Influence of drying methods on the structure and properties of cellulose formate and its application as a reducing agent.

Cellulose formate (CF) with surface formyl groups can be prepared through the esterification between cellulose and formic acid (FA). The properties of CF are sensitive to temperature, which is of great importance for its end application. In this work, the effect of four drying methods on the structure and properties of the resultant CF was investigated. Results showed that the CF samples as special cellulose nanofibrils with cellulose II crystal form and fibrous structure were sensitive to drying temperature and drying time. The freeze-dried CF sample maintained its original structure, while the air-dried and oven-dried CF samples with amorphous structure showed the aggregation state. Furthermore, the CF/Ag composites were prepared using silver mirror reaction where the never dried CF was used as a reducing agent. SEM and TEM images exhibited a large number of Ag nanoparticles with the diameter of 20-50 nm on the surface of CF samples. As expected, the fabricated CF/Ag composites showed strong antibacterial activity against both Escherichia coli and Bacillus subtilis, and thus the prepared composites have great potential applications in antibacterial daily necessities and medical supplies.

Covalently-bonded hyperbranched poly(styrene-divinylbenzene)-based anion exchangers for ion chromatography.

A number of covalently-bonded hyperbranched poly(styrene-divinylbenzene)-based (PS-DVB) anion exchangers having functional ion exchange layers of different branching degrees are prepared and investigated. The attachment of the hyperbranched functional layers to the substrate surface is realized via anchor secondary amino groups inserted into the polymeric backbone by means of acylation with acetic anhydride followed by reductive amination with methylamine. Further modification of the obtained secondary amino groups is provided by repeating the steps of alkylation with 1,4-butanediol diglycidyl ether (1,4-BDDGE) and amination of the terminal epoxide rings with methylamine (MA). The variation of the number of cycles including modification with 1,4-BDDGE and MA results in selectivity alterations for the obtained anion exchangers. Chromatographic parameters of the obtained stationary phases are evaluated using the model mixtures of anions (F-, HCOO-, Cl-, EtCOO-, BrO3-, NO2-, Br-, NO3-, SO42-, PO43-) with hydroxide and carbonate/bicarbonate eluents. The anion exchangers show the increase of NO2-/EtCOO- and NO2-/BrO3- selectivity and the decrease of EtCOO-/Cl- selectivity with increasing the number of modification cycles. In case of anion exchanger obtained after three modification cycles, the calculated values of column efficiencies for polarizable NO2- and Br- are up to 18,000 and 16,000N/m, respectively.

Selective conversion of organic pollutant p-chlorophenol to formic acid using zeolite Fenton catalyst.

Effective remediation technologies which can converse the harmful organic pollutants to high-value chemicals are crucial both for wastewater treatment and energy regeneration. This study provides an evidence that extracting useful chemicals from wastewater is feasible through selective conversion of p-chlorophenol to high value formic acid as an example. The reported system works with a readily available Fe-containing ZSM-5 catalyst, water as the solvent and hydrogen peroxide as the oxidant. The yield of formic acid reached up to 50.7% when the Si/Al ratio of ZSM-5 was 80 and the Fe-content was 1.4%. By X-ray adsorption fine structure (XAFS), NH3 temperature-programmed desorption (NH3-TPD) technique, the pyridine adsorption Fourier-transition infrared (Py-IR) spectroscopy and adsorption measurements, it was concluded that the controllable degradation of p-CP could be approached through selective adsorption, the moderate Brønsted acid sites for H2O2 activation and the properly selective conversion control due to extra-framework coordination unsaturated sites (CUS) of Fe. This approach might provide a new avenue for the field of organic pollutant remediation.

In-line coupling of microextractions across polymer inclusion membranes to capillary zone electrophoresis for rapid determination of formate in blood samples.

