|
Frequently Asked Questions
Here are some of the frequently asked questions we've received from you regarding our products.
What is your advice on fittings for uPLC?
I try to use Valco fittings whenever I need a metal fitting. I have used the Valco fittings upto 15000psi without too much trouble. The main trick with connecting the metal fittings (1/16th) to fused silica tubing is to use a PEEK tubing sleeve. If you use teflon or FEP you will blow your fittings around 4,000-5,000 psi. Also investing in high quality tubing cutters (PEEK and fused silica) is money really really well spent.
I also really like the high pressure fittings from valvo that connect directly to fused silica tubing. They take a little bit of practice to get the fitting to be the right tightness. Too little and it leaks, too tight and you block the flow. Best to follow the instructions as closely as you can. I have found the metal fitting with the PEEK nut/ferrule worked the best for me.
It turns out fittings are a real art in nanoLC, probably the same with uPLC.
What is your advice on using a long sample loading time (~15 minutes) at a high flow rate (~1 uL/min), and then switching to a low flow rate of 300nL/minute for the chromatography with a splitless pump?
It is much easier to do the fast load/slow gradient with a splitter on a conventional or microflow pump then on a splitless pump such as the Microtech system. The reason to do this is that it is faster. Say you are loading a 5 ul sample, this takes 5 min at 1 ul/min and almost 17 min at 300 nl/min. The problem with the Microtech system is that the only place for the pressurized solvent to go is out through your column so you build up a big pressure at 1 ul/min and when you switch to 300 nl/min you still have this big pressure so you have to wait until enough solvent has left the end of the column to equilibrate to the pressure required to run at 300 nl/min. Since the pumps are still moving, albeit slower, this can take a long time! Some other splitless pumps such as the Eksigent can apparently handle this mode of operation.
|
