Showing papers in "Analytical Sciences in 1997"
TL;DR: In this paper, a column-switching technique using a titania (TiO2) precolumn and an anion-exchange analytical column was developed for the analysis of the phosphorylation products of a kemptide.
Abstract: A highly selective organic phosphates analyzer was developed based on a column-switching technique using a titania (TiO2) precolumn and an anion-exchange analytical column. In the preliminary examination, it was proved that the titania column strongly retains the organic phosphates under acidic conditions while it shows no retention in alkaline eluents. Based on these findings, the organic phosphates were selectively trapped on the titania precolumn in an acidic eluent, transferred to an anion-exchange column by a basic eluent and detected by coloration after a postcolumn phosphomolybdic acid reaction. When 25.0μM each of phospho-amino acids solution was determined (injection volume, 100μl), the relative standard deviations were 2.3-2.8% (n=5). The detection limits (S/N=3) of the phospho-amino acids were ca. 2.0μM as the injected concentration. The present analyzer was successfully applied to the analysis of the phosphorylation products of a heptapeptide (kemptide).
97 citations
TL;DR: In this paper, the solvent extraction of copper(II) in 1 mol dm -3 Na(SCN, NO 3 ), in which the thiocyanate concentration was 0.01 to 1 mol Dm −3, with tetrabutylammonium ions (tba + ) into chloroform and with trioctylphosphine oxide (TOPO) into hexane was studied.
Abstract: The solvent extraction of copper(II) in 1 mol dm -3 Na(SCN, NO 3 ), in which the thiocyanate concentration was 0.01 to 1 mol dm -3 , with tetrabutylammonium ions (tba + ) into chloroform and with trioctylphosphine oxide (TOPO) into hexane was studied. Also, the solvent extraction of copper(I), which was formed by reducing copper(II) by ascorbic acid in these aqueous solutions, was studied. By a statistical analysis of the extraction data, it was concluded that copper(I) was extracted as tba + Cu I (SCN) 2 - and Cu I SCN(TOPO) 3 , and copper(II) was extracted as (tba + ) 2 Cu II (SCN) 4 2- and Cu II (SCN) 2 (TOPO) 3 . Although copper(I) was extracted with both extractants better than copper(II) in the lower thiocyanate concentration range, copper(II) was extracted better in the higher thiocyanate concentration range. This was concluded to be due to better extraction of the extractable species of copper(I) than those of copper(II); however. copper(I) formed unextractable complexes much more than did copper(II) in the higher thiocyanate concentration range in the aqueous phase.
50 citations
43 citations
TL;DR: Chromium(III) and Chromium(VI) have been speciated by capillary electrophoresis (CE) with on-column UV-Vis detection at 254nm and a negative potential as mentioned in this paper.
Abstract: Chromium(III) and Chromium(VI) have been speciated by capillary electrophoresis(CE) with on-column UV-Vis detection at 254nm and a negative potential. Chromium(III) has been converted to an anionic complex using ethylenediaminetetraacetate (EDTA) to be detected simultaneously with Cr(VI) by CE. A cationic surfactant, cetyltrimethylammonium bromide (CTAB), was added to a buffer solution of 10mM phosphate in order to reverse the electroosmotic flow (EOF) in the capillary. This results in a short analysis time and better peak shapes. The effect of the buffer pH over the range of 6 to 11 on the separation of each species has been observed. Nitrate and chromate have been nicely separated at a higher pH. Linear calibrations for chromate and a chromic EDTA complex were established over the concentration range of 50-200pg/nl with detection limits of 1.5pg/nl and 5pg/nl, respectively, using a 10mM phosphate buffer and a 0.5mM CTAB solution.
37 citations
TL;DR: In this article, a coprecipitation method with hafnium hydroxide was studied for the determination of chromium(III) and chromium (VI) in water by graphite-furnace atomic absorption spectrometry.
