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Direct immersion solid-phase microextraction (DI-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was developed for rapid analysis of clenbuterol in pork for the first time. In this work, a low-cost homemade 44 µm polydimethylsiloxane (PDMS) SPME fiber was employed to extract clenbuterol in pork. After extraction, derivatization was performed by suspending the fiber in the headspace of the 2 mL sample vial saturated with a vapor of 100 µL hexamethyldisilazane. Lastly, the fiber was directly introduced to GC-MS for analysis. All parameters that influenced absorption (extraction time), derivatization (derivatization reagent, time and temperature) and desorption (desorption time) were optimized. Under optimized conditions, the method offered a wide linear range (10-1000 ng g(-1)) and a low detection limit (3.6 ng g(-1)). Finally, the method was successfully applied in the analysis of pork from the market, and recoveries of the method for spiked pork were 97.4-105.7%. Compared with the traditional solvent extraction method, the proposed method was much cheaper and fast., (© The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

A capillary electrophoretic method has been established for the separation of the enantiomers of clenbuterol. The effects of pH value, composition of the background electrolyte, concentration of carboxymethyl-β-cyclodextrin (CM-β-CD), capillary temperature and running voltage have been investigated. The two enantiomers were separated in an uncoated capillary with phosphate buffer (50 mmol/L, pH 3.5) containing 10 mmol/L CM-β-CD. The capillary temperature was at 15°C and applied voltage was at 20 kV. The inclusion complex of CM-β-CD and clenbuterol was synthesized and characterized by two-dimensional rotating frame spectroscopy (2D ROESY). Based on the 2D ROESY analysis, an inclusion structure of the clenbuterol/CM-β-CD complex was proposed, in which clenbuterol penetrated CM-β-CD in a tilted manner due to the interaction of intermolecular hydrogen bonds between clenbuterol and CM-β-CD.

More specific official methodology is needed to survey the illegal use of clenbuterol in animal production plus the synthesis of new compounds that currently elude routine analytical methods. The identification of a new adrenergic agonist, N1-(2-(4-amino-3,5-dichlorophenyl)-2-hydroxyethyl)-N1-isopropyl-propanamide (known as compound A) in animal feed has prompted studies to verify if the existing cleanup procedures developed for clenbuterol are really effective. This study considers the ion-exchange mechanism on cyanopropyl (CN), sulfonic cation exchange (SCX), mixed phase (MPH) (C8 + SCX), and nonendcapped C18 (C18NE) solid-phase extraction (SPE) columns. Results indicate that compound A (by contrast with clenbuterol) is not efficiently retained on the CN, SCX, and MPH SPE columns (recovery <10%). This finding thus leads to the development of a gas chromatography-tandem mass spectrometry procedure based on C18NE SPE that is able to purify both agonists from bovine livers spiked at 0.5, 1.0, and 2.0 ppb with a mean recovery of 93% for clenbuterol and 92% for compound A.