Aqueous Ammonium Hydroxide Research Articles

Efficient Elimination of Matrix Effects for the Rapid Screening of β-Agonist Residues in Porcine Urine by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS)

An efficient and innovative clean-up method was developed for the rapid screening of β-agonists residues in porcine urine by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). 1% Aqueous ammonium hydroxide was shown to be effective for the removal of matrix components as a wash step in solid phase extraction (SPE). A significant reduction in matrix effects was observed with values from 81% to 108%. Furthermore, under the optimized conditions, the recoveries of all analytes at 0.3, 0.6, and 3.0 μg/L ranged from 70.1% to 109.0% when employing the external standard method for quantitative analysis, rather than relying on matrix-matched standards or isotope-labelled internal standards to mitigate matrix effects. The limits of detection (LOD) and limits of quantification (LOQ) were 0.1 μg/L and 0.3 μg/L, respectively. This method has been successfully applied to screen β-agonists in porcine urine and is a promising tool for multi-residue analysis.

Annealing temperature induced micro-structural, opto-electronic, electrical and fluorescence properties of the sol–gel synthesized CdO nanoparticles through the analytical study of vacancy-type defects

Cadmium oxide (CdO) nanoparticles (NPs) have been synthesized through the simple sol–gel route using cadmium nitrate tetrahydrate and aqueous ammonium hydroxide as precursors. Synthesised products were annealed at different temperatures in the range of 250 °C–500 °C. The annealed samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Selected area electron diffraction (SAED), Field emission scanning electron microscopy (FESEM), UV–visible absorption (UV–Vis), room temperature Fluorescence (FL) measurements, Positron annihilation lifetime spectroscopic measurements (PALS) and resistivity measurements. Through the utilization of XRD method, it was shown that the particle size varies from 15 nm to 35 nm and unit cell volume exhibit an increase, while the lattice strain decreases as the annealing temperature is raised. The interplanar distance reduces as temperature increases, and the presence of defects can explain the minimal fluctuation in lattice characteristics. There is an inverse relationship between lattice strain and dislocation density of the pristine CdO NPs. The Williamson-Hall (W-H) analysis demonstrated a decrease in compressive lattice strain as particle sizes increased. The TEM and FESEM techniques were used to analyze the nearlyspherical morphological characteristics of CdO NPs, and thesize-related XRD results were further supported by the histogram plots from TEM. UV–Vis spectroscopy revealed that the band gap energy drops from 4.02 eV to 3.33 eV as the particle size increases, which may be attributed to the quantum confinement effect and the presence of defect states in the energy band gap. The distinct emission peaks of CdO NPs are detected in the fluorescence spectra at the wavelengths 488 nm, 529 nm and 584 nm. These findings indicate a modest correlation between the emission bands and the energy band gap. The strength of the emission peaks has been amplified as the annealing temperature increases, indicating a higher concentration of oxygen vacancies with increase in annealing temperatures. PALS shows the concentration of vacancy-clusters are reduced with the increase in temperature, which justifies the decrease in resistivity (from ∼ 1 × 102 to 2 × 10−2 Ω cm) with rise in annealing temperature as measured by the standard four-probe method. These characteristics of the NPs can be utilized in various optoelectronic and energy storage applications.

Efficient One‐Pot Multicomponent Approach to 3‐Phenylpyrrolo[1,2‐a]Pyrazine and Novel 3‐Phenylpyrazino[1,2‐a]Indole in Aqueous Medium

AbstractA facile and atom‐efficient route via a new aqueous synthetic protocol for the greener and more efficient preparation of 3‐phenylpyrrolo[1,2‐a]pyrazine and 3‐phenylpyrazino[1,2‐a]indole by the one‐pot, three‐component method under mild reaction conditions is developed with substituted phenacyl bromides, aqueous ammonium hydroxide, and the corresponding 1H‐pyrrole‐2‐carbaldehyde and 1H‐indole‐2‐carbaldehyde. A reaction cascade consisting of N‐alkylation, imine formation, and annulation by condensation produces a sequence of three C−N bonds.

