An infrared grating spectrophotometer newly designed for polarization modulation measurements is described. The spectrometer can be characterized by the grating monochromator inclined by 45° with respect to the planes of polarized incident beams. This polarization modulation apparatus allowed us to measure a single monolayer of stearic acid formed on an Ag mirror in a good S/N ratio. At the same time the resolution of the obtained spectrum was sufficient for discriminating among different absorption bands due to the C-H stretching vibrations. The apparatus was employed to characterize an anisotropic structure of cadmium arachidate monolayers built up on Cu substrate surfaces. By means of the same technique, the infrared spectrum of a polyvinylacetate film 10nm thick on Si could be obtained by using the optimum angle of incidence.
The potential response of a sulfide-based silver ion selective electrode was examined in various metal buffer solutions. In every system tested, the potential response of the electrode was rapid and the electrode potential correctly reflected the free silver ion concentration in the solution. The stability constants of silver complexes with seven ligands were determined. This electrode was used also to measure the free cyanide ion concentration in the solutions containing silver, cyanide and a second metal ion. The stability constants of zinc and cadmium cyano complexes were obtained. The behavior of the silver ion selective electrode is discussed in contrast to that of the mixed sulfide membrane electrodes.
An electrochemical method of analysis, which can avoid the interference of dissolved oxygen by using twin electrodes in a flow cell, was extensively applied to a variety of quinones and carbonyls. The quantitation by this method was occasionally affected by parallel or following chemical reactions coupled with the electrolytic reduction at the first electrode (generating electrode). The loss of reductant was caused by the reoxidation by dissolved oxygen, hydrolysis and/or adsorption of reduced entity before arriving at the second electrode (detecting electrode), and sometimes the photochemical reduction interfered with the analysis. The variation of the detection limit; mitomycin C 5nmol, daunomycin 2nmol, vitamin K3 0.1nmol, actinomycin D 0.2nmol and tetracycline 0.05 nmol, was interpreted in terms of these coupled chemical reactions.
The development and optimization of a miniaturized hydride generation system for atomic absorption spectrometry of selenium(IV, VI) by suction-flow on-line prereduction of selenium(VI) to selenium(IV) are described. A discrete aqueous sample is sucked into a concentrated hydrochloric acid line and brought to the prereduction coil (95°C) by a peristaltic pump. Then the mixture and sodium tetrahydroborate solution are delivered by the pump to gas-liquid separators. The evolved hydrogen selenide is swept into an electrically heated quartz cell of an atomic absorption spectrometer. A transient absorption signal is recorded on a strip chart recorder. The 3σ detection limit is 0.7ng cm-3 selenium and the calibration is linear up to 30ng cm-3 with 1cm3 sample solution. The relative standard deviation (n=10) is 3.0% for 25ng cm-3 selenium. The sample throughput is 30h-1. Results of analysis of some certified biological reference materials are given.
Several K-benzoyl-K-phenylhydroxylamine derivatives were synthesized. Their acid dissociation constants, pKa, were determined spectrophotometrically. There was a linear relationship between the constants and Hammett′s σm values. Furthermore the distribution constants, KDL, of their reagents between the aqueous and chloroform phases were determined. It was found that both the extraction constants, Kex, of their copper complexes and the pH values at half extraction, pH1/2, are practically constant although the pKa values decrease because of the electron-withdrawing nature of the substituted group. It cdn be assumed that the values of logKDC, (where KDC is the distribution constant of the copper complex) are nearly equal to the values of 2 log KDL, since the values of log KDC and log KDL are proportional to molecular volume on the basis of the regular solution theory; that is, a relationship between KDC and KDL can be expressed as follows; logKDC=2logKDL+constant. Since the values of Kex and KDCKDL-2 for each of the chelates can be regarded as constant, an analogous relationship between Ka and β2 can also be derived as follows: logβ2=2pKa+constant.
The color reaction between o-hydroxyhydroquinonephthalein(Qnph), titanium(IV)[Ti(IV)] and hydrogen peroxide was studied. The spectrophotometric determination of micro amounts of Ti(IV) using Qnph and hydrogen peroxide in a weak acidic media is then discussed. The optimum acidities were pH 4.2-5.0; the molar absorptivity of Qnph-hydrogen peroxide-Ti(IV) solution was 3.1×105dm3 mol-1 cm-1 at 595nm. The color intensity of Ti(IV) complex solution was stable for 2h, and was found to obey Beer′s law within the concentration range of 0.2-2.5μg per 10ml. The method was simple and reliable, and may be applied to the determination of Ti(IV) in various concentrations of titanium alloys and pigments.
Based on the fact that several kinds of anions take part in the solvent extraction of nickel with 8-quinolinol(Hql), the precipitate formation of nickel 8-quinolinol complexes was examined using aqueous nickel(II) solutions containing perchlorate and sulfate anions. The precipitate formed at pH 4.0 from the perchlorate solution contains a large amount of perchlorate ions; its mole ratio of nickel, 8-quinolinol and perchlorate ion is close to 1:3:0.5, which is that of the dimeric ion-pair complex, [Ni2ql3(Hql)3]ClO4. The precipitate formed at pH 9.0 contains no perchlorate ion; it seems to be the mixture of Niql22Hql and Niql22H2O. On the other hand, the precipitate formed from the sulfate solution contains no sulfate ions, regardless of pH. The precipitates formed in the range of pH 4-8 seem to be a mixture of Ni2ql42Hql, Niql22Hql or Niql22H2O according to pH, but the precipitate for pH 9.0 is Niql22H2O. The composition of these precipitates was ascertained and is discussed on the basis of the results of their TG-DTA and IR spectra.