Abstract: A coprecipitation method with hafnium hydroxide was studied for the determination of chromium(III) and chromium(VI) in water by graphite-furnace atomic absorption spectrometry. Both 0.04 - 1.6 μg of chromium(III) and 0.04 - 1.6 μg of chromium(VI) in a 200 cm 3 water sample were quantitatively coprecipitated with hafnium hydroxide at pH 5.7; 0.04 - 1.6 μg of chromium(III) alone was done at pH 11. Each of the precipitates obtained at pH 5.7 and 11 was dissolved in nitric acid; the solutions were then diluted to 10 cm 3 and subjected to determinations of the total amount of chromium(III) and chromium(VI) and the amount of chromium(III) alone, respectively. The detection limits were 0.02 ng cm -3 of chromium(III) and chromium(VI) in 200 cm 3 of the initial sample solutions. The thirty four matrix ions tested did not produce any serious interference effects in the chromium(III) determination. Although the presence of fluoride, phosphate, and sulfate tended to reduce the recovery of chromium(VI), they could coexist up to amounts of 1 mg, 1 mg, and 50 mg, respectively.
37 citations
TL;DR: In this article, a highly reliable optical sensor for oxygen-pressure measurements was developed based on the phosphorescence quenching of platinum octaethylporphyrin incorporated in polymer films by oxygen.
Abstract: A highly reliable optical sensor for oxygen-pressure measurements was developed. It was based on the phosphorescence quenching of platinum octaethylporphyrin incorporated in polymer films by oxygen. In this work, in order to overcome the shortcomings when the traditional spectrophotometer is used for oxygen sensing, the sensor behaviors were studied using a CCD-camera scanning technique. The Stern-Volmer plots of oxygen sensors showed improved linearity, compared with those of the traditional luminometer. The sensor was proved to have a good operational stability and <10% of the photobleaching was observed after storage for more than 1 year in the absence of light at room temperature.
36 citations
TL;DR: In this paper, a method for determination of bovine serum albumin (BSA) and γ-globulin (γ-IgG) at nanogram levels is proposed by using a common spectrofluorometer to detect the intensity of resonance light-scattering.
Abstract: A method for determination of bovine serum albumin (BSA) and γ-globulin (γ-IgG) at nanogram levels is proposed by using a common spectrofluorometer to detect the intensity of resonance light-scattering. In the presence of BSA or γ-IgG at pH 1.86 and ionic strength 0.04, the aggregation of α, β, γ, δ-tetrakis(4-sulfophenyl)porphine (TPPS4) was observed. It was found to result in strong enhanced resonance light-scattering (RLS) signal with a scattering peak at 490.0nm. But at pH 1.86 and ionic strength 0.11, only BSA can induce the aggregation of TPPS4 resulting in the strong enhanced RLS. Determination for synthetic samples by making use of the effect of ionic strength showed that if the ratio of γ-IgG in the mixture of γ-IgG and BSA is lower than 0.20, the results for the simultaneous determination of BSA and γ-IgG fractions without separation are satisfactory, but if the content of γ-IgG in the mixture is too high, the determination error is significant. However, the total content of BSA and γ-IgG in human serum can be determined with results identical to those obtained according to the Bradford method using CBB G-250.
36 citations
TL;DR: In this article, the authors used a bis(2,4,6-trichlorophenyl)oxalate(TCPO)hydrogen peroxide (H202) system with fluorescent compounds, such as Eosin Y, rhodamine B isothiocyanate, tetramethylrhodamine R isomer R and fluorescamine.
Abstract: In the past several years, capillary electrophoresis (CE) has been shown to be a powerful and efficient analytical separation technique. One of the major areas of study is the development of sensitive detection methods. Oncolumn optical detection modes, such as UV absorption and fluorescence detection, are the most commonly used, on account of the extremely small sample zone and the small capillary dimensions in CE. Chemiluminescence (CL) has been verified to be a highly sensitive detection method in both flow injection analysis (FIA) and highperformance liquid chromatography (HPLC).1 Due to its simple optical system and low background nature, CL is expected also to be an ideal detection method for CE. Recently, the applicability of CL detection in CE has been successfully demonstrated. Several CL reagents, such as luminol2'3, acridinium4 and peroxyoxalate5,6 have been utilized. The present authors have for the first time reported on a CL detection of proteins separated by CE,5,6 The bis(2,4,6-trichlorophenyl)oxalate(TCPO)hydrogen peroxide(H202) system was used together with fluorescent compounds, such as Eosin Y, rhodamine B isothiocyanate, tetramethylrhodamine isothiocyanate isomer R and fluorescamine. The proteins labeled with them were quantitatively analyzed by the CE-CL detection method with detection limits of 10.8 -10-7 mol dm 3 orders. It is well known that the CL emitted by luminol in the presence of H202 is remarkably enhanced by a catalyst, such as metal ions and their complex compounds. It has been used for the determination of a small amount of
33 citations
TL;DR: In this paper, the authors describe the construction and preliminary characterization of open tubular capillary column ion chromatography, and two different kinds of columns were developed and investigated for capillary ion ion chromation.
