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gradient or isocratic?
Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.
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I have developed and validated three analytical methods for detection of various bioactive molecules--Vitamin A; Thiamine; and Riboflavin. When I presented them at a "break out session" at a regional nutrition science conference, two of the audience members questioned--why I'm not using gradient elutions. I responded to them that why use a gradient when isocratic worked just fine--it's much simpler & faster to prepare runs (a major point) and less taxing on the software-regulated proportioning valves (but that is a minor issue). I'm curious--How would you'all here defend such a thesis?
Jumpshooter
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isocratic methods are more robust when transferrring from instrument to instrument, especially if mobile phase is premixed (versus online mixing).
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Isocratic method is faster as long as the capacity factor is similar for your analytes because there is no re-equilibration between runs. Faster means less expensive.
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We always use isocratic if it works for the assay. Like the other posters stated: different systems will be "more different" with gradients, and I've seen many issues with insufficient post-run or re-equilibration time/volumes. So real throughput is usually more with isocratic.
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