The lipophilicity values of selected acridinone (imidazoacridinone and triazoloacridinone) derivatives were measured by gradient reversed-phase high-performance liquid chromatography (RP-HPLC) using a C18 stationary phase with a water/acetonitrile mixture as a mobile phase. The retention times obtained served as input data and appropriate log kw values (i.e., the retention factor log kw extrapolated to 0% organic modifier) as an alternative to log P were calculated using the DryLab program. The relationships between the lipophilicity (log kw) and the chemical structure of the studied compounds, as well as correlation between experimentally determined lipophilicities (log k_w) and log P data calculated using some commonly available software, are discussed.

In the present work it is shown that the linear elution strength (LES) model can be employed to predict retention times for segmented-temperature gradients based on temperature-gradient input data in liquid chromatography (LC) with high accuracy using DryLab-software. In order to predict retention times for temperature gradients with different start temperatures in LC, another relationship is required to describe the influence of temperature on retention. It could be shown that a plot of lnk vs. T yields more reliable isothermal/isocratic retention time predictions than a plot of lnk vs. 1/T which is usually employed. Retention times can be predicted with a maximal relative error of 5.5%(average relative error: 2.9%). As an example, the systematic method development for an isothermal as well as a temperature gradient separation of selected sulfonamides by means of the adapted LES model is demonstrated using a pure water mobile phase. 

DryLab^® was used with excellent results with superficially porous particles (Fused-Core^®) which were designed with 160 Å pores. These particles show superior kinetics (lower resistance to mass transfer), allowing fast separations of peptides and small proteins (molecular weights of 15,000). The high efficiency and relatively low back pressure of these 2.7 μm Fused-Core particles has been maintained so that separations can be performed with conventional HPLC instruments.11 synthetic peptides (50 ng each) Fig. 12 show an excellent comparison of DryLab^® predicted chromatogram to experimental ones. Chromatographic optimizations were conducted using DryLab^® from the Molnár-Institute for Applied Chromatography. Longer columns can be used for higher resolution of complex mixtures of peptides, such as proteolytic digests. Highly reproducible separations of peptides at elevated temperatures with low pH mobile phases are maintained as a result of a stable bonded stationary phase. The utility of such highly stable materials is exemplified by separations of problematic amyloid peptides at low pH (TFA mobile phase) at an operational temperature of 100 °C.

A method for the assay of an active pharmaceutical ingredient (API) and five known and unknown impurities was developed in accordance with Quality by Design (QbD) principles and using DryLab as a modeling software. Highly influential separation parameters were simultaneously and systematically studied so that the quality of the HPLC method could be understood, controlled and ensured. Consequently, during routine analysis out of specification (OOS) results can be corrected more effectively.

Monoclonal antibodies (mAbs) are an emerging class of therapeutic agents that have recently gained importance. To attain acceptable kinetic performance with mAbs in reversed phase liquid chromatography, there is a need to work with the latest generation of wide-pore sub-2 µm fully porous or core-shell particles stationary phases and the DryLab selectivity modeling software. In addition, temperature in the range 60-90 °C was found to be mandatory to limit adsorption phenomenon of mAbs and their fragments.  A generic method development strategy was proposed to account for the selectivity, efficiency, recovery, and the possible thermal Degradation using DryLab.  This study also demonstrated that the gradient steepness and temperature cannot be optimized using van't Hoff type linear models. Similarly, the common linear solvent strength model also generated some error in predicting the retention times. In contrast, when quadratic models were employed, the prediction accuracy of retention times was found to be excellent (relative error between 0.5 and 1%) using a reasonable number of experiments (9 or 6 experiments for optimization of gradient time and temperature, which requires between 6 and 8 h). Two separations of mAbs fragments were performed to demonstrate the reliability of the quadratic approach.