Identification of phenolic compounds in rosemary honey using solid-phase extraction by capillary electrophoresis–electrospray ionization-mass spectrometry

Complex extracts of rosemary honey constituents often require very effective separation techniques to allow the identification of different compounds. Capillary electrophoresis (CE) coupled to mass spectrometry (MS) detection can provide structure-selective information about the analytes in such matrices and has turned out to be an attractive alternative to HPLC methods. A simple and cost-effective analytical method involving solid-phase extraction (SPE) and capillary zone electrophoresis coupled to electrospray ionization-ion trap mass spectrometry (CZE-ESI-MS) to identify and characterize phenolic compounds in rosemary honey is described. The SPE, CE and ESI-MS parameters were optimized in order to maximize the number of phenolic compounds detected and the sensitivity of their determination. All CE–ESI-MS experiments were performed with uncoated fused-silica capillaries and an alkaline volatile buffer system consisting of 100 mM NH4Oac with 10% of 2-propanol at pH 10. Since sheath liquids can made significant effects on the sensitivity in typical CE–ESI-MS application, the effect of type and flow rate of the sheath liquid on the sensitivity of phenolic compounds were investigated. As result, the best sensitivity was obtained with a sheath liquid containing 2-propanol/water 60:40 (v/v) and 0.1% (v/v) of triethylamine at 3 μL/min in the negative ion mode. We describe the first method for the analysis of phenolic compounds in rosemary honey at mg/L levels by using a simple SPE before CE–ESI-MS analysis.