title: Urea and lactate determined in 1-microL whole-blood samples with a miniaturized thermal biosensor.
abstract: A miniaturized flow-injected thermal biosensor was developed for the determination of urea and L-lactate in undiluted blood in 1-microL samples. The sensor employed a small enzyme column constructed of stainless steel tubing and microbead thermistors. Urease and lactate oxidase/catalase were separately immobilized onto controlled-pore glass beads, which, in turn, were charged into the enzyme column. With a flow rate of 70 microL/min, linear analytical ranges from 0.2 to at least 50 mmol/L and 0.2 to 14 mmol/L were obtained for urea and lactate, respectively. The relative standard deviations (CVs) for measurements of analyte in buffer were 0.91% for urea and 1.84% for lactate. For urea in whole blood, the CV for 50 determinations was 4.1%. Contrived samples containing various concentrations of urea and L-lactate in whole blood were determined with this sensor and with a spectrophotometric method. Comparisons of the results gave correlation coefficients of 0.989 and 0.984 for 30 blood urea and 30 blood lactate assays in concentrations ranging from 4 to 20.9 mmol/L and from 1.7 to 12.7 mmol/L, respectively.
authors.affiliation: Lund University, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Xie
authors.forename: U
authors.initials: U
authors.lastname: Harborn
authors.forename: M
authors.initials: M
authors.lastname: Mecklenburg
authors.forename: B
authors.initials: B
authors.lastname: Danielsson
mesh_terms: D015374:Biosensing Techniques; D002021:Buffers; D002374:Catalase; D004800:Enzymes, Immobilized; D015444:Exercise / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000097:blood*; D019344:Lactic Acid; D008904:Miniaturization; D006899:Mixed Function Oxygenases; D013816:Thermodynamics; D014508:Urea / Q000097:blood*; D014510:Urease
chemical_list: D002021:Buffers; D004800:Enzymes, Immobilized; D007773:Lactates; D019344:Lactic Acid; D014508:Urea; D006899:Mixed Function Oxygenases; D002374:Catalase; C021497:lactate 2-monooxygenase; D014510:Urease