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A Capillary Electrophoresis method was developed and applied successfully to test the quality of different drug formulations for release and stability studies. In the method an uncoated fused‐silica capillary was employed containing a phosphoric acid buffer electrolyte which was brought to pH by triethylamine. The benzalkonium chlorides (BAC‐C12 and BAC‐C14) present in the standard were completely separated from each other and from the peaks of the main compound. Performance results of the method in terms of system repeatability, precision and accuracy are discussed. © 1998 John Wiley & Sons, Ltd.

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In agriforensics, time of administration is often debated when illegal drug residues, such as clenbuterol, are found in frequently traded cattle. In this proof-of-concept work, the feasibility of obtaining retrospective timeline information from segmented calf tail hair analyses has been studied. First, an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) hair analysis method was adapted to accommodate smaller sample sizes and in-house validated. Then, longitudinal 1 cm segments of calf tail hair were analyzed to obtain clenbuterol concentration profiles. The profiles found were in good agreement with calculated, theoretical positions of the clenbuterol residues along the hair. Following assessment of the average growth rate of calf tail hair, time of clenbuterol administration could be retrospectively determined from segmented hair analysis data. The data from the initial animal treatment study (n = 2) suggest that time of treatment can be retrospectively estimated with an error of 3-17 days.