Showing papers in "Analytical Sciences in 1991"

Peroxyoxalate Chemiluminescence Assay of Hydrogen Peroxide and Glucose Using 2,4,6,8-Tetrathiomorpholinopyrimido(5,4-d)pyrimidine as a Fluorescent Component.

Abstract: Peroxyoxalate chemiluminescence (CL) assay of hydrogen peroxide (H2O2) or glucose was developed by using 2, 4, 6, 8-tetrathiomorpholinopyrimido[5, 4-d]pyrimidine as a fluorescent component and bis(2, 4, 6-trichlorophenyl)oxalate (TCPO) as an oxalate. Linear relationships between CL intensity and final concentration of H2O2 from 10-8 to 10-4M were obtained. The detection limit at the ratio of CL intensities for sample and blank (S/B) of 3 was 10nM. The precision for five replicate measurements at 10-5 and 10-6M of H2O2 were 17.6 and 15.7% of relative standard deviations, respectively. α-D-Glucose was transformed to β-D-glucose with mutarotase and converted to H2O2 and D-gluconic acid with glucose oxidase, which was detected by using peroxyoxalate CL reaction. A linear calibration graph was obtained up to 1.5×10-4M of glucose solution. The method was applied to the assay of glucose in human serum. The recovery was 98.2% (n=4). The method correlated well with the conventional colorimetric method (r=0.968).

Annular-Shaped Microwave-Induced Nitrogen Plasma at Atmospheric Pressure for Emission Spectrometry of Solutions

Abstract: A high-power high-efficiency microwave-induced nitrogen and air plasma (N 2 and air MIP) for trace element analysis is presented using a new simple surface wave excitor. The excitor consists of two parts: one part is a flat rectangular waveguide with a reduced height, and the other part is a mode transfer consisting of an inner conductor and an outer cylindrical conductor terminated by a front plate. The preliminary analytical performance of the N 2 MIP was examined by measuring the line intensities of Ca II (393.4 nm), Zr II (343.8 nm) and N 2 + (391.4 nm). The plasma is a sensitive ionization source

Preconcentration of trace elements by sorption

Abstract: In the determination of trace elements in complex matrices, enrichment and separation of the analytes is of special importance. A wide variety of methods have been proposed for preconcentration according to the nature of the samples, the types and concentrations of the analytes, and the methods to be used for measurement. Among them, the preconcentration techniques based on sorption seem to be convenient, rapid and capable of attaining a high concentration factor. Various efforts have been made to improve selectivity, rate and capacity of sorption, specially for heavy metals in natural waters. The use of silica gel as a support for loading or chemically immobilizing with complexing agents is a particular example. In this paper, the preparation and characterization of complex-forming adsorbents for the sorption of heavy metals will be critically reviewed, laying stress on the utilization of silica gel as a supporting material.

Determination of Diamino- and Aminopyrenes by High Performance Liquid Chromatography with Chemiluminescence Detection

Abstract: A high performance liquid chromatographic (HPLC) method with chemiluminescence (CL) detection was developed for the sensitive determination of 1, 3-diaminopyrene (1, 3-DAP), 1, 6-DAP, 1, 8-DAP and 1-aminopyrene (1-AP). The HPLC conditions were as follows: column, Cosmosil 5C18 (4.6mm i.d.×250mm); mobile phase, 10mM imidazole- perchloric acid buffer(pH 7.6)-acetonitrile (1:1, v/v); CL reagent, 0.02mM bis(2, 4, 6-trichlorophenyl)oxalate (TCPO) and 15mM hydrogen peroxide in acetonitrile. The oxidative degradation of DAPS and AP in the presence of metals was prevented by adding ascorbic acid to sample solutions. The calibration curves were straight over 2 orders of magnitude for all analytes, and their detection limits (as S/N was 3) were in the sub-fmol range. Dinitro- and nitropyrenes in sooty emissions of diesel- and gasoline-engine cars could be determined by this HPLC after reductive conversion into DAPs and AP, respectively, by refluxing the samples in the presence of sodium hydrosulfide.

