Highly sensitive chemiluminescence flow injection analysis system using microbial peroxidase and a photodiode detector

A highly sensitive chemiluminescence flow injection analysis system (CL-FIA) was developed using an Si-photodiode as a detector. The CL-FIA system with peroxidase from Artheromyces ramosus (ARP) showed a higher chemiluminescence intensity than that with the enhanced chemiluminescence of horse radish peroxidase (HRP) and p-iodophenol. The optimum conditions for chemiluminescence using ARP were a carbonate buffer (pH 10.1) containing 17.5 mu M luminol in the flow cell. The photocurrent of the photodiode was linearly related to the hydrogen peroxide concentration in a log-log plot from 3 nM to 10 mu M under these optimum conditions. The RSD was estimated to be 3.2% for 1 mu M of hydrogen peroxide, and the time for one analysis was less than 20 s. A CL-FIA system for hypoxanthine (Hx) measurement was also constructed with this CL-FIA system by addition of a bioreactor column of xanthine oxidase. With its compactness, ease of use, and sensitivity comparable with CL-FIA using a photomultiplier tube, this system has potential applicability for daily measurements in the industrial field.