Synermed® IR700 total bilirubin is not based upon the diazo reaction and is therefore not subject to chemical interference from hemoglobin as are all diazo methods. Urinary indicans which are measured by most automated diazobilirubin methods have no effect in the infrared method. Chromatic interferences are minimized by detection at 700 nm where hemoglobin and lipemia have little absorbance. The method is optimized for performing bilirubin assays on sera which contain hemoglobin along with high levels of bilirubin, such as often occurs with pediatric samples.
The sample containing both conjugated and unconjugated bilirubin is dissolved in the reagent and both conjugated and unconjugated bilirubin are oxidized in the presence of the electron transfer agent KHC3 to form a stable blue-green infrared light absorbing chromophore cholecyanin.
Bilirubin -> cholecyanin
The reaction product is detected at 700 nm in the near-infrared region of the spectrum.