Development of enantioselective high-performance liquid chromatography-tandem mass spectrometry method for quantitative determination of methylone and some of its metabolites in oral fluid

In the present study an enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the first time for quantitative determination of the recreational drug of abuse methylone and its major metabolites in oral fluid. The simultaneous chemo- and enantioseparation of methylone and its major metabolites was performed on a polysaccharide-based chiral column based on amylose tris(5-chloro-3-methylphenylcarbamate) as chiral selector (Lux i-Amylose-3) with methanol containing 0.4 % (v/v) aqueous ammonium hydroxide as mobile phase. The time required for enantioselective analysis of methylone and its 2 major metabolites was 15 min. This method was fully validated following the Organization of Scientific Area Committees (OSAC) for Forensic Science guidelines.This method was applied for the enantioselective determination of methylone and its metabolites in oral fluid and enantioselectivity in metabolism and pharmacokinetic of the parent compound and metabolites was observed.While the first enantiomer of methylone was found at higher concentration, both metabolites shown greater concentration for the second enantiomer. The results revealed that MET undergoes an enantioselective biotransformation to its metabolites HMMC and MDC, with S-(−)-MET more rapidly metabolized and eliminated from the body.

Liquid phase exfoliation of metal–organic frameworks in aqueous quaternary ammonium hydroxide solution enables highly efficient photocatalytic CO2 reduction

Metal−organic framework nanosheets (MONs) show promising applications in many fields, but the production of large amounts of high-quality MONs remains a challenge. Here, we report a general liquid-phase stripped approach to exfoliate a benzoic acid linked MOF (Al2(OH)2TCPP-Co) in water by using quaternary ammonium hydroxides as deprotonation reagent, intercalator and stabilizer simultaneously. It is shown that the stripped yield is high up to 27.5%, the thickness of MONs is mainly 1–3 nm, and the horizontalsize is less than one hundred nanometers. The molecular geometry and alkalinity of quaternary ammonium hydroxides play vital roles in the exfoliation of MONs. Moreover, the MONs have been applied as photocatalysts for the conversion of CO2 to CO in a gas–solid model under UV–visible light illumination without using anyphotosensitizer and sacrificialagents. The productivity rate of CO is 118.7 μmol g−1 h−1, which outperforms most of the photocatalysts reported previously. Thus, the liquid phase stripping method reported in this work has great potential in the large-scale production of MONs for efficient photocatalysis of CO2 reduction in the gaseous phase.

Long chain fatty acids analysis of intertidal biofilm by direct injection liquid chromatography time of flight mass spectrometry

The critical importance of mono- and polyunsaturated fatty acids (FAs) in a variety of biological functions, including animal nutrition and as an environmental stress monitor, is well recognized. However, while methods exist for monitoring of fatty acids, few are specific either to the profile of a microphytobenthos matrix or practical in application to multiple, diverse intertidal biofilm sample sets. In the current study, a sensitive liquid chromatography (LC) quadrupole time of flight mass spectrometry (QTOF) method was developed for the quantitative analysis of 31 FAs specific to intertidal biofilm, a thin mucilaginous layer of microalgae, bacteria, and other organisms on the surface of coastal mudflats, which provide a rich source of FAs for migratory birds. Preliminary screening of diverse biofilm samples collected from shorebird feeding grounds highlighted eight saturated (SFA), seven monounsaturated (MUFA), and sixteen polyunsaturated FAs (PUFA) that were selected for analysis. Improved method detection limits in the range 0.3–2.6 ngmL−1 were achieved, excepting for stearic acid at 10.6 ngmL−1. These excellent results were obtained without use of complex sample extraction and clean-up procedures undertaken by other published methods. An alkaline matrix of dilute aqueous ammonium hydroxide with methanol was shown to be selective for extraction and stability of the more hydrophilic fatty acid components. The direct injection method showed excellent precision and accuracy both during validation and application to hundreds of real-world intertidal biofilm samples from the Fraser River estuary (British Columbia, Canada) and other areas of the region frequented by shoreline birds.

