Bioaffinity interactions

ITP [15], especially transient FTP, are used for small and large molecules stacking. In this technique, the sample is mixed with appropriate leading and terminating ions [16] as described in Chapter 13. This technique is used to selectively enrich low-abundance compounds (e.g., peptides in the absence of any bioaffinity interactions) [20]. This method is more difficult in practice, but it offers the benefits of speed and very high concentration. 

Guijt RM, Baltussen E, van Dedem GWK (2002) Use of bioaffinity interactions in electrokinetically controlled assays on micro-fabricated devices. Electrophoresis 23(6) 823-835... 

A urea sensor has conventionally consisted of a urease-immobilized membrane and electrode for the determination of the metabolites electrodes for ammonium ion (20), pH (27), ammonia gas (22), and carbon dioxide (23) have been used. These sensors were all potentiometric ones to give Nernstian responses, the linear concentration range of which was typically between 10" and 10 M of urea. If one wishes to detect urea with using the ion- or gas-selective electrodes, urease is indispensable not only for the specific recognition based on the bioaffinity interaction but also for chemical conversion of urea to detectable species, since urea is essentially electro-inactive. On the contrary, the polymer-modified electrode described here does not rely upon enzymes the concentration of urea can be determined directly. 

Katz E, Heleg-Shabtai V, Bardea A, Willner I, Rau HK, Haehnel W. Fully integrated biocatalytic electrodes based on bioaffinity interactions. Biosens Bioelectron 1998 13 741-756. 

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