Abstract: Construction and preliminary characterization of open tubular capillary column ion chromatography is described. Increasing the column temperature resulted in a dramatic increase of the column efficiency. Two different kinds of columns were developed and investigated for capillary ion chromatography. One was a 50μm i.d. fused silica capillary tubing, and another was a 50μm i.d. silica capillary coated with Latex particles (diameter: about 360nm). Both columns showed good separations of inorganic anions, although the capillary coated with Latex particles showed much larger retention than a bare silica capillary.
33 citations
TL;DR: In this article, a water-soluble cationic chelate, iron(II)-tris(1, 10-phenanthroline) [Fe(phen)3]2+, was well extracted into the polymer phase as the ion-pair with perchlorate.
Abstract: When an aqueous solution of a water-soluble polymer, poly(N-isopropylacrylamide) (PNIPAAm), was heated above 32°C, the polymer became insoluble, and then formed paste-like precipitates (polymer phase) having a very small volume fraction. A water-soluble cationic chelate, iron(II)-tris(1, 10-phenanthroline) [Fe(phen)3]2+, was well extracted into the polymer phase as the ion-pair with perchlorate. On the basis of the volume fractions of the aqueous and polymer phases, the logarithmic distribution constant of the ion pair evaluated was 2.53±0.05, promising high efficiency in the concentration of the ion pair. Based on the spectra of 1-(4-hydroxyphenyl)-2, 4, 5-triphenylpyridinium hydroxide inner salt and 1-ethyl-4-carboxymethoxypyridinium iodide in the polymer phase, the polar parameters, ET(1) and Kosower′s Z values of the PNIPAAm phase were 257 and 333kJ mol-1. These results suggest that the solvent properties of the polymer phase correspond to those of alcoholic solvents, such as methanol or ethanol. The high extractability of the [Fe(phen)3]2+(ClO4-)2 ion pair was ascribable to the polar properties of the polymer phase.
31 citations
TL;DR: In this article, the electron inelastic mean free path (IMFP) was estimated to be 1.00nm, which was one half of the usually accepted length, for 1630eV kinetic energy electrons in Ag from the reduction factor of the backgrounds of the total reflection X-ray photoelectron spectra.
Abstract: X-Ray photoelectron spectra were measured when the excited X-rays were impinged on a Ag surface with a grazing angle. The spectral backgrounds owing to the electron inelastic scattering in solids were lower when the incident X-rays were totally reflected than when the X-rays were not totally reflected. We developed a new method to estimate the electron inelastic mean free path (IMFP). The IMFP was estimated to be 1.00nm, which was one half of the usually accepted length, for 1630eV kinetic energy electrons in Ag from the reduction factor of the backgrounds of the total reflection X- ray photoelectron spectra.
TL;DR: In this article, a method based on preconcentration on a membrane filter with a finely pulverized anion exchange resin was developed for the determination of gallium in water samples by electrothermal atomic absorption spectrometry.
Abstract: A sensitive method based on preconcentration on a membrane filter with a finely pulverized anion-exchange resin has been developed for the determination of gallium in water samples by electrothermal atomic absorption spectrometry. Gallium (10-60)ng, in 20-500ml of a sample solution, was retained as a Pyrocatechol Violet complex anion on a resin at pH 5; the resulting resin was filtered through a membrane filter. A portion of the resin with the membrane filter (3mm in diameter) was inserted into a cuvette, and the absorbance of gallium was measured at 294.4nm. The relative standard deviations for five measurements at 30ng of gallium was 5%. The detection limit was 1.5ng of gallium in 500ml (3ngGa l-1) of the water sample. The interference of various ions was studied, and the optimum conditions were developed for the determination of gallium in mine-drainage and river-water samples.