Clean Conversion of Aqueous Ammonia Using a Solid Oxide Cell

Ammonia (NH3) is present as an impurity in coke oven gas (COG), which is a by-product of coke-making processes required for the manufacture of steel. Due to its highly corrosive and toxic nature, ammonia is removed from COG by water scrubbing processes generating a highly problematic aqueous waste stream containing ammonia (19 vol%), hydrogen sulphide (4 vol%), carbon dioxide (14 vol%) and tars. At Tata Steel Port Talbot (South Wales, UK) alone, approximately 44,000 m3 of COG and 264 kg of ammonia are produced every hour. This is currently disposed of via incineration, contributing to air pollutant emissions and wasting a valuable and useful resource.It is well known that solid oxide fuel cells (SOFCs) can convert ammonia gas to electrical power and heat when operating in fuel cell mode [1-3]. In this work, conversion of a liquid aqueous ammonium hydroxide solution (35%) using a commercially available anode-supported button cell was investigated in fuel cell and electrolysis mode. This mixture served as a basic initial simulation of the waste ammonia streams produced from coke-making processes. The electrical performance of the cell was characterised using I-V curves and electrochemical impedance spectroscopy, and the output gases of the cell were measured in real-time using quadrupole mass spectrometry (QMS).The QMS data show the ammonia decomposed to nitrogen and hydrogen at the open circuit voltage (OCV). In fuel cell mode, the cell utilised hydrogen to produce electrical power. I-V curves were measured showing the effect of the ammonium hydroxide solution on cell efficiency compared with deionised water (see figure). Increasing the deionised water flow rate decreased the OCV considerably and substantially increased the concentration losses; under a 20/80 vol% H2/H2O mixture, the cell produced 50-80% of the current yielded under pure H2. With the ammonium hydroxide solution, OCV and concentration losses were affected much less as the flow rate of the mixture was increased, indicating conversion of ammonia into electrical power with high efficiency. The I-V curves and electrochemical impedance spectra indicated very low activation losses.In electrolysis mode, the presence of ammonium hydroxide decreased performance and this was attributed to the decreased presence of H2O, which the I-V curves (see figure b) and impedance spectra show increased the activation and concentration losses. However, the QMS data have demonstrated that electrolysis of H2/NH4OH mixtures increases the H2 production by a factor of approx. 2.3 and yields a gas mixture composed of approx. 87 vol% H2 balanced in N2, with no NO x production observed.

Greenness profile assessment of selective liquid chromatographic methods for determination of a quaternary antimigraine combination along with three of their related official impurities

Two selective, sensitive and environmentally safe LC methods were developed and validated for determination of paracetamol, caffeine, ergotamine tartrate and metoclopramide in coformulated antimigraine tablets along with p-aminophenol, p-nitrophenol and theophylline as officially specified impurities. The first is based on high-performance thin-layer chromatography (HPTLC) coupled with densitometric quantitation. Separation was achieved on HPTLC silica gel 60 F254 plates as stationary phase using ethyl acetate:aqueous ammonium hydroxide solution:glacial acetic acid (10.0:0.4:0.1, by volume) as a developing system followed by scanning of the separated bands at 210.0 nm. The subsequent method depends on HPLC with diode array detection. The LC separation was accomplished on a Scharlau C18 (250 × 4.6 mm, 5 μm) column using a mixture of 20.0 mm sodium dihydrogen phosphate, pH 3.0, adjusted with o-phosphoric acid and methanol, at a flow rate of 1.3 mL/min in a gradient elution program. The separated peaks were detected at 210.0 nm. The proposed methods have been validated and proven to meet the requirements outlined in the International Council for Harmonisation (ICH) guidelines. The greenness profile evaluation was carried out using three tools, namely, the National Environmental Method Index, the Analytical EcoScale and the Green Analytical Procedure Index tool, and a comparative study was then conducted. Successful application of the developed methods for determination of the cited quaternary mixture in Metograine tablets confirms their suitability regarding the analytical performance and ecological impact in quality control assay and impurity profiling purposes.

