Chromatographic purity
Adsorbent:
0.25-mm layer of chromatographic silica gel mixture coating on a thin-layer chromatographic plate, previously washed with methanol.
Test solution:
100 mg per mL, in methanol.
Standard solutions:
1.0, 0.5, 0.25, and 0.1 mg per mL in methanol to obtain Standard solutions A, B, C, and D, respectively.
Application volume:
20 µL.
Developing solvent system:
a freshly prepared mixture of toluene and alcohol (4:1) in a paper-lined equilibrated tank in an atmosphere of ammonia vapors.
Procedure
Proceed as directed for
Thin-Layer Chromatography under
Chromatography 621. Examine the plate under short-wavelength UV light. Expose the plate to iodine vapors, and observe again under white light: the chromatograms show principal spots at about the same
RF value. Estimate the concentration of any spot observed in the chromatogram of the
Test solution, other than the principal spot and that observed at the origin (which may appear because of the presence of ammonium chloride), by comparison with the principal spots in the chromatograms of
Standard solutions B,
C, and
D: the intensity of any secondary spot is not greater than that of the principal spot obtained from
Standard solution B (0.5%), and the sum of all secondary spots is not greater than the intensity of the principal spot obtained from
Standard solution A (1.0%).
Assay
Dissolve about 180 mg of Tocainide Hydrochloride, accurately weighed, in about 40 mL of glacial acetic acid and 15 mL of a 6 in 100 solution of mercuric acetate in glacial acetic acid, and titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically, using a platinum ring electrode and a sleeve-type calomel electrode containing 0.1 N lithium perchlorate in acetic anhydride (see
Titrimetry 541). Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 22.87 mg of C
11H
16N
2O·HCl.