TL;DR: In this paper, an accurate and simple quantitative method for determining levodopa and methyldopa is proposed, which has been extended to the determination of these drugs in dosage forms.
Abstract: An accurate and simple quantitative method for determining levodopa and methyldopa is proposed. Cerium(IV) has been successively used to react with drugs in 2M H2SO4†at 80°C. The absorbance of colored products was measured at 510 and 550nm for levodopa and methyldopa, respectively. The method has been extended to the determination of these drugs in dosage forms. The results have been statistically compared with those obtained by the reference method.
TL;DR: In this article, the application of chelation ion exchange resins I-IX for selective extraction of certain metal ions was evaluated on the basis of the distribution ratio (D) showing the following order: DFe(III), Cu(II), Cd(II) and Pb(II).
Abstract: Chloromethylated polystyrene resin was chemically modified with ethylenediamine, diethylenetnamine and triethylene- tetramine to polystyrene-polyamine resins (I-III). The latter resins were further reacted with two formylsalicylic acid isomers, 3-formylsalicylic acid and 5-formylsalicylic acid, to produce the cross-linking polystyrene-polyamine- formylsalicylic acid resins (IV-IX). The possible chemical structure of I-IX was confirmed from the elemental analysis and FT-IR studies. The applicability of I-IX to extraction of Fe(III), Cu(II), Cd(II) and Pb(II) from aqueous solutions was also studied by using the batch equilibrium technique in different buffer solutions and at different shaking time. Several trends were drawn out from the metal capacity values concerning the chemical structure of the amine and formylsalicylic acid moieties. The application of chelation ion exchange resins I-IX for selective extraction of certain metal ions was evaluated on the basis of the distribution ratio (D) showing the following order: DFe(III)_??_DCd(II)> DPb(II)>DCu(II).
TL;DR: Cation exchange and size exclusion methods with postcolumn fluorescence detection using 5-sulfo-8-quinolinol were applied to the chemical speciation of aluminum in soil-extract samples as mentioned in this paper.
Abstract: Cation exchange and size exclusion high-performance liquid-chromatographic methods with postcolumn fluorescence detection using 5-sulfo-8-quinolinol were applied to the chemical speciation of aluminum in soil-extract samples The addition of an appropriate amount of F- to the postcolumn reagent solution makes it possible to eliminate the interference of F- in a sample with Al3+ detection The reliability of this method was evaluated by a computer-assisted equilibrium calculation for aluminum species and ICP atomic emission spectrometry Considerable parts of water-soluble Al3+ (the Al3+ fraction extracted into distilled water) in both sedimentary and granitoid soil samples were found to be complexed with organic substances On the other hand, exchangeable Al3+ (the Al3+ fraction extracted into 1mol dm-3 KCl) in granitoid soil samples was mostly free Al3+
TL;DR: In this paper, the xanthomonasin A was identified with the molecular mass measured by FABMS, using micellar electrokinetic chromatography (MEKC) with a 20mM sodium dodecyl sulfate (SDS) solution containing 50mM phosphate buffer, pH 7.0, and 20% acetonitorile.
Abstract: Capillary electrophoretic methods have been developed for the analysis of Monascus yellow pigments for food additives. Monascus yellow pigments were successfully separated by micellar electrokinetic chromatography (MEKC) with a 20mM sodium dodecyl sulfate (SDS) solution containing 50mM phosphate buffer, pH 7.0, and 20% acetonitorile or a 2.0% butyl acrylate/butyl methacrylate/methacrylic acid copolymer sodium salts (BBMA) solution containing 20mM ammonium formate buffer, pH 7.0, and 10% methanol. The xanthomonasin A was identified with the molecular mass measured by FABMS. Monascus yellow pigments were extracted from candies with solid phase extraction and analyzed by the developed technique.
TL;DR: In this paper, double-stranded DNA was immobilized on poly(N-isopropylacrylamide), which is temperature-sensitive and gives precipitates from an aqueous solution when heated over 31°C.
