ABSTRACT
A biological fluid is not a simple mixture, but a very complex one containing many different components which may subtly react with one another and hence contribute to some sort of interference with the end point, perhaps by elevating the response, or by altering the actual values by degradation. This chapter describes some of the special problems which arise from the nature of the fluid and its constituents. Maickel has produced an excellent practical review of the application of separation science to the analysis of biological samples. Blood is the most complex of the biological fluids mentioned. The chief feature of plasma and serum is the presence of large amounts of protein. Obviously, the protein itself is chemically and physically different from the small-molecule drugs normally being measured. In microbiological assays, only the free drug is measured but because standards are also run in the same fluid as that being measured.