Voltammetry with an Ion-Selective Microelectrode Based on Polarizable Oil/Water Interface

Abstract: Theoretical expressions are presented for the potential step chronoamperometry, normal pulse voltammetry and cyclic voltammetry of the ion-transfer at an ion-selective microelectrode in which a polarizable nitrobenzene/water interface is formed at the tip of a micropipet of μm-order diameter with the nitrobenzene phase inside the micropipet. Experiment includes the ion transfer voltammetry of acetylcholine at the microelectrode. The experimental results are well explained by the theoretical predictions. Stripping voltammetry with the microelectrode is also studied; this proved to be promising for determination of acetylcholine at micromolar concentration levels.

Surface enhanced infrared absorption spectroscopy : mechanism and application to trace analysis

Abstract: Infrared (IR) absorption of molecules is enhanced greatly (10 1 -10 3 times) when they are adsorbed on or near vacuum-evaporated Ag or Au thin films. By using this Surface Enhanced IR Absorption (SEIRA) phenomenon, we could obtained IR spcctra of some organic molecules of a few picogram amount in good signal-to-noise ratios. Thus, the SEIRA spectroscopy is promising as a new trace analytical technique. General properties of SEIRA found in our experiments are summarized. An electromagnetic theory of this phenomenon is proposed

High-performance liquid chromatographic determination of ofloxacin in serum

Abstract: A high-performance liquid chromatographic method was developed for the assay of ofloxacin in serum. The serum samples were filtered through a Molcut II membrane filter after partial deproteinization in order to remove proteins. The filtrate was preseparated on a reversed-phase precolumn and introduced onto a reversed-phase analytical column by applying column-switching techniques. Ofloxacin and nalidixic acid as internal standards were detected by absorbance measurements at 300nm. Using this system the concentration of ofloxacin could be determined at a limit of the order of 20ng/ml, with a linear dynamic range of 80-4000ng/ml. This procedure was applied to pharmacokinetic studies of healthy volunteers treated with ofloxacin.

Determination of Nicotinic Acid and Nicotinamide in Human Serum by High-Peformance Liquid Chromatography with Postcolumn Ultraviolet-Irradiation and Fluorescence Detection

Abstract: A high performance liquid chromatographic method involving postcolumn ultraviolet (UV) irradiation and fluorometric detection has been developed for the simultaneous determination of nicotinic acid and nicotinamide in human serum. These compounds are separated by reversed-phase chromatography using a 0.07 M potassium dihydrogen-phosphate solution (pH 4.5) containing 75 mM hydrogen peroxide and 5 μM copper(II) sulfate as a mobile phase. The compounds in the column effluent are irradiated with ultraviolet light to produce fluorescence. This fluorescence is monitored with excitation at 322 nm and emission at 380 nm

Micellar Electrokinetic Capillary Chromatography of Porphinato Chelates as a Spectrophotometric Approach to Sub-Femtomole Detection of Metal Chelates

