Silica Gel GF₂₅₄

Silica Gel GF ₂₅₄ A fine, white, homogeneous powder of an average particle size of about 15  µm containing about 13% of calcium sulphate hemihydrate and about 1.5% of a fluorescent indicator having a maximum intensity at 254  nm. It complies with the tests for Content of calcium sulphate and Acidity or alkalinity described under silica gel  G and with the following requirement.

Fluorescence Carry out the method for thin-layer chromatography using a mixture of 10 volumes of anhydrous formic acid and 90 volumes of propan-2-ol as the mobile phase, but allowing the solvent front to ascend 10  cm above the line of application. Apply separately to the plate 10 quantities from 1 to 10  µl of a 0.1% w/v solution of benzoic acid in the mobile phase. After removal of the plate, dry it in a current of warm air and examine under ultraviolet light (254  nm) . The benzoic acid appears as dark spots on a fluorescent background in the upper third of the chromatogram at levels of 2  µg and greater.