Comparison of four mass analyzers for determining carbosulfan and its metabolites in citrus by liquid chromatography/mass spectrometry

Abstract Four liquid chromatography/mass spectrometry (LC/MS) systems, equipped with single quadrupole, triple quadrupole (QqQ), quadrupole ion trap (QIT) and quadrupole time‐of‐flight (QqTOF) mass analyzers, were evaluated for the analysis of carbosulfan and its main transformation products. The comparison of quantitative aspects (sensitivity, precision and accuracy) was emphasized. Results showed that the triple quadrupole instrument reaches at least 20‐fold higher sensitivity (LOD from 0.04 to 0.4 µg kg −1 ) compared to the single quadrupole (4–70 µg kg −1 ), the QIT (4–25 µg kg −1 ) and the QqTOF (4–23 µg kg −1 ) instruments. Recoveries were over 70% for all the analytes, except dibutylamine and 7‐phenolcarbofuran. Repeatabilities (within‐day) were slightly better by the single quadrupole (5–10%) and the QqQ (5–9%) than by the QIT (12–16%) and the QqTOF (9–16%). Both the QqTOF and QIT offer a linear dynamic range of two orders of magnitude whereas the single quadrupole and QqQ of, at least, three orders of magnitude. The method was applied to analyze carbosulfan field‐treated orange samples, in which carbosulfan, carbofuran, 3‐hydroxycarbofuran, and dibutylamine were found. As an example, the mean carbosulfan concentration was 20 ± 0.6 µg kg −1 measured by the QqQ, 22 ± 1.2 µg kg −1 by the single quadrupole, 25 ± 2.8 µg kg −1 by the QIT, and 20 ± 1.8 µg kg −1 by the QqTOF. Although the QqQ is more sensitive and precise, the mean values obtained by the four instruments are acceptable and comparable. The potential of each technique for the verification of the identity of residues detected in oranges is discussed using the concept of identification points. Copyright © 2006 John Wiley & Sons, Ltd.