Analysis of bronopol (2-bromo-2-nitropropan-1, 3-diol) residues in rice (Oryza sativa L.) by SPE using Bond Elut Plexa and liquid chromatography-tandem mass spectrometry.

A novel method has been developed for the direct, sensitive, and rapid detection of bronopol in rice using a simple solid-phase extraction (SPE) procedure followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), with electrospray ionization (ESI). Bronopol was stable under acidic conditions, and an acidic environment was thus needed before sample loading to ensure the stability of bronopol. Rice extracts containing bronopol were pretreated using a hydrophilic-lipophilic balanced (Bond Elut Plexa) cartridge to reduce the matrix effect. An XDB-C18 column (150 mm × 2.1 mm, 3.5 μm) was used for chromatographic separations, with a mobile phase comprising methanol and aqueous ammonium formate (5 mM). The linearity of the method was satisfactory with regression coefficient (R 2) = 0.9992. The limit of quantification was 3.3 μg kg-1. Three spiked levels (25, 125 and 625 μg kg-1) were used to determine the recovery of bronopol, which was found to be 73.3-96.7%, with relative standard deviations (RSD) in the range 1.2-7.9%. The RSD for intra-day precision (n = 7) was 7.6% and the RSD for inter-day precision (n = 15) was 8.3%. The newly developed analytical method was successfully used to quantify bronopol in rice samples.