Clenbuterol, solid-phase extraction

When using PFT with a neutral selector, it is quite difficult to avoid any entrance of the chiral selector into the ionization source, particularly at a high pH, where EOF is important. The use of BGE at low pH and/or coated capillary to minimize EOF is therefore mandatory. However, the coaxial sheath gas, which generally assists the ionization process, leads to an aspirating phenomenon of the chiral selector in the MS direction. Javerfalk et al. were the first to apply PFT with a neutral methyl-/i-CD for the separation of racemic bupivacaine and ropivacaine with a polyacrylamide-coated capillary and an acidic pH buffer (pH 3). Cherkaoui et al. employed another neutral CD (HP-/1-CD) with a PVA-coated capillary for the analysis of amphetamines and their derivatives. To prevent a detrimental aspiration effect, analyses were carried out without nebulization pressure. Numerous other studies presented excellent results such as the enantioselective separation of adrenoreceptor antagonist drugs using tandem mass spectrometry (MS/MS) the separation of clenbuterol enantiomers after solid-phase extraction (SPE) of plasma samples or the use of CD dual system for the simultaneous chiral determination of amphetamine, methamphetamine, dimethamphetamine, and p-hydroxymethamphetamine in urine. 

Unlike clenbuterol, salbutamol is a difficult compound to analyze due to its particular chemical attributes. It is a basic compound subjected to protein binding poor recoveries are obtained especially when protein precipitation techniques are used to prepare the extracts (145). In addition, salbutamol is charged at all pH values and does not readily lend itself to simple, specific back-extracting procedures. This severely restricts the options of sample cleanup. However, a Subtilisin protease digestion step followed by acid clarification and solid-phase extraction has been suggested (146) as an adequate extraction and cleanup procedure prior to the end-point determination of salbutamol by an enzyme immunoassay (139) based on the cross-reactivity of anticlenbuterol antibodies. 

C. Crescenzi, S. Bayoudh, P. A. G. Cormack, T. Klein, and K. Ensing, Determination of Clenbuterol in Bovine Liver by Combining Matrix Solid-Phase Dispersion and Molecularly Imprinted Solid-Phase Extraction Followed by Liquid Chromatography/Mass Spectrometry, Anal. Chem. 2001, 73, 2171 ... 

Crescenzi, C. Bayoudh, S. Cormack, P.A.G. Klein, T. Ensing, K. Determination of clenbuterol in bovine liver by combining matrix solid-phase dispersion and molecularly imprinted solid-phase extraction followed by liquid chromatography/electrospray ion trap multiple-stage mass spectrometry. Anal. Chem. 2001, 73, 2171 2177. 

B.A. Rashid, P. Kwasowski and D. Stevenson, Solid phase extraction of clenbuterol from plasma using immunoafiinity followed by HPLC, J. Pharm. Biomed. Anal., 1999, 21, 635-639. 

C. Berggren, S. Bayoudh, D. Sherrington and K. Ensing, Use of molecularly imprinted solid-phase extraction for the selective clean-up of clenbuterol from calf urine,/. Chromatogr. A, 889 (1-2) 105-110, 2000. 

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