Preparation And Application Of A Polymer Silica-microspheres-encapsulated Monolithic Column For Microextraction

Clenbuterol (CLB) is a β2-adrenergic receptor agonist that is therapeutically used for thetreatment of bronchial asthma. However, this drug is abused as a doping agent by athletes toimprove their sport performance, because high doses administered can bring the stimulationon the central nervous system and promotion of some anabolic effects. So CLB has beenadded to the prohibited list of doping agents by the International Olympic Committee.Nonetheless, it is quite difficult for the UV detector to analyze trace amounts of CLB in biologicalmatrixes. Therefore, it is necessary to establish a technique for pre-concentration of the traceamounts of CLB.Solid-phase microextraction (SPME) was introduced as an excellent sample preparationtechnique, since it possesses several attractive features including high sensitivity, solventlessextraction, small sample volume, simplicity, and easy automation. Polymer monolithmicroextraction is one of kind solid phase microextraction using polymer monolith as theextraction material. In-situ-polymerization to form a monolithic column shows severalattractive features including frit-free construction, easy preparation, good permeability,excellent biocompatibility and the extended pH working range. Therefore, monolithic columnhave found increasing attention in the extraction of analytes from complex matrixes likeenvironmental and biological samples.In the present study, a polymer silica-microspheres-encapsulated monolithic column wasprepared by in-situ polymerization of methacrylic acid and ethylene dimethacrylate in a530μm i.d. fused silica capillary packed with silica-micropheres for microextraction ofclenbuterol. The optimal conditions for preparing the colume were established. After severalparameters including composition of extraction mobile phase, extraction volumn, sampleflow rate, pH value of the sample matrix and the content of NaCl in the sample matrix wereoptimized,the prepared column was applied to enrich the clenbuterol in a standard samplesolution and urine sample solution, and an about300times high enrichment factor wasobtained. The possible reason for the high enrichment factor was discussed. The method hasbeen applied successfully for the determination of trace clenbuterol in urine.