Question

Match List - I with List - II. List - I List - II
A. Phenolphthalein assay I. When oxidised and catalyzed by heme, it emits an intense yellowish green light
B. Benzidine assay II. It is catalyzed by heme with hydrogen peroxide as the oxidant
C. Fluorescein assay III. These are heme derivatives in which ferrous ion of the heme forms two bonds with nitrogenous base
D. Hemochromagen crystal assay IV. It is catalyzed by heme to produce blue to dark blue colour
Choose the correct answer from the options given below :

• A. A-II, B-III, C-I, D-IV
• B. A-I, B-III, C-IV, D-II
• C. A-II, B-IV, C-I, D-III
• D. A-IV, B-I, C-II, D-III

Hint:

Phenolphthalein → Pink (heme + H₂O₂), Benzidine → Blue, Fluorescein → Glow, Hemochromagen → Crystals.

Answer 1

The Correct Option is C

Concept: Various presumptive and confirmatory tests for blood detection rely on the catalytic activity of heme (iron-containing component of hemoglobin) or on formation of characteristic derivatives. Each test produces a specific observable result such as color change or fluorescence.

Step 1: Understanding Phenolphthalein assay (A).
Phenolphthalein (Kastle–Meyer test) is a presumptive test for blood. It works when reduced phenolphthalein is oxidized in the presence of hydrogen peroxide, catalyzed by heme, producing a pink color.
Thus, it is catalyzed by heme with hydrogen peroxide → A $\rightarrow$ II.

Step 2: Understanding Benzidine assay (B).
Benzidine test produces a blue to dark blue color when oxidized in presence of blood (heme acts as catalyst).
Thus, B $\rightarrow$ IV.

Step 3: Understanding Fluorescein assay (C).
Fluorescein reacts in the presence of blood and hydrogen peroxide to produce a yellowish-green fluorescence under suitable light conditions.
Thus, C $\rightarrow$ I.

Step 4: Understanding Hemochromagen crystal assay (D).
This is a confirmatory test where characteristic hemochromogen crystals are formed. These are heme derivatives where ferrous iron binds with nitrogenous bases.
Thus, D $\rightarrow$ III.

Step 5: Forming correct combination.
\[ A-II,\quad B-IV,\quad C-I,\quad D-III \] Final Conclusion:
Hence, the correct answer is option (3).