Abstract: Liquid chromatography (LC) is a powerful tool in trace metal analysisl-3, especially in cases where the available quantity of samples is strictly limited, e.g. clinical examination, air pollution monitoring, and quality control in the electronics industry. Although the current sensitivity is high, it is often limited by peak broadening due to the large elution volume used and slow mass-transfer kinetics. In fact, the LC column is an effective dilution device.4 A powerful alternative seems to be the micellar electrokinetic capillary chromatography (MECC) system in which the electroosmotic delivery of a mobile aqueous phase with a micellar pseudo-stationary phase is utilized; this system was first described by Terabe and coworkers.5-' In this type chromatography, an almost ideal plug-flow velocity profile of electroosmotic fluids and a micellar pseudo-stationary phase of colloidal dimension dispersed in a bulk aqueous phase provide extremely high theoretical plate numbers (more than 2X105 plates/60 cm, HETP=(2 4) μm).56 Excellent success of the MECC system has been demonstrated for the separation of phenols5, amino acids', B6 vitamers9, oligonucleotides10, and metal chelates11, as well as a theoretical bases for the separation processes presented.6,12,13 Although such extremely high efficiency of the MECC (sharpness of peaks) can undoubtedly afford an improvement of the spectrophotometric detection limits (D.L.), there is a possible disadvantage associated with the minute detector volume and short light path length. In the case of the oncolumn absorbance detection mode, the detector light path is as long as the diameter of the capillary used (typically 0.05 mm), which is by a factor of 1/200 shorter than that of ordinary 10 mm cells. Nonetheless, indeed, the very low detection limit on a mass basis (1.4 fmol f or the 4-(2-pyridylazo)resorcinolatoCr(III) chelate) has been suggested.ll An investigation has thus been conducted to assess the attainable D.L. of metals with the MECC-spectrophotometric detection system using water-soluble porphines as precolumn labeling agents, since they have enormous great molar absorption coefficients (E~ 7X105 cm 1 M-1) at the Soret absorption bands.14 Among the porphine analogs examined, aj3,y,S-tetrakis(4carboxyphenyl)porphine (TCPP) was found to be one of the most promising reagents for MECC application using a sodium dodecyl sulfate (SDS) micellar solution. The present work describes the first access to the subfemtomole detection of metal chelates in solution with a spectrophotometric means coupled with the MECC separation scheme without any preconcentration processes.

Micellar-Enhanced Highly Sensitive Reaction of Rare Earths with Xylenol Orange and Surfactants. Study of Reaction Conditions and Optimization of Spectrophotometric Method

Abstract: Reaction conditions in rare earths(RE)-Xylenol Orange(XO)-cationic surfactant ternary system were studied in detail. Conditional molar absorptivities up to 150000 mmol -1 cm 2 were reached. Highly sensitive spectrophotometric method for 15 RE elements (REE) was evaluated under optimal conditions of 0.06 mmol dm -3 XO, 0.6 mmol dm -3 cetylpyridinium bromide, and 0.01 mol dm -3 acetate buffer of pH 4.50

Preparation of radioactive multitracer solutions from Au, Ag, and Cu foils irradiated with high-energy heavy ions

Abstract: Au, Ag, and Cu foils were irradiated with high-energy heavy ions accelerated by the RIKEN Ring Cyclotron. Each foil was dissolved in aqua regia or nitric acid. The target materials, Au, Ag, and Cu, were precipitated as metallic Au, AgCl, and CuSCN, respectively, and filtered out to yield carrier- and salt-free multitracer solutions containing a large number of radioactive nuclides

Capillary electrophoresis with o/w microemulsions of water/sds/1-butanol/heptane

Abstract: Capillary electrophoresis which utilized o/w microemulsions (ME) composed of water/sodium dodecyl sulfate/l-butanol/heptane as the electrophoretic media was demonstrated. Effects of composition of ME and pH were examined on the migration behavior of neutral and ionic sample solutes

Separation and determination of divalent metal ions with uv-absorbing chelating agents by capillary electrophoresis

Abstract: Capillary electrophoresis separation of several divalent metal ions, as well as iron(III) and silver(I) was examined with chelating agents. The metal chelates separated in the capillary were measured by on-column UV-absorption detection. When 1, 2-cyclohexanediamine-N, N, N' N'-tetraacetic acid(CyDTA) was used as an chelating agent in a carrier solution (pH 9) the order of the migration time (tm) of metal ions was as follows: Ba2+ Zn2+) and Cd2+

Crystal Structure of (2, 2′-Bipyridine)dichloropalladium(II)

