Residue Methodology for AMDRO Fire Ant Insecticide (AC 217,300) in Pasture Grass and Crops

Abstract

Residue methodology is described for the determination of AC 217,300 residues in pasture grass and crop samples. After extraction and subsequent cleanup on an XAD-2 column, residues of AC 217,300 are determined by liquid chromatography (LC), using a reverse phase paired-ion chromatographic system and detection at 300 nm. The method has a validated limit of sensitivity of 0.05 ppm with corresponding control values for the commodities analyzed of <0.01 ppm. Apparent residues over 0.05 ppm can be confirmed by either gas chromatography with an electron capture detector (GC-EC) or gas chromatographynegative ion chemical ionization mass spectrometry (GC-NICI). The direct GC-NICI method circumvents the need for sample cleanup on the XAD-2 column, and offers a greatly simplified procedure that is useful for screening samples. Recoveries of AC 217,300 from the commodities analyzed have been satisfactory with all methods of analysis

Simplified moving-belt interface for liquid chromatography/mass spectrometry

“…AC 217,300 was selected as the first test compound. While AC 217,300 was previously analyzed by GC/NICI, it was not easily chromatographed by GC (20). The NICI (CH4) mass spectrum of 50 ng of AC 217,300 shown in Figure 3 is in almost perfect agreement with those obtained previously (20,21).…”

“…While AC 217,300 was previously analyzed by GC/NICI, it was not easily chromatographed by GC (20). The NICI (CH4) mass spectrum of 50 ng of AC 217,300 shown in Figure 3 is in almost perfect agreement with those obtained previously (20,21). AC 222,293 and AC 243,997 cannot be analyzed by gas chromatography without derivatization because of decomposition in the GC injector port.…”

“…Of the three major current approaches to interfacing liquid chromatography and mass spectrometry, none is without limitations. The direct liquid introduction (DLI) approach is limited by the ability of the mass spectrometer's vacuum system to handle a solvent load of typically [10][11][12][13][14][15][16][17][18][19][20] yuL/min (2). Consequently, either the LC effluent is split and a small portion taken to the mass spectrometer (3) or microbore LC is used (4).…”