FOLLOWING IS THE USP METHOD ATTACHED - PART ------------------------------------------------------
Solution A— Prepare a solution containing 4.76 g of monobasic potassium phosphate per L. Adjust with dilute phosphoric acid (l in 10) or potassium hydroxide (45% w/v) to a pH of 4.4. Pass this solution through a C18 filtration kit.
Solution B— Use acetonitrile.
Mobile phase— Use variable mixtures of Solution A and Solution B as directed under Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621 ).
Diluting solution— Prepare a mixture of acetonitrile and water (50:50).
Standard solution A— Transfer about 75 mg of USP Clarithromycin RS, accurately weighed, to a 50-mL volumetric flask, and dissolve in 25 mL of acetonitrile. Dilute with water to volume, and mix.
Standard solution B— Transfer 5.0 mL of Standard solution A to a 100-mL volumetric flask, dilute with Diluting solution to volume, and mix.
Standard solution C— Transfer 1.0 mL of Standard solution B to a 10-mL volumetric flask, dilute with Diluting solution to volume, and mix. This solution contains about 0.0075 mg of USP Clarithromycin RS per mL.
Standard solution D— Transfer about 15 mg of USP Clarithromycin Identity RS, accurately weighed, to a 10-mL volumetric flask, dissolve in 5.0 mL of acetonitrile, dilute with water to volume, and mix.
Test solution— Transfer about 75 mg of Clarithromycin, accurately weighed, to a 50-mL volumetric flask, dissolve in 25 mL of acetonitrile, dilute with water to volume, and mix.
Chromatographic system (see Chromatography 621 )— The liquid chromatograph is equipped with a 205-nm detector and a 4.6-mm × 10-cm column that contains packing L1 and is maintained at a constant temperature of about 40. The flow rate is about 1.1 mL per minute. The chromatograph is programmed as follows.
Time
(minutes) Solution A
(%) Solution B
(%) Elution
0®32 75®40 25®60 linear gradient
32®34 40 60 isocratic
34®36 40®75 60®25 linear gradient
36®42 75 25 isocratic
Relative retention times with reference to clarithromycin (retention time = about 11 minutes) include the following: impurity I = about 0.38; impurity C = about 0.89; impurity F = about 1.33; impurity A = about 0.42; impurity D = about 0.96; impurity P = about 1.35; impurity J = about 0.63; impurity N = about 1.15; impurity K = about 1.59; impurity L = about 0.74; impurity E = about 1.27; impurity G = about 1.72; impurity B = about 0.79; impurity 0 = about 1.38; impurity H = about 1.82; and impurity M = about 0.81.
System suitability— Chromatograph Standard solution B, and record the responses as directed for Procedure: the tailing factor for the main clarithromycin peak is not more than 1.7. Chromatograph Standard solution D, and record the responses as directed for Procedure: the peak-to-valley ratio ( H P / H V ) of impurity D and clarithromycin is not less than 3.0, where H P is the height above the baseline of the peak due to impurity D; and H V is the height above the baseline of the lowest point of the curve separating this peak from the peak due to clarithromycin.
Procedure— Separately inject equal volumes (about 10 µL) of the Diluting solution, Standard solution B, Standard solution D, Standard solution C, and the Test solution into the chromatograph, record the chromatograms, and measure the peak area responses. Calculate the percentage of each impurity in the Clarithromycin taken by the formula:
50( C C / W)( r i F / r C )P,
in which C C is the concentration, in mg per mL, of USP Clarithromycin .
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As told earlier This method is currently official in USP and EP. Hence in all cases we have to follow this as this method can separate many impurities which will be diificult to synthesize and required for development of an IH method for these.
If we are using USP method, RRT Mentioned here can solve the purpose of identification for such impurities.
Rgds
Shashi Kant Tiwari