Abstract: Palladium(II) complexes, cis-[PdL2X2] and cis-[Pd(biL)X2] (L=monodentate and biL=bidentate ligand; X=halide ion), are of great interest because of their cis geometry, which is analogous to that of antitumor platinum complexes. In this study a Pd(II) complex having a cis-planar geometry was synthesized using 2,2'-bipyridine (bpy); the structure was determined by X-ray crystallography. A yellow prism-like single crystal of [Pd(bpy)Cl2] was obtained from a mixture of [Pd(PhCN)2C12] (PhCN= benzonitrile) (19.2 mg, 0.05 mmol), [Pd(dba)2] (dba=dibenzylideneacetone) (28.8 mg, 0.05 mmol) and bpy (15.6 mg, 0.10 mmol) in CH2C12 (10 ml). Data collection was performed on a Rigaku AFC-5R diffractometer under the conditions given in Table 1. The structure was solved by a direct method (MITHRIL)1 and an empirical, spherical, absorption correction was performed using a program called DIFABS2 after an isotropic refinement for all nonhydrogen atoms. The scattering factors and anomalous dispersion corrections for non-hydrogen atoms were taken from ref. 3. A refinement of non-hydrogen atomic

Coprecipitation of Traces of Heavy Metals with Indium Hydroxide for Graphite-Furnace Atomic Absorption Spectrometry

Abstract: Nanogram quantities of copper(II), chromium(III) and manganese(II) in a 100-ml water sample were quantitatively coprecipitated with indium hydroxide at pH 9.5. The precipitate was centrifuged and dissolved in 0.5M hydrobromic acid. The desired heavy metals in the solution (5ml) were directly determined by graphite-furnace atomic absorption spectrometry, where the indium was nearly completely removed by volatilization as bromide at the ashing step. Though no loss of the analytes mentioned above was observed, cadmium and lead were significantly lost during the ashing stage. The time required for the coprecipitation and determination was about 30min.

Separation and detection of protein as a supramolecular complex using capillary electrophoresis

Abstract: From a high performance capillary electrophoretic experiment in a phosphate buffer (pH 3.5), Eosine Y was found for the first time to migrate together with protein in a capillary tube as a supramolecular complex. This finding gave us not only the possibility to overcome the serious problems in protein estimation, but also the possibility to measure the Eosine Y in place of protein much more sensitively by several methods. However the results obtained so far were not so good

Flow-Injection Analysis with Chemiluminescence Detection of Glucose and Uric Acid Using Immobilized Enzyme Reactor

Abstract: A rapid and sensitive flow-injection method with peroxyoxalate chemiluminescence (CL) detection for the determination of glucose and uric acid by using an immobilized enzyme reactor is described. CL produced in a flow cell by the reaction of hydrogen peroxide with bis(2, 4, 6-trichlorophenyl)oxalate and a fluorescent compound, 2, 4, 6, 8-tetrathiomorpholinopyrimido[5, 4-d]pyrimidine, was monitored. Linear responses between the concentration and the CL intensity for glucose and uric acid were obtained up to 3×10-4M (6nmol per 20μl injection, r=0.999) and 1×10-5M (0.2nmol per 20μl injection, r=1.000), respectively; both limits of detection were the same (5×10-7M, 10pmol per 20μl injection, S/N>3). The relative standard deviations for ten replicate measurements were 1.1% for glucose (2×10-5M, 0.4 nmol/injection) and 2.2% for uric acid (5×10-6M, 0.1nmol/injection). Good correlations between the results of serum glucose or uric acid assay by the proposed methods and by the conventional colorimetric methods (r=0.994for glucose and r=0.986 for uric acid) were obtained.

Organotin compounds in marine mussels collected from italian coasts

Abstract: Organotin compounds were determined in mussel samples collected in several Italian harbours and coastal environments. Interesting data were obtained from La Spezia and Taranto harbours (organotin levels in mussels were found to be relatively high), were some of the most representative Italian mussel farms are located. Preliminary results are here summarized and discussed.

Separation chemistry for the nuclear industry

Abstract: A review of the actinide and lanthanide extraction chemistry by N, N-dialkylamides and N, N'- tetraalkylamides is given. It includes the extraction equilibria of inorganic acids. The prospects of using. these completely incinerable extractants in the nuclear fuels cycle is discussed.

