A new kind of biosensor for the detection of urea with a high selectivity, sensitivity and wide detection range was designed based on the secretion of carnation petals cells paste covered over a graphite-epoxy composite basic electrode surface. The carnation petal paste from mashed fresh carnation petals was tightly fixed on the basic electrode surface with Teflon thin film to keep it in contact with the electrode surface. Urea in aqueous solution was detected by differential pulse voltammetry based on the oxidation peak current at 0.316 V (vs. SCE) of the secreted species of carnation petal cells during the mashing process, which interacts with urea molecules and results in the decrease of the oxidation peak current. The oxidation peak current decreases linearly with the logarithm of urea concentration in the range of 1.3 ? 10(-16)-4.57 ? 10(-8) M and 3.4 ? 10(-7)-1.3 ? 10(-1) M with a detection limit of 7.5 ? 10(-16) M. The biosensor was characterized by electrochemistry and fluorescent spectrometry, and applied to the determination of urea in waste water from a river around Shenyang Normal University campus with a recovery of 104.5% (RSD is 5.00%). The presence of larger amounts of ammonium ion and nitrate ion up to the molar ratio of 10(4) do not interfere with the urea detection.
Biosensing Techniques Dianthus