Several simple UV spectrophotometric methods of assay are available for the estimation of ephedrine in pharmaceutical formulations.

A. Method I

1. 20 g of powdered plant material is shaken frequently with 200 ml of a 1:3 mixture of chloroform and ether.
2. 10 ml of 10% ammonia solution and 1 g of anhydrous sodium carbonate are added and the mixture shaken for 4 h at frequent intervals and allowed to stand overnight.
3. The mixture is carefully packed in a percolator and percolated with the 100 ml ether-chloroform mixture for 4 h and then further percolated with 100 ml ether for another 3 h for complete extraction of alkaloids.
4. The combined percolates are shaken with successive portions of 4 × 20 ml of N/3 HCl.
5. The combined acid extracts are filtered and treated with 1N NaOH solution to a pH of 4 to 5; 10 g anhydrous sodium carbonate and sufficient NaCl are added to saturate the solution.
6. The clear alkaline solution is extracted with four successive portions of 60, 50, 50 and 30 ml of ether and then with 25 ml portions of ether until extraction of the alkaloids is complete.
7. The combined ether extracts are allowed to stand until clear and then decanted through a filter into a beaker. The ether solution is warmed and poured off from any crystals which may separate.
8. The ether is evaporated to a volume of approximately 10 ml and the residual solvent allowed to evaporate in air.
9. The residue is dissolved in excess of 0.1N sulphuric acid, 20 ml distilled water is added and the excess acid back titrated with 0.1 N NaOH using methyl red as indicator.
10. Each 1 ml of 0.1 N H₂SO₄ is equivalent to 0.01651 g of total alkaloids calculated as ephedrine.

B. Method II

1. A solution of ephedrine (5–500 mg) is taken with 10–15 ml of 50% NaOH in a distillation flask and quickly distilled.
2. The distillate is collected in an excess of standard sulphuric acid. Depending on the amount of ephedrine present 50–150 ml of distillate is collected. Neutral reaction of the distillate to litmus gives an indication of the completeness of distillation.
3. The excess acid is back titrated with standard NaOH using methyl red as indicator .1 ml of 0.1 N H₂SO₄ is equivalent to 0.01652 g of anhydrous ephedrine.

C. Method III

1. Dissolve about 500 mg of ephedrine hydrochloride, accurately weighed in 25 ml of glacial acetic acid.
2. Add 10 ml of mecuric acetate TS and two drops of crystal violet TS, and titrate with 0.1N perchloric acid (test solution) to an emerald-green end point.
3. Perform a blank determination and make any necessary correction. Each ml of 0.1N perchloric acid is equivalent to 20.17 mg of ephedrine hydrochloride.