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PLC Strategies - Renewal and Upgrade

Chromatography history of longer than a century. And preparative liquid chromatography was on its the beginning, because the first Tsvet experiments were nothing than a PLC. In the form of column chromatography, without pumps and detectors with samples sucked to the sorbent layer in a glass cylinder is kept in laboratories till today.

While liquid chromatography analytical branch is now rather unified due to the onset of HPLC in eighties, preparative method is still very diverse - from the original glass cylinders to fully automated chromatographs, from the separation of milligrams of substances up to industrial cleaning of drugs in quantity of tons.

This diversity also encounter many "schools" of preparative chromatography that were developed not only in universities and research institutes, but also in manufacturing companies with a long tradition of chromatography. Many of these centres of separation are staying in front of a question - how to proceed now. How to modernize and streamline the methodology and equipment to be on adequate level of modern PLC. Not in all cases, however, is necessary to implement rather costly fully new equipments.

Separlab offers all those interested in upgrading or refurbishment of existing preparative chromatography consulting services, as well as the possibility of repair and upgrade of parts of older systems. Attention should be focused primarily on mobile phase delivery systems. Older PLC applications were based almost exclusively on low-pressure applications. MP is often moved by gravity or by peristaltic pumps (low-pressure piston pumps are used industry). Today's trend is clearly to medium pressure or high pressure applications that use sorbents with smaller particle size. Columns can have higher flow rates and capacity of the device increases. Good quality pump is necessary condition for.

The situation is simpler for detection. Requirements for preparative chromatography are not nearly as high as in analytical chromatography, mainly because we meet with several times higher concentrations of the monitored substances. Often it is therefore sufficient to adapt to the new system analytical detector no longer used. In most cases is enough to furnish its cell with automatic bypass device.

Columns in older systems are made of glass or stainless steel. Because at that time were not so effective systems for mobile phase distribution to the whole cross-section of the cylinder forming the column, old fashioned columns are usually tightened at the ends. Adaptation options for such columns are not large. Chance is greater for conventional cylindrical columns, where one can add only new face plate with a good distribution of the mobile phase and modern high-capacity frits.

Great opportunities present an automation, but even today it is not possible to operate preparative chromatograph automatically unattended. For small installations, the operation is too expensive than, at large, there is still risk of losing separated mixture and risk of a leakage of large amounts of solvents. However, using a reasonable number of sensors monitoring the process (along with high-quality software) allows the use only intermittent control. Automated system than for example, with the same number of employees, can work in three shifts instead of one.