In this paper, a modified expanded graphite composite electrode based on natural zeolitic volcanic tuff modified with silver (EG-Ag-Z-Epoxy) was developed. Cyclic voltammetry measurements revealed a reasonably fast electron transfer and a good stability of the electrode in 0.1 M NaOH supporting electrolyte. This modified electrode exhibited moderate electrocatalytic effect towards urea oxidatio...

Although many methods for the determination of urea nitrogen have been described, few have proved highly convenient for the accurate determination of small amounts of urea nitrogen without having to make use of special apparatus or techniques. Among the older methods, the Van Slyke gasometric method (1) is generally considered the most accurate, with an allowable error of 1 per cent. This metho...

A novel determination method for urea using an acid urease column-FIA system was developed, and the system was applied to the determination of urea in rice wine. This novel FIA system was characterized by CO2 detection due to the property of acid urease and by a microfluidic gas-diffusion device with the use of an ultra-thin hollow fiber membrane. A biosensing system fabricated in this study wa...

For determination of the dynamics of parotid urea secretion in conscious sheep, a previously standardized transit time ultrasonic flow metering system was used to measure bilateral parotid flow. Six ewes fed for ad libitum consumption were prepared under halothane anesthesia with ultrasonic probes around both parotid ducts; these ducts were also cannulated orally. After probe encapsulation (8 d...

The method outlined in the foregoing. paper for the estimation of urea in blood is perfectly reliable for larger quantities of urea (up to 25 mgms. or perhaps more). Its adaptation to the determination of urea in urine using only a small amount of the urine is shown in this paper. The method to be described is slightly more accurate than the rapid clinical method proposed earlier.’ The reason f...

The observation was made some 6 years ago that chickens were not poisoned by the parenteral injection of large quantities of crystalline urease, unless urea was also injected (1). However, rabbits were killed after urease was injected when the blood ammonia nitrogen reached a value of 5 mg. per 100 cc. (2). These observations offer sufficient evidence to make many of the values reported for ure...