(a) F-C reagent (b) NBS-celestine blue (c) Sulphanilamide (d) Azocarmine G
Measurement of the absorbance of blue colored chromogen Unreacted NBS measured using celestine blue in acid medium Measurement of pink colored coupled product of drug with diazotized sulphanilamide with drug Chloroform extractable 1 : 1 ion-pair complex was measured
720 540 520 540
4–28 2–12 1–10 2.5–25
Multistep, unstable oxidant, strict pH control, and tedious extraction procedure