Identification—
Constitute a vial of Thiothixene Hydrochloride for Injection with 2.2 mL of water. Further dilute one volume of the constituted solution with 4 volumes of methanol to obtain a test solution containing 1 mg of thiothixene per mL. Apply 10 µL of this test solution and 10 µL of a Standard solution containing 1 mg of
USP Thiothixene RS per mL in the same medium to a suitable thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of isopropyl alcohol and diethylamine (25:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, air-dry for 30 minutes, and then oven-dry at 110
for 30 minutes. Locate the spots on the plate by viewing under short-wavelength UV light. Spray the plate with alkaline permanganate spray reagent (prepared by dissolving 0.5 g of potassium permanganate and 2.0 g of sodium carbonate in 100 mL of water): the
RF value of the principal spot obtained from the test solution, under both detection conditions, corresponds to that obtained from the Standard solution.
Assay—
[NOTE—Perform the dilution operations in low-actinic glassware.
]
Mobile phase
,
Standard preparation, and
Chromatographic system—Prepare as directed in the
Assay under
Thiothixene.
Assay preparation—
Constitute a vial of Thiothixene Hydrochloride for Injection with an accurately measured volume (VL mL) of water as directed in the labeling. Transfer an accurately measured volume (VF mL) of the constituted solution, equivalent to about 5 mg of thiothixene, to a 250-mL volumetric flask, dilute with methanol to volume, and mix.
Procedure—
Proceed as directed for
Procedure in the
Assay under
Thiothixene. Calculate the quantity, in mg, of C
23H
29N
3O
2S
2 in each mL of the constituted solution taken by the formula:
(250CVL / VF)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Thiothixene RS in the
Standard preparation, and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
