Let’s talk about HPLC sample prep, because this is where most of the errors occur in the entire analytical procedure.
We call this pre-analytical error, and those are errors that happen before we get to the instrument.
We could measure the precision, the accuracy, and we could measure the carryover on the instrument, but what we really want to talk about is where the errors occur, and that is when we’re dissolving the sample, filtering the sample, and working with the sample – sample prep.
Preparing The Sample For The Instrument
Let’s take a big picture look and say that HPLC sample prep is preparing the sample for the instrument. So, when we’re running HPLC, what does that mean? The only thing that can hurt your HPLC really is particulates, because particulates will clog the frit to the top of the column and will permanently damage your column.
So, as an absolute minimum, I recommend that you filter every sample through a half micron, 0.45 micron, 0.2 micron, 0.1 micron filter in order to eliminate that problem. If the sample is soluble in the mobile phase, it cannot do any damage to the instrument. So, think about that. As long as your sample is soluble in the mobile phase, if you dissolve your sample in the mobile phase and you filter it, then there’s no damage that can happen later on. Because if it dissolves in the mobile phase, clearly it is going to eventually come off the column.
Examples: Aspirin Tablets vs Soft Drinks
So, if you think back to some of the other webinars that we’ve done, in the one where we did Aspirin tablets, find the webinar here, there was a lot more HPLC sample prep because we had dissolution, we had filtering, we had to figure out the right solvent for dissolution and the right amount of time and sonication. Then we did the webinar on soft drinks(Half Caf, Decaf or no-caf), find the webinar here. That was pretty simple. We just took a can of Coke, opened it up, and pulled some sample out and put it right in the vial.
So, you look at the sample and you decide what to do to get the sample ready for HPLC, and in our world of LC, you really think about, is it soluble in the mobile phase and is it free of particulates? If so, then you are good to go.
So, come back and check out some of our other webinars so you can see the details on how we actually do HPLC sample prep.