Identification—
Triturate a quantity of finely powdered Tablets, equivalent to about 100 mg of carbenicillin, with 10 mL of a solvent mixture consisting of acetone, ethyl acetate, water, pyridine, and glacial acetic acid (200:100:75:25:1.5). Shake the mixture for 5 minutes, and dilute 1 volume of it with 9 volumes of the solvent mixture. Apply 10 µL each of this solution and of a solution of
USP Carbenicillin Indanyl Sodium RS in the same solvent mixture containing 1 mg of carbenicillin per mL 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 acetone, ethyl acetate, water, pyridine, and glacial acetic acid (400:300:75:25:2) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, mark the solvent front, and heat the plate at 80
for 30 minutes. Allow the plate to cool, and expose it to iodine vapors in a closed chamber for about 30 seconds. Spray the plate with a reagent consisting of a 1 in 100 solution of ferric chloride in 0.1 N hydrochloric acid, potassium ferricyanide solution (1 in 100), and methanol (4:4:3): the principal spots from the test solution and the Standard solution are blue on a yellow-green background, and the
RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution (
RF about 0.5).
Dissolution 711—
Medium:
water; 900 mL.
Apparatus 1:
100 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of carbenicillin (C
17 H
18N
2O
6S) equivalent dissolved from the difference between UV absorbances at the wavelengths of maximum and minimum absorbance at about 267 nm and 254 nm, respectively, of filtered portions of the solution under test, suitably diluted with water, in comparison with a Standard solution having a known concentration of
USP Carbenicillin Indanyl Sodium RS in the same medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of C17H18N2O6S equivalent is dissolved in 45 minutes.
Assay—
Mobile phase
, Diluting solvent, Standard preparation, and Chromatographic system—Proceed as directed in the Assay under Carbenicillin Indanyl Sodium.
Assay preparation—
Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 111 mg of carbenicillin (C17H18N2O6S), to a 50-mL volumetric flask, dissolve in Diluting solvent with the aid of sonication, dilute with Diluting solvent to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with Diluting solvent to volume, and mix.
Procedure—
Proceed as directed for
Procedure in the
Assay under
Carbenicillin Indanyl Sodium. Calculate the quantity, in mg, of carbenicillin (C
17H
18N
2O
6S) in the portion of Tablets taken by the formula:
0.5CP(rU / rS),
in which the terms are as defined therein.
