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A post on Flow Injection Analysis (FIA) tubing. A post brought to you by a dirty dirty mind.

FIA is some great stuff, you can do a lot of neat things with it, like automated analysis. In consists of a peristaltic pump (PP), some pump tubing with varying inner diameters to adjust the fluid speed, and the rest of the tubing to carry the pumped fluid.

There are a lot of tubing types, Tefzel (fluoropolymer like Teflon), PEEK (Poly ether ethyl ketone, or soemthing like that), Stainless steel (mainly used in HPLC), and FEP. I think there are others, but they arent really important.

PP tubing is some rubbery type tubing, generally 1/8" in outer diameter (OD), with varying inner diameters (ID). Common inner diameters are 0.005", 0.010", 0.015", 0.020", 0.025", etc etc, pretty much as big as you need to go.

Tefzel tubing is some good stuff, mainly, it is bought in 0.0625" OD, with varying ID possible. the most common are 0.010", 0.020", and 0.030". Tefzel is pretty good in that it is very flexible, we can create "super-serpentine" coils which is the tubing bent in on itself, a lot. But, this flexibility can have a down side. Trying to stick 0.0625" OD tubing into a hole that is 0.010" in diameter is freaking hard, especially when there is no lube. Using lube is pretty much not possible, because large amounts of friction is needed to keep the large OD tefzel tubing in the small ID hole in the PP tubing. This is where PEEK tubing comes in.

PEEK is hard and stiff. With the penetrating end shaped properly, sticking 0.0625 PEEK tubing into that same 0.010" hole in the PP tubing is fairly easy. Again, there is no lube, so its a bit tougher, but, with a little work, its possible.

So, in conclusion -
Small hole + bent tubing = pain in the ass
Small hole + stiff tubing = tubing in hole, and fluid flowing properly.