Determination of NH(3) gas by combination of nanosized LaCoO(3) converter with chemiluminescence detector

Combination of a novel NH₃ converter based on nanosized materials with chemiluminescence (CL) detector for the determination of NH₃ gas was demonstrated in this paper. NH₃ gas is oxidized on different nanosized catalysts to produce NO_x, which can react with luminol to generate CL emission. Eight nanosized materials were investigated as catalyst, and CL was detected from seven of them. The nanosized LaCoO₃ was chosen as the catalyst for preparing the converter because of its higher activity than others. Under the optimized conditions, the linear range of CL intensity versus concentration of NH₃ gas is 0.04-10 ppm (r=0.9951, n=14) with the detection limit of 0.014 ppm. The method offers advantages of long lifetime of the converter, fast response and high selectivity to NH₃. There was no response while the foreign substances, such as hydrogen, oxygen, nitrogen, formaldehyde, acetone and gasoline passing through the CL detection system, and the interference of CCl₄, ethanol, ethylene and toluene was insignificant.     

Ruthenium (II) 1,10-Phenanthroline Salts as Mobile Phase Additives for the Separation and Indirect Detection of Free Amino Acids

Abstract

Ruthenium (II) 1,10-phenanthroline, Ru(phen)²⁺ ₃, salts are used as ion interaction reagents in a basic mobile phase for the retention, resolution, and indirect photometric detection (IPD) of free amino acids on a polystyrene divinylbenzene (Hamilton PRP-1) column. Mobile phase Ru(phen)²⁺ ₃ concentration and pH and type and concentration of organic modifier and counteranion affect retention and IPD. Underivatized amino acid elution order is influenced by side chain structure typical of ion exchange processes. Detection limits for the separation and detection of free amino acids using an isocratic elution condition are about 0.1 nmole for lower retained amino acids and 0.25 nmole for higher retained amino acids for a 3:1 signal:noise ratio. Gradient elution is possible but at higher detection limits.     

Analysis of Adenosine and Other Adenine Compounds in Patients With Immunodeficiency Diseases

Abstract

Adenine compounds can be measured in picomole amounts using liquid chromatography of the fluorescent 1, N⁶-etheno derivatives. The limit of detection for the etheno derivatives in tissue extracts, however, is tissue-dependent due to interference by nucleotides and fluorescent components which are normally present. Prior to derivatization nucleotides were partially removed from extracts of lymphocytes and erythrocytes by treatment with Dowex AG1-X2 anion exchange resin. Samples were analyzed using either a Partisil PXS 10/25 SCX column eluted with 100 mM NH₄H₂PO₄, pH 4.5, at a flow rate of 2 ml/min; or using two μBondapak/C₁₈ reversed-phase columns eluted with 5 mM KH₂PO,₄:25% methanol (V/V) pH 7.5, at a flow rate of 1 ml/min. Adenosine was found to be 0.07 nmole/ml in normal adult human plasma. The urine of a child with severe combined immunodeficiency disease associated with absence of adenosine deaminase contained a normal amount of adenosine (5–6 nmole/ml), but contained a high level (～60 nmole/ml) of deoxyadenosine. Deoxyadenosine was not detected (<0.01 nmole/ml) in normal adult urine. Because of its sensitivity and selectivity, this method of analysis should be applicable to studies of the physiological roles of adenine compounds.     

Luminol chemiluminescence HPLC reaction detector for amino acids and other ligands

A detector for HPLC is based on suppression of chemiluminescence from the Cu(II)-luminol-peroxide reaction. Analytes which complex Cu(II) reduce the free Cu(II) concentration and thus the observed chemiluminescence intensity. The degree of chemiluminescence suppression is a measure of the analyte concentrations. Detection limits are in the range of 1 pmole-1 nmole for amino acids (both primary and secondary without derivatization), CN^–, amines, catecholamines, catechol, and aminoglycoside antibiotics. The detection approach is demonstrated with an ion-exchange separation of amino acids, a reverse phase separation of catecholamines, and an ion-pair separation of the three components of gentamicin C in commercial gentamicin sulfate.     

