by
lmh » Thu Nov 30, 2017 11:20 am
Flow-rate, agree.
Nomenclature: People get terribly stressed about names of techniques and instruments, I think because there's a perception that manufacturers try to make their product look better than it is by adding extra letters to the abbreviation, and are disparaging towards those who can't claim the extra letter. Hopefully chromatographers are bright enough to see through the meaningless flannel.
But it really is helpful to have different names for different sorts of instruments, and the test is whether a name sticks around (it won't, if it's not useful). UPLC is an unhelpful abbreviation because it belongs to Waters. UHPLC is a good abbreviation because it defines an instrument that can run at over 400 bar and is optimised for rapid runs and narrow peaks, to current standards. The pressure limit may feel arbitrary, and that really we're trying to draw a boundary half way up a gradual slope, but actually the history wasn't like that: for aeons all HPLCs went up to 400 bar. Quite suddenly, Waters changed all that with their first UPLC; all the other manufacturers declared it would never work, while frenetically developing their own extra-high-pressure systems. The goal posts that had been still for ages, suddenly moved very fast indeed. People rapidly realised that high pressure was only half the story, and the rest of the system had to be optimised for small dead volumes or the peaks wouldn't get narrower. Autosamplers had to get faster, because otherwise 1 minute runs were messed up by 2 minute injection cycles. And so we have the situation today, where you can buy, cheaply, a large-dead-volume, 400-bar traditional instrument (often cost-effective and useful) and call it an HPLC, or you can buy a 1000-bar optimised instrument with an autosampler riddled with complex patents, and benefit from UHPLC.
