Identification of Coal Tar Dyes by Reversed-Phase TLC/FABMS with a Sample Condensation Technique

Naoko OZEKI; Hisao OKA; Yoshitomo IKAI; Tsutomu OHNO; Junko HAYAKAWA; Takeo SATO; Motome ITO; Ryoji SUZUKI

doi:10.3358/shokueishi.34.512

Naoko OZEKI, Hisao OKA, Yoshitomo IKAI, Tsutomu OHNO, Junko HAYAKAWA, Takeo SATO, Motome ITO, Ryoji SUZUKI

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Keywords: thin-layer chromatography/fast-atom bombardment mass spectrometry, food coal tar dyes, sample condensation technique, reversed-phase thin-layer chromatography

JOURNAL FREE ACCESS

1993 Volume 34 Issue 6 Pages 512-516_1

DOI https://doi.org/10.3358/shokueishi.34.512

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Abstract

We have established a reversed-phase thin-layer chromatography/fast-atom bombardment mass spectrometric (TLC/FABMS) method incorporating an analyte condensation technique for the identification of the 12 permitted coal tar dyes in Japan. Use of “magic bullet” as a matrix enabled us to measure the FAB mass spectra of the food coal tar dyes except for Food Blue No. 2 (indigo carmine). Two solvent systems, methyl ethyl ketone-methanol-5% aqueous sodium sulfate solution=1:1:1 and methanol-acetonitrile-5% aqueous sodium sulfate solution=3:3:10 were selected for the separation of the xanthene dyes and the others, respectively on a reversed-phase TLC plate. The condensation technique, which concentrates a diffused sample spot on a TLC plate, improved the detection limit 150-fold with good reproducibility. The established TLC/FABMS method was successfully applied to identification of coal tar dyes in commercial foods.

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