Polymer inclusion membranes (PIMs) have several important features, i.e., PIMs are dry and non-porous membranes, which can be prepared ahead of use and stored without noticeable deterioration in extraction performance. In this contribution, in-line coupling of microextractions across PIMs to a separation method for clinical purposes was demonstrated for the first time. Formate (the major metabolite in methanol poisoning) was determined in undiluted human serum and whole blood by capillary zone electrophoresis (CZE) with simultaneous capacitively coupled contactless conductivity detection (C(4)D) and UV-Vis detection. A purpose-made microextraction device with PIM was coupled to a commercial CZE instrument in order to ensure complete automation of the entire analytical procedure, i.e., of formate extraction, injection, CZE separation and quantification. PIMs for formate extractions consisted of 60% (w/w) cellulose triacetate as base polymer and 40% (w/w) Aliquat™ 336 as anion carrier. The method was characterized by good repeatability of peak areas (≤7.0%) and migration times (≤0.8%) and by good linearity of calibration curves (r(2) = 0.993-0.999). Limits of detection in various matrices ranged from 15 to 54 µM for C(4)D and from 200 to 635 µM for UV-Vis detection and were sufficiently low to clearly distinguish between endogenous and toxic levels of formate in healthy and methanol intoxicated individuals. In addition, PIMs proved that they may act as phase interfaces with excellent long-term stability since once prepared, they retained their extractions properties for, at least, two months of storage.

Electro-biocatalytic production of formate from carbon dioxide using an oxygen-stable whole cell biocatalyst.

The use of biocatalysts to convert CO2 into useful chemicals is a promising alternative to chemical conversion. In this study, the electro-biocatalytic conversion of CO2 to formate was attempted with a whole cell biocatalyst. Eight species of Methylobacteria were tested for CO2 reduction, and one of them, Methylobacterium extorquens AM1, exhibited an exceptionally higher capability to synthesize formate from CO2 by supplying electrons with electrodes, which produced formate concentrations of up to 60mM. The oxygen stability of the biocatalyst was investigated, and the results indicated that the whole cell catalyst still exhibited CO2 reduction activity even after being exposed to oxygen gas. From the results, we could demonstrate the electro-biocatalytic conversion of CO2 to formate using an obligate aerobe, M. extorquens AM1, as a whole cell biocatalyst without providing extra cofactors or hydrogen gas. This electro-biocatalytic process suggests a promising approach toward feasible way of CO2 conversion to formate.

Antimicrobial activity of secondary metabolites from Streptomyces sp. K15, an endophyte in Houttuynia cordata Thunb.

We isolated Streptomyces sp. K15 from the root tissue of Houttuynia cordata Thunb and found that some of its secondary metabolites exhibited significant antimicrobial activity against Botrytis cinerea. Moreover, we separated, purified and identified the major active ingredient to be 2-pyrrol formic acid by using silica gel column chromatography, high-performance liquid chromatography and NMR analysis of the spectral data. 2-Pyrrol formic acid critically inhibited the growth of some phytopathogenic bacteria. Therefore, it has potential value in agricultural applications.

Contaminant degradation by irradiated semiconducting silver chloride particles: kinetics and modelling.

The kinetics and mechanism of light-mediated formic acid (HCOO(-)) degradation in the presence of semiconducting silver chloride particles are investigated in this study. Our experimental results show that visible-light irradiation of AgCl(s) results in generation of holes and electrons with the photo-generated holes and its initial oxidation product carbonate radical, oxidizing HCOO(-) to form CO2. The HCOO(-) degradation rate increases with increase in silver concentration due to increase in rate of photo-generation of holes while the increase in chloride concentration decreases the degradation rate of HCOO(-) as a result of the scavenging of holes by Cl(-), thereby resulting in decreased holes and carbonate radical concentration. The results obtained indicate that a variety of other solution conditions including dioxygen concentration, bicarbonate concentration and pH influence the availability of holes and hence the HCOO(-) degradation rate in a manner consistent with our understanding of key processes. Based on our experimental results, we have developed a kinetic model capable of predicting AgCl(s)-mediated HCOO(-) photo-degradation over a wide range of conditions.

Optimal design and experimental validation of a simulated moving bed chromatography for continuous recovery of formic acid in a model mixture of three organic acids from Actinobacillus bacteria fermentation.

