I currently have a Biomek NXp from Beckman Coulter. I want to determine that the volumes being dispensed are correct. If anyone has any ideas on how to confirm this I would be greatful

You might be able to locate a protocol if you check Beckman FX user groups (I'm told they exist). Alternatively, you can do a weighing excercise as well. Here is what is involved. 1st, take a standard 96 well microplate, clean and dry from a shipping bag. 2nd, weigh it on a top loading balance to +/- 1mg. Then place it on the NX and have the NX dispense 50 uL / well into a column of wells (say the "1" column). 3rd, THen repeat with three more columns on themicrplate. 4th- Now promptly reweigh (without spilling) the filled microplate. Divide the total weight gain (in mg) by 32. If you wish, correct for density as well. Be sure to use pure water as the pipetted liquid. You should observe a weight very close to 50 mg. If not, that represents the bias. 5th - repeat these steps (#1-4) for larger volumes such as 75 uL, 100uL. You should now see whether there is a net bias in the delivery of the pipetting system. If you do a regression equation using these (specified voumes vs observed volume), you can see the correction needed to get the system to deliver an accurate volume (or so that is the way it is supposed to work). Happy pipetting!