The frit in any HPLC column is a possible cause of flow blockage resulting in high back pressures and other possible issues that can affect your results. The frit pore size in the column is a distribution of size with an average of only 2um wide and therefore can be easily blocked by small un-dissolved sample matrix or other particulate matter that was not filtered out during sample prep or generated by your instrument. Note: The frits used in HPLC columns are actually compressed powders and therefore the consistency of pore size does vary a bit, with higher flow rates they become more susceptible to blockage.

Blockage of a column is most likely at the inlet side of the frit: frits can be removed and replaced but it is NOT recommended that you attempt to replace them as it is easy to disrupt the column stationary phase packed bed when the frit cap or end fitting is removed. Therefore, the best way to repair a blocked frit in your lab is to try to dislodge or dissolve the particle on the frit using solvents that the particle might be soluble.

To remove a particle lodged in a column frit, place the column in reverse direction on your HPLC system from what you were using it when it got blocked. Without creating any pressure shock, slowly and gently run 100% HPLC grade water through the column starting a 0ml/minute and holding the flow rate at 0.5ml/minute for 3.0 or 4.6mm ID columns. Hold at this flow rate for about 2-3 hours then reduce the flow rate gently back to 0ml/min. Using 100% Acetonitrile as the flow solvent, repeat the above. If this does not work, we have found the 50% Methanol: 50% Water also works for many biological samples as the flow solvent. If your samples are not soluble in water or acetonitrile, it is recommend to use solvents in the above manner as long as you are sure they will not damage or alter your column.

For 2.1mm ID columns, follow the same procedure but ramp the flow rate from 0ml/min to 0.05ml/minute.

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