The economically-efficient separation of formic acid from acetic acid and succinic acid has been a key issue in the production of formic acid with the Actinobacillus bacteria fermentation. To address this issue, an optimal three-zone simulated moving bed (SMB) chromatography for continuous separation of formic acid from acetic acid and succinic acid was developed in this study. As a first step for this task, the adsorption isotherm and mass-transfer parameters of each organic acid on the qualified adsorbent (Amberchrom-CG300C) were determined through a series of multiple frontal experiments. The determined parameters were then used in optimizing the SMB process for the considered separation. During such optimization, the additional investigation for selecting a proper SMB port configuration, which could be more advantageous for attaining better process performances, was carried out between two possible configurations. It was found that if the properly selected port configuration was adopted in the SMB of interest, the throughout and the formic-acid product concentration could be increased by 82% and 181% respectively. Finally, the optimized SMB process based on the properly selected port configuration was tested experimentally using a self-assembled SMB unit with three zones. The SMB experimental results and the relevant computer simulation verified that the developed process in this study was successful in continuous recovery of formic acid from a ternary organic-acid mixture of interest with high throughput, high purity, high yield, and high product concentration.

A simple complex on the verge of breakdown: isolation of the elusive cyanoformate ion.

Why does cyanide not react destructively with the proximal iron center at the active site of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase, an enzyme central to the biosynthesis of ethylene in plants? It has long been postulated that the cyanoformate anion, [NCCO2](-), forms and then decomposes to carbon dioxide and cyanide during this process. We have now isolated and crystallographically characterized this elusive anion as its tetraphenylphosphonium salt. Theoretical calculations show that cyanoformate has a very weak C-C bond and that it is thermodynamically stable only in low dielectric media. Solution stability studies have substantiated the latter result. We propose that cyanoformate shuttles the potentially toxic cyanide away from the low dielectric active site of ACC oxidase before breaking down in the higher dielectric medium of the cell.

Separation of oxalate, formate and glycolate in human body fluid samples by capillary electrophoresis with contactless conductometric detection.

A new method for rapid determination of toxic metabolites after methanol and ethylene glycol intoxication - oxalate, formate and glycolate in various body fluid samples (blood serum, saliva, urine, exhaled breath condensate) by capillary electrophoresis with contactless conductometric detection was developed. A selective separation of the three target analytes from other constituents present in the analyzed biological matrices was achieved in less than 6min in a fused silica capillary of 25µm I.D. using an electrolyte comprising 50mM l-histidine and 50mM 2-(N-morpholino)ethanesulfonic acid at pH 6.1. The only sample preparation was dilution with deionized water. The limits of detection were 0.4, 0.6 and 1.3µM and limits of quantitation 1.3, 1.9 and 4.2µM for oxalate, formate and glycolate, respectively. The method provides a simple and rapid diagnostic test in suspected intoxication and is able to distinguish the ingested liquid, based on its metabolite trace. The method presents a fast screening tool that can be applicable in clinical practice.

Orthoformimycin, a selective inhibitor of bacterial translation elongation from Streptomyces containing an unusual orthoformate.

Upon high throughput screening of 6700 microbial fermentation extracts, we discovered a compound, designated orthoformimycin, capable of inhibiting protein synthesis in vitro with high efficiency. The molecule, whose structure was elucidated by chemical, spectrometric, and spectroscopic methods, contains an unusual orthoformate moiety (hence the name) and belongs to a novel class of translation inhibitors. This antibiotic does not affect any function of the 30S ribosomal subunit but binds to the 50S subunit causing inhibition of translation elongation and yielding polypeptide products of reduced length. Analysis by fluorescence stopped flow kinetics revealed that EF-G-dependent mRNA translocation is inhibited by orthoformimycin, whereas, surprisingly, translocation of the aminoacyl-tRNA seems to be unaffected.

Needle trap extraction for GC analysis of formic and acetic acids in aqueous solution.

Formic and acetic acids are ubiquitous in the environment, food, and most of the natural products. Extraction of the acids from aqueous solution is required for their isotope analysis by the gas chromatography-isotope ratio mass spectrometry. To this objective, we have previously developed a purge-and-trap technique using the dynamic solid-phase microextraction technology, the NeedlEX. The extraction efficiency, however, remains unexamined. Here, we address this question using the flame ionization detector and isotope ratio mass spectrometer while comparing it with that of the CAR/PDMS fiber. The results show that the NeedlEX is applicable at a wide range of concentration through coordination of purge volume given the minimum amount 3.7 ng and 1.8 ng of formic and acetic, respectively, is extracted. The efficiency of NeedlEX was 6-7 times lower than the fiber at 1000 µg/mL depending on the analyte. It is, however, superior to the latter at 10 µg/mL or less owing to its lower detection limit. The extraction efficiency of both acids is equivalent in molar amount. This is, however, disguised by the different response of the flame ionization detector. The isotope ratio mass spectrometor overcomes this problem but is compromised by relatively large errors. These results are particularly useful for isotopic analysis of carboxylic acids.

