title: Optical biosensor for urea with improved response time.
abstract: An optical biosensor for urea measurements was developed. The operation of the sensor is based on the well-known urease enzyme-catalyzed hydrolysis of urea. The ammonium ions liberated in the reaction are detected with an ion selective optode membrane containing nonactin as ion selective ionophore and ETH 5294 chromoionophore in a thin (1 microm) plasticized poly(vinylchloride) film. The basic sensing element was home made of a microscope glass slide, a HeNe laser light source, photodiode light detector and light in coupling, de-coupling elements. The transducer membrane and the enzyme containing reaction layer were sandwich-cast with spin coating onto the surface of the sensing slide. The attenuation of the laser light propagating inside the glass wave-guide was used as signal for urea measurements. With this arrangement membranes provided good sensitivity (0.05 absorption unit when going from 0.1 to 1 mM urea) and short (16-20 s) response time. Taking advantage on the improved response time, flow injection urea measurements were made in the 0.01-2 mM concentration range. Thirty sample/hour analysis-rate, good peak-to-peak reproducibility (RSD=0.02) and recovery (95-104%) was achieved with buffer diluted urea solutions. Applications for the analysis of real samples are planned to do in the future.
authors.affiliation: Department for General and Physical Chemistry, University of Pécs, 7624 Pécs, Ifjúság u. 6, Hungary.
authors.forename: Barna
authors.initials: B
authors.lastname: Kovács
authors.forename: Géza
authors.initials: G
authors.lastname: Nagy
authors.forename: Roland
authors.initials: R
authors.lastname: Dombi
authors.forename: Klára
authors.initials: K
authors.lastname: Tóth
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D002138:Calibration; D003959:Diamines; D004800:Enzymes, Immobilized; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation* / Q000379:methods; D018942:Macrolides; D008567:Membranes, Artificial; D008832:Microchemistry / Q000379:methods; D055095:Optics and Photonics / Q000295:instrumentation*; D010078:Oxazines; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000379:methods; D014508:Urea / Q000032:analysis*
chemical_list: D003959:Diamines; D004800:Enzymes, Immobilized; D018942:Macrolides; D008567:Membranes, Artificial; D010078:Oxazines; C008619:Nile Blue; C045768:ETH 1001; D014508:Urea; C050476:nonactin