Azobenzene (AB) and 4-nitroazobenzene (NAB) were covalently bonded to carbon surfaces by electrochemical reduction of their diazonium derivatives. The N(1s) features of XPS spectra of modified surfaces had intensities expected for monolayer coverage. However, the Raman spectra were significantly more intense than expected, implying an increase in scattering cross section upon chemisorption. A l...

Isotope effect may cause partial chromatographic separation of labeled (heavy) and unlabeled (light) isotopologue pairs. Together with a simultaneous matrix effect, this could lead to unacceptable accuracy in quantitative liquid chromatography-mass spectrometry assays, especially when electrospray ionization is used. Four biologically relevant reactive aldehydes (acrolein, malondialdehyde, 4-hy...

In order to understand the role of dipolar interactions vs. H-bonding, a series hydrazones were synthesised from 4-alkoxy-, 3,4-dialkoxy- or 3,4,5-trialkoxybenzaldehydes and phenyl, bromo- nitrophenylhydrazine, respectively. Their mesomorphic properties investigated by differential scanning calorimetry (DSC), polarising optical microscopy (POM), X-ray diffraction (WAXS, SAXS) compared with know...

The dinitrophenylhydrazine method for the determination of ascorbic acid is based upon treatment with 85% HzS04 of the chromogen formed by the coupling of 2,4-dinitrophenylhydrazine with oxidized ascorbic acid. In the original publication of this method, Roe and Kuether (1) set the temperature of the coupling reaction at 37” and used a 3-hour incubation period. These authors showed that a low t...

A simplified version of the 2, 4-DNPH assay for flavonoids has been improvised. The assay includes incubating test sample with DNPH in a 4.5 mL reaction volume in hot water at about 80 C containing 2 mL methanol at about 0.2 N HCl, cooling samples to room temperature, adding 3 mL 1M NaOH, and monitoring red color at 470 nm at 10-15 minutes. The reagent has been found capable of assaying both fl...