Conformation resolved induced infrared activity: trans- and cis-formic acid isolated in solid molecular hydrogen.

We report combined experimental and theoretical studies of infrared absorptions induced in solid molecular hydrogen by different conformers of formic acid (HCOOH, FA). FTIR spectra recorded in the H(2) fundamental region (4120-4160 cm(-1)) reveal a number of relatively strong trans-FA induced Q-branch absorptions that are assigned by studying both FA-doped parahydrogen (pH(2)) and normal hydrogen (nH(2)) samples. The induced H(2) absorptions are also studied for HCOOD doped nH(2) crystals for both the trans and cis conformers that show resolvable differences. Samples containing >90% of the higher energy cis-HCOOD conformer are produced by in situ IR pumping of the OD stretching overtone of trans-HCOOD using narrow-band IR light. Minimum energy structures for 1:1 complexes of H(2) and FA are determined using ab initio methods. The measured differences in the cis- versus trans-HCOOD induced spectra are in qualitative agreement with the frequencies and intensities calculated for the identified cluster structures as discussed in terms of the model of specific interactions.

Versatile microanalytical system with porous polypropylene capillary membrane for calibration gas generation and trace gaseous pollutants sampling applied to the analysis of formaldehyde, formic acid, acetic acid and ammonia in outdoor air.

The analytical determination of atmospheric pollutants still presents challenges due to the low-level concentrations (frequently in the µg m(-3) range) and their variations with sampling site and time. In this work, a capillary membrane diffusion scrubber (CMDS) was scaled down to match with capillary electrophoresis (CE), a quick separation technique that requires nothing more than some nanoliters of sample and, when combined with capacitively coupled contactless conductometric detection (C(4)D), is particularly favorable for ionic species that do not absorb in the UV-vis region, like the target analytes formaldehyde, formic acid, acetic acid and ammonium. The CMDS was coaxially assembled inside a PTFE tube and fed with acceptor phase (deionized water for species with a high Henry's constant such as formaldehyde and carboxylic acids, or acidic solution for ammonia sampling with equilibrium displacement to the non-volatile ammonium ion) at a low flow rate (8.3 nL s(-1)), while the sample was aspirated through the annular gap of the concentric tubes at 2.5 mL s(-1). A second unit, in all similar to the CMDS, was operated as a capillary membrane diffusion emitter (CMDE), generating a gas flow with know concentrations of ammonia for the evaluation of the CMDS. The fluids of the system were driven with inexpensive aquarium air pumps, and the collected samples were stored in vials cooled by a Peltier element. Complete protocols were developed for the analysis, in air, of NH(3), CH(3)COOH, HCOOH and, with a derivatization setup, CH(2)O, by associating the CMDS collection with the determination by CE-C(4)D. The ammonia concentrations obtained by electrophoresis were checked against the reference spectrophotometric method based on Berthelot's reaction. Sensitivity enhancements of this reference method were achieved by using a modified Berthelot reaction, solenoid micro-pumps for liquid propulsion and a long optical path cell based on a liquid core waveguide (LCW). All techniques and methods of this work are in line with the green analytical chemistry trends.

Degradation of a mixture of pollutants in water using the UV/H2O2 process.

The degradation reaction of a simple mixture of pollutants (dichloroacetic acid + formic acid) employing H2O2 and UVC radiation (253.7 nm) has been studied in a well-mixed reactor which operates inside a recycling system. The aim of this work is to develop a systematic methodology for treating degradation of mixtures of pollutants, starting from a rather manageable system to more complex aggregates. In this contribution, the effects of different variables such as hydrogen peroxide/pollutant mixture initial concentration ratio, pH and incident radiation at the reactor wall were studied. The results show that the best degrading conditions are: pH = 3.5 and hydrogen peroxide concentrations from 3.9 to 11.8 mM (134-400 mg/L), for initial concentrations of 1.10 and 0.39 mM for formic acid and dichoroacetic acid respectively (50 mg/L for both pollutants). The influence of the incident radiation at the reactor wall on the degradation rates of the mixture is significant. In addition to this, it has been shown that in the employed aqueous solution no stable reaction intermediates are formed. On this basis, a complete reaction scheme for the mixture is proposed that is suitable for a reaction kinetics mathematical modeling of the mixture and further studies of increasing complexity.

