This is a great idea, however keep in mind that ammonium acetate and formate are not soluble in neat acetonitrile. Therefore, you will need to add some water to this mobile phase in order to allow for dissolution. 10% aqueous is usually a good choice or starting point, although if you need your compounds to retain longer at the start of an ANP gradient, you may wan to use as low a concentration as 5%.

Also be sure to always vacuum filter any mobile phase containing dissolved solids in case they are not completely dissolved.