Removing phorbol esters from the biomass to add extra value to the byproduct from deoiling seeds of Jatropha curcas in the biodiesel industry

Either pressing or solvent extraction of Jatropha curcas seed oil results in great amounts of cake as a byproduct. The direct use of these fresh biomasses threats the health of mammals as they contain phorbol esters (PEs), a highly toxic class of substance. Five different treatments were bench-assayed to degrade PEs: (i) ammonium hydroxide, (ii) urea, (iii) heat, (iv) ultraviolet radiation, and (v) gamma radiation. All used methods were evaluated for their efficiency on removing PEs from the biomass resulting from deoiling seeds of J. curcas. The treatments were variably effective in reducing PEs contents to nontoxic levels. Aqueous ammonium hydroxide solution (3% w/w) at 70 °C was found to reduce the contents of PEs down to 0.084 mg g−1 (cake) and 0.083 mg g−1 (bran). The treatment with an aqueous solution NH4OH 7% w/w with heating at 90 °C led to the most effective reduction, rendering PEs contents as low as 0.063 mg g−1 (cake) and 0.066 mg g−1 (bran). These are below the critical toxicity threshold, namely 0.1 mg g−1, which is found in seeds of nontoxic J. curcas varieties. The corresponding results from cytotoxicity tests and assessments of nutritional characteristics confirmed that these treated samples have become safe enough, making this affordable technology potentially scalable to be used in the feeding of livestock at the industrial level.

8-Fluoro-N-2-isobutyryl-2′-deoxyguanosine: Synthesis and Reactivity

3′,5′-O-Bis(tert-butyldimethylsilyl)-8-fluoro-N-2-isobutyryl-2′-deoxyguanosine was synthesized from 3′,5′-O-bis(tert-butyldimethylsilyl)-N-2-isobutyryl-2′-deoxyguanosine by the treatment with N-fluorobenzenesulfonimide. A similar fluorination reaction with 3′,5′-O-bis(tert-butyldimethylsilyl)-N-2-(N,N-dimethylformamidine)-2′-deoxyguanosine, however, failed to give the corresponding fluorinated product. It was found that 8-fluoro-N-2-isobutyryl-2′-deoxyguanosine is labile under acidic conditions, but sufficiently stable in dichloroacetic acid used in solid phase synthesis. Incorporation of 8-fluoro-N-2-isobutyryl-2′-deoxyguanosine into oligonucleotides through the phosphoramidite chemistry-based solid phase synthesis failed to give the desired products. Furthermore, treatment of 8-fluoro-N-2-isobutyryl-2′-deoxyguanosine with aqueous ammonium hydroxide did not give 8-fluoro-2′-deoxyguanosine, but led to the formation of a mixture consisting of 8-amino-N-2-isobutyryl-2′-deoxyguanosine and C8:5′-O-cyclo-2′-deoxyguanosine. Taken together, an alternative N-protecting group and possibly modified solid phase synthetic cycle conditions will be required for the incorporation of 8-fluoro-2′-deoxyguanosine into oligonucleotides through the phosphoramidite chemistry-based solid phase synthesis.

The role of urea in the solubility of cellulose in aqueous quaternary ammonium hydroxide.

We examine the role of water and urea in cellulose solubility in tetrabutylammonium hydroxide (TBAH). Molecular dynamics simulations were performed for several different solvent compositions with a fixed cellulose fraction. For each composition, two simulations were carried out with cellulose fixed in each of the crystalline and the dissolved states. From the enthalpy and the entropy of the two states, the difference in Gibbs free energy (ΔG) and hence the spontaneity is determined. A comparison with solubility experiments showed a strong correlation between the calculated ΔG and the experimental measurements. A breakdown of the enthalpic and entropic contributions reveals the roles of water and urea in solubility. At high water concentration, a drop in solubility is attributed to both increased enthalpy and decreased entropy of dissolution. Water displaces strong IL–cellulose interactions for weaker water–cellulose interactions, resulting in an overall enthalpy increase. This is accompanied by a strong decrease in entropy, which is primarily attributed to both water and the entropy of mixing. Adding urea to TBAH(aq) increases solubility by an addition to the mixing term and by reducing losses in solvent entropy upon dissolution. In the absence of urea, the flexible [TBA]+ ions lose substantial degrees of freedom when they interact with cellulose. When urea is present, it partially replaces [TBA]+ and to a lesser extent OH− near cellulose, losing less entropy because of its rigid structure. This suggests that one way to boost the dissolving power of an ionic liquid is to limit the number of degrees of freedom from the outset.

