Assay
Internal standard solution
Dissolve triphenylantimony in dimethylformamide to obtain a solution containing about 2 mg per mL.
Standard preparation
Transfer about 30 mg of
USP Spectinomycin Hydrochloride RS, accurately weighed, to a glass-stoppered, 25-mL conical flask. Add 10.0 mL of
Internal standard solution and 1.0 mL of hexamethyldisilazane, and shake intermittently for 1 hour.
Assay preparation
Proceed as directed under Standard preparation using Spectinomycin Hydrochloride.
Chromatographic system
(see
Chromatography 621)The gas chromatograph is equipped with a flame-ionization detector and contains a 3-mm × 60-cm glass column packed with 5 percent phase G27 on 80- to 100-mesh support S1AB. The column and detector are maintained at about 190
and 220
, respectively, and the injection port at about 215
, and dry helium is used as the carrier gas at a flow rate of about 45 mL per minute. Chromatograph the
Standard preparation, and record the chromatogram as directed for
Procedure: the resolution,
R, between the major peaks is not less than 2.0; and the relative standard deviation of the peak response ratios,
RS, from replicate injections of the
Standard preparation is not more than 3.5%.
Procedure
Separately inject equal volumes (about 1 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 ratio,
RU, of the response of the spectinomycin peak to the response of the internal standard peak in the chromatogram from the
Assay preparation, and similarly calculate the ratio,
RS, in the chromatogram from the
Standard preparation. Calculate the quantity, in µg, of C
14H
24N
2O
7 in the portion of Spectinomycin Hydrochloride taken to prepare the
Assay preparation by the formula:
P(WS)(RU / RS),
in which
P is the potency of
USP Spectinomycin Hydrochloride RS, in µg of spectinomycin per mg; and
WS is the weight, in mg, of
USP Spectinomycin Hydrochloride RS taken from the
Standard preparation; and the other terms are as defined above.