A sensitive non‐aqueous capillary electrophoresis‐mass spectrometric method for multiresidue analyses of β‐agonists in pork

Non‐aqueous capillary electrophoresis–mass spectrometry (NACE‐MS) was developed for trace analyses of β‐agonists (i.e. clenbuterol, salbutamol and terbutaline) in pork. The NACE was in 18 mM ammonium acetate in methanol–acetonitrile–glacial acetic acid (66 : 33 : 1, v/v/v) using a voltage of 28 kV. The hyphenation of CE with a time‐of‐flight MS was performed by electrospray ionization interface employing 5 mM ammonium acetate in methanol–water (80 : 20, v/v) as the sheath liquid at a flow rate of 2 μL/min. Method sensitivity was enhanced by a co‐injection technique (combination of hydrodynamic and electrokinetic injection) using a pressure of 50 mbar and a voltage of 10 kV for 12 s. The method was validated in comparison with HPLC–MS‐MS. The NACE‐MS procedure provided excellent detection limits of 0.3 ppb for all analytes. Method linearity was good (r² > 0.999, in a range of 0.8–1000 ppb for all analytes). Precision showed %RSDs of <17.7%. Sample pre‐treatment was carried out by solid‐phase extraction using mixed mode reversed phase/cation exchange cartridges yielding recoveries between 69 and 80%. The NACE‐MS could be successfully used for the analysis of β‐agonists in pork samples and results showed no statistical differences from the values reported by the Ministry of Public Health, Thailand using HPLC‐MS‐MS method. Copyright © 2009 John Wiley & Sons, Ltd.