by
lmh » Mon Sep 27, 2021 9:12 am
The trouble with literature is that so much of it is appalling. And journal editors sometimes don't know their nose from their eyeball, and some reviewers shouldn't be allowed to read the newspaper without someone there to help them with the big words.
I'm looking at the moment at a paper in Analytical and Bioanalytical Chemistry (so there's no excuse, this is an analytical journal). It's a methods paper, with a title along the lines of Quantification of Favourite Analyte in red blood cells by LC-MS", so you'd expect describing the method to be a fairly high priority.
The method claims steps of 0-0.8min 100%A; rise to 70% B in 4.8min; to 100% B in 0.1min; hold 100% B for 0.2 min; followed by a 3.5min equilibration. Then, the next sentence summarises that the overall run time was 8.5 min, with an injection volume of 5 uL. I have added up those step-times in every way I can imagine, and can I get 8.5 min? The paper has a typical chromatogram of a standard, showing the peak eluting nicely at 6.3min. Which would place it firmly in the re-equilibration part of the gradient, whether I use the gradient quoted, or the 8.5min figure. I'm guessing that actually the method is 9.5, not 8.5 (a typo) and that they dropped from 100%B to 100%A over 0.1min but missed this bit out. I'm also guessing (at least hoping) that the typical chromatogram with a 6.3min elution time came from an earlier, slower run before they optimised the gradient. The alternative is to hope that their system has a huge dead volume, because otherwise, at the very least, this target was only just eluting at 100%B, and the whole 0-70 bit was a waste of time.
If a methods paper in an analytical journal can't actually quote its gradient correctly, and none of the reviewers even notice, what is the point of having literature methods to follow? As usual, this means we can use the paper to get a rough idea of the sort of column-chemistry that might work (assuming they haven't messed that up too), and otherwise, we develop our own method.