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PubMed2002

The ultrasonically induced reaction of benzoyl chloride with nitrobenzene: an unexpected sonochemical effect and a possible mechanism.

A mixture of benzoyl chloride and nitrobenzene is not known to be chemically reactive, indeed the mixture is chemically inert when subjected individually to either ultrasonic irradiation or heating. However, if this system is initially subjected to ultrasound and then heated for several hours at 200 degrees C, a reaction does occur and the products are benzoic anhydride, hydrochloric acid, nitrous and nitric acid together with some minor products. To the best of our knowledge, this is the first example of a reaction where the effect of ultrasound does not appear to be the consequence of the direct action of acoustic cavitation bubbles. A possible explanation of this behaviour is advanced which involves an electron transfer reaction in which nitrobenzene is first activated by ultrasound and then acts as oxidant in the thermal stage of reaction.

Journal Article↗

PubMed2004

Surface functionalization of silicon nanoparticles produced by laser-driven pyrolysis of silane followed by HF-HNO3 etching.

CO2 laser induced pyrolysis of silane was used to produce silicon nanoparticles with an average diameter as small as 5 nm at high rates (up to 200 mg/h). Etching these particles with a mixture of hydrofluoric acid (HF) and nitric acid (HNO3) reduces their size and passivates their surface such that they exhibit bright visible photoluminescence (PL). This paper describes the attachment of organic molecules to hydrogen-terminated and hydroxyl-terminated surfaces of these nanoparticles. Stable particle dispersions in various solvents were obtained by treatment of hydrogen-terminated surfaces with octadecene or undecylenic acid and by treatment of hydroxyl-terminated surfaces with octadecyltrimethoxysilane. Transmission electron microscopy showed that the surface-functionalized particles were well dispersed and crystalline. FTIR spectroscopy confirmed the expected reactions of the organic molecules with the particle surfaces. Photoluminescence measurements showed that surface treatment significantly stabilized the PL properties of the nanoparticles against degradation. Size selective precipitation was applied to particle dispersions and allowed some narrowing and tuning of the PL spectrum.

Journal Article↗

PubMed2002

Quantitative trace-level speciation of arsenite and arsenate in drinking water by ion chromatography.

We describe an improved method for the determination of inorganic arsenic in drinking water. The method is based on comprehensive optimization of the anion-exchange ion chromatographic (IC) separation of arsenite and arsenate with post-column generation and detection of the arsenate-molybdate heteropoly acid (AMHPA) complex ion. The arsenite capacity factor was improved from 0.081 to 0.13 by using a mobile phase (2.0 mL min(-1)) composed of 2.5 mM Na2CO3 and 0.91 mM NaHCO3 (pH 10.5). A post-column photo-oxidation reactor (2.5 m x 0.7 mm) was optimized (0.37 microM potassium persulfate at 0.50 mL min(-1)) such that arsenite was converted to arsenate with 99.8 +/- 4.2% efficiency. Multi-variate optimization of the complexation reaction conditions yielded the following levels: 1.3 mM ammonium molybdate, 7.7 mM ascorbic acid, 0.48 M nitric acid, 0.17 mM potassium antimony tartrate, and 1.0% (v/v) glycerol. A long-path length flow cell (Teflon AF, 100-cm) was used to measure the absorption of the AMHPA complex (818 +/- 2 nm). Figures of merit for arsenite/arsenate include: limit of detection (1.6/0.40 microg L(-1)): standard error in absorbance (5.1 x 10(-3)/3.5 x 10(-3)); and sensitivity (2.9 x 10(-3)/2.2 x 10(-3) absorbance units per ppb). Successful application of the method to fortified surface and ground waters (100 microL samples) is also described.

Arsenates↗

PubMed2006

Chemical extraction of arsenic from contaminated soil.

