Extending the Total Pore Blocking method to normal phase high performance liquid chromatography

It has been demonstrated that it is possible to extend the Total Pore Blocking (TBP)-method for the determination of the external porosity (ɛe) of packed bed columns from reversed-phase (RP) chromatography to normal-phase (NP) chromatography conditions by switching the nature of the blocking agent and the interstitial void flushing liquid, i.e., by using a hydrophilic blocking agent (pure or buffered water at pH 3.0 or pH 7.0) and a hydrophobic flushing liquid (linear alkanes such as decane). Several parameters that might influence the accuracy of the method, such as the applicable range of flow rates and the meso-pore size of the particles have been investigated. The influence of several different parameters on the obtained external porosity value has been investigated. From a wide selection of possible t0-markers, the class of linear alkanes has been shown to be the single possible one. This brings along the need to use refractive index detection to measure the signal of the linear alkane tracer (e.g., dodecane) in a stream of (another) linear alkane. The results of the newly established NP-TPB method have been compared to the values of the external porosity obtained by ISEC and proved to generate the same results, however with a much smaller read-out error (being only of the order of 0.1%).