Innovative determination of polar organophosphonate pesticides based on high‐resolution Orbitrap mass spectrometry |
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Authors: | Juan Antonio Padilla‐Sánchez Patricia Plaza‐Bolaños Roberto Romero‐González Ángel Grande‐Martínez Earl Michael Thurman Antonia Garrido‐Frenich |
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Institution: | 1. Department of Hydrogeology and Analytical Chemistry, University of Almeria, Andalusian Center for the Assessment and Monitoring of Global Change (CAESCG), Agrifood Campus of International Excellence, ceiA3, , E‐04120 Almeria, Spain;2. Department of Analytical Chemistry, University of Granada, , E‐18071 Granada, Spain;3. Center for Environmental Mass Spectrometry, Department of Civil, Environmental and Architectural Engineering, University of Colorado, , Boulder, CO, 80309, USA;4. + 0034 950015985+ 0034 950015483 |
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Abstract: | The determination of compounds showing a very low molecular weight (i.e. < 200 Da) can be complicated when low‐resolution mass spectrometry is used in the selected‐reaction monitoring mode, since the possible number of product ions is reduced and the obtained reactions are not selective enough to overcome background noise and/or matrix interferences. In this study, the use of high‐resolution mass spectrometry based on Exactive Orbitrap was applied for the determination of a group of polar organophosphonate pesticides and transformation products (TPs), which show the aforementioned features, in agricultural soils. Namely, glyphosate, glufosinate, ethephon and their TPs, aminomethyl phosphonic acid (AMPA), 3‐methylphosphinicopropionic acid, N‐acetyl‐glufosinate and 2‐hydroxyethylphosphonic acid were analyzed. The M‐H]‐ ions 168.00564, 180.04202, 142.96593, 110.00016, 151.01547, 222.05259 and 124.99982 were used, respectively, for the detection and identification of the compounds. Confirmation was carried out by using accurate mass measurements of ion fragments for each compound, from neutral losses of CO2, H2O and H2CO (formaldehyde). Furthermore, the recently reported tool, relative isotopic mass defect (RΔm), was also used to support the confirmation protocol. The optimized method was fully validated at low levels, including the estimation of a not commonly used parameter: the limit of confirmation (LOC). This LOC is expressed as the lowest concentration of compound that can be confirmed using a fragment or the RΔm, and it ranged from 10 to 50 µg kg?1 for all compounds. All the data was obtained in a single injection. Finally, the method was applied to real soil samples, and glyphosate and AMPA were found at 265 µg kg?1 and 105 µg kg?1, respectively. Copyright © 2012 John Wiley & Sons, Ltd. |
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Keywords: | high‐resolution mass spectrometry low molecular weight compounds confirmation strategies acidic organophosphonate pesticides soils |
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