A series of batch extraction experiments were conducted using a fortified soil with different extracting solutions such as inorganic acids (hydrochloric acid (HCl), sulfuric acid (H2SO4), phosphoric acid (H3PO4), perchloric acid (HClO4), or nitric acid (HNO3)), organic acids (acetic acid (C2H4O2), citric acid (C6H8O7)) and alkaline agent (NaOH). Various concentrations were used to investigate the removal efficiency and to optimise the concentration of each extractant. In the present investigation a Kuroboku soil contaminated with arsenite (As(III)) was used as a model soil. Arsenic was extracted most efficiently by 5% H3PO4 with a maximum of more than 99% from the model soil. Sulfuric acid also showed high percentage extraction efficiency. On the other hand, C2H4O2 and oxidizing acids such as HNO3 and HClO4 showed low efficiency of As extraction compared with C6H8O7. Although, NaOH also showed higher extraction efficiencies compared with organic and oxidizing acids but mainly arsenate (As(V)) was found to be the major component. A significant fraction of the As(III) was oxidized to As(V) during mineral acid and alkaline extraction and extraction efficiency also varied with the concentration of the acid and alkali solution.

Acids↗

PubMed1996

Quantitative analysis of the dentin adhesive interface by Auger spectroscopy.

The ultimate success of a dentin adhesive bond is dependent in large part on specific conditions at the interface between the tooth and the adhesive. Most current dentin adhesive systems use some sort of pre-treatment to demineralize the first few microns of the dentin surface, leaving a meshwork of collagen into which the adhesive resin can penetrate, infiltrate, and polymerize. The general hypothesis tested in this experiment was that the penetration and distribution of adhesive resin into the demineralized zone are a function of the conditioner used as a pre-treatment for the adhesive application. Four commercially available adhesive systems were modified to incorporate hydroxyethylthiomethacrylate (HETMA), a sulfur-substituted, traceable analogue of 2-hydroxyethylmethacrylate (HEMA), thereby allowing for a qualitative measurement of the amount and distribution of monomer in the treated dentin substrate by energy-dispersive x-ray spectroscopy (EDS) and a quantitative measurement by Auger electron spectroscopy (AES). The dentin pre-treatments investigated were: (1) 10% citric acid/3% ferric chloride, (2) 10% maleic acid, (3) 2.5% nitric acid, and (4) an alcoholic solution of HEMA with a phosphorus acid ester. These pre-treatments were applied to freshly extracted teeth that had been sectioned to expose the dentin and ground to simulate the smeared layer. After the appropriate pre-treatment was applied, a 10% (v/v) solution of HETMA in acetone was applied to the surface, followed by the corresponding adhesive resin, which was then polymerized. The samples were then processed for observation by scanning transmission electron microscopy (STEM), AES, and STEM/EDS analysis. The results indicated significant differences in the ability of HETMA to penetrate the dentin surface conditioned by the four pretreatments investigated here. This study also demonstrated that AES and STEM/EDS could be used in a correlative fashion to determine the distribution of HETMA within or adjacent to the treated dentin surface.

Dentin-Bonding Agents↗

PubMed1978

Determination of zirconium in natural water by spectrophotometry following the concentration step with yield tracer.

Zirconium in natural water samples was determined spectrophotometrically after concentration using95Zr as a yield tracer. Acidified sample (1l) with a known amount of 95Zr was evaporated to dryness, treated with hydrofluoric and nitric acids, and then with nitric and perchloric acids, and evaporated nearly to dryness. The residue was taken up with 2 M perchloric acid and zirconium in the solution was extracted with 0.1 M thenoyltrifluoroacetone (TTA) in benzene. The TTA complex solution was converted to hydrochloric acid solution. After the recovery yield was estimated by measuring the radioactivity of 95Zr in the final solution, zirconium was then determined by spectrophotometry with Arsenazo III. Zirconium contents in lake and hot and cold spring samples from Nikko and Shiobara districts were found to be 0.29-2.8 microgram/l by this method.

Fresh Water↗

PubMedDate not supplied

Determination of arsenic in traditional Chinese medicine by microwave digestion with flow injection-inductively coupled plasma mass spectrometry (FI-ICP-MS).

