Chromatography Forum

I'm curious as to how others are measuring column flow? Restek's website has a flow calculator which uses the RT of an unretained peak. You also have to know the column length which is probably not what is written on the box. The gas flow meter I have says it's accurate down to around 5 mL/min, but what if my column flow is less than that? I'd be interested to hear what anyone else is doing.

Thanks,

Dave

I inject something that will not be retained and measure the time it takes to reach the detector. That gives me linear flow rate (if I know the column length) which is what matters. Separations are actually quite robust to flow, so not knowing the column length exactly is of no concern.

Peter

I do as Peter does. Linear velocity is the key parameter. It's generally measured in cm/s so you can be off in length (a few cm out of 30 - 60 m) but still hit your flow target quickly. There's a timer built into the keypad of all of my Agilent GC's so it's really easy to measure as well. I use methane.

I've done what others have posted above.

I've also inserted the column end through a cylindrical septum, broken off a few mm to remove any septum clog, and then inserted that into the tubing of an electronic flow detector. Of course, that septum must fit snugly into that plastic tubing, you may need an adapter tube.