Huai You Wang

Spectrophotometric determination of procaine hydrochloride in pharmaceutical products using 1,2-naphthoquinone-4-sulfonic acid as the chromogenic reagent.

Spectrophotometric determination of procaine hydrochloride is described. The procaine hydrochloride reacts with 1,2-naphthoquinone-4-sulfonic acid in pH 3.60 buffer solution to form a salmon pink compound, and its maximum absorption wavelength is at 484 nm, epsilon(484)=5.22 x 10(3).The absorbance for procaine hydrochloride from 0.30 to 100 microg ml(-1) obeys Beers law. The linear regression equation of the calibration graph is C=19.23A-0.03, with a linear regression correlative coefficient is 0.9996, the detection limit is 0.28 microg ml(-1); recovery is from 98.0 to 105.2%. Effects of pH, surfactant, organic solvent, foreign ions, and standing time on the determination of procaine hydrochloride have been examined. This method is rapid and simple, and can be used for the determination of procaine hydrochloride in injection solution of procaine hydrochloride. The results obtained by this method agreed with those by the official method (dead-stop titration).

Study of a fluorescence quenching mechanism of enoxacin and its determination in human serum and urine samples

The maximum emission wavelength of dopamine is 317 nm with excitation at 290 nm. The relative fluorescence intensity of dopamine decreased in the presence of enoxacin, which showed that fluorescence quenching occurred. The Stern-Volmer (S-V) plot showed a nonlinear relationship between the relative fluorescence intensity of dopamine and the concentration of enoxain. The quenching mechanism was studied and the results suggested that both dynamic and static quenching processes were responsible for the observed positive deviation in the S-V plot. When the S-V plot was modified by logarithm, the linear relationship was obtained between logF0/F and C in the range of 0.10 to 13.0 μg/mL (where F0 is the relative fluorescence intensity of dopamine, F is the relative fluorescence intensity of dopamine in the presence of enoxacin, and C is the concentration of enoxacin). The fluorescence quenching method for the determination of enoxacin was developed. The linear regression equation of the calibration graph of enoxacin was C = 13.70 (logF0/F) − 0.5836, with the correlation coefficient 0.9984. The detection limit was 2.0 ng/mL and the relative standard deviation was 2.52%. The effects of pH, the stability of dopamine in the presence of enoxacin, and foreign ions on the determination of enoxacin have been examined. The recovery of enoxacin was from 94.9 to 103.0% in a human serum sample and from 94.9 to 108.0% in a urine sample. The method is simple, rapid, and can be used for the determination of enoxacin in human serum and urine samples with satisfactory results.

Highly Sensitive Spectrofluorimetric Determination of Trace Amounts of Indium with 5-Bromine-Salicylaldehyde Salicyloylhygrazone

The fluorescence reaction of 5-bromine-salicylaldehyde salicyloylhydrazone (5-Br-SASH) with indium was studied in detail. Based on this chelating reaction, a sensitive spectrofluorimetric method was developed for the determination of indium in a water–ethanol (63%) medium at PH 4.6. Under these conditions, the In-5-Br-SASH complex has excitation and emission maxima at 395 nm and 461 nm, respectively. The linear range of the method is from 0 to 1000 ng mL–1and the detection limit is 2.4 ng mL–1of indium. The molar ratio of indium to the reagent is 1 : 3. Interferences from other ions were studied. The method was successfully applied to the determination of indium in lead, tin, spelter, zinc sulfide using the standard additions method.

Spectroscopic study of the competitive interaction between streptomycin and Evans blue to bovine serum albumin.

The mechanism of the competitive interaction of streptomycin and Evans blue (EB) to bovine serum albumin (BSA) has been studied by using both fluorimetry and spectrophtometry. Effects of pH, streptomycin and concentration of EB on the competitive interaction of streptomycin and EB were examined. A static fluorescence quenching process was confirmed in the light of Stern-Volmer plot. The test result showed that there were strong and weak binding sites on BSA molecule and the binding constant of EB-BSA complex and the number of binding site n were obtained. These facts revealed that the competitive interaction was occurred between EB and streptomycin, which can possibly provide useful message in investigation of the interaction of antibiotic with BSA.