Acetate buffer(pH3.5) Take 25g of ammonium acetate, add 25ml of water to dissolve it, add 7mol/L hydrochloric acid solution 38ml, use 2mol/L hydrochloric acid solution or 5mol/L ammonia solution to adjust the pH to 3.5(potentiometric indication) accurately, and then dilute it to 100ml with water, then it is obtained. Acetic acid - lithium salt buffer (pH3.0) Take 50ml of glacial acetic acid, add 800ml of water and mix, adjust the pH value to 3.0 with lithium hydroxide, and then dilute with water to 1000ml, it is obtained. Acetic acid-sodium acetate buffer (pH3.6) Take sodium acetate 5.1g, add glacial acetic acid 20ml, then dilute with water to 250ml, that is obtained. Acetic acid - sodium acetate buffer (pH3.7) Take anhydrous sodium acetate 20g, add water 300ml to dissolve, add bromophenol blue indicator 1ml and glacial acetic acid 60-80ml, until the solution changes from blue to pure green, then add water to dilute to 1000ml, it is obtained. Acetic acid - sodium acetate buffer (pH3.8) Take 2 mol / L sodium acetate solution 13 ml and 2 mol / L acetic acid solution 87 ml, add 1 mg of copper per 1 ml of copper sulfate solution 0.5 ml, and then diluted to 1000 ml of water, that is, obtained. Acetic acid - sodium acetate buffer (pH4.5) Take sodium acetate 18g, add glacial acetic acid 9.8ml, then dilute with water to 1000ml, it is obtained. Acetic acid-sodium acetate buffer (pH4.6) Take sodium acetate 5.4g, add water 50ml to make it dissolve, adjust the pH value to 4.6 with glacial acetic acid, then add water to dilute to 100ml, that is to say, it is obtained. Acetic acid - sodium acetate buffer (pH 6.0) Take sodium acetate 54.6g, add 1 mol / L acetic acid solution 20ml dissolved, diluted with water to 500ml, it is obtained. Acetic acid - potassium acetate buffer (pH 4.3) Take 14g of potassium acetate, add 20.5ml of glacial acetic acid, then dilute with water to 1000ml, it is obtained. Acetic acid - ammonium acetate buffer (pH4.5) Take ammonium acetate 7.7g, add 50ml of water to dissolve, add glacial acetic acid 6ml and the appropriate amount of water to make 100ml, that is obtained.