A simple, rapid, and sensitive method with high sample throughput was developed for determining arsenic in traditional Chinese medicine (TCM) in the form of uncoated tablets, sugar-coated tablets, black pills, capsules, powders, and syrups. The method involves microwave digestion with flow injection-inductively coupled plasma mass spectrometry (FI-ICP-MS). Method precision was 2.7-10.1% (relative standard deviation, n = 6) for different concentrations of arsenic in different TCM samples analyzed by different analysts on different days. Method accuracy was checked with a certified reference material (sea lettuce, Ulva lactuca, BCR CRM 279) for external calibration and by spiking arsenic standard into different TCMs. Recoveries of 89-92% were obtained for the certified reference material and higher than 95% for spiked TCMs. Matrix interference was insignificant for samples analyzed by the method of standard addition. Hence, no correction equation was used in the analysis of arsenic in the samples studied. Sample preparation using microwave digestion gave results that were very similar to those obtained by conventional wet acid digestion using nitric acid.

Arsenic↗

PubMed2002

PCR-DGGE analysis of denitrifying bacteria in a metallurgic wastewater treatment process.

The wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of acids such as nitric acid and of salts. Biological nitrogen removal from this wastewater was attempted by using a circulating bioreactor system equipped with an anoxic packed bed or an anoxic fluidized bed and an aerobic three-phase fluidized bed. The system was found to effectively remove nitrogen from the diluted wastewater (T-N; 1,000-4,000 mg litre(-1)). The microbial population structure of activated sludge in an anoxic reactor was analyzed by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA (rDNA) fragments. DGGE analysis under different operating conditions demonstrated the presence of some distinguishable bands in the separation pattern, which were most likely derived from many different species constituting the microbial communities. Furthermore, the population diversity varied in accordance with the nitrate-loading rate, water temperature and reactor condition. Some major DGGE bands were excised, reamplified and directly sequenced. It was revealed that the dominant population in the anoxic reactor were affiliated with the beta subclass of the class Proteobacteria.

Bioreactors↗

PubMed2002

[Simultaneous determination of the total content of As, Ba, Cd, Cr, Hg, Pb, Se, Sb in paint coating on toys by ICP-AES].

ICP-AES was used for the simultaneous determination of the total content of As, Ba, Cd, Cr, Hg, Pb, Se, Sb in paint coating on toys. Digestion procedures of these materials with different acid mixtures have been developed. The sample was dissvolved in the acid mixture of nitric acid, tartaric acid, and a little phosphoric acid. The matrix elements effect was studied and the preferable experimental conditions were investigated. The recovery rates of this procedure were between 99% and 109%. The RSD was within 1.5%. The proposed method was simple, rapid and can be used in daily inspection of toys.

Arsenic↗

PubMed2006

The effects of folic acid and nitric oxide synthase inhibition on coronary flow and oxidative stress markers in isolated rat heart.

The aim of this study was to assess the effects of folic acid on coronary flow and oxidative stress markers with or without non-specific inhibition of nitric oxide synthase by L-NAME in isolated rat hearts. The hearts of male Wistar albino rats (n = 12, age 8 weeks, body mass 180-200 g) were retrograde perfused according to the Langendorff technique at gradually increased constant perfusion pressure (40-120 cmH2O). Coronary flow and markers of oxidative stress: nitrite outflow, superoxide anion production, and index of lipid peroxidation (by measuring thiobarbituric acid reactive substances) in coronary effluent were calculated. The experiments were performed during control conditions and in presence of folic acid (100 microM) alone or folic acid (100 microM) plus L-NAME (30 microM). Control values of coronary flow varied in range from 4.37 +/- 0.10 ml/min/g wt at 40 cmH2O to 12.05 +/- 0.42 ml/min/g wt at 120 cmH2O. Nitrite outflow varied from 1.68 +/- 0.17 nmol/min/g wt at 40 cmH2O to 3.56 +/- 0.17 nmol/min/g wt at 120 cmH2O and was parallel with coronary perfusion pressure-coronary flow curve. Folic acid significantly increased coronary flow (40-120 cmH2O, 5.63 +/- 0.10 ml/min/g wt and 15.2 +/- 0.42 ml/min/g wt, respectively) and was accompanied by significant increase in nitrite outflow (2.28 +/- 0.29 nmol/min/g wt at 40 cmH2O to 6.66 +/- 0.50 nmol/min/g wt at 120 cmH2O). In addition, folic acid significantly decreased superoxide anion production especially at upper coronary perfusion pressure values (60% at 120 cmH2O) and increased index of lipid peroxidation (37.16% at 120 cmH2O), respectively. Folic acid plus L-NAME did not change control values of coronary flow significantly. However, folic acid plus L-NAME increased nitrite outflow especially at upper coronary perfusion pressure values (43.05% at 120 cmH2O) and did not change significantly superoxide anion production or index of lipid peroxidation versus control values, respectively. The results clearly showed that on isolated rat hearts at gradually increased constant perfusion pressure, folic acid increased coronary flow, increased nitrite outflow, decreased superoxide anion production, and increased index of lipid peroxidation. These effects were reversed or blocked by L-NAME thus demonstrating mediation or at least participation of NO in the mechanism of the folic acid-induced effects.

