假设配一升100mmol/L (即0.1mol/L)pH6.0的磷酸缓冲液:
pH = pKa2 + Log([HPO42-]/[H2PO4-])
6.0 = 7.2 + Log([HPO42-]/[H2PO4-])= 7.2 + Log(HPO42-摩尔/H2PO4-摩尔)
(HPO42-摩尔/H2PO4-摩尔)=10^(-1.2)= 0.0631
HPO42-摩尔 + H2PO4-摩尔 = 0.1
HPO42-摩尔=0.006 摩尔===〉0.1mol/LNa2HPO4 =(0.006/0.1)= 0.06L =60mL
H2PO4-摩尔=0.094 摩尔===〉0.1mol/L NaH2PO4= (0.094/0.1)=0.94L
=940mL
答案:量取60mL0.1mol/L的磷酸氢二钠和940mL0.1mol/L的磷酸二氢钠,就可配制成1L pH6.0的100mmol/L磷酸缓冲液.