"Two companies launched on-line HPLC in the 1980’s, Applied Automation and Waters. Both companies had some successful installations, but the volume was not sufficient to support a product line. The major reasons for this include sampling and sample preparation difficulties, cost of the purchase and disposal of solvents, hazards of flammable solvents, high maintenance costs, the need for specialised staff and a lack of willingness to train staff, long sample times and the general complexity of the instrument. These all increased costs and outweighed the benefits of on-line sample preparation, although the other factors have played a significant part in the lack of popularity of the technique for on-line process analysis.

Recently, there have been successful applications, particularly in analysis of river water and fermentation monitoring. The success in these areas has been achieved through the use of reliable sampling systems based on ultrafiltration technology. Developments in HPLC and data processing should enable the complexity, running and maintenance costs of the instrument to be significantly reduced, whilst increasing the reliability of the data produced.