SIRE-TECHNOLOGY - PART I - AMPEROMETRIC BIOSENSOR BASED ON FLOW-INJECTION OF THE RECOGNITION ELEMENT AND DIFFERENTIAL MEASUREMENTS

An amperometric biosensor with injection of the recognition element (S IRE) is described. An oxidase enzyme is injected into the measuring ch amber, separated from the sample by a semi-permeable membrane. It is p ossible to make measurements in the presence and absence of enzyme and subtract the background current. This differential measuring techniqu e has been difficult with previous sensors because it is very difficul t to match two sensors. The versatility of the biosensor was demonstra ted by determination of several different metabolites (glucose, lactat e, phenyl alanine, and galactose). The system was not optimized for th e individual analytes, but showed a linear response for each up to app roximately 10 mM. For glucose, a detection limit of approximately 2 mu M was achieved. By using the differential measuring technique, glucos e could be determined by direct measurement in a urine sample with the standard addition method. The repeatability was found to be lower tha n 3.7 % (n=5) over the range 0.3 - 5.0 mM for glucose, and the reprodu cibility better than 5 % (n=5). The biosensor showed no decrease in re sponse at temperatures up to 60 degrees C and could easily be cleaned with a solution of hydrogen peroxide and by sweeping of the potential. Thus, this amperometric biosensor was found to have several advantage s compared to conventional ones.