A protein assay with the determination sensitivity at nanogram levels has been developed based on measurement of enhanced resonance light scattering (RLS). In a neutral aqueous medium, the interactions of ABGX with different proteins were found to result in strongly enhanced RLS signals. With the enhanced RLS signals at 398.0 nm, proteins, including bovine serum albumin (BSA), human serum albumin (HAS), pepsin (Pep) and cellulase (Cel), can be determined with the limit of detection below 30 ng/ml. The results of determinations for artificial samples were in agreement with the desired values, and those for human serum samples were identical with those obtained according to the Bradford method using CBB G-250.
The fluorescence spectral characteristics and interaction of several metal complexes of bis(salicylidene)-ethylenediamine (salen) with DNA are described. Among the complexes tested, Co-salen bound to DNA showed a marked decrease in the fluorescence intensity with a bathochromic shift of the excitation and emission peaks. A hypochromism in the UV absorption spectra was also observed. KI quenching and competitive binding to DNA between Co-salen and ethidium bromide were studied in connection with other experimental observations to show that the interactive model between Co-salen and DNA is an intercalative one. The pH and salt effect on the fluorescence properties was also investigated. The intrinsic binding constant and the binding site number were estimated to be 5.76 × 106 mol L-1 in base pairs and 0.058, respectively. A linear relationship between F/F0 and the concentration of calf thymus DNA covers 1.0 × 10-6 - 5 × 10-4 mol L-1, which can be utilized for determining traces of calf thymus DNA with a detection limit of 4.6 × 10-7 mol L-1 in base pairs.
Physanum polycephahum chromosomes were first imaged by a lateral force microscope. We observed the fine structure of metaphase and prophase chromosomes, which indicates that the lateral force microscope has a potential application for exploring chromosome structure. The principle of a 0° scan angle lateral force microscope is also discussed.
A new method for a mutagenicity test with spectrophotometry is presented in this paper. The mutagenic activity was examined by monitoring the growth situation of the Salmonella typhimurium TA98 strain. It was found that this strain could mutate and regain its growth capability owing to the impact of dimethyl sulfate; thus, metabolites of the strain caused the culture system to exhibit turbidness. The optimum experimental conditions were obtained. The effect of the dose of the mutagen on the absorbance was also studied. The result showed that there was a good linear relationship between the absorbance and the dose of the mutagen over the range of 2.5 - 20 µg/ml; the regression equation was A = 1.27×10-3 + 0.0134C, where A is the absorbance and C in µg/ml is the concentration of the mutagen. This method requires no immobilization or preincubation of the microorganism, and can be directly applied to mutagen detection. It is thus rapid and convenient.
A highly sensitive, rapid and economical differential pulse polarographic method was developed for the simultaneous determination of trace amounts of zinc and manganese in commercial sodium salts, mineral water, human hair and environmental waste liquid and solid samples. Ammonium tetraphenylborate-microcrystalline naphthalene coprecipitate, loaded in a plastic syringe-type cartridge (i.d. 10 mm, length 100 mm), was used as a column for the preconcentration of zinc and manganese as their 2-(2-pyridylazo)-5-diethylaminophenolates. The retention was quantitative in the pH range 7.5 - 11.0 and 9.0 - 11.5 for Zn and Mn, respectively. Preconcentration factors of 50 and 75 were obtained at a flow rate of 10 ml/min for zinc and manganese, respectively. The detection limits were 300 ng for Zn and 500 ng for Mn in 10 ml of the final solution at signal-to-noise ratio of 3. Various parameters were studied and the developed analytical methodology was validated by analyzing NIES certified reference materials such as human hair, chlorella and tea leaves.
The complex formation constants between alkali metal ions and monoaza- or diazacrown ethers (L) in acetonitrile have been obtained by the analytical method of d.c. polarography, in which a positive shift in E1/2 of the mercury-dissolution wave of L in the presence of a large excess of M+ is utilized. By the conventional method using a negative potential shift of the reduction of ML+ in the presence of a large excess of L, similar values of the complex formation constants were given for the 1:1 interaction (ML+ formation) between M+ and L. Concerning the stability of the Li+ and Na+ complexs of 12-crown-4, 15-crown-5, and 18-crown-6, the effects of the NH groups in the crown ethers have been discussed. The interaction between alkaline earth metal ions and L was too strong to obtain the formation constant, except for the BaL2+ species of 1-aza-12-crown-4. The anodic processes of L on DME were clarified: the diaza-12-crown-4 as well as the monoazacrown ethers caused an anodic wave of one-electron for L (i.e., the formation of 1/2[HgL2]2+), whereas 1,7-diaza-15-crown-5 gave successive two anodic waves. The formation of the monomeric mercurous ion (Hg+) seemed to be stabilized by the diaza-15-crown-5 in the course of the anodic process into [HgL]2+.
