mobile phase expiry times

<p><span>Hello,</span></p><p></p><p><span>I'd like to hold an unofficial poll to see how long users are leaving their aqueous mobile phases on the Acquity system. The official advice is change every 24 - 48 hours but I have heard that some groups routinely run for 1 week with no problems. Our group is using a 72 hour expiry and our aqueous phase is typically 0.1% formic acid.</span></p><p></p><p><span>Thanks</span></p><p><span>David</span></p>

Answers

  • We change the aqueous mobile phase every 24-48 hours, based on experimental evidence in our lab. The mobile phase was 0.1% formic filtered to 0.22 um, and microbiological examination of the solvent was conducted over time. Appreciable bacterial counts were detected after only 36-48 hours.

    The best advice anyone can give you here is "you have been given good advice - if you choose to ignore it, then it is your fault"! On the other hand, if keeping mobile phases on the instruments for longer works OK in YOUR lab, then good luck to you. You can always go back to a protocol that you know works.

    How much of a hassle is it for you to change the mobile phase more frequently? My experience suggests that making up 500mL at a time (especially if it is something as simple as 0.1% formic) is no great hardship, especially for the peace of mind I get knowing that I am not going to block a column at a crucial moment. I also insist on using a fresh reservoir bottle rather than topping up a bottle. This means that I only have to exchange the reservoir, perform a 3 min prime, and carry on going.

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