Allow the chromatogram to develop in a pre-equilibrated chamber until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, and air-dry. View the plate using the visualization technique(s) specified. Locate any spots other than the principal spot, in the chromatogram of the Test Solution, and determine their relative intensities by comparison with the chromatograms of the appropriate Standard Solutions. The total of any ordinary impurities observed does not exceed 2.0%, unless otherwise specified in the individual monograph.

(1) Use UV light at 254 nm and at about 366 nm.

(2) Use Iodoplatinate TS.

(3) Solution A—Mix 850 mg of bismuth subnitrate with 40 mL of water and 10 mL of glacial acetic acid.

Solution B—Dissolve 8 g of potassium iodide in 20 mL of water. Mix A and B together to obtain a Stock Solution which can be stored for several months in a dark bottle. Mix 10 mL of the Stock Solution with 20 mL of glacial acetic acid, and dilute with water to make 100 mL, to prepare the spray reagent.

(4) Ninhydrin Spray—Dissolve 200 mg of ninhydrin in 100 mL of alcohol. Heat the plate after spraying.

(5) Acid Spray—In an ice bath, add slowly and cautiously, with stirring, 10 mL of sulfuric acid to 90 mL of alcohol. Spray the plate, and heat until charred.

(6) Acid-Dichromate Spray—Add sufficient potassium dichromate to 100 mL of sulfuric acid to make a saturated solution. Spray the plate, and heat until charred.

(7) Vanillin—Dissolve 1 g of vanillin in 100 mL of sulfuric acid.

(8) Chloramine T-Trichloroacetic Acid—Mix 10 mL of a 3% aqueous solution of chloramine T with 40 mL of a 25% alcoholic solution of trichloroacetic acid. Prepare immediately before use.

(9) Folin-C—Add 10 g of sodium tungstate and 2.5 g of sodium molybdate to 70 mL of water, add 5 mL of 85% phosphoric acid and 10 mL of 36% hydrochloric acid, and reflux this solution for 10 hours.

(10) KMnO4—Dissolve 100 mg of Potassium Permanganate in 100 mL of water.

(11) DAB—Mix 1 g of p-dimethylaminobenzaldehyde in 100 mL of 0.6 N hydrochloric acid.

(12) DAC—Mix 100 mg of p-dimethylaminocinnamaldehyde in 100 mL of 1 N hydrochloric acid.

(13) Ferricyanide—Mix equal volumes of a 1% ferric chloride solution and a 1% potassium ferricyanide solution. Use immediately.

(14) Fast Blue B—Reagent A—Dissolve 500 mg of Fast Blue B Salt in 100 mL of water.

Reagent B—0.1 N sodium hydroxide.

Spray first with A, then with B.

(15) Alkaline Ferric Cyanide—Dilute 1.5 mL of a 1% potassium ferricyanide solution with water to 20 mL, and add 10 mL of 15% sodium hydroxide solution.

(16) Iodine Spray—Prepare a 0.5% solution of iodine in chloroform.

(17) Expose the plate for 10 minutes to iodine vapors in a pre-equilibrated closed chamber, on the bottom of which there are iodine crystals.

(18) Solution A—Dissolve 0.5 g of potassium iodide in 50 mL of water.

Solution B—Prepare a solution of 0.5 g of soluble starch in 50 mL of hot water.

Just prior to use, mix equal volumes of Solution A and Solution B.

(19) PTSS—Dissolve 20 g of p-toluenesulfonic acid in 100 mL of alcohol, spray the plate, dry for 15 minutes at 110, and view under UV light at 366 nm.

(20) o-Tolidine Spray—Dissolve 160 mg of o-tolidine in 30 mL of glacial acetic acid, dilute with water to make 500 mL, add 1 g of potassium iodide, and mix until the potassium iodide has dissolved.

(21) Mix 3 mL of chloroplatinic acid solution (1 in 10) with 97 mL of water, followed by the addition of 100 mL of potassium iodide solution (6 in 100) to prepare the spray reagent.

(22) Iodine–Methanol Spray—Prepare a mixture of iodine TS and methanol (1:1).