Medium: water; 500 mL.

Apparatus 1: 100 rpm.

Time: 45 minutes.

Procedure— Filter a portion of about 20 mL of the solution under test. Transfer about 5 mL of the eluant into a small test tube, and add 250 µL of 0.01 M sodium sulfate internal standard solution. Evaporate until dry using a vacuum centrifuge. Add 10.0 µL of water to the precipitate and place on a vortex mixer until all solid material is dissolved. Transfer this solution to a capillary tube, place it in a Raman spectrometer, and obtain the Raman spectrum using suitable instrumental conditions (see Spectrophotometry and Light-scattering 851). Integrate the Raman intensity, applying baseline corrections, between 660 cm1 and 720 cm1. Divide this result by the integrated intensity between 966 cm1 and 994 cm1. Determine the amount of C18H34N2O6S dissolved in comparison with an aqueous Standard solution having a known concentration of USP Lincomycin Hydrochloride RS.

Tolerances— Not less than 75% (Q) of the labeled amount of C18H34N2O6S is dissolved in 45 minutes.

Mobile phase, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Lincomycin Hydrochloride.

Assay preparation— Remove, as completely as possible, the contents of not less than 10 Capsules, taking care to prevent capsule shell fragments from being combined with the capsule contents and to remove any shell fragments from the contents. Weigh and mix the combined contents, and transfer an accurately weighed portion of the powder, equivalent to about 50 mg of lincomycin, to a suitable container. Add 50.0 mL of Mobile phase, and shake by mechanical means for 5 minutes. Use the solution thus obtained as the Assay preparation.

Procedure— Proceed as directed for Procedure in the Assay under Lincomycin Hydrochloride. Calculate the quantity, in mg, of lincomycin (C18H34N2O6S) in the portion of Capsule contents taken by the formula: in which the terms are as defined therein.