**2. Materials and Methods**

#### *2.1. Chemicals and Reagents*

Seventeen standard analytes of PAHs, namely, naphthalene, pyrene, fluorene, chrysene, benzo(k)fluoranthene, benzo(g, h, i) perylene, acenaphthylene, dibenzo(a, h)anthracene, acenaphthene, benzo(a)pyrene, phenanthrene, indeno(1, 2, 3-cd)pyrene, benzo(a)anthracene, fluoranthene, benzo(b)fluoranthene, anthracene and pyrene butyric acid, were purchased from Dr. Ehrenstorfer GmbH (Augsbury, Germany). Peroxidase-labelled goat anti-mouse immunoglobulins (HRP-IgG), OVA, serum-free cell freezing medium, Freund's complete adjuvant (FCA), BSA, hypoxanthine-aminopterin-thymidine (HAT), Freund's incomplete adjuvant (FIA) and PEG1450 were bought from Sigma (St. Louis, MO, USA). All other chemicals and organic solvents used were obtained from reagent grade or better.
