Rapid determination of fosetyl-aluminum residues in lettuce by liquid chromatography/electrospray tandem mass spectrometry.
This paper describes a new method for the sensitive and selective determination of fosetyl-aluminum (Al) residues in vegetable samples. The method involves extraction with water by using a high-speed blender and subsequent injection of the 5-fold diluted extract into the liquid chromatograph. Fosetyl-Al is determined by liquid chromatography with electrospray tandem mass spectrometry after the addition of tetrabutylammonium acetate as the ion-pairing reagent. The method has been used to assay lettuce samples spiked at 2 and 0.2 mg/kg. Recoveries were satisfactory, with mean values of 98 and 106%, respectively, and relative standard deviations were < 10%. The limit of quantitation was 0.2 mg/kg, and the limit of detection was as low as 0.05 mg/kg. Matrix-matched calibration was used for quantitation, and the addition of an internal standard improved repeatability. The developed method allows the accurate and rapid determination of low levels of fosetyl-Al residues in lettuce with very little sample handling and good sensitivity; it was shown to be robust by the analysis of almost 100 samples.
D002853:Chromatography, Liquid / Q000379:methods*; D004350:Drug Residues / Q000032:analysis*; D005506:Food Contamination; D005659:Fungicides, Industrial / Q000032:analysis*; D018545:Lactuca / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000032:analysis*; D011786:Quality Control; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D005659:Fungicides, Industrial; D009943:Organophosphorus Compounds; C053504:fosetyl-Al