Formate-nitrite transporters: optimisation of expression, purification and analysis of prokaryotic and eukaryotic representatives.

The formate-nitrite transporter family is composed of integral membrane proteins that possess six to eight alpha-helical transmembrane domains. Genes encoding these proteins are observed widely in prokaryotic genomes as well as certain groups of lower eukaryotes. Thus far, no structural information is available for this transporter family. Towards this aim, and to provide protein for biophysical studies, overexpression of a prokaryotic (TpNirC, from the hyperthermophilic archaebacterium Thermofilum pendens) and an eukaryotic (AnNitA, from the fungus Aspergillus nidulans) representative was achieved in Escherichia coli and Pichia pastoris hosts, respectively. The proteins were purified to >95% homogeneity yielding quantities sufficient for crystallisation trials and were shown by Circular Dichroism (CD) spectroscopy to have a highly alpha-helical content as expected from in silico predictions. Preliminary investigations by size exclusion chromatography of the oligomeric state of the purified AnNitA protein suggested that it most likely exists as a tetramer.

Environmentally benign methanolysis of polycarbonate to recover bisphenol A and dimethyl carbonate in ionic liquids.

An environmentally friendly strategy for methanolysis of polycarbonate (PC) to recover bisphenol A (BPA) and dimethyl carbonate (DMC) was developed in which PC could be methanolyzed in an ionic liquid without any acid or base catalyst under moderate conditions. The effects of ionic liquid kinds, temperature, time, and methanol dosage on methanolysis results of PC were examined. It was showed that the methanolysis conversion of PC was almost 100% and the yields of both BPA and DMC were over 95% in presence of ionic liquid 1-n-butyl-3-methylimidazolium chloride ([Bmim][Cl]) and under the conditions of m(PC):m(CH(3)OH):m([Bmim][Cl])=2:3:2, reaction temperature 105 degrees C and time 2.5h. After easily separated from the product, the ionic liquid could be reused 8 times without obvious decrease in the conversion of PC and yields of BPA and DMC.

Extraction of formic and acetic acids from aqueous solution by dynamic headspace-needle trap extraction temperature and pH optimization.

A combined method of dynamic headspace-needle trap sample preparation and gas chromatography for the determination of formic and acetic acids in aqueous solution was developed in this study. A needle extraction device coupled with a gas aspirating pump was intended to perform sampling and preconcentration of target compounds from aqueous sample before gas chromatographic analysis. The needle trap extraction (NTE) technique allows for the successful sampling of short chain fatty acids under dynamic conditions while keeping the headspace (HS) volume constant. Two important parameters, including extraction temperature and effect of acidification, have been optimized and evaluated using the needle trap device. The method detection limits for the compounds estimated were 87.2microg/L for acetic acid and 234.8microg/L for formic acid in spite of the low flame ionization detection response for formic acid and its low Henry's law constant in aqueous solution. Precision was determined based on the two real samples and ranged between 4.7 and 10.7%. The validated headspace-needle trap extraction method was also successfully applied to several environmental samples.

Purification of pharmaceutical excipients with supercritical fluid extraction.

Supercritical fluid extraction (SFE), with carbon dioxide as the solvent, was tested for its ability to remove common reactive impurities from several pharmaceutical excipient powders including starch, microcrystalline cellulose (MCC), hydroxypropylcellulose (HPC), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP). Extraction of the small molecule impurities, formic acid and formaldehyde, was conducted using SFE methods under conditions that did not result in visible physical changes to polymeric excipient powders. It could be shown that spiked, largely surface-bound, impurities could be removed effectively; however, SFE could only remove embedded impurities in the excipient particles after significant exposure times due to slow diffusion of the impurities to the particle surfaces. Attempts at hydrogen peroxide extraction were hindered by its low solubility in CO2, thereby effectively precluding SFE for removal of hydrogen peroxide from excipients. This work suggests that SFE will only be commercially useful for removal of low molecular weight impurities in polymeric excipients when migration of the impurities to the particle surfaces is sufficiently rapid for extraction to be completed in a reasonable time frame.