Capillary electrophoresis–mass spectrometry as a new approach to analyze neonicotinoid insecticides

• Neonicotinoid insecticides were analyzed by CE–ESI-MS for the first time.
• The seven neonicotinoids were simultaneously determined in less than 11 min.
• Low limits of quantification were achieved for all compounds (3.5–7.2 μg/L).
• Trace levels of neonicotinoids were monitored in beeswax with the proposed method.
• Oxalic acid has proven to be effective to remove neonicotinoids from beeswax.

This paper represents the first report of a capillary electrophoresis (CE) method compatible with mass spectrometry (MS) detection for simultaneously analyzing seven neonicotinoid insecticides (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid and thiamethoxam). Different variables affecting CE separation (buffer concentration, pH, applied voltage and injection time) and MS detection (electrospray parameters) were studied. Low limits of detection (LOD) and quantification (LOQ) were achieved for all analytes, ranging from 1.0 to 2.3 μg/L, and from 3.5 to 7.2 μg/L, respectively. In addition, the proposed method showed itself to be linear in the range from LOQ to 1000 μg/L and to be precise, as the relative standard deviations of the migration times were lower than 4% in all cases. Finally, the proposed CE–MS method was applied to assess the efficacy of a beeswax cleaning treatment with oxalic acid to remove residues of three of the most commonly used neonicotinoids (clothianidin, imidacloprid and thiamethoxam), use of which has recently been restricted by the European Union.