Development and optimisation of (bio) analytic procedures for difficult matrices

by Sabine Thiessen, Susanne Janku and Christoph Höppner

Non-clinical biodistribution or in-vitro skin-penetration studies may be crucial in the development of new pharmaceutical products. These studies require development of robust analytical methods for elucidation of both total concentration and distribution of the substance of interest in its biological matrix. This especially holds true when the work with 14C- or 3H-radiolabelled compounds is not possible for one reason or another. The development of "cold" analytics consists of defining the right combination of preparatory work, extraction procedure and chromatographic technique with the ultimate intention to create a method uniting all favourable characteristics. Ideally, the method should be robust, sensitive, accurate and reproducible. Additionally, it should be quick, simple and inexpensive. While bioanalytics from plasma, serum, urine and other predominantly liquid biological matrices may be challenging at times, there is an escalation. BSL BIOSERVICE (Eurofins partner lab) in Germany has acquired expertise in developing strategies for matrices that combine diverse unfavourable characteristics, e.g. skin and other organ tissues.

The strategies for method development can be diverse and labour intensive at times. Ideal results are obtained by wise definition of three key procedures. First, the homogenisation device and protocol best suited for the matrix/analyte combination must be defined. Stability of the analyte in the face of transient heat exposition as a result of violent homogenisation procedures must be taken into account, and alternative methods (e.g. liquid nitrogen deep-freeze followed by mortar pulverisation) may be considered. For extraction of the solvent, dilution factor for the homogenate and time/temperature combination are selected. Time-point for addition of the internal standard must serve the purpose while being practical and technically feasible. Thirdly, the ideal HPLC and MS settings, including choice of column, solvent and run parameters need to be found, often trading off run-time versus sensitivity. Satisfying recovery and accuracy in an analytical method that is fit for analysis of large sample numbers is the goal.

With every new project, the company's expert advice and customer-oriented efforts are essential to providing clients with the best analytical solutions.

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