Junko Hayakawa

Identification of unlawful food dyes by thin-layer chromatography-fast atom bombardment mass spectrometry

A thin-layer chromatographic-fast atom bombardment mass spectrometric (TLC-FAB-MS) method incorporating an analyte condensation technique was established for the identification of the 27 food dyes consisting the twelve dyes permitted for use in foods and the fifteen unlawful dyes in Japan. The use of magic bullet [1,4-dithiothreitol-1,4-dithioerythritol (3:1)] as a matrix allowed the measurement of the FAB mass spectra of the food dyes except for Food Blue No. 2 (Indigo Carmine). The separation was performed on a C18-modified silica gel TLC plate using the following two solvent systems: methanol-acetonitrile-5% aqueous sodium sulphate solution (3:3:10) and methyl ethyl ketone-methanol-5% aqueous sodium sulphate solution (1:1:1). The condensation technique for concentration of a diffuse sample spot on the TLC plate improved the detection limit 4-20-fold with good reproducibility. The method was successfully applied to the identification of unlawful dyes in imported foods.

Improvement of chemical analysis of antibiotics. XVII : Application of an amino cartridge to the determination of residual sulphonamide antibacterials in meat, fish and egg

A simple, rapid and reliable method for the determination of residual sulphonamide antibacterials (SAs) (sulphathiazole, sulphisozole, sulphamethoxazole, sulphadiazine, sulphamerazine, sulphadimidine, sulphamonomethoxine, sulphadimethoxine, sulphamethoxypyridazine and sulphaquinoxaline) in meat, fish and egg was developed using a combination of high-performance liquid chromatography (HPLC) and clean-up with an amino-type prepacked cartridge. SAs were extracted with ethyl acetate and applied to a Baker 10 amino cartridge. After elution from the cartridge, SAs were determined by HPLC. The recoveries at the level of 0.5 ppm were 73.7-99.1% and the detection limits were 0.05 ppm. The analysis time per sample was about 45 min.

Isolation of Colistin A and B Using High-Speed Countercurrent Chromatography

Abstract High-speed countercurrent chromatography was successfully applied to the isolation of colistin-A and colistin-B from a commercial colistin preparation. As the first step. TLC and HPLC analysis conditions for the colistin components were established. Using these techniques, a two-phase solvent system composed of n-butanol-0.04M aqueous trifluoroacetic acid (TFA) (1:1) was selected for high-speed CCC, where the concentration of TFA was the major factor in controlling the partition coefficients of the colistin components. Yields of colistin-A and colistin-B were 9 mg each from 20 mg of the commercial sample, and the purity of each component was over 90%. Fast atom bombardment (FAB) mass spectrometry was utilized to confirm the nature of the isolated components.

Purification of food color red no. 106 (acid red) using high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) has been successfully applied to the separation of the components of Food Color Red No. 106 (R-106). The separation was performed using 25 mg of the sample with a two-phase solvent system composed of n-butanol and 0.01 M trifluoroacetic acid (1:1, v/v). Analyses by thin-layer chromatography, high-performance liquid chromatography and fast atom bombardment mass spectrometry confirmed that HSCCC was effective in the purification of the components of R-106. The separation gave 21 mg of a 99.9% pure main component (Acid Red) and 0.9 mg of 98.0% pure subsidiary dye which is probably a des-ethyl derivative.

Discrepancy Between the Theoretical Plate Number (N) and Peak Resolution (Rs) for Optimizing the Flow Rate in Countercurrent Chromatography

Abstract This paper deals with a problem in optimizing the flow rate of the mobile phase in countercurrent chromatography (CCC), A set of data including theoretical plate number (N), resolution factor (Rs), % retention, etc. are obtained from the separation of three indole auxins in a two-phase solvent system of n-hexane / ethyl acetate / methanol / water (1:1:1:1) by applying the flow rates of the mobile phase at 0.5- 8.0ml/min. The experimental results revealed a disagreement between the efficiencies expressed in parameters N and Rs at the high flow rates of the mobile phase in the CCC separation. Namely, the partition efficiency expressed in terms of Rs decreases with an increased flow rate of the mobile phase, while the N rises with increasing the flow rate. Since Rs represents the actual separation of the solute peaks, the results indicate that the N used in high performance liquid chromatography is not always a reliable measure in CCC separation. However, the application of a high flow rate yields b...