Q: purified primers for sequencing??????

[Landry Pierre-Alexandre]

Dear all,

I am just about to send a couple of samples to a sequencing service, and 
I noticed that they require "purified primers". I checked the primers 
that I have (Operon) and It is specified on the label "unpurified". 
What does the purification process implies? Also, what is wrong with the 
use of unpurified primers for sequencing?

Thanks in advance,

Ax