cleaning PCR primers

[Biochemistry Lab computer]

We have just made some oligos for PCR on a 50pmol scale, cleaved them from 
the column, deprotected and dried them down.  When they are redissolved in 
water there is visible rubbish in the tube, which does spin down.  I have 
tried using the clear supernatant, diluted, in a PCR reaction and get 
nothing.  My question is, does anyone know if dirty primers can inhibit the 
PCR reaction?  And if so what is the best method (and simplest) for 
cleaning them up?  I have, in the past, purified oligos off an acrylamide 
gel, but when I was using a larger scale synthesis.  My concern is, that 
there may not be enough oligo to purify off a gel, considering the losses. I 
have previously not needed to purify the 0.2nmol scale synthesis, finding 
they always worked.  
Thanks in advance. 
Jo Caine