 5 releasers in petrolatum, (iii) 12 prepared aqueous solutions of formaldehyde-releasers and (iv) water that had been in contact with petrolatum test samples. In none of the five petrolatum test substances was free formaldehyde found. In all nine commercial aqueous patch test substances and 9 of the 12 prepared solutions, free formaldehyde was demonstrated with concentrations ranging from 0.019% to 0.37% (detection limit 0.01%). Contact of the petrolatum test samples with water resulted in the release of formaldehyde. Most aqueous solutions of formaldehyde-releasers contain free formaldehyde. Petrolatum-based patch test materials with formaldehyde-releasers do not contain free formaldehyde, but probably start releasing it upon contact with water. Therefore, in future studies, determination of free and releasable formaldehyde may be preferable.

Hydroxymethylation of rhodanine

Rhodanine in alcohol solution reacts with formaldehyde aqueous solution to form 3-hydroxymethylrhodanine. In the presence of triethylamine occurred also bis-hydroxymethylation at 5 position of the thiazolidine ring, but we failed to isolate the 3,5,5-trishydroxymethyl derivative in an individual form. The treatment of crude rhodanine 3,5,5-trishydroxymethyl derivative with benzaldehyde in boron trifluoride etherate leads to thioxo-8-phenyl-7,9-dioxa-1-thia-3-azaspiro[4.5]decan-4-one. The dissolution of the latter in aqueous alkali followed by neutralization with acid gives 5-sulfanyl-2-phenyl-1,3-dioxane-5-carboxylic acid.

Acid-base properties and stability of sulfoxylic acid in aqueous solutions

A comparative study of decomposition of sulfoxylic acid S(OH) 2 and sulfoxylate anion and their reactions with formaldehyde in aqueous solutions with different acidity was carried out. Using the obtained results, the pK1 value of S(OH) 2 was determined for the first time.

Determination of formaldehyde in aqueous solutions by a novel fluorescence energy transfer system

An efficient fluorescence energy transfer (FET) system between CePO(4):Tb(3+) nanocrystals as donor and 6-mercapto-5-triazole[4,3-b]-S-tetrazine as acceptor was built. CePO(4):Tb(3+) nanocrystals were synthesized in aqueous solutions, and characterized by transmission electron microscopy, electron diffraction pattern spectroscopy and spectrofluorometry. Under alkaline conditions, 6-mercapto-5-triazole[4,3-b]-S-tetrazine was generated by redox reaction of formaldehyde (HCHO) with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT) at room temperature. The degree of the overlap was effective for FET between the emission spectrum of CePO(4):Tb(3+) and the absorption spectrum of 6-mercapto-5-triazole[4,3-b]-S-tetrazine. Based on this system, a simple and sensitive fluorescence method for the selective determination of formaldehyde in aqueous solutions was developed. Under optimal conditions, the quenched fluorescence intensity increased linearly with the concentration of HCHO ranging from 1.03 x 10(-9) to 1.03 x 10(-5) mg mL(-1) with a correlation coefficient of 0.9976. The limit of detection was 1.65 x 10(-10) mg mL(-1). Compared with several methods, the proposed method had a wider linear range, higher selectivity and sensitivity. Moreover, analytical application of the method was demonstrated by water samples.

Stabilization by meglumine of an amine compound degraded by formaldehyde in tablets

[3-[(2R)-[[(2R)-(3-Chlorophenyl)-2-hydroxyethyl]amino]proryl]-1 H-indol-7-yloxy]acetic acid (AJ-9677), which was being developed as an antidiabetic, was observed to degrade in tablet preparations. The main degradation product in tablets, AD-9889, was a carbon adduct of the drug substance. When the drug substance was exposed to formaldehyde in aqueous solutions, a correlation was found between the level of formaldehyde and the quantity of AD-9889 formed during storage. Comprehensive one- and two-dimensional NMR analysis of the reaction product identified the location of the carbon atom which originated from formaldehyde, thus proving that AD-9889 was produced by a reaction with formaldehyde. Since it was demonstrated in our previous report that meglumine is an amine that can react with, and reduce amounts of formaldehyde, its stabilizing effect on AJ-9677 was examined. The results showed that in a solution system containing AJ-9677, formaldehyde and meglumine, meglumine reduced formaldehyde levels and suppressed degradation. Addition of meglumine into the tablet formulation of AJ-9677 was also effective in suppressing degradation and successfully stabilized the drug substance. This effect was almost certainly due to meglumine absorbing formaldehyde from around the drug substance and we believe that meglumine can be used with many other drug substances degraded by formaldehyde.

