Step/Methods

USP/NF 38

FCC 9

Recommended

Saponification

5 g potassium hydroxide, 50 mL alcohol, reflux 1 h.

2 g potassium hydroxide, 40 mL alcohol reflux 1 h “or until saponification is complete”.

2 g sodium hydroxide, minimal water, 50 mL ethyl alcohol, 1 h reflux.

Transfer

Cool. Transfer to separatory funnel with two 50 mL portions of water. Add 100 mL ethyl ether.

Transfer to cylinder bring to 40 mL with alcohol; add 40 mL H₂O, add 50 mL petroleum ether.

No transfer-continue in conical flask.

Solvent

Ethyl ether.

Petroleum ether.

Heptane.

Procedure

Gently rotate or shake the separator;

do not agitate violently. Repeat with two (2) times more 100 mL portions of ether.

Shake vigorously 1 min.

Wait until both layers become clear. Siphon off top layer. Repeat five (5) times.

Heat, stir to obtain single phase, separate into 2 layers, draw off top layer, repeat six (6) times.

Wash

Repeat the KOH solution-water wash sequence three times. Wash the ether extract with 40 mL portion of water until the last washing is not reddened by the addition of 2 drops of phenolphthalein TS.

Wash combined petroleum ether

portions with 10% alcohol until wash water does not turn phenolphthalein red.

Combined heptanes portions stirred with 1:1 EtOH:H₂O with hydrochloric acidacid to methyl orange.

Dry and weight

Evaporate the ether on a steam bath, and add 6 mL of acetone to the residue. Dry the residue at 105˚C until successive weighing’s differ by not more than 1 mg.

Transfer to a tared beaker. Evaporate on steam bath just to dryness and then at 100˚C for 30 min, and weigh.

Transfer the heptane extract to the beaker in boiling water, including glass beads. Drive off the heptane in a 100˚C oven overnight. Cool, weigh the residue.