Automated solid-liquid extraction system

Automation of wet chemical analytical procedures, particularly titration, photometry and chromatography, have wide application in industrial laboratories. Very often some sample pretreatment must be carried out to transfer the sample into a suitable state for the measurement or chromatographic process. In industrial analysis, samples are very often solids which must be reduced in size and dissolved in a suitable solvent. In manual analysis the size reduction is effected by grinding either using a pestle and mortar or a suitable mill, the crushed sample is then dissolved and excess residue filtered off. Instruments which automate these processes to a greater or lesser extent have been designed, in each the solvent is added so that both grinding and dissolution are carried out simultaneously. Of these neither the Assayomat [1] nor the Beckmann AMA 40 [2] has been successfully used and the solid prep [3] is limited to use with large batches of similar samples in conjunction with AutoAnalyzer systems [4]. With the increasing use of automated measurement in wet chemical analyses the associated manual sample preparation then becomes the most significant time consuming tedious and least satisfactory operation. It is, therefore, highly desirable to design and develop a highly reliable universal solid liquid extraction device. To be practically useful the device should encompass a number of other features: It should be able to handle a wide range of solid samples and extract them with the wide variety of solvents normally used in manual analysis. It should mimic manual processes so as not to compromise the analyst into modifying his techniques. Large batches of similar samples or more varied batches should be incorporated with equal dexterity. The device shouldbe suitable to operate both in a stand-alone configuration and to be integrated into a more complex automatic system i.e. coupled to solution handling, spectro-photometers or electranalytical techniques [5]. Provided that a high degree of reliability is designed into the device it should improve the analytical reproducibility, any cross contamination between samples should be minimised. Good reproducibility can be obtained by reducing the sample size to the order of a few um in a short time and by minimising the surface contact area, this should also be simple and easy to wash. Any cross contamination can be reduced by designing a flexible washing system which can be automatically applied. In addition the level of automation should release the highest percentage of staff time for other tasks in the laboratory.