[newcastler]

I have some samples which I will like to test with HPLC for the detection of cyclopsorin.

The cyclosporin standards are dissolved in methanol.

My samples are extracted in methanol follow by column chromatography using dichloromethane and methanol.

After a few runs of the HPLC, I think some of the material will be 'stuck' on the column. Especially for those sample with higher concentrations. I will like to check which solvent is good to wash the column in between runs. Is it methanol? Or Dichloromethane.

Thanxs!!

[jwesterway]

your running a solvent program with DCM --> methanol or methanol --> DCM conc gradient?
Anyway... It would depend on which of the solvents the analyte is more soluble in, but in HPLC material does not usually get 'stuck' on the column, if it is being retained and the peak is broad this usually means your flow rate is too low and diffusion is occuring. And if you are concerned about the higher concs being retained (where or how i dont know) then lower the concs of all standards and unknowns by ratio to eliminate this problem, you should not be using such concentrations which would flood the detector (possibly damaging it) in any HPLC analysis.
However you can also just do a few blank runs and run the complete sequence for the time of analysis and while running the temp program between actual runs (this would waste alot of resources and instrument time though you realise?)

-Josh

[profmsg]

i got this problem before. my column was contaminated with one of the impurity with highest area count. the mobile phase used was methanol and water in 50:50. so i carried out about 20 injection of methanol  with run time 1 min. To check whether it wroked or not, a injection of dissolution solvent was carried out and found no peak on chromatogram.
 so i think, you should carry out few injection of methanol or dcm in which the sample most dissolves