A study of some practical aspects of high temperature liquid chromatography in pharmaceutical applications

In the pharmaceutical industry fast and efficient separation techniques play an increasing role among analytical methods because the samples to be investigated grow both in complexity and number, and there is an increasing time pressure to complete the analysis. Reducing the analysis time without decreasing the efficiency is possible using higher pressures, elevated temperatures, smaller particle sizes, or a combination of these approaches. Recently developed chromatographic techniques such as the UHPLC (ultra high performance liquid chromatography) and HTLC (high temperature liquid chromatography) are highly promising in meeting these demands. In this study, high temperature liquid chromatography (HTLC) with a zirconia-based column and temperatures elevated up to 150°C was used. We investigated the chromatographic behaviour of a steroid active pharmaceutical ingredient (levonorgestrel) and its structurally related impurities as model compounds. The effect of the temperature in the range of 50-150°C and the flow-rate in the range of 0.5-3.0 ml/min, and using methanol as an organic modifier, were studied for optimisation of the separation method.