磷酸缓冲溶液PB的配制1.用NaH2PO4和Na2HPO4配置体积1L浓度0.05mol/LPH7.8的磷酸缓冲液,需要NaH2PO4和Na2HPO4各多少克?写出解题方法和缓冲液配置过程。用NaH2PO4和Na2HPO4配置体积1L浓度0.05mol/LPH7.8的磷酸缓冲液,需要NaH2PO4和Na2HPO4各多少克?写出解题方法和缓冲液配置过程设NaH2PO4磷酸二氢钠,Na2HPO4磷酸氢二钠浓度分别为c1,c2mol/L.由题意,c1+c2=0.05再根据缓冲溶液ph计算公式:pH=pKa+lg(c碱/c酸)可得7.2+lg(c2/c1)=7.8其中7.2是磷酸二氢根的pKa值,7.8是溶液的pH值.联立解得c1=0.01,c2=0.04所以磷酸二氢钠质量为0.01*120.0=1.20克m=nM=cvM磷酸氢二钠质量为0.04*142.0=5.68克称取1.20克无水磷酸二氢钠(或1.38克一水磷酸二氢钠,1.56克二水磷酸二氢钠M156.01)和5.68克无水磷酸氢二钠(或10.72克七水磷酸氢二钠,14.32克十二水磷酸氢二钠M358.14),置于烧杯中,加少量蒸馏水溶解.固体全部溶解后,将溶液转移到1000毫升容量瓶中.用蒸馏水润洗溶解用的烧杯三次,润洗后的水也加入到容量瓶中,定容,即得。2.ph7.40磷酸盐缓冲溶液中一磷酸氢根和磷酸二氢根的比值由反应式:H2PO4-=HPO42-+H+即此缓冲溶液中的缓冲对是:H2PO4-~HPO42-计算式是:pH=pKa2(H2PO4-)-lgc(H2PO4-)/c(HPO42-)查得磷酸的二级电离常数:pKa2=7.20代入上式:7.4=7.2-lgc(H2PO4-)/c(HPO42-)c(H2PO4-)/c(HPO42-)=0.63磷酸缓冲溶液PBS的配制PBS是最普遍不过的实验室缓冲液,但其配方各异。以下是总结:母液的配制:0.2MNa2HPO4:称取71.6gNa2HPO4•12H2O,溶于1000mL水0.2MNaH2PO4:称取31.2gNaH2PO4•2H2O,溶于1000mL水各种浓度PBS(pH=7.4)的配制:先配0.2MPBS(pH=7.4,100ml):取19ml0.2mol/L的NaH2PO4,81ml0.2mol/L的Na2HPO4,即可。然后,只需将0.2MPBS(pH=7.4)按相应比例适当稀释即可。如:0.1MPBS(pH=7.4):取500ml0.2MPBS,加水稀释至1000ml即可。0.01MPBS(pH=7.4):取50ml0.2MPBS,加水稀释至1000ml即可。0.02MPBS(pH=7.4):取100ml0.2MPBS,加水稀释至1000ml即可。若需要NaCl的话,加入NaCl至0.9%(g/100mL)生理盐水即可。另:其它各种PH值的0.2MPBS(100mL)配方:pH0.2MNaH2PO4(mL)0.2MNa2HPO4(mL)5.793.56.55.89285.990106.087.712.36.185156.281.518.56.377.522.56.473.526.56.568.531.56.662.537.56.756.543.56.851496.945557.038627.133677.228727.323777.419817.516847.613877.710.589.57.88.591.57.97938.05.394.7