Synthesis of amorphous SiO2 nanowires by one-step low temperature hydrothermal process

A novel procedure for the growth of amorphous SiO2 nanowires by a one-step hydrothermal process directly using commercial silicate glass in cheap aqueous ammonium hydroxide without any other catalyst is reported. The effect of concentration of aqueous ammonium hydroxide and reaction time on synthesized product was investigated. It was found that SiO2 nanowires with high aspect ratio can be synthesized using silicate glass at 170 °C in 2.5 mol l−1 aqueous ammonium hydroxide for 7 h. Scanning electron microscopy, high resolution transmission electron microscopy and x-ray diffraction results showed that the products were amorphous SiO2 nanowires with diameters of 20∼100 nm and lengths of several tens of micrometers. X-ray photoelectron spectroscopy (XPS) indicated that the SiO2 nanowires retained small amounts of MgO and CaO from the silicate glass. The result of photoluminescence (PL) spectra of the nanowires exhibited a strong, sharp photoluminescence (PL) emission peak, centered at 426 nm. Based on the results, the OH-assisted hydrolysis of the glass has been proposed as the growth mechanism of the SiO2 nanowires.

Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides.

Electrospray ionization (ESI) can transfer an aqueous-phase peptide or peptide complex to the gas-phase while conserving its mass, overall charge, metal-binding interactions, and conformational shape. Coupling ESI with ion mobility-mass spectrometry (IM-MS) provides an instrumental technique that allows for simultaneous measurement of a peptide's mass-to-charge (m/z) and collision cross section (CCS) that relate to its stoichiometry, protonation state, and conformational shape. The overall charge of a peptide complex is controlled by the protonation of 1) the peptide's acidic and basic sites and 2) the oxidation state of the metal ion(s). Therefore, the overall charge state of a complex is a function of the pH of the solution that affects the peptides metal ion binding affinity. For ESI-IM-MS analyses, peptide and metal ions solutions are prepared from aqueous-only solutions, with the pH adjusted with dilute aqueous acetic acid or ammonium hydroxide. This allows for pH dependence and metal ion selectivity to be determined for a specific peptide. Furthermore, the m/z and CCS of a peptide complex can be used with B3LYP/LanL2DZ molecular modeling to discern binding sites of the metal ion coordination and tertiary structure of the complex. The results show how ESI-IM-MS can characterize the selective chelating performance of a set of alternative methanobactin peptides and compare them to the copper-binding peptide methanobactin.

Characterization of the perylenequinone pigments in Japanese Andosols and Cambisol

ABSTRACT The green fraction of humic acid (Pg) and the chloroform-extractable green fraction (CEGF) are characteristic soil organic matter (SOM) components. These alkaline solutions are green-colored due to the presence of 4,9-dihydroxyperylene-3,10-quinone (DHPQ) chromophore. While both of which are potential indicators for the effect of land use and paleoclimatic environment in the fields of soil science as well as geochemistry, CEGF as well as its relationship with Pg in soils are not yet fully documented. In this study, we firstly investigated the chemical properties of soil CEGF fractions by ultraviolet–visible (UV–Vis) and infrared (IR) method. Two CEGF components were separated by sequential liquid-liquid extraction using aqueous ammonium hydroxide (NH4OH) followed by aqueous sodium hydroxide (NaOH). Results showed that the UV–Vis spectral shape of NH4OH-extractable component is very similar to that of DHPQ, except that it is red-shifted. The solubility and UV–Vis spectrum of the NaOH-extractable fraction were completely identical with those of synthesized DHPQ. Their IR spectral shapes were also almost the same. Subsequently, the distribution of CEGF in humic acid (HA), fulvic acid (FA) and humin (HN) from Japanese Andosols and Cambisol was quantitatively evaluated by sequential extraction. Most of CEGF was detected in the HA (60–78%) and HN (22–40%), but not in the FA. While the UV–Vis spectral shape of CEGF extracted from Andosols HAs showed a relatively higher proportion of DHPQ than its derivative, the opposite was observed in Cambisol HA, whose CEGF is similar to that of sclerotium grain (one of the possible origin of CEGF). These results suggest the diversity of CEGF-producing soil fungi. Quantitative data also indicated that 35–49% of Pg consisted of a chloroform-soluble fraction (i.e., CEGF) and the remaining 51–65% of Pg was chloroform-insoluble. Based on these results, we propose that CEGF is composed of DHPQ and DHPQ-derivatives and that CEGF is one of the major fractions of Pg.

