Salbutamol cleanup

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. 

Liquid-liquid partitioning cleanup is generally carried out at alkaline conditions using ethyl acetate (481, 484), ethyl acetate/tert.-butanol mixture (482), diethyl ether (478), or tert.-butylmethyl ether/n-butanol (485) as extraction solvents. The organic extracts are then either concentrated to dryness (482), or repartitioned with dilute acid to facilitate back-extraction of the analytes into the acidic solution. A literature survey shows that liquid-liquid partitioning cleanup resulted in good recoveries of substituted anilines such as clenbuterol (478, 481, 484), but it was less effective for more polar compounds such as salbutamol (482). 

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