Action and use
Fluoroquinolone antibacterial.
DEFINITION
Enrofloxacin Solution for Use in Drinking Water is a solution of Enrofloxacin in a suitable vehicle.
The solution complies with the requirements stated under Oral Liquids and with the following requirements.
Content of enrofloxacin, C19H22FN3O3
95.0 to 105.0% of the stated amount.
IDENTIFICATION
A. To a quantity of the solution containing 0.1 g of Enrofloxacin, add 10 mL of dichloromethane, shake and allow to separate. Discard the upper aqueous layer and wash the lower dichloromethane layer with three 20-mL quantities of water. Dry the washed dichloromethane with sodium sulfate, filter and evaporate the filtrate to dryness. The infrared absorption spectrum of the dried residue, Appendix II A, is concordant with the reference spectrum of enrofloxacin (RSV 55).
B. In the Assay, the retention time of the principal peak in the chromatogram obtained with solution (1) is similar to that of the peak in the chromatogram obtained with solution (2).
TESTS
Related substances
Carry out the method for liquid chromatography, Appendix III D, using the following solutions prepared in 0.1M formic acid.
(1) Dilute a quantity of the solution containing 50 mg of Enrofloxacin to 100 mL.
(2) Dilute 1 volume of solution (1) to 100 volumes.
(3) 0.05% w/v of enrofloxacin BPCRS and 0.0005% w/v of ciprofloxacin hydrochloride BPCRS (impurity B).
(4) Dilute 3 volumes of solution (2) to 10 volumes.
CHROMATOGRAPHIC CONDITIONS
(a) Use a stainless steel column (25 cm × 4.0 mm) packed with octadecylsilyl silica gel for chromatography (10 μm) (Nucleosil RP18 is suitable).
(b) Use isocratic elution and the mobile phase described below.
(c) Use a flow rate of 2.0 mL per minute.
(d) Use a column temperature of 40°.
(e) Use a detection wavelength of 278 nm.
(f) Inject 5 μL of each solution.
(g) Allow the chromatography to proceed for twice the retention time of enrofloxacin.
MOBILE PHASE
100 volumes of a solution containing 1.1% w/v of sodium heptanesulfonate monohydrate and 2.72% w/v of potassium dihydrogen orthophosphate, 190 volumes of acetonitrile and 710 volumes of water, adjust the pH of the mixture to 2.1 with orthophosphoric acid.
SYSTEM SUITABILITY
The test is not valid unless, in the chromatogram obtained with solution (3), the resolution between the peaks corresponding to impurity B and enrofloxacin is at least 2.0.
CALCULATION OF IMPURITIES
For each impurity, use the concentration of enrofloxacin in solution (2).
For the reporting threshold, use the concentration of enrofloxacin in solution (4).
For peak identification, use solution (3).
Enrofloxacin retention time: about 9 minutes.
Relative retention: impurity B, about 0.8.
LIMITS
— unspecified impurities: for each impurity, not more than 1.0%;
— total impurities: not more than 2.0%;
— reporting threshold: 0.3%.
ASSAY
Carry out the method for liquid chromatography, Appendix III D, using the following solutions prepared in 0.1M formic acid.
(1) Dilute a weighed quantity of the solution containing 50 mg of Enrofloxacin to 100 mL.
(2) 0.05% w/v of enrofloxacin BPCRS.
(3) 0.05% w/v of enrofloxacin BPCRS and 0.0005% w/v of ciprofloxacin hydrochloride BPCRS (impurity B).
CHROMATOGRAPHIC CONDITIONS
The chromatographic conditions described under Related substances may be used.
SYSTEM SUITABILITY
The test is not valid unless, in the chromatogram obtained with solution (3), the resolution between the peaks corresponding to impurity B and enrofloxacin is at least 2.0.
DETERMINATION OF CONTENT
Determine the weight per mL of the solution, Appendix V G, and calculate the content of C19H22FN3O3 in the solution from the chromatograms obtained and using the declared content of C19H22FN3O3 in enrofloxacin BPCRS.
IMPURITIES
The impurities limited by the requirements of this monograph include impurity B listed under Enrofloxacin.