Animals↗

PubMed2005

Lipoteichoic acid-induced nitric oxide synthase expression in RAW 264.7 macrophages is mediated by cyclooxygenase-2, prostaglandin E2, protein kinase A, p38 MAPK, and nuclear factor-kappaB pathways.

We recently reported that lipoteichoic acid (LTA), a cell wall component of the gram-positive bacterium Staphylococcus aureus, stimulated inducible nitric oxide synthase (iNOS) expression, nitric oxide (NO) release, and cyclooxygenase-2 (COX-2) expression in RAW 264.7 macrophages. This study was carried out to further investigate the roles of COX-2 and prostaglandin E2 (PGE2) in LTA-induced iNOS expression and NO release in RAW 264.7 macrophages. Treatment of RAW 264.7 macrophages with LTA caused a time-dependent increase in PGE2 release. LTA-induced iNOS expression and NO release were inhibited by a non-selective COX inhibitor (indomethacin), a selective COX-2 inhibitor (NS-398), an adenylyl cyclase (AC) inhibitor (dideoxyadenosine, DDA), and a protein kinase A (PKA) inhibitor (KT-5720). Furthermore, both PGE2 and the direct PKA activator, dibutyryl-cAMP, also induced iNOS expression in a concentration-dependent manner. Stimulation of RAW 264.7 macrophages with LTA, PGE2, and dibutyryl-cAMP all caused p38 MAPK activation in a time-dependent manner. LTA-mediated p38 MAPK activation was inhibited by indomethacin, NS-398, and SB 203580, but not by PD 98059. The PGE2-mediated p38 MAPK activation was inhibited by DDA, KT-5720, and SB 203580, but not by PD 98059. LTA caused time-dependent activation of the nuclear factor-kappaB (NF-kappaB)-specific DNA-protein complex formation. The LTA-induced increase in kappaB-luciferase activity was inhibited by indomethacin, NS-398, KT-5720, and a dominant negative mutant of p38 alphaMAPK (p38 alphaMAPK DN). These results suggest that LTA-induced iNOS expression and NO release involve COX-2-generated PGE2 production, and AC, PKA, p38 MAPK, and NF-kappaB activation in RAW 264.7 macrophages.

Adenylyl Cyclases↗

PubMed2002

Branched chain fatty acids induce nitric oxide-dependent apoptosis in vascular smooth muscle cells.

Clinical observations in patients with peroxisomal disorders and studies employing corresponding mouse models have shown that supraphysiological concentrations of dietary branched chain fatty acids (BCFAs) are associated with a high level of toxicity, which is poorly understood at present. Here we show that phytanic and pristanic acid, two BCFAs that are metabolized in peroxisomes, promote apoptosis in cultured vascular smooth muscle cells of human, rat, and porcine origin. Under the conditions used, the apoptosis-promoting effect of BCFAs was neither shared by saturated or unsaturated straight chain fatty acids nor by artificial peroxisome proliferators, which, like phytanic and pristanic acid, have been shown to activate the peroxisome proliferator-activated receptor alpha (PPARalpha). We could demonstrate, however, that BCFA induced tumor necrosis factor alpha (TNFalpha) activation and secretion, which is an obligatory step required for induction of apoptosis by BCFAs. Furthermore, incubation of VSMCs with BCFA increased inducible nitric-oxide synthase (iNOS) mRNA and protein concentrations markedly within 2 h of treatment. Correspondingly, apoptosis was significantly reduced when the cells were co-treated with the competitive NOS inhibitors monomethyl-L-arginine monoacetate and aminoguanidine. Moreover, co-incubation with TGFbeta1, previously shown to destabilize iNOS mRNA, also abolished apoptosis. These results establish a new signaling cascade in which natural BCFA induced NO-dependent apoptosis, which is apparently triggered by autocrine secretion of TNFalpha in cultured VSMCs.

