Using spectrophotometry with para-dimethyl-amino-benzaldehyde as chromogenic agent to determine macro and micro urea in aqueous solution.

Lemon-yellow material will be produced when para-dimethyl-amino-benzaldehyde(PDAB) reacts with urea under acidic condition,which can be used to determine the macro and micro urea concentration in aqueous solution with colorimetry.Standard curve and specific testing method regarding using spectrophotometry to determine urea concentration with PDAB as chromogenic agent were established through condition experiment and precision and accuracy experiment in the paper.422 nm was selected as testing wavelength,10 mL as the addition dosage of PDAB solution,4 mL as sulfuric acid addition dosage and 10 min as reaction time.Under the conditions,the standard curve obtained embodied highly significant linear relationship ranging 0-1 000 μg·mL-1 and the detection limit was 0.5 μg·mL-1.The method has high accuracy and precision as well as good stability and reliability.