Invitrogen recommends the following reconstitution procedure -
- Centrifuge the tube for a few seconds to get all the DNA to the bottom of the tube.
- To make a 25 μM stock, add YμL of sterile H2O to X nmoles of dry primer stock. (See equations below).
- Allow to sit for 2 mins, then vortex for 15 secs.
The number of nmoles of material in the tube (X) should be listed on the pages accompanying your primer order.
See Reconstituting primers for a lot of useful information including why you should use TE buffer rather than water for reconstituting primers.