Inspired by the success of using monometalloporphyrin complexes as ionic carriers for salicylate-sensitive electrodes, several μ-oxo-bismetalloporphyrin complexes were synthesized by the reaction of monometalloporphyrins with NaOH. A mu-oxo-bis[5-(p-hydroxylphenyl)-10,15,20-triphenyl-porphinatomanganese(III)] [[Mn(5-HP)TPP]2O]-based sensor responds to salicylate ion over the concentration range 6.3 × 10-7 - 1.0 × 10-1 mol L-1 with a Nernstian slope and a response time of 50 s, which is faster than that of monometalloporphyrin counterparts. The electrode exhibits anti-Hofmeister selectivity toward salicylate with respect to common co-existing anions and shows a stable response for more than six months. The effect of the compositions of the electrode membrane has been studied and the experimental conditions optimized. The interaction mode of [Mn(5-HP)TPP]2O with Sal- has also been investigated. The electrode was preliminarily applied to the determination of salicylate in urine.
A simple method for multi-element analysis of geological samples has been developed. In this work, compromise conditions involving optimizing the operating parameters of the ICP, adjustment of ion optics voltages and selection of internal standards were carefully investigated. Matrix trace element-matching procedures were employed, in which the external calibration solutions were prepared by dividing the elements of interest into seven groups of different concentration levels according to their average contents of 20 typical standard reference rock samples. The proposed method offered simple procedure of sample preparation, instrument calibration, improved precision and reasonable element coverage. Detection limits ranged from 0.003 - 0.1 µg g-1 for heavier mass elements to 0.01 - 1 µg g-1 for lighter mass elements. Precision was near 1.1 - 10% RSD (lighter mass elements) and 2.0 - 8.0% RSD (heavier mass elements), respectively, with the exceptions of tungsten, molybdenum and thorium. Good agreement between certified and found values were achieved for standard reference rock samples AGV-1, BHVO-2 and GSR-3. Analytical data for rare earth elements were in conformity with values from the chondrite normalized curve.
A great enhancement in the extraction of iron(III) with 4-isopropyltropolone (Hipt) has been observed upon the addition of 3,5-dichlorophenol (DCP) as a hydrogen-bond donor, and highly efficient synergistic extraction system for iron(III) was presented using nonpolar solvents such as heptane and cyclohexane. An equilibrium study of the heptane system has demonstrated the formation of the adduct complexes of not only the iron(III) chelate, Fe(ipt)3·nDCP (n = 1 - 3), but the reagent, Hipt·nDCP (n = 1, 2). The formation constants (βM,n = [Fe(ipt)3·nDCP]org/[Fe(ipt)3]org[DCP]orgn, βH,n = [Hipt·nDCP]org/[Hipt]org[DCP]orgn) of the corresponding complexes were determined and evaluated by comparing with those of acetylacetone (Hacac). The values obtained for Fe(ipt)3 and Hipt were larger than those for Fe(acac)3 and Hacac, respectively, suggesting the higher hydrogen-bond accepting power and basicity of the former ligand.
The adsorption behavior of 60 elements at the 10 ng ml-1 level on high-porous cross-linked chitosan in a packed mini-column was systematically examined. The chitosan used could adsorb anionic species quantitatively as oxoanions or chloro complex anions of metals, such as Ti, V, Mo, W, Ga, Bi, Au(III), Pt(IV) and Pd(II), in sample solutions by an ion-exchange mechanism, and could adsorb some metal ions by a chelating mechanism. Most of the metal ions adsorbed on the chitosan were eluted with 1 M nitric acid, and other noble metals, such as Au, Pt and Pd, were eluted by a solution containing 1 M hydrochloric acid and 0.05 M thiourea. The adsorption fraction of metal ions was investigated by measuring metal ions in eluates by ICP-MS. By using the proposed column pretreatment method, metal ions present as their oxoanions in river-water samples, such as Ti, V, Mo, W, Ga and Bi, were collected on the cross-linked chitosan, eluted and determined. The method was applied to an analysis of reference materials distributed by the Japan Society for Analytical Chemistry: JAC 0031 and JAC 0032. The analytical results agreed closely with other reference values.
