I used a RP-trimethy (USP L13)column, the mobile phase contained laury sulfate sodium and phosphonic acid. After analysis, How can I do to wash the column?

Depends what's left on it.

If your samples are relatively "clean" (i.e., little or no strongly bound material likely to remain), then simply washing with buffer-free mobile phase (i.e., organic solvent + water only) should do the trick.

If you have strongly bound material (lipophilic stuff) left behind, then start with buffer-free mobile phase as above, then switch to the pure organic solvent after you've pumped 10 - 20 column volumes. After 10-20 column volumes of organic, go back to your buffer-free mobile phase.

If you have "irreversibly" bound or precipitated material, then you will need to identify a solvent which will solubilize the stuff. The choice will vary with the type of material (e.g., methylene chloride for lipids, iPrOH for proteins, etc. You may have to use intermediate solvents to prevent precipitation, immiscibility, etc.

If you want more details, you might check out Dolan and Snyder's book "Troubleshooting LC Systems" (Humana Press) or Snyder, Glajch, and Kirkland's "Practical HPLC Method Development" (Wiley).

-- Tom Jupille / LC Resources