(Official January 1, 2007)

Internal standard solution, Standard preparation, Chromatographic system, and System suitability test— Proceed as directed in the Assay under Terpin Hydrate.

Assay preparation— Pipet 10 mL of Oral Solution into a separator, add 20 mL of water and 10 mL of 5 N sodium hydroxide, and extract with three 25-mL portions of chloroform, filtering each, successively, through cotton. Rinse the cotton with chloroform. To the combined rinse and extracts add 5.00 mL of Internal standard solution, and mix.

Procedure— Inject about 1 µL of the Standard preparation into a suitable gas chromatograph, and record the chromatogram. Similarly, inject about 1 µL of the Assay preparation, and record the chromatogram. Calculate the quantity, in mg, of terpin hydrate (C10H20O2·H2O) in each mL of the Oral Solution taken by the formula: in which 190.28 and 172.27 are the molecular weights of terpin hydrate (C10H20O2·H2O) and anhydrous terpin (C10H20O2), respectively; WS is the weight, in mg, of USP Terpin Hydrate RS, calculated on the anhydrous basis; and RU and RS are the area-ratios of terpin to biphenyl obtained from the chromatograms for the Assay preparation and the Standard preparation, respectively.