ABSTRACT
A study was carried out to evaluate the possible presence of thiamethoxam, clothianidin and imidacloprid, as well as the metabolic breakdown products of these three neonicotinoids in pollen and honey obtained from brood chamber combs of honeybee colonies located next to sunflower and maize crops from coated seeds. Samples were analyzed by liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry detector, in combination with accurate mass tools such as diagnostic ions by exact mass, chlorine mass filters, and MS/MS experiments. The presence of thiamethoxam and clothianidin was confirmed in some of the pollen samples analyzed. Moreover, different metabolites of neonicotinoids were tentatively detected in the pollen and honey samples collected. The results suggested that four metabolites were found in the honey samples, while for pollen samples eleven metabolites were identified; among these, five were considered for the first time as metabolic breakdown products in sunflower and maize plants.
Subject(s)
Chemistry Techniques, Analytical/methods , Crops, Agricultural/chemistry , Guanidines/analysis , Honey/analysis , Imidazoles/analysis , Nitro Compounds/analysis , Oxazines/analysis , Pollen/chemistry , Thiazoles/analysis , Animals , Chromatography, Liquid , Guanidines/metabolism , Helianthus/chemistry , Imidazoles/metabolism , Neonicotinoids , Nitro Compounds/metabolism , Oxazines/metabolism , Reproducibility of Results , Seeds/chemistry , Tandem Mass Spectrometry , Thiamethoxam , Thiazoles/metabolism , Zea mays/chemistryABSTRACT
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 2.3µg/L, and from 3.5 to 7.2µg/L, respectively. In addition, the proposed method showed itself to be linear in the range from LOQ to 1000µg/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.