Animals↗

PubMed1987

Flameless atomic absorption spectrophotometric determination of platinum in tissues solubilized in hyamine hydroxide.

Processing biological samples by solubilization in Hyamine hydroxide (methylbenzethonium hydroxide) as an alternative to wet ashing with concentrated nitric acid for atomic absorption determination of platinum has been explored. The concentrations of platinum in tissues removed from rats 2 h after they had received the antitumor drug Carboplatin (60 mg/kg, iv) were comparable using either of the procedures, indicating the utility of tissue solubilization. Limits of detection were also comparable between the Hyamine hydroxide (0.25 microgram platinum/g) and nitric acid (0.15 microgram/g) procedures. The solubilization method, however, has advantages over wet digestion because of its simplicity and greater safety.

Animals↗

PubMed2006

Clinical diagnostic indicators of renal and bone damage in rats intramuscularly injected with depleted uranium.

The toxic effects and changes in biochemical markers related to kidney and bone in depleted uranium (DU)-injected rats were examined in order to clarify the relation between clinical biochemical markers and the degree of damage in these organs. Male Wistar rats received a single injection in the femoral muscles of 0.2, 1.0 or 2.0 mg kg(-1) of DU which was dissolved in nitric acid solution adjusted to pH 3.2, for comparison with the group injected with nitric acid solution, and the control group. Urine and faeces were collected periodically over a 24 h period. Thereafter, the rats were killed at 28 d after DU injection. The body weights of the DU-injected groups decreased dose-dependently for the first 3-7 d, and then began to increase. The DU concentrations in the urine and faeces decreased rapidly within 3-7 d after DU injection. Urinary N-acetyl-beta-D-glucosaminidase (NAG)/creatinine peaked at the third day after DU injection, with a high correlation to the injected DU doses. There were high correlations among the injected DU doses, DU concentrations in the kidney and urinary NAG/creatinine values that were obtained at 28 d, respectively. The blood urea nitrogen (BUN) and creatinine in the serum also showed a high correlation with the DU-injected doses. The results indicated that urinary NAG/creatinine, BUN and creatinine in serum were useful indicators to diagnose the renal damage by DU, as well as to estimate the DU intake and concentration in the kidney when the intake is >2 mg kg(-1) DU. The total bone mineral density of the proximal metaphysis of the tibia decreased in the 2 mg kg(-1) DU group. In addition, alterations of the trabecular bone structure by inhibiting bone formation and promoting bone resorption were observed by bone histomorphometery. The bone biochemical markers osteocalcin, tartrate-resistance acid phosphatase, pyridinoline and rat-parathyroid hormone increased in all the DU injected groups, indicating that these markers were useful as sensitive indicators for diagnosing bone damage, even if the DU dose injected is low.

Animals↗

PubMed2005

The formation, role and removal of NO3-N during corona discharge in air for phenol removal.

Pulsed corona discharge carried out in the gas phase has been shown to be a low cost solution for wastewater treatment. In this study, the results show that the nitrogen dissociated during corona discharge in the gas phase formed nitric acid in solution, which resulted in a drop in solution pH. The phenol removal could be described in accordance with a first-order reaction in a basic buffer solution, but not in initial neutral and basic non-buffered solutions. This indicates that basic conditions facilitate phenol removal, whilst the formation of nitric acid in solution resulted in decrease in the phenol removal rate. This study also shows that most of the oxidants used for phenol removal came mainly from the dissociation of water molecules at the surface of the liquid phase and/or the gas phase very close to the liquid surface in discharging conditions, not from the gas dissociation in the bulk gas phase, and therefore, it is more effective to keep the solution basic than to change the component of gas in the reactor when removing phenol from water using corona discharge.

