Measuring urea concentrations in water samples v1

Colorimetric assay for direct (vs. enzymatic) measurement of urea to a detection limit of 0.4 µM concentration. The reaction of urea with diacetylmonoxime (DAM) to form a colored product is enhanced by addition of thiosemicarbazide (TSC). The original direct method was adapted for use with a single mixed reagent and incubation at room temperature (vs. the “high temperature direct method” that incubates at 85ºC for 30 minutes). NOTE: This protocol is written for measurement in 24-well plates.