Investigation of oxygen- and hydrogen peroxide-reduction on platinum particles dispersed on poly(o-phenylenediamine) film modified glassy carbon electrodes

Composite membrane modified electrodes were prepared by electrochemical deposition of platinum particles in a poly(o-phenylenediamine) (PPD) him coated on glassy carbon (GC) electrodes. The modified electrodes showed high catalytic activity towards the reduction of oxygen and hydrogen peroxide. A four-electron transfer process predominated the reduction process. The pH dependence and the stability of the electrodes were also studied

Continuous lactate measurement that combines a portable ultrafiltration storage device with an enzyme sensor

A simple portable continuous L-lactate monitoring system combining elegant ultrafiltration sample collection and storage with a lactate biosensor has been developed. The sensor has a detection range from 0.05mM to 30mM lactate dependent on different assignments of the PCS hydrogel complex layer. The sensor shows excellent performance on sensitivity and validity as well as operational stability over one month. Samples containing different concentrations of lactate were collected in six hours with an ultrafiltration probe and stored in a 6m long PEEK tube of 125 mu m in internal diameter. The ultraslow flow rate of 100 to 350nl/min was controlled by adjusting the restriction in the portable plastic syringe pump and a constant flow can be maintained over 24 hours. The collected samples were then detected after reversing the now with a lactate sensor. The total weight of the collection system is only 8g, allowing free movement of the person being tested

Designing an amperometric thick-film microbial BOD sensor

Thick film oxygen electrodes manufactured by screen print method have been used as a transducer for a biochemical oxygen demand (BOD) sensor. The kinetics of the immobilized yeast, Arxula adeninivorans (Arxula) has been studied. The apparent K-M of immobilized Arxula (>100 muM) is higher than free cells of Arxula (70 muM). The increase in K-M caused by the effect of immobilization extends the linear range of the sensor. End-point measurement and quasi-kinetic measurement have been studied comparatively as measurement procedures with a good correlation. The V-max for end-point measurement is 790.7 muM/s and that for quasi-kinetic measurement is 537.3 muM/s. The limit of detection is calculated 1.24 mg/l BOD. Using the quasi-kinetic measurement, instead of end-point measurements, the measuring time can be reduced from 5-30 min to 100 s. The sensor layer thickness or increase in the layer of covering gel can increase the K-M that is accompanied with the extension of the linear range of the sensor. Nevertheless, increase in the layer of covering gel will not increase the saturation signal. Domestic wastewater was checked by the thick film BOD sensor and the results are satisfactory. (C) 2000 Published by Elsevier Science S.A

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl) sulfonate (PCS) part I: Construction and characterization of the microbial sensor

A microbial biosensor based on the yeast Arxula adeninivorans LS3 has been developed for measurement of biodegradable substances. Arxula is immobilized in the hydrogel poly(carbamoyl) sulfonate (PCS). The immobilized yeast membrane is placed in front of an oxygen electrode with - 600 mV versus Ag/AgCl. Arxula is salt tolerant; it can give a stable signal up to 2.5 M NaCl in sample (120 mM in measuring cell). The sensor's measurements are highly correlated to BOD5 measurements. It has a very high stability which can last for 40 days without any decrease in signal. The linear range of the sensor is up to a corresponding BOD value of 550 mg/l. (C) 1999 Elsevier Science S.A. All rights reserved

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl)sulfonate (PCS) Part II: Application of the novel biosensor to real samples from coastal and island regions

A microbial sensor for rapid measurement of the amount of biodegradable substances based on the salt-tolerant yeast Arxula adeninivorans LS3 has been developed especially for coastal and island regions. Our parameter, the so- called sensorBOD, that is available after only a few minutes, agrees with the 5-day value for the biochemical oxygen demand (BOD5) very well. We have employed the Arxula sensor in the short-time estimation and supervision of the BOD of both domestic and industrial wastewater with high salinity. The novel sensor makes it possible to monitor the different types of wastewater rapidly without pretreatment, and it can be used for an active process control of sewage treatment works. Compared to a commercially available sensor, the novel sensor achieves better agreement between sensorBOD and BOD5 measurements with salt containing samples.link_to_subscribed_fulltex