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Injecting air segments

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

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I have a high pressure mixer, binary pump HPLC system with an autosampler (Beckman 125 pump, 508 autosampler, 166 detector). After a long period of troubleshooting injection-to-injection reproducibility, I was able to determine that enabling the air segment option in the autosampler settings produced more consistent injection volumes (as measured by the total area count after integration, %RSDs that were in excess of 4 or 5 dropped down to 0.2-0.5). This is for a partial loop fill, obviously putting a smaller loop and doing a full loop fill would be a better long term solution, but it's more convenient to be able to vary the injection volume without making a change to the hardware.

My question is: Are there any negative consequences to injecting that air-segment? Is it just going to immediately be dissolved in the mobile phase, due to the high-pressure nature of the system? Do small amounts of air disturb the packing at all, if they aren't fully dissolved?

I haven't heard or experienced any negative consequences from it for analytical scale (not nano) experiments. Otherwise, it wouldn't be offered as an option...
2 posts Page 1 of 1

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