Correlation studies of anodic peak potentials and ionization potentials for polycyclic aromatic hydrocarbons

Area of Science:

• Electrochemistry
• Chemical Carcinogenesis
• Molecular Toxicology

Background:

• One-electron oxidation of polycyclic aromatic hydrocarbons (PAH) is a key pathway for forming ultimate carcinogens.
• Ionization potential (IP) is critical for predicting PAH susceptibility to one-electron oxidation.
• Accurate IP determination is essential for understanding PAH carcinogenicity.

Purpose of the Study:

• To develop a general, simple, and accurate technique for measuring the ionization potential (IP) of polycyclic aromatic hydrocarbons (PAH).
• To correlate electrochemical measurements with IP values for a large set of PAH.
• To establish predictive models for PAH bioactivation based on IP.

Main Methods:

• Cyclic voltammetry was used to measure anodic peak potentials (Eap) for 90 PAH under irreversible oxidation conditions.
• Least-squares regression analysis was employed to correlate Eap with known IP values.
• Further studies under reversible voltammetric conditions determined formal oxidation potentials (Eo) and electron transfer numbers (n).

Main Results:

• A regression equation (IP = 1.70Eap + 5.29) was derived for calculating IP from Eap with high accuracy.
• Substituted PAH, specifically those with methyl groups, showed a distinct correlation (IP = 1.65Eap + 5.27).
• The calculated IP values demonstrated superior correlation compared to existing tabulated data.

Conclusions:

• The developed electrochemical method provides a reliable and efficient way to determine PAH ionization potentials.
• This method facilitates the prediction of metabolic activation pathways for carcinogenic PAH.
• The findings contribute to a better understanding of the molecular mechanisms underlying PAH-induced cancer.