U.S. PHARMACOPEIA

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Monensin Premix
» Monensin Premix contains Monensin Granulated mixed with suitable diluents and inactive ingredients. It contains the equivalent of not less than 85.0 percent and not more than 115.0 percent of the labeled amount of monensin.
Packaging and storage— Preserve in well-closed containers. Avoid moisture and excessive heat.
Labeling— Label it to indicate that it is for veterinary use only. The label bears the statement “Do not feed undiluted.”
Identification— The chromatogram of the Assay preparation obtained as directed in the Assay exhibits a major peak for monensin A and a minor peak for monensin B, the retention times of which correspond to those exhibited in the chromatogram of the Standard preparation obtained as directed in the Assay.
Loss on drying 731— Dry it in vacuum at 60 for 2 hours: it loses not more than 10% of its weight.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay—
Mobile phase , Neutralized methanol, Diluent, Derivatizing reagent, Standard preparation, Resolution solution, and Chromatographic system—Proceed as directed in the Assay under Monensin.
Assay preparation— Transfer about 5 g of Premix, accurately weighed, to a 250-mL flask, add 200.0 mL of Diluent, and shake by mechanical means for 1 hour. Allow the solids to settle, and dilute an accurately measured volume of the clear supernatant quantitatively with Diluent to obtain a solution containing about 20 µg of monensin per mL.
Procedure— Proceed as directed for Procedure in the Assay under Monensin. Calculate the quantity, in mg, of monensin A in each g of the Premix taken by the formula:
(CFD / 100,000W)(rU / rS),
in which C is the concentration, in µg per mL, of monensin activity in the Standard preparation, based on the quantity of USP Monensin Sodium RS taken, its designated potency, in µg per mg, and the extent of dilution, F is the designated percentage of monensin A in USP Monensin Sodium RS, D is the dilution factor used in preparing the Assay preparation, W is the quantity, in g, of Premix taken to prepare the Assay preparation, and rU and rS are the monensin A peak responses obtained from the Assay preparation and the Standard preparation, respectively. Calculate the quantity, in mg, of monensin B in each g of the Premix taken by the same formula, except that rU is the monensin B peak response obtained from the Assay preparation and rS is the monensin A peak response obtained from the Standard preparation. Calculate the quantity, in mg, of monensin C/D in each g of the Premix taken by the same formula, except that rU is the monensin C/D peak response obtained from the Assay preparation. Calculate the potency, in mg of monensin, in each g of the Premix taken by the formula:
A + 0.28B + 1.5C / D,
in which A is the quantity, in mg, of monensin A in each g of the Premix taken, as calculated above, and B is the quantity, in mg, of monensin B in each g of the Premix taken, and C/D is the quantity, in mg, of monensin C/D in each g of Premix taken, as calculated above.
Auxiliary Information— Staff Liaison : Ian DeVeau, Ph.D., Associate Director
Expert Committee : (VET05) Veterinary Drugs 05
USP29–NF24 Page 1453
Phone Number : 1-301-816-8178