Six years of robots

published in lournal ofAutomatic Chemistry, Vol. 12, No. 6. not readily accepted because the apparatus was unreliable. However, the use of Bondelut cartridges was becoming increasingly popular and was the obvious next target for robotic automation. At this point, the decision was made to develop robotic systems, capable of executing any of our liquidor solidphase extraction methods. Also, single-function systems were considered to be unproductive, since there would be times when a particular assay type would not be required, resulting in idle robots. Therefore the second robot system incorporated solid-phase capability, in addition to liquid extraction by vortex. The main drawback of these Zymate systems was that, although vortex extraction is fast, efficient, reliable and easy to use, the number of organic solvents that vortex well with aqueous solutions is limited. The efficiency ofliquid/liquid extractions is dependent on the effective mixing ofthe liquid layers to promote a rapid and quantitative recovery of analytes. Previous experience with linear shakers had shown that unless vigorous agitation was used, this form of extraction was slow and prone to poor recoveries. It was for this reason that the Zymark linear shakerwhich oscillates gently was considered unsuitable for our use. Tumble mixers were popular in our laboratory: they had demonstrated efficient mixing of liquid layers and were known to give efficient and reliable recoveries. The need for such a device, suitable for use on the Zymate robots, led to the development ofa rotary mixer. Implementation of this device allowed extractions using organic solvents, which were unsuitable for vortexing, to be automated. Even though these devices worked well, assays using this technique were dogged by the necessity to screw-cap extraction tubes, which is a far from reliable process on a Zymate robot. Consequently, they have now been replaced by Zymark tumble mixers, where screw-capping is not required. As the demand for solid-phase extraction increased, the use of different size cartridges adversely affected the versatility ofthe robots, as only one size ofcartridge could be accommodated on any single table. Hence certain assays could only be catered for on specific machines. This problem was resolved by designing a multifunctional Bondelut workstation capable ofaccepting any size cartridge (see the section on Special modules). The robot systems at ICI Pharmaceuticals are capable of performing liquid extractions by vortex or tumble mixing, along with solid-phase extractions on any type of Bondelut cartridge. Combinations ofthese techniques are also possible, thus making the systems truly versatile and multitasking.