Economical, environmental friendly synthesis, characterization for the production of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles with enhanced CO2 adsorption

Zeolitic imidazole framework 8 (ZIF-8) nanoparticles were successfully synthesized in an aqueous solution at the ambient condition with a relatively low molar ratio of zinc salt and an organic ligand, Zn+2/Hmim (1: 8). ZIF-8 has remarkable thermal and chemical stability, tunable microporous structure, and a great potential for absorption, adsorption, and separation. Various physicochemical characterization techniques like X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), attenuated total reflected infrared spectroscopy (ATR-IR), thermogravimetric analysis (TGA), and surface area with pore textural properties by micromeritics gas adsorption equipment were performed to investigate the effect of base type additive triethylamine (TEA) on the morphology, crystallinity, yield, particle and crystal size, thermal stability and microporosity of ZIF-8 nanoparticles. The total quantity of basic sites and carbon dioxide (CO2) desorption aptitude was also calculated using CO2 temperature-programmed desorption (CO2-TPD) system. The pure ZIF-8 nanoparticles of 177 nm were formed at TEA/total mole ratio of 0.002. Furthermore, the size of ZIF-8 nanoparticles was decreased to 77 nm with increasing TEA/total mole ratio up to 0.004. The structures, particle sizes and textural properties of ammonia modified ZIF-8 particle can easily be tailored by the amount of aqueous ammonium hydroxide solution. The smallest ZIF-8 nanoparticles obtained were 75 nm after ammonia modification which shows excellent thermal stability and improved microporosity. The ZIF-8 basicity and uptakes of CO2 improved with TEA and ammonia modification which followed the order: A25ml–Z4 > Z4 > Z3 > Z5 > Z2 > A50ml–Z4. The proposed economical and efficient synthesis method has great potential for large-scale production of ZIF-8.

Simultaneous Release and Labeling of O- and N-Glycans Allowing for Rapid Glycomic Analysis by Online LC-UV-ESI-MS/MS.

Most glycoproteins and biological protein samples undergo both O- and N-glycosylation, making characterization of their structures very complicated and time-consuming. Nevertheless, to fully understand the biological functions of glycosylation, both the glycosylation forms need to be analyzed. Herein we report a versatile, convenient one-pot method in which O- and N-glycans are simultaneously released from glycoproteins and chromogenically labeled in situ and thus available for further characterization. In this procedure, glycoproteins are incubated with 1-phenyl-3-methyl-5-pyrazolone (PMP) in aqueous ammonium hydroxide, making O-glycans released from protein backbones by β-elimination and N-glycans liberated by alkaline hydrolysis. The released glycans are promptly derivatized with PMP in situ by Knoevenagel condensation and Michael addition, with peeling degradation almost completely prevented. The recovered mixture of O- and N-glycans as bis-PMP derivatives features strong ultraviolet (UV) absorbing ability and hydrophobicity, allowing for high-resolution chromatographic separation and high-sensitivity spectrometric detection. Using this technique, O- and N-glycans were simultaneously prepared from some model glycoproteins and complex biological samples, without significant peeling, desialylation, deacetylation, desulfation or other side-reactions, and then comprehensively analyzed by online HILIC-UV-ESI-MS/MS and RP-HPLC-UV-ESI-MS/MS, with which some novel O- and N-glycan structures were first found. This method provides a simple, versatile strategy for high-throughput glycomics analysis.

Mechanistic Insights into the Decarboxylative Electrophilic Trifluoromethylthiolation of β‐Ketocarboxylic Acids

A metal‐free protocol for the domino trifluoromethylthiolation/decarboxylation of β‐ketocarboxylic acids is described. The catalytic reactions take place in acetonitrile in the presence of aqueous ammonium hydroxide and N‐trifluoromethylthiosaccharin. The sequence of events and reaction mechanism were established experimentally and using density functional theory calculations. This synthetic method offers a convenient alternative to known routes for the synthesis of α‐trifluoromethylthio‐substituted ketones.

