Laboratory operations assay selection

Obviously, the universal goal of any measurement technique is to obtain reproducible results regardless whether the samples come from different sources with different matrix effects, are run by different operators, in different laboratories, on different occasions and using different lots of reagents. This is usually accomplished by characterization of the newly developed assay in terms of sensitivity, selectivity, robustness and correctness (i.e., accuracy and precision). Evaluation of sensitivity and precision does not normally constitute a problem for a newly developed immunoassay, and accuracy can be attained by comparison with the results obtained by a reference ( standard ) method. However, the evolution of assay standardization from this point on is much more difflcult. The following section deals with application-specific problems related to validation and standardization of immimoassay. 

To conclude this section, it is intriguing to observe how developments in instrumental analysis have led to an increase of sensitivity and a dramatic decrease of analysis time required by procedures based on isothermal distillation. The method of Conway, developed more than 35 years ago [4.11], still in use in clinical and pharmaceutical laboratories, requires many hours to perform an assay of a volatile species. The samples are kept in small, enclosed chambers containing the donor and the acceptor liquid, respectively, and after the diffusion process has reached equilibrium, the acceptor liquid is titrated. Gas-sensing probes, which operate on the principles of ion-selective electrodes, separated from the... 

During feasibility studies, preliminary estimates of repeatability should be obtained. Selected sera from a bank of reference sera used to determine the assay s D-SN and D-SP can be tested using a series of runs of the assay within the same laboratory. It is useful to have several operators of the assay system do this exercise independently. This will provide an indication of assay repeatability that addresses the... 

Enzymes, as you probably know, are proteins that can make chemical reactions happen in a more selective and faster way. At the end of each reaction cycle the enzymes remain unchanged so they act as catalysts. Since they occur in the living world we call them biocatalysts. Aside from proteins, ribonucleic acids and their fragments can act as catalysts and are called ribozymes, by analogy to enzymes. Enzymes are extracted from living tissues, for example, milk, saliva, liver, muscle have to be stored under carefully maintained conditions and, once outside living tissue, lose their activity fast. Isolation and purification of enzymes and assaying their activity have been major operations in biochemical and biomedical laboratories. Today,... 

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