High Performance Liquid Chromatographic Separation of Estradiol-17 α and -17/β in Biological Fluids; Application to Plasma,Milk and Urine of Cows

Abstract

A rapid HPLC technique was developed to separate estradiol epimers. In order to improve the sensitivity of the detection, a radioitmmunoassay was used.

Estrone, estradiol-17α and estradiol-17β were separated within 20 min using 10 ml of chloroform: acetone (90:10), as the mobile phase. The efficiency of the technique was assessed with ₃ steroids and the assay of collected fractions with antlsera specific to each estrogen. Using a non-specific radioimmunoassay, profiles of endogenous estrogens in different biological fluids (blood plasma, milk, urine) were obtained.

The efficiency of HPLC as a separation method and the high sensitivity of radioimmunoassay as a detector allows us to obtain profiles of estrogens from biological samples where steroid concentration is below lOOpg/ml.     

First example of ruthenium nitroso monoammine complex. Crystal structure of [Ru(NO)(NH3)3(H2O)Cl] × [Ru(no)(NH3)3(OH)Cl][Ru(NO)(NH3)Cl4]2Cl·2H2O

The structure of the interaction products of (NH₄)₂[Ru(NO)Cl₅] solution with ammonium acetate on heating is studied. The crystal structure of the [Ru(NO)(NH₃)₃(H₂O)Cl][Ru(NO)(NH₃)₃(OH)Cl] × [Ru(NO)(NH₃)Cl₄]₂Cl-2H₂O compound (compound I) containing a previously unknown anion of the nitrosomonoammine series is determined: Cc space group; a = 33.530(7) ?, b = 8.202(2) ?, c = 11.844(2) ?; β= 101.54(3)°.     

Supercritical fluid chromatography with redox chemiluminescence detection

Summary The new selective and sensitive redox chemiluminescence detector (RCD), originally developed for gas chromatography, has been successfully interfaced with a capillary column supercritical fluid chromatograph. Interfacing the SFC-RCD was accomplished simply through utilization of the redox reaction chamber presently used for both capillary and packed column GC. The feasibility of this new separation-detection scheme was demonstrated with SFC chromatograms of antioxidant isomers and some compounds of biological relevance. Mobile phase compatibility and signal quenching are also discussed.

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Chromatographie mit überkritischen fluiden phasen unter Verwendung der Redox-Chemiluminescenz-Detektion

     

Organosilicon Amine Complexes of Cobalt(II), Cromium(III), and Neodymium(III): Synthesis and Properties

Organosilicon amine complexes [Co(NH₂R¹)₂Cl₂] (I), [Cr(NH₂R¹)₃Cl₃] (II), and [Nd(NH₂R¹)₃Cl₃] (III) [R¹ = CH₂CH₂CH₂Si(OEt)₃] were synthesized by reacting anhydrous cobalt, chromium, or neodymium chlorides with 3-aminopropyltriethoxysilane (NH₂R¹). Complexes I–III occur as colored viscous liquids that polymerize in air due to hydrolysis of triethoxy groups and condensation of the obtained silanol groups. Organosilicon films with a thickness of 10–200 m on glass and quartz substrates were obtained from liquid compositions containing complexes I–III, siloxanediols HO(SiMe₂O) _n H (n = 2–5), and alkoxysilanes NH₂R¹, MeSi(OMe)₃, and PhSi(OMe)₃ by solidification in air or vacuum. The obtained films were characterized by IR and electron spectroscopies, photoluminescence, transmission electron microscopy, and energy dispersion X-ray fluorescence analyses. IR and electron spectroscopies were used to study the structurization of the films and their behavior when heated to 100–300°C or exposed to gaseous O₂, NO, NH₃, or HCl. The film containing complex I was found to withstand heating in air to 250°C and to change its color in the atmosphere of NO, NH₃, and HCl. Complex I reversibly absorbs oxygen, and in the atmosphere of HCl, it converts into [NH₃R]₂[CoCl₄]. The Z-scanning method was used to uncover the cubic nonlinear-optical properties of the metal complexes.     

