Captopril Oral Solution
» Captopril Oral Solution contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of captopril (C9H15NO3S). Prepare Captopril Oral Solution 0.75 mg per mL as follows (see Pharmaceutical CompoundingNonsterile Preparations 795. See also Captopril Oral Suspension):
Add Captopril powder and about 10 mL of Vehicle to a mortar, and mix. Add the Vehicle in small portions almost to volume, and mix thoroughly after each addition. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add enough Vehicle to bring to final volume, and mix well.
Packaging and storage Preserve in tight, light-resistant containers. Store in a cold place.
Labeling Label it to state the beyond-use date.
pH 791: between 3.8 and 4.3.
Beyond-use date: 7 days after the day on which it was compounded.
Mobile phase Prepare a filtered and degassed mixture of methanol and water (11:9) containing 0.5 mL of phosphoric acid. Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation Dissolve USP Captopril RS in water to obtain a solution having a known concentration of 7.5 µg per mL.
Assay preparation Agitate the container of Oral Solution for 30 minutes on a rotating mixer, remove a 5-mL sample, and store in a clear glass vial at 70 until analyzed. At the time of analysis, remove the sample from the freezer, allow it to reach room temperature, and mix with a vortex mixer for 30 seconds. Pipet 1.0 mL of the sample into a 100-mL volumetric flask, and dilute with Mobile phase to volume.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 220-nm detector and a 4.6-mm × 25-cm analytical column that contains 5-µm packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the retention time is about 5.0 minutes; and the relative standard deviation for replicate injections is not more than 0.9%.
Procedure Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of captopril (C9H15NO3S) in the volume of Oral Solution taken by the formula:
100(C / V)(rU / rS)in which C is the concentration, in µg per mL, of USP Captopril RS in the Standard preparation; V is the volume, in mL, of Oral Solution taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.
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USP32NF27 Page 1780Pharmacopeial Forum: Volume No. 32(1) Page 63