Trouble shooting with assay Clopidogrel by HPLC

[phucto]

I am running HPLC for Clopidogrel bisulfate as the method in USP 34.

Mobile phase: a mixture of monobasic potassium phosphate 10mM and acetonitril (75:25). My column (new column purchased from Shinwa) is ULtron ES-OVM (150 x 4.6, 5 micro) but I have prolems with peak taling of Clopidogrel. (the assymatry is above 2.5). Anyone can share me the solution for this problems. I tried to make adjustment mobile phase rate, column temperature, running in 2 different HPLC machine, rinse the column as manufacture' guidance but no appovement.

[tom jupille]

It is possible that you have a head space or partially blocked frit. Check with the vendor to find out if the column can be back-flushed (I *think* it can, but best to be certain!). If possible, try running the column in reverse. If the symmetry improves, return it to the original flow direction.

If that fails, then try increasing the buffer concentration (10 mM is a bit on the low side).

You have looked at everything else, so a remaining possibility is that you have a dead column.