Submitted to: Laboratory Automation Robotics International Symposium
Publication Type: Proceedings
Publication Acceptance Date: October 22, 1997
Publication Date: N/A
Interpretive Summary: Metolachlor is a herbicide widely used to control weeds in corn, soybeans and other crops, and procedures for its extraction from soil are needed to monitor this herbicide. Current methods for extraction of metolachlor from soil require labor intensive technical manipulation, large amounts of hazardous solvents and are time consuming. A robotized procedure would speed up the extraction, assure consistent extraction, and free technician time for sample weighing and robot setup. A robot can perform all necessary steps in the extraction procedure except a filtration step to dry the hexane solvent. Commercial robots do not have this solvent drying filter available. The objective of this study was to modify a robot to include a unique solvent drying filter necessary for development of an innovative extraction procedure. A solvent drying station was designed, developed and installed on a Zymark model robot. Computer programs were developed to accommodate innovations in the robotized procedure. The addition of the drying station completed the modifications necessary to program a robotized extraction procedure. Using this new robotized extraction procedure, laboratory workers are enabled to process samples more rapidly using less hazardous chemicals and at much greater cost savings.
Technical Abstract: Current methods for extraction of metolachlor (2-chloro-N-(2-ethyl-6-methyl l)-N-(2-methoxy-1-methylethyl)acetamide) from soil are tedious and time consuming. A procedure was developed to provide a quick and reliable automated multi-step method of metholachlor extraction from soil. A robotic solvent drying station containing anhydrous sodium sulfate was configured with a glass filter device. A custom made 27-mm OD by 20-mm ID 1 mm thick Teflon gasket as fitted between the top and bottom portion of the filter to prevent solvent leakage. A filter support was machined from a 100 by 50 by 18-mm aluminum bar and attached to the liquid-solid station tower. A hole cut in the liquid-solid station tower allowed repositioning of the pneumatic toggle clamp. A 30-mm ID centrifuge tube holder was fashioned from Teflon and positioned on the liquid-solid station shuttle in the output position. The robot was programmed to access the new station for drying the hexane-metolachlor solution, use the pneumatic toggle clamp with the Teflon cap assembly to move the sample into a large collection tube, and rinse the sodium sulfate with the appropriate solvent to ensure removal of all solvent-metholachlor solution. The computer was programmed to divide each large centrifuge rack, use each of the four positions in the centrifuge for four separate extractions, move the liquid-solid station shuttle to collect the dried hexane-metolachlor solvent and use one position on a second master-lab station as a solvent dilution-delivery module.