TLC determination of biotin in a lyophilized multivitamin preparation

A TLC method for the determination of biotin was developed. The method is selective and sensitive and permits the determination of biotin in the presence of all water-soluble vitamins as well as glycine, edetate sodium, and methylparaben. The main steps are: dissolution of the lyophilized multivitamin preparation in water, addition of the internal standard, application on a thin-layer plate, separation from interfering components, visualization by spraying with 4-dimethylaminocinnamaldehyde, and in situ determination by reflectance measurements. Spraying the plate with paraffin after the coloring procedure increases the sensitivity of the method. The coefficient of variation is 2.3% with 0.15 microgram of biotin/spot. Quantities as low as 10 ng/spot can be determined.