Reagent contaminations increase the background concentration of the analytes present in a sample. 
 
Because of this, laboratories purchase expensive high-purity acids for trace metal (element) analyses. With small samples sizes it is critical to keep blank levels low for good reproducibility. There is an alternative to the purchase of expensive high purity acids: Milestone has developed the DuoPUR and SubPUR, a sub-boiling distillation system which allows laboratories to make their own high purity acids at dramatically reduced costs.