Analytical Method and Interlaboratory Study for the Quantitation of Aminocyclopyrachlor Residues in Vegetation by Liquid Chromatography/Tandem Mass Spectrometry

The quick, easy, cheap, effective, rugged, and safe (QuEChERS) and the U.S. Food and Drug Administration pesticide multiresidue methods were systematically tested for the analysis of aminocyclopyrachlor, a new synthetic auxin herbicide. Results revealed that these procedures are not suitable, highlighting the need for a publicly available residue method for this new active ingredient. Such a method has been developed and is reported herein for aminocyclopyrachlor residue analysis in vegetation, including white pine, Norway spruce, grass forage, and grass hay. Aminocyclopyrachlor residues were purified from plant tissue extracts by filtration through SPE cartridges with strong anion exchange stationary phases and analyzed using LC/MS/MS. This method was validated at five laboratories across the United States; their results were compared to evaluate reproducibility and ruggedness. The method LOQ was 0.01 mg/kg (ppm) and the LOD 0.003 mg/kg (ppm) for the matrixes tested. A qualitative procedure to confirm the molecular identity of residues based on retention time measurements and ion transition peak area ratios (m/z 214 --> 681m/z 214 --> 101) is also presented.