Figure 1.

Selected ion current profile chromatograms of phenol derivatives in cigarette and waterpipe smoke. According to the National Institute of Standards and Technology library, the numbers are assigned to (a) phenol and cresol derivatives, namely, 1: 2-ethylphenol, 2: 4-ethylphenol, 3: 2,5-dimethylphenol, 4: 3,5-dimethylphenol, 5: 2,6-dimethylphenol, and 6: 2,3-dimethylphenol and (b) catechol, resorcinol, and hydroquinone derivatives, namely, 1: 4-methylcatechol, 2: 3-methylcatechol, 3: 2-methylresorcinol, and 4: 2-methylhydroquinone.