Determination of Sugars by LC with On-Line Electrogenerated Cu(HIO6)2]5−–Luminol Chemiluminescence Detection

A novel method was developed for the determination of sugars such as glucose, fructose and lactose by column liquid chromatography coupled with chemiluminescence detection. The LC separation used a Kromasil NH₂ column (250 × 4.6 mm, i.d.: 5 μm, pore size, 100 Å) with a mobile phase consisting of acetonitrile and water. The chemiluminescence detection was based on the enhancement effect of the selected sugars on the chemiluminescence intensity between luminol and [Cu(HIO₆)₂]^5?, which was on-line electrogenerated by constant current electrolysis. The limits of detection for determination of glucose, fructose and lactose were 4, 3 and 20 μg mL^?1, respectively. The proposed method has been successfully applied to the determination of glucose and fructose in grape samples and lactose in milk samples.     

Rapid Quantitation of Verapamil in Plasma by High-Performance Liquid Chromatography

Abstract

A simple and sensitive liquid chromatographic assay procedure using a fluorescence detector for the quantitative determination of verapamil in plasma without extraction was developed. After precipitating the protein with acetonitrile, the resulting supernatant liquid was injected onto the column for analysis. Chromatographic separation was achieved on C₁₈ reversed phase column and the eluting solvent was the isocratic mixture of methanol, acetonitrile and pH 3.0 glycine buffer (1:4:5). With this mobile phase the drug and its internal standard were well separated from the interference of the plasma sample. The average recovery of verapamil from 3 replicate samples of different concentration (100–600 ng/mL) were 95.5 ± 5.68%. The minimum amount of verapamil detectable by this method was 40 ng/mL of sample. The elimination half-life (β-phase) of this drug in rabbits was found to be 3.7 hours.     

Insights into the selective catalytic reduction of NO by NH<Subscript>3</Subscript> over Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>(110): a DFT study coupled with microkinetic analysis

Nitric oxide (NO_x), as one of the main pollutants, can contribute to a series of environmental problems, and to date the selective catalytic reduction (SCR) of NO_x with NH₃ in the presence of excess of O₂ over the catalysts has served as one of the most effective methods, in which Mn-based catalysts have been widely studied owing to their excellent low-temperature activity toward NH₃-SCR. However, the related structure-activity relation was not satisfactorily explored at the atomic level. By virtue of DFT+U calculations together with microkinetic analysis, we systemically investigate the selective catalytic reduction process of NO with NH₃ over Mn₃O₄(110), and identify the crucial thermodynamic and kinetic factors that limit the catalytic activity and selectivity. It is found that NH₃ prefers to adsorb on the Lewis acid site and then dehydrogenates into NH₂* assisted by either the two- or three-fold lattice oxygen; NH₂* would then react with the gaseous NO to form an important intermediate NH₂NO that prefers to convert into N₂O rather than N₂ after the sequential dehydrogenation, while the residual H atoms interact with O₂ and left the surface in the form of H₂O. The rate-determining step is proposed to be the coupling reaction between NH₂* and gaseous NO. Regarding the complex surface structure of Mn₃O₄(110), the main active sites are quantitatively revealed to be O_3c and Mn_4c.     

