text: If you donot want to use acetic/ formic acid then it ay be tough for you to get pH 4-5. The only option remaining is some thing to do with HCl\nBut it may spoinl the things..\nYou can prepare pH 4-5 solution as follows:\nTake 1mL of HCl (Concentrated) and dilute it to 50mL. The pH of this solution will be around 4.3 (I used to make this solution during my first days of research). You can try..