ALL-SOLID-STATE MINIATURIZED FLUORESCENCE SENSOR ARRAY FOR THE DETERMINATION OF CRITICAL GASES AND ELECTROLYTES IN BLOOD

We describe a six-channel, all-solid-state, miniaturized fluorescence sensor array for the precise determination of blood analytes for medic al diagnostic purposes, The device features superblue LEDs as light so urces, GRIN optics, and photodiodes, assembled according to pigtailing procedures (Bruno, A, E.; et al. Trends Anal. Chem. 1994, 13, 190-198 ). The numerical aperture of the fluorescence optics is 0.46, renderin g a collection efficiency of 2.4%. The performance of this instrument has been evaluated in terms of dynamic response, linearity, channel re producibility, reversibility, long-term drifts, photobleaching of indi cator, cross-talk, ionic strength, and selectivity in pH measurements. The responses of the pH sensing membranes were optimized in the physi ological range. Responses are linear with typical values of similar to 1.5 V/pH unit, with limits of decision of 24 mV, which corresponds to pH resolutions of 0.03 pH unit, Under continuous illumination, using calibration buffers, the sensors display nonstatistical differences wi thin 2 standard deviations over a period of 6 h, and it is shown that, under discontinuous illumination, the membranes can be used in more t han 2000 measurements without need of calibration, in contrast to elec trochemical sensors which require periodic calibration, After selectin g the appropriate combination of LEDs, excitation and emission filters , and sensing membranes, the instrument was used to determine the conc entrations of various critical blood analytes in buffer solutions in t he various channels. Similar measurements in untreated blood reproduce the reported results.