The Nitrogen Economy: The Feasibility of Using Nitrogen-Based Alternative Fuels

We present herein a techno-economic feasibility for implementation of nitrogen-based fuels. Firstly, we compared the nitrogen- and carbon-based routes for chemical hydrogen storage. The above hydrogen carrier routes were evaluated on an energy basis, under defined system boundaries by comparing seven alternative fuels. Ammonia was found to be the best energy vector, followed by methane, methanol, and aqueous ammonium-hydroxide urea. Secondly, we evaluated the economic feasibility of a model nitrogen-based fuel by using levelized cost of storage analysis. The results indicated that a nitrogen-based fuel is competitive with other storage technologies under development. Furthermore, a decrease in the hydrogen cost can lead nitrogen-based fuels to be competitive with currently-used mature technologies. Thirdly, the utilization of the nitrogen-based fuel route was demonstrated. The auto-ignition process of a model fuel, aqueous urea ammonium nitrate (UAN) was described. The results indicate that this fuel is safe to use, store and handle under ambient pressure. We studies potential storage and reaction vessel materials, pointing out favorable metal alloys for these purposes. In addition, a catalyst screening study aimed at pollution reduction during batch combustion of this fuel is reported, as are preliminary results for continuous catalytic combustion. This work demonstrates the feasibility of catalytic pollution abatement for UAN combustion and the clean utilization of this fuel.

Comparison of HILIC columns for residue analysis of dithiocarbamate fungicides

ABSTRACTSelective determination of dithiocarbamate (DTC) fungicides is mainly performed by hydrophilic interaction liquid chromatography (HILIC). According to Crnogorac and Schwack, DTC analyses by HILIC only lead to meaningful results with a zwitterionic polymer-based hydrophilic interaction liquid chromatography (ZIC-pHILIC) column. Considering the limited availability of this special type of column and the importance of DTC residue analysis, several new HILIC columns were evaluated as alternatives to the ZIC-pHILIC column. Detection was carried out by ultraviolet light and by mass spectrometry (MS) on a single quadrupole mass spectrometer coupled to an electrospray ionization interface operating in negative mode. On nearly all tested columns, separation of dimethyldithiocarbamates, ethylenebis(dithiocarbamates), and propylenebis(dithiocarbamates) was achieved with ammonium acetate eluents (pH 6.8). However, due to ion suppression by the buffer and the limited alkaline pH stability, the tested silica-based columns were not suitable for the sensitive analysis of DTCs. The polymer-based iHILIC-Fusion was the only alternative that offered high MS sensitivity, when a buffer containing 15 mM aqueous ammonium hydroxide and 7.5 mM ammonium hydrogen carbonate (pH 9.8) was used, but the separation of the three DTC subclasses was poor. Thus, considering both selectivity and sensitivity, the originally proposed polymer-based ZIC-pHILIC column still outperformed all the tested newly available alternative HILIC columns.

Ammonium hydroxide addition and its influence on the catalytic activities of Pt-based catalysts for methane oxidation

A series of binary chromium-platinum catalysts were prepared and the catalytic activity was tested in methane oxidation. The effects of aqueous ammonium hydroxide addition into binary catalyst chromium-platinum catalysts were investigated. All the catalysts were prepared by impregnation method. The reactant gases were consisted of methane-oxygen-argon. The reaction was conducted at an atmospheric pressure and the temperature was ranged from 573 to 773 K. The products were analyzed using thermal conductivity detector. Under this experiment conditions, the only products were carbon dioxide and water. The catalysts were characterized using carbon monoxide chemisorptions and x-ray photoelectron spectrometer. The catalytic activity results showed that the catalyst with the addition of aqueous ammonium hydroxide has smaller platinum metal particle size and its catalytic activity is the highest compared to the other catalysts. X-ray photoelectron spectrometer recorded higher intensities and clear peaks on high pH catalysts indicating a change of interaction between chromium and platinum on alumina. However, active state of chromium was not observed on catalyst surface.