The determination of trace levels of mercury by flow injection cold-vapor atomic absorption spectrometry with gold amalgamation was evaluated for organic and inorganic mercury species. The effect of the sodium tetrahydroborate(III) and hydrochloric acid concentrations as well as various instrumental parameters on the analytical performance was studied. The influence of the blank as well as the laboratory procedure for reagent purification was evaluated. The procedure was applied to the determination of mercury in lake water, while focusing on the importance of the sampling protocols.
An analytical method, referred to as “derivatization-electron probe X-ray microanalysis (XMA)”, has been developed to determine the distribution of small amounts of hydroxyl groups formed by the oxidation and the hydrolysis of polymers. A suitable condition for a derivatization reaction with hydroxyl groups in polymers was investigated. It was found that hydroxyl groups in polymers were derivatized selectively using gas-phase esterification with trichloroacetic anhydride (TCAA). The most suitable amount of TCAA in a 50-ml vial was 50 µl. After setting a sample in the vial without directly contacting the reagent, by heating the reagent and the sample at 60°C for 90 min, the highest reaction yield and selectivity were obtained. By derivatization-XMA using this reaction condition, a distribution measurement of small amounts of hydroxyl groups in the polymer became feasible. Actual applications to a depth analysis of degraded polyethylene and polyester proved that the present method is useful for the characterization of polymers and for the study of polymer degradation.
The oxidation reaction of ascorbic acid by copper(II) has been studied by chemiluminescence system of luminol/copper(II) in alkaline solution. Oxygen and halide anions (Cl, Br- and I-) can greatly catalyze the oxidation of ascorbic acid, which produces active oxygen (H2O2 and oxygen free radical) and sensitizes the CL emission of luminol. Based on the catalytic effects of halide anions, a direct CL method without conversion of these halide anions prior to the CL reaction for the determination of halide anions is first proposed. CL intensity is linear to the concentration of Cl-, Br- and I- in the range of 1.0 × 10-5 - 3.2 × 10-3 mol l-1 , 1.0 × 10-5 - 3.2 × 10-3 mol l-1 and 4.6 × 10-5 - 4.2 × 10-3 mol l-1 respectively. Furthermore, in the presence of catalyst (oxygen and chloride anion), a sensitive and selective CL method for the determination of ascorbic acid is also proposed, the linear range and detection limit are 1.0 × 10-7 - 1.0 × 10-5 mol l-1 and 5.8 × 10-8 mol l-1, respectively.
A specially designed experimental setup including a newly constructed KBr cell, a light source, a monochromator and an IR detection system suitable for strictly calibrated IR absorption measurements was constructed in order to elucidate strange phenomenon associated with cis-trans photo-isomerization at 6.26 µm of the azobenzene core located at the center of an aryl-ether dendrimer (L5AZO). The setup used an ordinary Nichrome source to measure the photon flux, irradiation area, and photon absorption rate as exactly as possible. The photon absorption rate was obtained as 1.2×10-3 photons/s·molecule and the absorption cross section of L5AZO molecules was estimated to be 3.1×10-19 cm2/molecule. Since these values of the absorption rate and absorption cross section are not abnormal, the occurrence of a simultaneous five-photon absorption is almost impossible. Therefore, the five-photon absorption and photo-isomerization shown by L5AZO suggested that the multiphoton process was not simultaneous absorption, but possibly a sequential absorption and energy storage until the equivalent energy of isomerization was reached.
This paper studies the perturbation of hydrogen peroxide in an oscillating chemical system involving the Mn(II)-catalyzed reaction between diacetone and potassium bromate in an acidic medium in a closed system (beaker) and an open system (continuous-flow-stirred tank reactor (CSTR)). The best reaction conditions and reactant concentrations are reported. The presence of H2O2 inhibits the oscillation and results in a longer oscillating periods. Potential and cyclic voltammetry were used to track the change of the reaction intermediates. The possible mechanism of the effect of hydrogen peroxide is discussed.
A potentiometric titration curve was expressed as a linear equation and solved by a linear least-squares method with a non-negative constraint to simultaneously estimate the pK value(s) and concentration(s) of acid(s). Artificial model titration curves based on a continuous pK distribution were also solved using the same method. Accurate estimates were made of the pK values and concentrations of acetic, formic, fumaric, and citric acids. Furthermore, the method was used to estimate the pK distributions and concentrations for continuous pK distribution systems.