Porous characteristics of carbon-coated silica gel beads prepared by liquid phase deposition of organic colloidal nanoparticles

Carbon-coated silica gel beads could be prepared by immersing porous silica gel beads in a resorcinol–formaldehyde (RF) aqueous solution and then following by drying and pyrolysis in nitrogen atmosphere. With the proposed method, deposition of colloidal nanoparticles formed during the sol–gel polycondensation of the RF solution was successfully prepared on the mesopores of the silica gel beads. Both size and concentration of the colloidal particles could be controlled by the gelation time and the mixing ratio (V EtOH /V RF ) of the RF solution to ethanol. The porous characteristics of the prepared carbon-coated silica gel beads and the amounts of deposited carbon could be controlled by changing V EtOH /V RF. Without any significant decrease in mesoporosity, the maximal carbon contents of carbon-coated silica gel beads could be increased up to 18 wt% in the inner part and 53 wt% on the outer surface, respectively.

Synthesis, Characterization, and Electrochemistry of a Series of Iron(II) Complexes Containing Self-Assembled 1,5-Diaza-3,7-diphosphabicyclo[3.3.1]nonane Ligands

The reaction between PPh(CH(2)OH)(2), iron(II) sulfate, ammonium sulfate, and formaldehyde in aqueous solution gives the iron(II) complex [Fe(kappa(2)-O(2)SO(2))L(2)] (1), where L is the bidentate phosphine ligand 3,7-diphenyl-1,5-diaza-3,7-diphosphabicyclo[3.3.1]nonane. During the course of the reaction, the ligand L self-assembles on the metal center. The reaction between PPh(CH(2)OH)(2), iron(II) chloride, ammonium chloride, and formaldehyde under similar conditions gives cis-[FeCl(2)L(2)] (cis-2). The complex cis-2 is converted into trans-2 in Et(2)O, whereas in water it is converted into cis-[Fe(OH(2))(2)L(2)](2+), though both of these interconversions are reversible. The chloro ligands in cis-2 are readily displaced by reaction with thiocyanate, azide, and carbonate to give cis- and trans-[Fe(NCS)(2)L(2)] (cis- and trans-3), cis- and trans-[Fe(N(3))(2)L(2)] (cis- and trans-4), and [Fe(kappa(2)-O(2)CO)L(2)] (5), respectively. The complex cis-2 reacts with CO in water to give trans-[FeCl(CO)L(2)]Cl (trans-6), whereas trans-2 reacts with CO in diethyl ether to give cis-[FeCl(CO)L(2)]Cl (cis-6), though cis-6 isomerizes in water to form trans-6. The reaction of cis-2 with sodium borohydride gives the hydride chloride complex trans-[FeCl(H)L(2)] (7). Electrochemical studies have been undertaken on complexes 1, cis-2, and 7. These reveal reversible oxidations for cis-2 and 7, with the latter giving rise to an unusual 17-electron iron(III) hydride chloride complex. Crystal structures have been obtained for 1, trans-2, trans-3, 5, and 7.

Carbon nanotubes based electrochemical biosensor for detection of formaldehyde released from a cancer cell line treated with formaldehyde-releasing anticancer prodrugs

This paper reports the development of an electrochemical biosensor for the detection of formaldehyde in aqueous solution, based on the coupling of the enzyme formaldehyde dehydrogenase and a carbon nanotubes (CNT)-modified screen-printed electrode (SPE). We monitored the amperometric response to formaldehyde released from U251 human glioblastoma cells situated in the biosensor chamber in response to treatment with various anticancer prodrugs of formaldehyde and butyric acid. The current response was higher for prodrugs that release two molecules of formaldehyde (AN-193) than for prodrugs that release only one molecule of formaldehyde (AN-1, AN-7). Homologous prodrugs that release one (AN-88) or two (AN-191) molecules of acetaldehyde, showed no signal. The sensor is rapid, sensitive, selective, inexpensive and disposable, as well as simple to manufacture and operate.

