Determination of Dibenzacridines in the Particulate Phase of Cigarette Smoke

This study attempted to resolve a controversy related to the presence of dibenz[a,j]acridine and dibenz[a,h]acridine in the particulate phase of cigarette smoke. Smoking was performed using FTC conditions (35 mL puff volume, 2 sec. puff, 1 min. interval) on a Borgwaldt RM 20/CS smoking machine. The particulate phase of forty cigarettes was collected on 92 mm Cambridge filter pads. Pads were combined to analyze the particulate phase of the mainstream smoke from between 120 and 320 cigarettes. In an initial scheme of analysis, the pads were extracted with an acidic aqueous solution. This aqueous solution was then washed with CH₂Cl₂ and the organic phase discarded. The aqueous solution was then changed to basic and extracted with CH₂Cl₂, which was concentrated and analyzed via GC/MS. The dibenzacridine could not be detected utilizing this scheme, even when the pads had been spiked with a few thousand nanograms of dibenzacridine. After using several other organic solvents (cyclohexane, CHCl₃, and benzene) to eliminate the possibility that the extraction efficiency of CH₂Cl₂ was poor, it was determined that dibenzacridine was being discarded with the first CH₂Cl₂ wash. A successful separation scheme was developed by extracting the smoked pad with an aqueous acidic solution, followed by extraction of the aqueous phase with CH₂Cl₂without pH change. The CH₂Cl₂ extract was concentrated under nitrogen and 1 µL injected for GC/MS analysis. Quantification was achieved by spiking the pads with dibenz[a,j]acridine-d₁₃ as an internal standard at a level equal to 1.7-2.5 ng/cig. The limit of detection for this technique was approximately 0.5 ng/cig. The chromatographic separation was performed with a 30 m BPX-5 column (0.25 mm i.d., 0.25 µm film thickness). Mass spectral data were acquired in selected ion monitoring (SIM) mode with m/z = 279 for the two dibenzacridine isomers and m/z = 292 for the deuterated internal standard. Three commercial cigarettes were analyzed: two commercial Full Flavor cigarettes, one commercial Light cigarette, and a 1R4F reference cigarette. Neither dibenzacridine isomer was detected in any of the samples analyzed.