Adsorption isotherms of organic modifiers and the determination of the dead volume in RPLC

• DOI: 10.1007/bf02265485
• Publication Date: 2005-12-08T15:38:29Z
• Authors: P. L. Zhu
• Keywords: 01 natural sciences; 6. Clean water; 0105 earth and related environmental sciences

In RPLC the dead volume can be defined as the difference between the maximum column hold-up volume and the volume of the adsorbed phase. The composition of the adsorbed phase depends on the composition of the mobile phase and therefore, the dead volume also varies with it. In this work, the alkyl bonded phase acetonitrile (ACN)-water mobile phase system is investigated. In the system, deuterated water (D2O) and deuterated acetonitrile (D-ACN) are retained due to the isotopic dilution effect. By means of D2O and D-ACN, the absolute adsorption isotherm of the organic modifier ACN is measured. Based on the isotherm, the chromatographic behaviour of ACN, D-ACN and D2O, the variation of the dead volume with the composition of the mobile phase, and the approach to determine the maximum column hold-up volumn are explained. In addition, the various approaches to determine the dead volume are compared and the recommendations are given for the case of common unbuffered binary systems (MeOH/H2O, THF/H2O and ACN/H2O).