What is true regarding the Jendrassik-Grof method for measuring bilirubin?

The Jendrassik-Grof method for measuring bilirubin primarily utilizes the reaction of bilirubin with diazotized sulfanilic acid to produce a colored complex, which can be quantified photometrically. This method helps in distinguishing between direct (conjugated) and total bilirubin levels, thus allowing for a more accurate assessment of bilirubin metabolism.

The statement regarding the addition of Fehling's reagent after the diazo reaction pertains to its role in reducing optical interference in the assay. Fehling's reagent is a solution that contains copper ions, which can interact with reducing substances, thus minimizing their impact on the optical density measurements. By adding it post-diazo reaction, the interference caused by substances like hemoglobin is effectively addressed, enhancing the assay's specificity and accuracy. This aspect is critical in clinical chemistry as it ensures reliable results when measuring bilirubin levels.

In contrast, the other statements are not aligned with the principles of the Jendrassik-Grof method. The method does not utilize the same diluent for both total and direct assays, does not involve the addition of HCl to prevent hemoglobin interference, and ascorbic acid does not serve to intensify the color of the azobilirubin product. Understanding