Chloride 
221
—
Dissolve 200 mg in a mixture of 75 mL of ether and 25 mL of water, agitate, and allow to separate: the water solution shows no more chloride than corresponds to 0.17 mL of 0.010 N hydrochloric acid (0.03%).
Ordinary impurities 466—
Test solution:
methanol.
Standard solution:
methanol.
Eluant:
a mixture of chloroform and acetone (7:3).
Visualization—
Expose the plate to chlorine gas for 1 minute, and air-dry the plate at room temperature for 2 minutes. Prepare a solution of 0.5 g of potassium iodide in 50 mL of water, and prepare a solution of 1.5 g of soluble starch in 50 mL of hot water. Mix 10 mL of each solution with 4 mL of alcohol to obtain the Detection reagent. [NOTE—The Detection reagent so obtained may be used for up to 3 or 4 days.] Spray the plate with the Detection reagent.
Assay—
Dissolve about 100 mg of Methohexital, accurately weighed, in chloroform, and dilute quantitatively and stepwise with chloroform to obtain a solution having a concentration of about 10 mg per mL. Dissolve an accurately weighed quantity of
USP Methohexital RS in chloroform, and dilute quantitatively and stepwise with chloroform to obtain a Standard solution having a known concentration of about 10 mg per mL. Concomitantly determine the absorbances of both solutions in 0.1-mm cells at the wavelength of maximum absorbance at about 5.93 µm, with a suitable spectrophotometer, using chloroform as the blank. Calculate the quantity, in mg, of C
14H
18N
2O
3 in the portion of Methohexital taken by the formula:
10C(AU / AS),
in which
C is the concentration, in mg per mL, of
USP Methohexital RS in the Standard solution; and
AU and
AS are the absorbances of the solution of Methohexital and the
Standard solution, respectively.
;)
and 96