Determination of Atrazine in Water at Low-and Sub-Parts-per-Trillion Levels by Using Solid-Phase Extraction and Gas Chromatography/High-Resolution Mass Spectrometry

A capillary column gas chromatography/high-resolution mass spectrometry (GC/HRMS) method was developed to determine atrazine In water at low-and sub-parts-per-trillion (ppt) levels. The method fills a need when the detection limits of routine GC, GC/MS, and high-performance liquid chromatography (HPLC) are Inadequate for studies to evaluate transport and fate of herbicides In deep ground water systems. Atrazine and the added Internal standard [¹³C₃]atrazlne were extracted from water samples by solid-phase extraction using a C₁₈ bonded silica cartridge. A column chromatography procedure with Florisil was developed to reduce when necessary further Interferences In the sample extract. The analysis was performed by GC/HRMS with the mass spectrometer operated In the selected Ion monitoring (SIM) mode; mass profiles were acquired. The precision and accuracy of the method are 15% (relative standard deviation, n = 8) and >85%, respectively, for standard water samples containing atrazine at 1 ppt. The method, which gives detection limits of 200-500 parts-per-quadrillion (ppq), has been successfully used to analyze water samples containing atrazine at concentration levels of 1-500 ppt.