Shah D N, Feldkamp J R, White J L, Hem S L
J Pharm Sci. 1982 Feb;71(2):266-8. doi: 10.1002/jps.2600710232.
The adsorption of magnesium nitrate, docusate sodium, and mannitol by chloride-containing aluminum hydroxide gel or aluminum hydroxycarbonate gel can be directly related to the surface charge characteristics of the aluminum hydroxide gel as determined by the pH-zero point of charge (ZPC) relationship. Magnesium cation is completely adsorbed under pH conditions where the gel has a negative surface charge, i.e. when the pH is above the ZPC. Docusate sodium is more strongly adsorbed when the pH-ZPC relationship causes the surface charge of aluminum when the pH-ZPC relationship causes the surface charge of aluminum hydroxycarbonate gel to be positive indicating adsorption of the docusate anion. However, adsorption also occurred when the pH was above the ZPC suggesting that adsorption of the hydrophobic portion of docusate anion by van der Waals forces also contributes to the overall adsorption mechanism. Mannitol is adsorbed under all pH conditions. However, greater adsorption occurs when the pH is above the ZPC. Maximum hydrogen bonding is believed to occur when mannitol acts as the proton donor and the negative aluminum hydroxycarbonate gel surface serves as the proton acceptor.
硝酸镁、多库酯钠和甘露醇被含氯氢氧化铝凝胶或碱式碳酸铝凝胶吸附的情况，可直接与通过电荷零点（ZPC）关系测定的氢氧化铝凝胶的表面电荷特性相关。镁阳离子在凝胶表面带负电荷的pH条件下被完全吸附，即pH高于ZPC时。当pH-ZPC关系导致碱式碳酸铝凝胶表面电荷为正时，多库酯钠的吸附更强，这表明多库酯阴离子被吸附。然而，当pH高于ZPC时也会发生吸附，这表明多库酯阴离子的疏水部分通过范德华力的吸附也有助于整体吸附机制。甘露醇在所有pH条件下都被吸附。然而，当pH高于ZPC时吸附量更大。据信，当甘露醇作为质子供体且碱式碳酸铝凝胶的负表面作为质子受体时，会发生最大程度的氢键作用。