Cost Control↗

PubMed2002

Analysis of biogenic carbonates by inductively coupled plasma-mass spectrometry (ICP-MS). Flow injection on-line solid-phase preconcentration for trace element determination in fish otoliths.

The aragonite deposits within the ear bones (otoliths) of teleost fish retain a chemical signal reflecting the life history of fish (similar to rings of trees) and the nature of fish habitats. Otoliths dissolved in acid solutions contain high concentrations of calcium and a variety of proteins. Elimination of matrix salts and organic interferences during preconcentration is essential for accurate determination of trace elements in otolith solutions by inductively coupled plasma-quadrupole mass spectrometry. An iminodiacetate-based chelating resin (Toyopearl AF-Chelate 650 M) has been used for on-line preconcentration and matrix separation for the determination of 31 transition and rare elements. Successful preconcentration of the elements was achieved at pH 5 by on-line buffering, except Mn which required pH 8.8. Sample solutions were loaded on to the column for 1 min at 3.2 mL min(-1), and then eluted directly into the mass spectrometer with 4% v/v nitric acid. This procedure enabled up to 25-fold preconcentration with successful removal of the calcium matrix. The effect of heat-assisted oxidation with concentrated nitric acid was investigated to eliminate the organic matrix. It was found that heating to dryness after dissolution and further mineralization with the acid significantly improved the retention of the transition elements. The method was validated by analysis of a certified reference material produced from saggittal otoliths of emperor snapper ( Lutjanus sebae), and then applied to the determination of trace metal concentrations in juvenile bluefin tuna ( Thunnus thynnus) from the Western Pacific Ocean.

Animals↗

PubMed2001

Electrolytic removal of nitrate from crop residues.

The Controlled Ecological Life Support System (CELSS) resource recovery system, which is a waste-processing system,uses aerobic and anaerobic bioreactors to recover plants nutrients and secondary foods from the inedible biomass. Crop residues contain a significant amount of nitrate. There are actually two major problems concerning nitrate: 1) both CELSS biomass production and resource recovery consume large quantities of nitric acid, and 2) nitrate causes a variety of problems in both aerobic and anaerobic bioreactors. The nitrate anion causes several problems in the resource recovery system in such a way that removal prior to the process is highly desirable. The technique proposed to remove nitrate from potato inedible biomass leachate and to satisfy the nitric acid demand was a four-compartment electrolytic cell. In order to establish the electrolytic cell performance variables, experiments were carried out using potato crop residue aqueous leachate as the diluate solution. The variables studied were the potato biomass leachate composition and electrical properties, preparation of compartment solutions to be compatible with the electrolytic system, limiting current density, nutrients removal rates as a function of current density, fluid hydrodynamic conditions, applied voltage, and process operating time during batch recirculation operation. Results indicated that the limiting current density (maximum operating current density) was directly proportional to the solution electrical conductivity an a power function of the linear fluid velocity in the range between 0.083 and 0.403 m/s. During the electrolytic cell once-through operation, the nitrate, potassium, and other nutrient removal rates were proportional to the current density and were inversely proportional to fluid velocity. The removal of monovalent ions was found to be higher than divalent ones. Under batch recirculation operation at constant applied voltage of 4.5 and 8.5 V, it was found that the nutrient removal rates were independent of applied voltage, but were proportional to the ions concentration and operating time.

Anions↗

PubMed1990

Comparative study of chemical modifiers for the determination of molybdenum in milk by electrothermal atomisation atomic absorption spectrometry.

A comparative study of various chemical modifiers for the determination of molybdenum in milk by electrothermal atomisation atomic absorption spectrometry was carried out. Methods with nitric acid or barium difluoride as the chemical modifier and in the absence of a chemical modifier were studied by introducing the milk samples directly into the graphite furnace with octyl alcohol. The graphite furnace programme, amount of modifier and the calibration and additions graphs were studied in all instances. The characteristic masses were 17.82, 18.64 and 12.08 pg of molybdenum in the absence of a chemical modifier and with nitric acid or barium difluoride as the chemical modifier, respectively. The precision, accuracy and interferences of the method were also investigated.

Animals↗