Determination of serum urea using an open-tubular immobilized enzyme reactor

Yasuda Kenji, Takata Yoshinori*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


An open-tubular enzyme reactor and an ammonium ion selective electrode using nonactin were prepared and connected sequentially to determine serum urea by flow injection method. Urease was immobilized on the inner surface of aminosilanized silicone rubber tubing. The effects of sample size, pH value and flow rate of the carrier solution on the enzyme reactor were investigated. The following practical standard conditions for the measurement were decided; sample size: 20 μl, pH value: 6.5, and flow rate of the carrier solution: 1.0ml min–1. The calibration range for urea concentration was from 2.0 up to 300 mM. The relative standard deviations for 10 replicate measurements of a urea standardand a control serum were 0.65% and 1.19%, respectively. Long-term stability of the urease reactor was improved by coating thin film of cellulose acetate over the whole immobilized enzyme layer. The measurement system was applied to serum samples from 20 healthy women. Good correlation between the present method and colorimetry was observed.

Original languageEnglish
Pages (from-to)755-760
Number of pages6
Issue number11
Publication statusPublished - 1990
Externally publishedYes


  • FIA
  • ammonium ion selective electrode
  • open-tubular immobilized urease reactor
  • serum urea determination

ASJC Scopus subject areas

  • Analytical Chemistry


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