BIOSENSOR FOR THE NONSPECIFIC DETERMINATION OF IONIC SURFACTANTS

We report the analytical figures of merit for the first biosensor for ionic surfactant quantification. The biosensor consists of a silanized silica optical fiber, onto which acrylodan-labeled bovine serum album in (BSA-Ac) is immobilized. Recent work from our laboratory on native BSA-Ac (Lundgren, J. S.; Bright, F. V. J. Phys. Chem. 1996, 100, 8580- 8586) has shown that ionic surfactants dehydrate the local environment surrounding the lone acrylodan residue, open up the pocket hosting th e acrylodan reporter group, and dramatically increase the segmental mo bility of domain I in BSA. In the current work, we use BSA-Ac as an ac tual biorecognition element for surfactant detection and quantificatio n. We also compare several BSA-Ac immobilization strategies and determ ine the analytical figures of merit for the BSA-Ac-based biosensor to a prototypical analyte, cetyltrimethylammonium bromide (CTAB), The bio sensor linear dynamic range extends from 5 to 60 mu M, and the t(90) r esponse time (90% of the total response) is less than 30 s. Biosensor response precision (relative standard deviation) during 34 sensing cyc les is 2.5%, On the down side, biosensor performance decreases 38% aft er 25 days of storage; however, this drift can be compensated. This wo rk also demonstrates the utility of BSA-Ac as a model biorecognition e lement-reporter group system for grading the suitability of different surface immobilization strategies.