Rapid Determination of Polar Herbicides in Soil Samples Using Accelerated Ultrasonic Extraction (AUE) in Combination with Dispersion and In-situ Derivatization

An effective novel ultrasonic extraction procedure coupled with gas chromatography and negative chemical ionization mass spectroscopy has been developed for quantitative recovery of polar herbicides in soil. This rapid one-step sample preparation methodology was named accelerated ultrasonic extraction (AUE), and is based on elevated temperatures, increased power and dispersing intimate contact. Simultaneously, in-situ derivatization was achieved by the addition of derivatization reagent, chelating agent and dispersing agent. The extraction efficiency was enhanced by the multiple applied force and elevated ultrasonic temperature. The in-situ derivatization efficiency was enhanced considerably by the use of ultrasonic energy. Dozens of samples can be extracted simultaneously with this method. The sensitivity was improved because of the remarkable reduced background noise achieved using GC-MS in negative chemical ionization (NCI) mode. The amount of reagent and various ultrasonic parameters, such as ultrasonic energy, ultrasonic time and ultrasonic temperature, were optimized. The reproducibility of replicate soil extraction determination of 9 herbicides in different matrix samples and at different concentrations (n=7) was in the range of 4.9-12.6% of the relative standard deviation. The obtained LOD values ranged between 0.02-0.37 g/kg for all herbicides. Here, we present an improved ultrasonic extraction procedure, which we have termed AUE, can serve as a rigorous high efficiency preparation methodology for polar organic contaminants and can be applied to solid sample pre-treatment extensively