codeine/syrup residue build up

[srdales]

We are seeing a codeine/syrup residue build up on the C8, 5 um, 150 x 4.6.

M.P. is 50/30/20 buffer/ACN/MeOH.

We are not analyzing for codeine.

Does anyone have a recommendation to wash the codeine and syrup build up from the column between runs?

Thanks

[tom jupille]

In the absence of more specific recommendations, try running a gradient from your existing mobile phase up to 60/40 ACN/MeOH and see what concentration of organic solvent it takes to elute your retained junk. Then periodically backwash your column with slightly higher organic.

[Mark Tracy]

In addition to Tom's advice to get rid of codeine and other hydrophobic stuff, there may be gum thickeners in the syrup that are poorly soluble in your mobile phase. Gums are polysaccharides that are more soluble in water, so try a wash with 25:75 organic:buffer. If your column will tolerate reverse flow, do that.

[srdales]

thank you both.