I checked with our Waters vials product manager and the news is not good. I don't think there are other options. We tested some PTFE Silicone cap mats but they proved to be a bit too tough to pierce. Basically, you have 4 wells in the same space where you have one well on a 96 well plate. The silicone/PTFE was simply too tough to pierce. So at this time we do not have any Waters options for the 384 well microplates.
Is it indeed true that 15 microliter of sample cannot be injected because of dead volume of this 384 wells plate?
This means that with samples of 20 microliter, only 25 % can be injected.
Or is there some new development that more can be injected?
Not necessarily. 15 uL is the residual volume at the default needle placement of 2.0 mm from the bottom of the plate. To access more sample, go into the ACQUITY UPLC Sampler Manager Advanced Settings, and change the needle placement to access more of the sample volume. Please take a look at page 57 of this pdf.
For further information on setting vial depth offsets, see the ACQUITY UPLC Operator's Guide or visit the ACQUITY UPLC Sample Manager Instrument Method Editor On-Line Help.
Since this discussion includes capmat piercing I will add some additional points.
Along with the use stainless steel needles for robust piercing, there are additional upgrades avilable for your system.
After June 2007 a new Y-carriage which works with ACQUITY UPLC driver version 1.30 and later, the piercing range of the Sample Manager pre-piercing needle was extended. This improves piercing in general.
Next time you service the system or your FSE visits ask him to identify if this for you.
Also, if your pre-peircing needle is dull there can be issues, and this is chnaged as part of the Sample Manager regular PM.
As Doug mentioned you can change the offset on a instrument method basis, this can also be set up permanently in the Sample Manager configuration in the Console software if you always use the same plates.