Subcritical Water Extraction Followed by Liquid Chromatography Mass Spectrometry for Determining Terbuthylazine and Its Metabolites in Aged and Incubated Soils

Due to the great potential of atrazine in contaminating groundwater, its use has been banned in several countries and often replaced by terbuthylazine (CBET). Little is known on the fate of CBET in soil. The purpose of this work has been (1) to develop a general method for analyzing CBET and its degradation products (DPs) in soil and (2) to use this method for elucidating the fate of CBET incubated in both surface and subsurface samples of an agricultural soil which had been receiving repeated CBET spills. This method involves analyte extraction from soil at 100°C by phosphate-buffered water. Analytes coming out of the extraction cell were collected by a graphitized carbon black extraction cartridge. After analyte elution with a suitable solvent mixture, the final extract was analyzed by LCMS. From an aged soil, our method extracted altogether quantities of CBET and its DPs respectively 2.1 and 1.4 times larger than those by two previously reported methods. For the analytes considered, limits of quantification (S/N 10) ranged between 0.22 and 5.5 ng per gram of soil. The laboratory CBET degradation experiment showed that (1) similarly to atrazine, remarkable amounts of hydroxylated metabolites were formed; (2) when the subsoil microflora was in the presence of rather large amounts of CBET, it degraded the herbicide with a rate similar to that of the topsoil microflora.