Assay and RCs for Metformin Hydrochloride Ext release table

[Murshad]

Hi Folks

Has any one analyzed analyzing Metformin Hydrochloride Extended-Release Tablets for assay and related compounds by USP31.

The mobile phase is 5% acetonitrile with 95% pH 3.85 buffer
(Buffer solution prepared by dissolving sodium heptanesulfonate and sodium chloride 1.00g each in 1800ml HPLC grade water and pH adjusted to exactly 3.85 with 0.06M phosphoric acid and diluted to volume)
Detector 218nm
column L1 300 x 3.9mm 10um
I am not getting any resolution between Metformin HCl and Metformin related compound B. It does not matter how much you decrease the concentration of acetonitrile these two do not resolve. I have also attempted another brand new L1 column but situation did not improve.
I have also considered the option of adjusting pH to 3.70 and 4.00 exactly instead of 3.85 but still no resolution.
This is USP method and we cant consider to go out certain limits.

Thanks with regards

[Uwe Neue]

What are the column dimensions that are specified?

[AdrianF]

Although I have expressed some doubts about Microbondapak (30cm)in some of my posts, it works for Metformin.

pH 3.5 phosphate with 0.09% pentane sulphonic acid with a gradient from .02 to to 10% acetonitrile.

component A buffer
component B Buffer with 10% acetonitrile

time - % A -- % B
0 ---- 98 -- 2
3 --- 98 -- 2
15 -- 85-- 15
40 -- 0 -- 100
42 -- 98 -- 2
50 -- 98 -- 2

The columns don't last a long time but it works.

sorry about the table spaces are ignored

[Murshad]

Dear AdrianF

Thanks for your reply. It is USP method and we are not allowed to go out limits set USP.

Your reply is an evidence that there is noting wrong with me as analyst.

But I am also trying to find anyone who has done this as per USP31.

Thanks

[AdrianF]

I have copied part of the method from the USP for metformin - the column to use is L9 which is a strong cation exchanger, not L1.

Related compounds—
Mobile phase— Prepare a solution in water, containing 17 g of monobasic ammonium phosphate per L, adjust with phosphoric acid to a pH of 3.0, and mix.
Standard solution— Prepare a solution of USP Metformin Related Compound A RS in water having a known concentration of about 0.2 mg per mL. Transfer 1.0 mL of this solution to a 200-mL volumetric flask, dilute with Mobile phase to volume, and mix. [NOTE—Metformin related compound A is 1-cyanoguanidine.]
Test solution— Transfer about 500 mg of Metformin Hydrochloride, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.
Diluted test solution— Transfer 1.0 mL of the Test solution to a 10-mL volumetric flask, dilute with Mobile phase to volume, and mix. Transfer 1.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Resolution solution— Prepare a solution in water containing about 0.25 mg of metformin hydrochloride and about 0.1 mg of melamine per mL. Transfer 1.0 mL of this solution to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 218-nm detector and a 4.6-mm × 25-cm column containing packing L9. The flow rate is about 1.0 to 1.7 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the resolution, R, between melamine and metformin is not less than 10.
Procedure— Separately inject equal volumes (about 20 µL) of the Test solution, the Standard solution, and the Diluted test solution into the chromatograph, record the chromatograms for not less than twice the retention time of metformin, and measure the peak areas. Calculate the percentage of metformin related compound A in the portion of Metformin Hydrochloride taken by the formula:
10C/W(rU / rS)

[Murshad]

Dear AdrianF

You are right but the method you pasted is from USP30 and is for metformin hydrochloride tablets.
Unfortunately I am attemptimg USP31 which is causing problem

Again thanks for you interest and quick response.

[AdrianF]

30cm column = microbondapak, are you using it?

USP 31 is not current yet - you can still use USP 30, also you could contact the relevant person at the USP to find out why they have changed the method.

[Murshad]

Hi

Method says 3.9mm x 300mm 10um L1 column. I tried two different manufacturers but no success

Even trying 5um size did not show any progress.

I contacted relevant person in USP but still waiting for answer.

Thanks a lot for your interest

[AdrianF]

The column specified is microbondapak - you cannot substitute it if you are trying to copy the method. Have you tried Waters Microbondapak?

[Murshad]

Hi

I have tried three columns from two different vendors (Phenomenex and Waters)

[Uwe Neue]

Murshad:

When it says in the USP "use a 3.9 mm x 300 mm 10 micron L1 column", it is microbondapak C18. You will not get equivalent results from a random L1 packing.

This is the prime example for the idea that not all C18s are created equal!!!