High performance liquid chromatography (HPLC) has been the predominant analytical technology for identification and quantification of compounds and materials in the pharmaceutical industry. As result, HPLC systems are widely used lab-equipment for drug discovery. Ultra performance liquid chromatography (UPLC) is a new category of analytical separation science that retains the practicality and principles of HPLC, while increasing the overall interlaced attributes of speed, sensitivity and resolution. This is poised to speed up drug discovery process by providing faster and higher quality analytical information.
Underlying principles of HPLC technology are governed by the van Deemter equation, which any student of chromatography is familiar with. The van Deemter equation is an empirical formula that describes the relationship between linear velocity (flow rate) and plate height (HETP - Height Equivalent Theoretical Plates, which is a measure of efficiency of HPLC column).
To improve the separation efficiency of a chromatographic column, 'the theoretical plate equivalent', i.e., the 'number of theoretical plates' needs to be maximized. Based on van Deemter curve, for a column of fixed length, the smaller the theoretical plate height (HETP) the more efficient is the separation. Furthermore, as we move towards lower particle size, the HETP is also smaller. Most HPLC columns use 5 µm particles and lowest HETP is about 12 µm at a linear velocity of 1 mm/sec. Increasing the linear velocity from 1 mm/sec increases the HETP and reduces the efficiency of column.
Chromatography efficiency is improved as the particle size is lowered. UPLC columns have a particle size of 1.7 µm. From van Deemter curve, at around 1.7 µm particle size, one can attain lowest HETP that is constant (or highest resolution) over a wide rage of flow rates. This gives the chromatographer more options with flow rates to improve speed and separation.
UPLC in drug discovery
UPLC improves the speed, sensitivity and resolution of chromatographic separations. When the particle diameter is reduced by one-third (5 to 1.7 µm), the chromatographic efficiency increases by three times and the resolution goes up by 70%. A typical HPLC run lasts 24 minutes. In comparison, a typical UPLC run lasts only 3 minutes. This dramatic improvement in run time, efficiency and resolution significantly adds to the productivity of the drug discovery process. Following is a case study of how UPLC is helping a University Laboratory working on drug discovery.
Generic pharmaceutical industry in India has grown rapidly in the recent years. Today, India is the fourth largest manufacturer of pharmaceutical products in the world in volume. With the opening of the Indian economy, substantial portion of pharmaceutical production is being exported from India. Pharmaceutical companies have to focus on the quality of their products because sales and profits are linked to product quality. To compete in the global economy, the improving accuracy of product analysis and productivity of QA/QC operation are key factors. Therefore, not surprisingly, India is one of the largest importers of HPLC systems in the world.
However, with India signing on to the patent regime, to succeed in the long term, the Indian pharmaceutical industry has recognized, it is important to develop new drug entities. This requires considerable investment. New lab equipment using UPLC technology will improve not only productivity but also quality of information obtained for drug discovery research. With increasing investments by the pharmaceutical companies in drug research, there will be greater adoption of UPLC technology in India.
(The authors are with Waters India Private Ltd, Bangalore )