Overpressured layer chromatographic

An overpressured layer chromatographic procedure,g with photodensitometric detection for the simultaneou determination of water-soluble vitamins in multivita-o min pharmaceutical preparations, was developed and evaluated. HPTLC on silica gel plates with 1- butanol-pyridine-water (50 35 15 vol/vol) as mobilegj phase was used. The quantitation was carried out withoutl ... 

An overpressured layer chromatographic procedure, with photodensitometric detection for the simultaneous determination of water-soluble vitamins in multivitamin pharmaceutical preparations, was developed and evaluated. HPTLC on silica gel plates with 1-butanol-pyridine-water (50 35 15 vol/vol) as mobile phase was used. The quantitation was carried out without derivatization [vitamin B2 (Rf value 0.30), vitamin Bg (Rf value 0.64), folic acid (Rf value 0.37), nicotinamide (Rf value 0.80), and vitamin C (Rf value 1.02)] or after spraying ninhydrin reagent [calcium panthothenate (Rf value 0.72)] or 4-demethylaminocin-namaldehyde [vitamin B12 (Rf value 1.84) and biotin (Rf value 0)]. 

W. Chai, C. Letaux, A. M. Lawson, and M. S. Still, On-hne overpressure thin layer chromatographic separation and electrospray mass spectrometry detection of glycolipids, Anal. Chem. 75, 118-125 (2003). 

Chai, W, Leteux, C., Lawson, A.M., Stoll, M.S. (2003) On-line overpressure thin-layer chromatographic separation and electrospray mass spectrometric detection of glycolipids. Analytical Chemistry, 75,118-125. 

Katy, Gy., Mincsovics, E., Szokan, Gy., and Tyihak, E. (1997). Comparison of thin layer chromatography and overpressured thin layer chromatographic techniques for the separation of ascorbigen and I -methylascorbigen. J. Chromatogr., A 764 103-109. 

Chromatographic analysis of the vitamin Bg complex, including sample preparation and pre-TLC extraction have been reviewed (14). Separation of pyridoxine from other water-soluble vitamins in pharmaceutical preparations may be facilitated by impregnating silica gel plates with zinc acetate to provide a self-indicating system after separation (7). Impregnation of plates with hexadecyltrimethyl-ammonium bromide has been used to improve the TLC analysis of vitamin in foods (9). Overpressure layer chromatography was found to provide better separation and resolution of B( from other compounds than HPTLC (11). 

Chromatographic analysis of folate compounds including methotrexate and other antifolates has been reviewed by McCormack and Newman (32). Process impurities in the reduced folate compound leucovorin calcium have been monitored using a TLC method with fluorescence detection (33). An overpressure layer HPTLC procedure has been used to improve the separation of folic acid from other water-soluble vitamins with good recovery and resolution. The method uses silica gel layers developed in butan-l-ol-pyridine-water (50 35 15) at a rate of 0.25 ml/min for baseline separation. Quantitation was achieved without derivatization (11). 

Tyihak, E. Mincsovisc, E. Kalasz, H. New planar liquid chromatographic technique Overpressured thin-layer chromatography. J. Chromatogr. 1979,174, 75-81. 

OPLC is a planar chromatographic technique in which the vapor phase has been eliminated, the sorbent layer being completely covered with an elastic membrane under external pressure. After introduction, by means of an appropriate dispenser, the mobile phase migrates through the layer (54) as a result of the cushion system at overpressure. Elimination of the open system enables separation to be performed in a closed system under controllable conditions. Thus, the chromatographic layer becomes a planar column. The principle of on-line OPLC (55) is shown schematically in Figure 8. 

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