Determination of ethylene oxide in mainstream cigarette smoke using hydrobromic acid derivatization and gas chromatography-mass spectrometry
Ethylene oxide is identified in the United States Food and Drug Administration (FDA) publication list of harmful and potentially harmful constituents (HPHCs) found in mainstream cigarette smoke. Most methods, directly analyze the gas phase cigarette smoke trapped into cryogenic methanol, or captured into a Tedlar bag, by gas chromatography-mass spectrometry (GC-MS) using a single quantitation ion (m/z = 44) for its determination. Direct analysis using this ion is vulnerable to matrix interferences which may not be chromatographically separated and bias yields.
In this study, ethylene oxide was determined using a hydrobromic acid (HBr) derivatization to convert ethylene oxide to 2-bromoethanol. Cigarette smoke, passed through a glass fibre filter disc (pad), was collected into cryogenic traps containing methanol. An aliquot of the trapping solution was dried with anhydrous sodium sulphate, derivatized with hydrobromic acid, and neutralized with sodium carbonate. The solution was spiked with d4-2-bromoethanol (internal standard), centrifuged, and injected onto the GC-MS using a single ion (m/z = 124) for quantitation and ion 107 as a qualifier.
Validation studies showed good calibration linearity with a regression coefficient of r2=0.999. Spike recoveries ranged from 81.1 to 94.4%. The limits of detection and quantification were 33.7 ng/cig and 112 ng/cig, respectively. Yields from Kentucky Reference 3R4F cigarette were found to be 8.37 ± 1.74 µg/cig (n=12) under the ISO smoking regimen and 26.03 ± 5.02 µg/cig (n=65) under the “Health Canada intensive” smoking regimen. These yields are less than 50% of those observed by the direct analysis of the cryogenic solution using ion 44. The selectivity of the derivatization, and ion used for quantification, provides chromatography more suitable for low yield products.