High-Performance Liquid Chromatographic Determination of Acetazolamide in Human Plasma

Abstract

A simple, rapid and specific HPLC method has been developed to determine acetazolamide concentrations in human plasma. The assay procedure requires only 250 μl of sample with direct injection of the organic supernatant after protein precipitation with acetonitrile. Chlorothiazide was used as an internal standard. A reversed-phase C₁₈ μBondapak column was employed for the chromatographic separation. The eluent was monitored at 265 nm using a UV variable wavelength detector. The retention times for acetazolamide (ACZ) and chlorothiazide (CTZ) were 6 and 8 min respectively. A linear relationship (r).995) was obtained over the 1-20 μg/ml concentration range. The limit of sensitivity for ACZ was 0.5 μg/ml, with greater than 85% recovery of ACZ and internal standard. The method was applied to human plasma samples obtained after administration of a 250 mg acetazolamide tablet.     

Improving continuous chemiluminescence determination method of formaldehyde in the atmosphere: reducing interference of acetaldehyde and others by using iodoform reaction

ABSTRACT

The continuous and selective determination method of formaldehyde (HCHO) in ambient air using chemiluminescence method has been developed. The counter current flow tube was used to collect gaseous formaldehyde. The major interferences of HCHO determination from acetaldehyde, ethanol, and ferrous ion were removed by applying iodoform reaction. Effect of acetaldehyde on chemiluminescence signal of formaldehyde at the same concentration was reduced from 19 to 0.3% by applying iodoform reaction. Subsequently, HCHO was online detected by measuring chemiluminescence produced from the reaction of HCHO, gallic acid, H₂O_2, and KOH. The limit of detection (S/N = 3) was 4.5 ppbv in air. The calibration graph was linear up to 6.25 ppmv. HCHO concentration measured by the present method showed good agreement with that obtained by the 2–4 DNPH-HPLC method.     

Microbore Liquid Chromatography For Analysis of Plasma Pindolol Concentrations

Abstract

Isocratic high-performance liquid chromatographic assay of pindolol with use of a microbore column was developed. the sample preparation involves extraction of alkalized plasma into ether and back extraction into 0.05 N H₂SO₄. Metoprolol was used as the internal standard. Chromatographic separation is performed on a microbore C18 (5 μm) column using acetonitrile-disodium hydrogenphosphate buffer (37:63) containing 20 mM sodium dodecyl sulfate as the mobile phase. the detection is achieved by using a fluorescence detector operated at the excitation and emission wavelengths of 260 and 310 nm, respectively. Acceptable reproducibility and accuracy data are presented over the concentration range normally encountered in human plasma samples. the lower detection limit is 2.5 ng/ml. This sensitivity has been found to be adequate for routine analysis of pindolol in human plasma samples, making the method applicable to pharmacokinetic studies and clinical trials.     

Sequential multiple analyses of atmospheric nitrous acid and nitrogen oxides

Sequential injection analysis (SIA) was applied to multi-gas monitoring for atmospheric analysis. HONO, NO₂ or NO was collected in an individual diffusion scrubber in which the channel array was filled with either HCl or triethanolamine solution. All analytes were collected in the form of nitrite ions in the scrubber, and were transferred via a 12-port selection valve into a 2.5-ml syringe. The reagent, 3-amino-1,5-naphthalenedisulfonic acid (C-acid) solution was subsequently introduced into the syringe, and inter-mixed with the nitrite sample, whereafter the mixed solution was transferred to a heated reactor and held for 3 min at 100 °C. After that, the sample/reagent solution was returned to the syringe and alkalinized. Then, the final solution was analyzed using a homemade fluorescence detector. Atmospheric HONO, NO₂ and NO were successfully monitored 3 or 4 times/h. The limits of detection were 0.22, 0.28 and 0.35 ppbv for HONO, NO₂ and NO, respectively. It was demonstrated for the first time that SIA is a good tool for multi-gas atmospheric analysis. These nitrogen-oxygen compounds are interconvertible, and the simultaneous measurement of these gases is important. Especially, HONO is a source of OH radicals which contribute greatly to atmospheric pollution, and indeed atmospheric chemistry. This method allows the three gases to be measured using one system. The NO₂ and NO data obtained by SIA was compared with those obtained using chemiluminescence instrument. SIA has been successfully applied to atmospheric measurements. Interestingly, it was observed that HONO levels rose toward the end of periods of rain.     