Chemical composition of kosa aerosol (yellow sand dust) collected in japan

Abstract: Typical Kosa aerosol was simultaneously collected at several sampling sites in Japan, during spring, 1988. After the sample was separated for water soluble fraction and insoluble fraction, many elements and ions in both fractions were determined by ICP-AES and IC. The higher atmospheric concentrations of crustal elements and NO 3 − and Non-sea-salt(nss)SO 4 2− were measured in Kosa aerosol than those in non-Kosa aerosol

Species analysis of inorganic compounds in workroom air by atomic spectroscopy

Abstract: Sampling methods for the determination of volatile inorganic compounds in workroom air are described. The main factor affecting the adsorption capacity of activated charcoal for iron pentacarbonyl is air flow rate. Nickel tetracarbonyl is collected quantitatively at flow rates of up to 1l/min if the volume of air sampled does not exceed 1001. Arsine, phosphine and stibine are collected quantitatively from air by use of a double filter air cassette Silver nitrate impregnated backing pads are shown to trap the hydrides with better than 99.9% efficiency. Several atomic spectroscopic methods have been applied to the determination of these volatile species, with electrothermal atomic absorption and inductively coupled plasma atomic emission spectroscopy being preferred. Concentrations of the hydrides in various workroom atmospheres were found to be well below the Threshold Limit Values.

Voltammetry for the ion transfer through a membrane

Abstract: The voltammogram, VITTM, is introduced for the transfer of an ion, i z , from one aqueous solution, W1, to the other aqueous solution, W2, through a membrane, M, of organic solution (Org). The voltammogram is considerably different from that for the transfer of i z at the W/Org interface, VITIES, as follows; (1) The potential window observed in VITTM is about the twice of that in VITIES. (2) The slope of a reversible ion transfer wave in VITTM is much smaller than that in VITIES

Determination of Germanium, Arsenic, Antimony, Tin and Mercury at Trace Levels by Continuous Hydride Generation-Helium Microwave-Induced Plasma Atomic Emission Spectrometry

Abstract: A method for the continuous introduction of volatile hydrides and mercury into a helium microwave-induced plasma using a hydrogen separation membrane has been developed. Upon passing the evolved gaseous species through a hollow-fiber membrane, hydrogen and water vapor were removed, while the hydrides and mercury were left and introduced into the plasma. The detection capabilities of a tangential flow torch and two capillary discharge tube torches were compared. The effects of the carrier and auxiliary gas flow rates, hydrogen separation temperature and volume of buffer tank were investigated for germanium. The detection limits for Ge, As, Sb, Sn and Hg were 0.04, 0.32, 6.1, 1.4 and 0.50ng/ml, respectively. The relative standard deviation of the emission intensities of Ge at 5ng/ml was 1.4% (n=7).

Effect of ligands on the redox reaction of metal ions and the use of a ligand buffer for improving the end-point detection in the potentiometric titration of vanadium(V) with iron(II).

Abstract: The effect of complexing agents on the titration of vanadium(V) with iron(II) was studied. Complexing agents which form more stable complexes with iron(III) than iron(II) produce a sharper titration of vanadium(V) with Iron(II). Citrate, pyrophosphate and EDTA improve the potential break at the equivalence point. The presence of excess EDTA decreases the formal potential of the V(V)/V(IV) couple due to the formation of vanadium(V)-EDTA complexes. The use of a ligand buffer with zinc(II) in excess over EDTA is very effective for improving the end-point detection in the titration, preventing the formation of vanadium(V)-EDTA complexes.

Analysis of products synthesized from simulated primitive planetary atmospheres. I: Amino acids

Abstract: Gas mixtures simulated primitive earth atmospheres were irradiated with high energy protons, and amino acids in the products were analyzed by liquid chromatography, gas-liquid chromatography and liquid ionization mass spectrometry. When a mixture of carbon monoxide, nitrogen and water was irradiated with 2.8-40MeV protons generated with accelerators, various kinds of amino acids were detected in the products. Hydrogen cyanide, which is believed to be a precursor of amino acids, was determined with a cyanide-selective electrode. G-value of glycine was about 0.02 when either methane or carbon monoxide was used as a carbon source in irradiation experiments. The present results show that cosmic rays are more effective energy sources for prebiotic synthesis of amino acids than conventionally considered energy sources like spark discharges.