Abstract: We immobilized double-stranded DNA on poly(N-isopropylacrylamide), which is temperature-sensitive and gives precipitates from an aqueous solution when heated over 31°C. Photochemical conjugation with a vinyl derivative of psoralen was demonstrated to make the DNA polymerizable with a vinyl monomer. The radical copolymerization with N-isopropylacrylamide gave the temperature-responsive conjugate. The conjugate was shown to capture ethidium, a D0NA-binding genotoxin, and precipitate with it when heated. About 95% of ethidium was separated from its highly diluted solution (3ppm).
TL;DR: An amperometric alcohol-sensing electrode prepared by immobilizing alcohol oxidase (AOx) in a polyion complex membrane showed permselectivity based on the solute size with a molecule weight cut-off of ca.
Abstract: An amperometric alcohol-sensing electrode was prepared by immobilizing alcohol oxidase (AOx) in a polyion complex membrane. Three kinds of aqueous solutions (poly(4-styrenesulfonate)-, AOx- and poly-L-lysine-containing solutions) were successively placed on the surface of a glassy carbon electrode and the electrode was allowed to dry. The anodic current (at 1V vs. Ag/AgCl) of the enzyme electrode increased immediately after the addition of alcohols (e.g., ethanol), and reached a steady state within 5s. A linear response to ethanol was observed up to 0.4mM with a detection limit of 0.5μM. The polyion complex membrane showed permselectivity based on the solute size with a molecule weight cut-off of ca. 100, which was very effective in suppressing the electrochemical interference by L-ascorbic acid and uric acid. The enzyme electrode was applied to the determination of ethanol in alcoholic drinks and soy sources. The electrode could be used for two weeks.
TL;DR: The quantitation of drug concentration in a cell using a new microscopic method, named laser-induced photo-thermal microscopy, was demonstrated and made possible highly sensitive detection of a drug in fixed organs.
Abstract: The quantitation of drug concentration in a cell using a new microscopic method, named laser-induced photo-thermal microscopy, was demonstrated We used a paraformaldehyde-glutaraldehyde- fixed guinea pig′s kidney to which we administered tobramycin and assayed the quantity of colloidal gold immunologically bound to the tobramycin in the epithelial cell of one renal tubule We could detect the locally concentrated tobramycin in the epithelial cell, as well as its local distribution quantitatively The detection limit of the tobramycin concentration (10zmol ) was 10-times superior to that of confocal scanning laser microscopy The colloidal gold which we used for immunochemical staining remained stable to laser-beam radiation and gave a low background Therefore, it makes possible highly sensitive detection of a drug in fixed organs
TL;DR: In this article, a portable micro-flow analyzer was used for on-site determination of phosphorus as ortho-phosphate at ppb-levels, and nitrogen as nitrite and nitrate in environmental samples.
Abstract: On-site analytical methods for the determination of trace amounts of phosphorus and nitrogen in environmental water samples were investigated by using flow-injection (Fl) technique. Detection reactions used for on-site chemical analysis for ortho-phosphate, nitrite and nitrate were examined. For economizing the reagents and cutting down waste arose along with chemical analysis to enhance zero emission, a micro-flow injection (μFI) technique, in which each flow rate was below one tenth of conventional FI systems and was 50μl min -1 , was investigated fundamentally and applied to on-site analysis, and also a micro-reactor such as a miniature column for the reduction of nitrate to nitrite was developed. To realize the on-site spectrophotometric measurement, an easy-to-move and a one-box type chemical analyzer was newly developed. The analyzer is based on a μFI technique, works with a battery (12V) and can analyze samples rapidly on site with better precision and higher sensitivity than conventional FI systems. For the sensitive determination of phosphate, an ion association reaction of molybdophosphate with Malachite Green was used. Nitrate and nitrite were determined spectrophotometrically on the basis of a diazotization-coupling reaction, where nitrate was reduced to nitrite with a Cd/Cu miniature column prior to the reactions. A newly developed portable micro-flow analyzer was found to be useful for on-site determination of phosphorus as ortho-phosphate at ppb-levels, and nitrogen as nitrite and nitrate at ppb-levels in environmental samples.
TL;DR: In this article, the authors have investigated the electrochemical behavior of double-stranded DNA and single-standed DNA adsorbed on conducting polymer modified electrode in presence of cobalt complex and discussed the possibility of using such electrode as gene detector.