A fluorescence reaction of epoxides with 3-phenyl-2, 7-naphthyridin-1(2H)-one (PNO) is described. Common epoxides and 12, 13-epoxytrichothecenes gave a green fluorescence (λex 441-467nm and λem 506-510nm) after reaction with PNO at 120°C for 90min in 1, 2-ethanediol/2- methoxyethanol mixture for the former and at 150°C for 30min on a solid phase for the latter, respectively, and followed by addition of N, N-dimethylformamide in both the cases. By the proposed methods, as little as 20-30pmol of common epoxides and 64-85pmol of trichothecenes could be determined with relative standard deviations of ranges 1.7-4.3% and 4.8-8.6%, respectively.
Fluorescein isothiocyanate (FITC) isomers and the intermediate products have been separated by reversed phase high performance liquid chromatography (HPLC), using a linear gradient formed from acetone and 0.01 M sodium phosphate buffer (pH 7.0) or an isocratic elution of 40% acetone in 0.1M pyridine-acetic acid (pH 7.0). This HPLC system was used to evaluate commercial FITC products. A method for the purification of the FITC product by HPLC was also described.
During zone electrophoresis in a polyacrylamide gel slab under the alkaline condition (pH 8.86), bond sharpening was observed, due to the action of acid. By placing a piece of filter paper impregnated with 2M acetic acid for 2min prior to running, the protein bands were sharpened and the resolution was improved. A similar phenomenon was observed in an acidic medium.
A film-coated glucose oxidase-immobilized benzoquinone-mixed carbon paste electrode was modified by placing a gold minigrid in front of the coating film. This modified biocatalyst electrode was proved to be used as a glucose sensor without interference with coexisting oxidizable substances. Other functional aspects of the pre-grid(s) are discussed.
The design and properties of a new enzyme electrode with response and selectivity for cyclic AMP(cAMP) are described. The cAMP sensor employs a double enzyme system held at the surface of an NH3-selective membrane electrode and has a detection limit of 5×10-9 moles cAMP as well as selectivity for cAMP over other nucleotides.
A series of water-soluble derivatives of pyridylazoaminophenol and pyridylazoaminobenzoic acid have been synthesized; they were evaluated as highly sensitive chromogenic reagents for metals. 2-(5-Bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (5-Br-PAPS) and 2-(3, 5-dibromo-2-pyridylazo)-5-(N-ethyl-N-sulfopropylamino) benzoic acid (DSAB) were found to be highly sensitive reagents, the former for zinc(ε=13.3×104 at 552nm) and uranyl (ε=6.6×104 at 578nm), and the latter for cobalt(III) (ε=15.2×104 at 670nm)and nickel (ε=13.7×104at 620nm).
The extraction of metal ions (Cu(II), Co(II), Ni(II), Zn(II), Pb(II), Fe(III)) with hydrophobic 5-dioctylaminomethyl-8-quinolinol (HN8Q) and 5-octyloxymethyl-8-quinolinol (HO8Q), which were newly synthesized, was investigated. Copper(II) was completely extracted with 0.01mol dm-3 HN8Q or HO8Q into chloroform even at pH 1.9, while cobalt(II), nickel(II), lead(II), and zinc(II) were not extracted at all under the same conditions. The extraction rate for copper(II) with these extractants was large, whereas the rates for other metal ions were remarkably small at the same pH region. The complete separation of copper(II) from iron(III) was acieved by adjustng pH to 1.9 for the extraction and subsequently stripping copper(II) from copper(II)-HO8Q in chloroform with 0.5mol dm-3 nitric acid solution. The extraction-pH curves for copper(II) shifted to a lower pH region with increasing the number of carbon atoms of alkyloxymethyl or dialkylamino groups.
Lipid peroxides in serum were determined by use of a high performance liquid chromatograph (HPLC) with fluorescence detection and 1, 3-diphenyl-2-thiobarbituric acid (DPTBA) instead of thiobarbituric acid (TBA). Optimum analytical conditions for lipid peroxides were determined by using serum and tetramethoxypropane (IMP) as the standard aqueous solution of malondialdehyde (MDA). The optimum pH for the reaction of TMP with DPTBA was found to be 2.5. The lipid peroxides and bilirubin, which reacts with DPTBA and interferes with the measurement of lipid peroxides, were separated by use of HPLC. A linear relation passing through the origin point was obtained between the fluorescence intensity and the concentration of MDA standard solution over the range of 0.06-0.24nmol/ml. The relative standard deviation was 2.21% (n=5). The detection limit of the lipid peroxides in serum was 12pmol/ml as S/N=10. The recovery of 0.6nmol MDA added to 50μl of serum was 97.8%. The sensitivity of HPLC-fluorescence detection method was 17 times greater than that of the HPLC-visible detection method and 192 times higher than that of the TBA method.