Submitted to: Minnesota Academy of Science Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 27, 1996
Publication Date: N/A
Technical Abstract: Current methods for extraction of metolachlor (2-chloro-N-(2-ethyl-6- methylphenyl)-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 metolachlor extraction from soil. A commercially available robotic system was modified and serialized. Programs were developed to split two forty-position centrifuge tube racks into four twenty-position racks, each with individual command codes and identifiers. The cannula sipping station was programmed to sip hexane from the upper liquid layer over a methanol-hexane meniscus. An extraction station was developed to remove water from a hexane extract. The existing dilution station was programmed to use hexane in addition to methanol and water solvents. Within the scheduled procedure, the robot performs multiple methanol extractions of soil followed by multiple hexane extractions of the methanol. The combined hexane extracts are poured through a water extraction station. The dried hexane eluent is evaporated, the residue re-dissolved in solvent and transferred to a gas chromatograph vial which is then sealed. Analysis for metolachlor was performed with a N/P detector. Results show that 70% of added metolachlor was recovered from soil samples when the eluent was evaporated under a nitrogen gas stream while 65% could be recovered when evaporated under a stream of compressed air. Using a Soxhlet extraction and rotary evaporation method, thirty soil extractions were performed in a 40-hr week. The robotic procedure allows extraction of 80 or more samples in the same period.