Answer
For the preparation of eluents only chemicals of a purity degree of at least "p.a." should be used. For diluting please use only ultrapure water.

Fresh eluents should always be microfiltered (0.45 ┬Ám filter) and degassed (with N2, He or vacuum). For alkaline eluents and eluents with low buffering capacity one should preferably use a CO2 adsorber.