Abstract: Detection of DNA is a very important task for molecular biology and biomedical field. We have investigated electrochemical behavior of double-stranded DNA and single-stranded DNA adsorbed on conducting polymer modified electrode in presence of cobalt complex. The possibility of using such electrode as gene detector is discussed.
TL;DR: Ion association properties of four kinds of anionic divalent azo dyes were investigated in an aqueous solution containing hydrophobic quaternary ammonium ions in this article.
Abstract: Ion association properties of four kinds of anionic divalent azo dyes were investigated in an aqueous solution containing hydrophobic quaternary ammonium ions. The dyes used in this study possessed a hydroxy and a sulfonate group, which existed as a divalent anion in an alkaline solution. In capillary electrophoresis measurements, the apparent electrophoretic mobility of the dyes decreased along with an increase in the concentration of quaternary ammonium ion (Q(+)) in a migrating solution. Ion association constants of the dyes with Q(+), K(ass), were determined by a simulation method of the mobility change using a non-linear least square method, when 1:1 ion associates formed. The increase in log K(ass) was about 0.07 log unit per one methylene group; that is, the hydrophobicity of a pairing ion played an important role in the ion association reaction in aqueous solutions, as well as ion association in solvent extraction systems. Nitro groups of the dyes slightly affected the ion association constants, whereas the position of the sulfonate group in the azo dyes showed a significant change in ion association constants.
TL;DR: In this paper, the authors reviewed the applications and recent developments of microwave digestion or extraction as a sample preparation technique and applied it successfully in both organic and inorganic determinations for various sample matrices.
Abstract: The present paper reviews the applications and recent developments of microwave digestion or extraction as a sample preparation technique. This technique has been applied successfully in both organic and inorganic determinations for various sample matrices. It offers the benefits of rapid sample preparation, ease of automation and reduction in background contamination. Good recoveries are generally obtained.
TL;DR: In this paper, an ultrasound-accelerated solid-liquid extraction prior to selenium determination in the phosphate-rich biological samples by electrothermal atomization atomic absorption spectrometry (ETAAS) with continuum-source background correction and nickel nitrate as a chemical modifier was established and compared with the results of conventional sample wet decomposition (however, this last item was not the object of this study).
Abstract: A novel method for sample preparation by ultrasound-accelerated solid-liquid extraction prior to selenium determination in the phosphate-rich biological samples by electrothermal atomization atomic absorption spectrometry (ETAAS) with continuum-source background correction and nickel nitrate as a chemical modifier was established and compared with the results of conventional sample wet decomposition (however, this last item was not the object of this study). Diluted (4%) nitric acid was used as an extraction medium. The evaluation of the analytical results for biological Certified Reference Materials indicates that the results of a selenium determination after wet acid digestion (HNO3+HCl+H2O2) agreed well with the certified values, whereas the proposed solid-liquid extraction procedure can be used for simple and rapid control of the selenium levels.
TL;DR: In this paper, a simple and highly sensitive fluorimetric high-performance liquid chromatographic (HPLC) method was developed for the determination of amantadine in plasma, after a single-step extraction from plasma (50 μl) with toluene, the drug and 1-(1-adamantyl)ethylamine (internal standard) were converted into the corresponding fluorescent derivatives by reaction with 3,4-dihydro-6,7-dimethoxy-4-methyl-3-oxo-quinoxaline-2-
Abstract: A simple and highly sensitive fluorimetric high-performance liquid chromatographic (HPLC) method was developed for the determination of amantadine in plasma. After a single-step extraction from plasma (50 μl) with toluene, the drug and 1-(1-adamantyl)ethylamine (internal standard) were converted into the corresponding fluorescent derivatives by reaction with 3,4-dihydro-6,7-dimethoxy-4-methyl-3-oxo-quinoxaline-2-carbonyl chloride, a fluorescence derivatization reagent for amines, in the presence of triethylamine. The derivatives were separated within 20 min on a reversed-phase column (YMC-Pack C 8 ) using isocratic elution with methanol-acetonitrile-water (35:35:30, v/v) and detected spectrofluorimetrically at 500 nm with excitation at 400 nm. The detection limit for amantadine added to plasma was 360 fmol (54 pg) ml-' plasma (18 fmol on column) at a signal-to-noise ratio of three.