Determination of Cefmenoxime in Human Serum by Ion-Pair Reverse-Phase High Performance Liquid Chromatography

Abstract

A highly reproducible ion-pair reverse-phase high performance liquid chromatographic assay for cefmenoxime in human serum has been developed. A simple sample cleanup procedure is employed. Cefoxitin is the internal standard and separation is achieved using a C-18 μ-Bondapak column. The mobile phase consists of 20% acetonitrile and 80% 0.05 M ammonium acetate buffer containing 0.005 M tetrabutylammonium hydrogen sulphate as the ion-pair agent. Samples are quantitated by UV detector at 254 nm and 0.02 aufs with an assay sensitivity of 0.625 μg/ml. The method has been successfully applied in a clinical setting.     

Asymmetric Anion‐selective Membrane Electrode for Determining Nitric Oxide Release Rates from Ppolymeric Films/Electrochemical Devices

A novel potentiometric method for the determination of nitric oxide (NO) is presented. The assessment of NO levels is based on the rapid reaction of NO with oxyhemoglobin, during which nitrate is formed and then detected potentiometrically using a polymeric membrane anion‐selective electrode. The composition of the anion‐selective membrane is optimized to eliminate the response to high levels of oxyhemoglobin reagent used to react with NO to form NO₃^?. The practical utility of the method is demonstrated by determining the NO release rates from NO donor‐doped polymeric films, as well as from a new electrochemical NO generation system within the range of 10 to 55×10^?10 mol ? min^?1. The values measured with the new assay system are shown to correlate well with a chemiluminescence reference method after accounting for the trapping efficiency of NO by the oxyhemoglobin solution.     

宽工作温度烟气脱硝催化剂制备及反应机理研究

以溶胶-凝胶法制备介孔TiO₂载体,采用分步浸渍法制备了V₂O₅-WO₃/TiO₂催化剂,借助BET、NH₃-TPD、H₂-TPR、SEM、活性评价、In-situ FT-IR等手段,考察了催化剂的结构、酸性、还原性、脱硝活性及反应机理等。介孔TiO₂载体比表面积为158.6 m²/g,制成催化剂后比表面积略有降低,约为136.7 m²/g。针对模拟烟气在φ_NH3/φ_NO=0.8的条件下测试催化剂的脱硝活性温度窗口为250~400 ℃,脱硝转化率达到80%。NH₃-TPD和H₂-TPR表征结果表明,催化剂在活性温度范围内具有典型的表面酸性位,载体TiO₂与V₂O₅之间存在的相互作用使得V₂O₅还原温度降低。利用In-situ FT-IR研究NH₃和NO在V₂O₅-WO₃/TiO₂催化剂表面吸附和氧化的反应过程发现,NH₃可同时吸附在L酸位和B酸位,NH₃在活性位上氧化脱氢形成NH₂物种是SCR脱硝反应的控制步骤。研究NO+O₂+NH₃反应时发现,吸附NH₃的催化剂引入NO和O₂后,共价吸附的NH₃首先消失。选择性催化还原反应发生在吸附态NH₃和气态或弱吸附态的NO之间,该反应遵从Eley-Rideal反应机理。     

A Simple Low-Cost Conductivity Cell for Flow Analysis Measurements

Abstract

A versatile low-cost conductivity flow-cell design is proposed. Its characteristics permit discrete variations in the cell volume and in the electrode area/distance ratio by varying the sealing gasket thickness, favoring high sensitivity applications in continuous flow measurements. Its dynamic characteristics as a flow conductivity detector were observed using a single-line FIA system and standard KC1 solutions, while its performance in routine work was tested by determining the NH₄ ⁺ content in plant Kjeldahl digests using FIA processing. These results are in good agreement with those obtained by the usual distillation/titration method.