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Abstract
A method basing on liquid chromatography–mass spectrometry (LC-MS/MS) was developed for sensitive determination of Organophosphorus pesticides namely Monochrotophos, Quinalphos and Chlorpyrifos in okra in Andhra Pradesh (South India). The method involves extraction of 10 g of homogenized okra samples (2 g of Sodium chloride + 8 g of Magnesium sulfate) with 10 mL of acetonitrile later cleaned up by dispersive solid phase extraction with the combination of primary secondary amine (PSA), graphitized carbon black (GCB), C18, and anhydrous magnesium sulfate. Final analysis was performed by liquid chromatography-electro spray ionization–tandem mass spectrometry operated in the multiple reaction monitoring (MRM) mode, acquiring two specific precursor-production transitions per target compound. The average recoveries measured at 10 µg/kg were in the range 81–106% for all of the compounds tested with relative standard deviations below 14%. The methodology has been proven to be highly efficient and robust and thus the method is highly suitable for monitoring the Maximum Residue Limits (MRL) compliance of the pesticides.
ACKNOWLEDGMENTS
The corresponding author (P. Venkateswarlu) is thankful to UGC, New Delhi, India for financial support of the project.
Notes
Q1: Molecular mass. [M+H]+.
Q2: Quantifier daughter ion.
Q3: Qualifier daughter ion.
a Declustering potential.
b Collision energy.
c Cell exit potential.
RSD (%): relative standard deviation; LOQ: limit of quantification.
a Each value in the mean of six determinations.
ND: not detected.
(Mean ± SD) (n = 3).
Eu: European union.
NL: The Netherlands.