Abstract: A unique stopped-flow flow injection analysis system for simultaneous synchronous spectrofluorimetric on-line dissolution monitoring of multi-component solid preparations that makes use of a fiber-optic sensor was presented. A new means of in vitro therapeutic drug monitoring was developed by hyphenating the fiber-optic sensor technique and a chemometric method. An artificial neural network method was applied to construct the mathematical model for the simultaneous analysis of the mixture of vitamins B-1, B-2 and B-6 by synchronous spectrofluorimetry. The selection of the wavelength interval, the pH of the carrier solution and other experimental conditions were investigated, and discussed. The proposed method has been applied to the dissolution monitoring of vitamin B tablets with satisfactory results. The recovery was 97.8-105%, and the relative standard deviation was 1.1-7.5%, The dissolution parameters of vitamins B-1, B-2 and B-6 in the vitamin B complex tablets, which were derived from a best mathematical model using the proposed method, were furnished. The system could provide a profitable new technique for simultaneous on-line process monitoring of therapeutic drugs and their metabolites in biological body fluids.

Abstract: Food was heated with 0.1 M H2SO4 at 120°C for 30 min followed by hydrolysis with Taka diastase at pH 5 and 45°C for 15 h. The solution was analyzed on a column (12.5 cm x 4 mm) of LiChrospher RP 18 (5 µm) with aqueous 33% methanol containing 0.1% hexanesulfonic acid, pH 3.6, as mobile phase (1.5 mL min-1). Detection was by post-column derivatization with 0.04% K3[Fe(CN)6] in 1.5% NaOH and fluorimetric measurement at 425 nm (excitation at 370 nm). The calibration graph was rectilinear between 40 and 400 ng mL-1 with recoveries of added thiamine between 98 and 100%. The coefficient of variation (n = 3) were 1 to 10%. By using another detector at 525 nm (excitation at 467 nm) before derivatization, vitamin B2 could be simultaneously determined.

Abstract: Urine (120 µL) was injected into a carrier stream (4 mL min-1) of water (pH 6 to 7), which merged with a water stream (4 mL min-1) before passing through a 12-cm reaction tube. The stream was irradiated with a Hg lamp and fluorescence due to riboflavine (I) was measured at 520 nm. The stream then merged with a reagent stream (4 mL min-1) containing 0.1 M MgSO4, which forms a fluorescent complex with doxycycline (II). Total fluoresence due to I and II was measured at 520 nm. Contributions to total fluorescence, and hence concentration, were calculated for I and II; the calibration graphs were rectilinear from 80 nM to 20 µm and 3 to 80 µM, respectively, with corresponding detection limits of 60 nM and 2 µM. Recoveries of I and II were 95 to 102%.