Automation of atrazine and alachlor extraction from soil using a laboratory robotic system

In order to analyze our ever-increasing number of samples, we developed an automated multistep procedure for the extraction of atrazine (6-chloro-N-ethyl-N′-[1-methyl ethyl]-1,3,5-triazine-2,4-diamine) and alachlor (2-chloro-N-[2,6-diethylphenyl]-N-[methoxymethyl] acetamide) from soil using a commercially available laboratory robotic system. The robotic system shakes the soil-extraction solvent mixture, separates solvent from soil, evaporates methanol from the solvent, performs a liquid-solid extraction on the remaining herbicide-water solution, transfers the eluate containing the herbicides and internal standard to a gas chromatograph (GC) vial, and caps the vial. Serial robotic processing of samples, compared with manual batch processing, increased sample throughput by a factor of three and decreased labor by 50%. Efficiency and precision of extraction of atrazine and alachlor increased to 89 ± 2% (robotic) from 79 ± 17% (manual). At present, the soil weight of 10 g results in a minimum detectable amount of 10 μg herbicide kg^-1 soil.