Membrane permeation continuous‐flow isotope ratio mass spectrometry for on‐line carbon isotope ratio determination

Gaseous membrane permeation (MP) technologies have been combined with continuous-flow isotope ratio mass spectrometry for on-line delta13C measurements. The experimental setup of membrane permeation-gas chromatography/combustion/isotope ratio mass spectrometry (MP-GC/C/IRMS) quantitatively traps gas streams in membrane permeation experiments under steady-state conditions and performs on-line gas transfer into a GC/C/IRMS system. A commercial polydimethylsiloxane (PDMS) membrane sheet was used for the experiments. Laboratory tests using CO2 demonstrate that the whole process does not fractionate the C isotopes of CO2. Moreover, the delta13C values of CO2 permeated on-line give the same isotopic results as off-line static dual-inlet IRMS delta13C measurements. Formaldehyde generated from aqueous formaldehyde solutions has also been used as the feed gas for permeation experiments and on-line delta13C determination. The feed-formaldehyde delta13C value was pre-determined by sampling the headspace of the thermostated aqueous formaldehyde solution. Comparison of the results obtained by headspace with those from direct aqueous formaldehyde injection confirms that the headspace sampling does not generate isotopic fractionation, but the permeated formaldehyde analyzed on-line yields a 13C enrichment relative to the feed delta13C value, the isotopic fractionation being 1.0026 +/- 0.0003. The delta13C values have been normalized using an adapted two-point isotopic calibration for delta13C values ranging from -42 to -10 per thousand. The MP-GC/C/IRMS system allows the delta13C determination of formaldehyde without chemical derivatization or additional analytical imprecision.

Preparation of platinum nanoparticles on polyaniline-coat multi-walled carbon nanotubes for adsorptive stripping voltammetric determination of formaldehyde in aqueous solution

Platinum nanoparticles on polyaniline-coat multi-walled carbon nanotubes were fabricated by electrochemical method at paraffin-impregnated graphite electrode (Pt/PAN/MWCNTs). The material was characterized by various methods including field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. The electrode has been effectively applied toward formaldehyde (HCHO) sensing. A good linear response curves from 1 × 10−9 to 1 × 10−3 M can be obtained with a lower detection limit of 4.6 × 10−11 M (S/N 3). The successful preparation of nanocomposites opens a new path to fabricate the promising sensor for HCHO.

Photografting of acrylic acid and methacrylic acid onto polyolefines initiated by formaldehyde in aqueous solutions

AbstractFormaldehyde aqueous solution can act as an effective photoinitiating system for water‐borne photografting. The photografting of acrylic acid (AA) and methacrylic acid (MAA) onto high‐density polyethylene (HDPE), low‐density polyethylene (LDPE) and polypropylene (PP) initiated by formaldehyde aqueous solutions has been reported. The effects of formaldehyde content and monomer concentration on grafting varied with the polymeric substrates and monomers used. For the grafting of AA onto HDPE, the extent of grafting increased with increasing formaldehyde content in the solution, monomer concentration had a little effect on grafting. Whereas for the grafting of MAA onto HDPE, the grafting performed in 8% formaldehyde aqueous solution lead to the highest extent of grafting, the extent of grafting increased with monomer concentration till 2.5 mol/L. MAA was easier to be grafted onto the polyolefins than AA. The easiness of grafting occurring on the polyolefins was in a decreasing order of LDPE > HDPE > PP. Qualitative and semi‐quantitative Fourier transform infrared (FTIR) characterizations of the grafted samples were performed. For both grafted LDPE and PP samples, at the same irradiation time, the carbonyl index of the samples grafted with MAA was higher than that grafted with AA. The FTIR results are in accord with the results obtained by gravimetric method. The water absorbency of the grafted samples increased almost linearly with the extent of grafting. The PE films grafted with AA adsorbed more water than those grafted with MAA. This study had broadened the water‐borne initiating system for photografting. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Anatomia dos ramos linguais do nervo hipoglosso em <em>Sus scrofa domesticus</em>, L., 1758

We studied the ramifications and distribution of the hypoglossal nerve after it penetrated the root of the tongue (36 antimeres) of adult swines (Sus scrofa domestica, L. 1758) from both sexes slaughtered in frigorific (metropolitan region of Goiânia, Goiás - Brazil). The material was chilled for transportation (4°C); placed in aqueous solution of formaldehyde (7%) for 72 hours; submerged in aqueous solution of nitric acid (15%) for 72 hours; dissected under magnifying glass (RASOR, II-20). The trunk and the primary, secondary and tertiary nervous branches were observed in the antimeres (method of Bittencourt et al., 1987). We followed the topography of the nerve starting from the posterior mandibular region between the myofascial structures of the mylohyoid and hypoglossal. On the root of the tongue the nerve crosses the lingual artery, becoming medial in relationship to the latter. It subdivides into three orders of dimension towards the superior longitudinal muscle as follows: left antimere, 4 to 13 primary branches, 4 to 21 secondary branches and 0 to 16 tertiary branches; on the right antimere, 8 to 18 primary branches, 3 to 13 secondary branches and 0 to 12 tertiary branches. In 27.59% of the analyzed antimeres, the branches of the hypoglossal nerve established joints with fibers from the lingual nerve of the correspondent antimere.