Improved method for the analysis of imazapyr in soil

A method for the analysis of imazapyr [2‐(4‐isopropyl‐4‐methyl‐5‐oxo‐2‐imidazolin‐2‐yl)nicotinic acid] residues in tropical and temperate soils was developed. Imazapyr residues, extracted from soil with ammonium hydrogen carbonate and cleaned‐up by centrifuging, anion‐exchange solid‐phase extraction (SPE), pH adjustment, and C18 SPE, were determined by HPLC. Recoveries from soils from Hawaii (Halii sandy clay loam), Texas (Houston Black clay), and Maryland (Codorus loam), USA, fortified with imazapyr (0‐5 μg g−1 soil) and equilibrated for 12‐18 h, were 99(±3)%, 104(±4)% and 89(±2)%, respectively. Recoveries were independent of fortification level, but dependent upon soil type. Methods previously described in the literature produced imazapyr recoveries of less than 60% with Halii soil. This improved method has a limit of detection of 5 ng g−1 (equivalent to or better than other methods) and affords higher recovery of imazapyr residues from tropical soil.