Determination of Hemin using a Parallel Catalytic Reduction Wave of its Protoporphyrin IX Ring

Abstract

Hemin, iron (III) protoporphyrin IX chloride, in NH₃‐NH₄Cl buffer solution of pH 9.5 produces an insensitive reduction wave at about −0.70 V (vs. saturated calomel reference electrode, SCE) by using single sweep polarography. Adding oxidant K₂S₂O₈ to the solution, hemin reduction wave is catalyzed, yielding a parallel catalytic wave. The catalytic current is 20 times of hemin original reduction current. The derivative peak height is linearly proportional to the hemin concentration in the range of 7.5×10⁻⁸ to 4.5×10⁻⁶ mol/l, the detection limit is 5.0×10⁻⁸ mol/l. Serum albumin, common amino acids, and metal ions have no interference with the hemin determination. The proposed method has been applied to the determination of hemin content in oral liquid samples with satisfactory results. The parallel catalytic wave is attributed to the catalytic reduction of porphyrin ring of hemin at the dropping mercury electrode. The new method could be useful in biochemical, clinical, and pharmaceutical analysis.

Keywords:

• Hemin
• potassium persulfate
• parallel catalytic wave
• single sweep polarography

The authors acknowledge the financial support from the Natural Science Foundation of Hubei Province, China (2005 ABA 001) and to the Natural Science Foundation of South‐Central University for Nationalities, Wuhan, China (YZY 06011).