Spectrophotometric determination of phosphorus in river water based on the reaction of vanadomolybdophosphate with malachite green

The formation of an ion-associate between vanadomolybdophosphate and malachite green in aqueous acidic solution (0.5 M sulfuric acid) enables trace amounts (0?1 × 10^?5M) of phosphate to be determined. The molar absorptivity is 1.05 × 10⁵ l mol^?1 cm^?1 at 620 nm. The complex was stabilized in solution by adding poly (vinyl alcohol). Other ions generally found in river waters did not interfere. Interference by silicate is less than that found in the corresponding malachite green molybdophosphate procedure; interference of arsenate is avoided by reduction with thiosulfate. The method is applied to the determination of μg l^?1 amounts of phosphorus in river water; the results obtained were in good agreement with those obtained by an extraction-spectrophotometric method with malachite green.     

Multi-quasiparticle excitations in ~(145)Tb

Nuclei with N and Z near magic number can be well described by the nuclear shell model. The 145Tb nucleus has a valence proton and a pair of neutron holes with respect to the doubly closed 146Gd nucleus. Therefore, it is expected that the excitations in 145Tb be dominated by single-particle configurations. A detailed measurement of the excitation scheme in 145Tb would give us an opportunity to examine the behavior of multi-particle excitations involving high angular momentum orbits and provi…     

On-line collection/concentration of trace amounts of formaldehyde in air with chromatomembrane cell and its sensitive determination by flow injection technique coupled with spectrophotometric and fluorometric detection

A simple, rapid and highly sensitive method for the determination of trace amounts of formaldehyde in air by using flow injection analysis (FIA) system coupled with a three-hole chromatomembrane cell (CMC) was investigated by using a spectrophotometer and a fluorometer. The CMC was applied to on-line collection/concentration of trace amounts of formaldehyde in air into water as an absorbing solution; formaldehyde in the air was found to be quantitatively transferred into the absorbing solution in CMC. The solution, containing absorbed formaldehyde, was introduced into the carrier stream of the FIA system. The amount of formaldehyde in an absorbing solution was measured spectrophotometrically and fluorometrically after the reaction with a mixed reagent of acetylacetone and ammonium acetate at pH 5.6–5.8. The amount of formaldehyde in the absorbing solution, measured by the proposed system, could be converted to the concentration of formaldehyde in the air sample. A calibration graph prepared by a series of standard formaldehyde aqueous solutions was adopted. The formaldehyde in indoor air, determined as exampled by the proposed spectrophotometric FIA, was found to be 5.14 ± 0.08 ppbv for 20 ml of the air sample at the air flow rate of 6 ml min⁻¹, and the relative standard deviation (R.S.D.) was 1.56%. The limit of detections (LODs) of HCHO in an absorbing solution was 2 × 10⁻⁸ M (0.6 ppb) and 8 × 10⁻⁹ M (0.2 ppb), respectively, by the spectrophotometric and the fluorometric FIA, and the LODs of HCHO in air sample of 40 ml were 0.05 and 0.03 ppbv, respectively. The interferences from foreign species were examined; tolerable concentrations of other aldehydes were more than 50-fold of formaldehyde (1 × 10⁻⁶ M).     

Stereospecific 2-vinylcyclohexanol formation via internal attack of an allylsilane moiety on an aldehyde group

Acid catalyzed cyclization of ($\text{E}$)-HCO-(CH₂)-₄-CH=C(Me)-CH(SPh)SiMe₃ affords $\text{cis}$-2-substituted cyclohexanol, while ($\text{Z}$) compound affords the $\text{trans}$ isomer. Those cyclized products are transformed to the corresponding α-methyl γ-lactones.     

Separation and determination of haloperidol, parabens and some of their degradation products by micellar electrokinetic chromatography

A micellar solution containing phosphate buffer, anionic surfactant, and water-miscible organic solvent was employed as a migration solution for the separation and the quantification of eleven analytes by micellar electrokinetic chromatography (MEKC): the analytes examined were haloperidol, methylparaben, ethylparaben, n-propylparaben, iso-propylparaben, n-butylparaben, iso-butylparaben, sec-butylparaben, 4-(4-chlorophenyl)-4-hydroxypiperidine, 4-fluorobenzoic acid and 4-hydroxybenzoic acid. In order to provide good separation between micelle and haloperidol, which showed strongest interaction with the micelle among the analytes, surfactant concentrations and organic modifier percentages were studied with phosphate buffer at pH 7.0. All the analytes were successfully resolved when 10 mM sodium dodecylsulfate and 15% ethanol were contained in the migration solution; the time window was very wide in the range from 14.8 to 65.5 min. Optimized applied voltage at 30 kV and capillary temperature at 45 degrees C enable analyze all compounds in less than 17 min with the best resolution, the shorter migration time window, the highest precision and lowest detection limit.     

Intramolecular Aryl Migration from Tin to Carbon via a Radical Atom-Transfer Process

Triethylborane-induced intramolecular 1,4-aryl migration from tin to a carbon-centered radical is described. Treatment of 3-iodoalkyldimethylphenylstannanes with Et(3)B in benzene at reflux followed by an addition of MeMgI provides 3-phenylalkyltrimethylstannanes in good yield via a radical atom-transfer process.