Analysis of selected carbonyl compounds in e-aerosols and e-liquids using pentafluorobenzyl hydroxylamine derivatization and gas chromatography-mass spectrometry
An improved gas chromatography-mass spectrometry (GC-MS) method using o-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride (PFBHA) derivatization has been developed for the analysis of carbonyl compounds in e-aerosols and e-liquids. In addition to formaldehyde, acetaldehyde, acetone, propionaldehyde, acrolein, methyl ethyl ketone (MEK), butyraldehyde, and crotonaldehyde, this method has also been validated for the determination of glycoaldehyde (a hydroxycarbonyl), dicarbonyls (glyoxal, methylglyoxl, 2,3-butanedione), and methyl vinyl ketone (MVK).
For e-cigarette aerosols, carbonyls were collected by passing the aerosol through a 44 mm glass fiber filter pad into a cryogenic trap (≤ 70 °C). The pad was extracted with the trapping solution. 1 mL of the extract was diluted with water and derivatized with PFBHA at room temperature for 24 hours. Three solvents were evaluated for trapping efficiency: methanol, isopropanol (IPA), and acetonitrile. All three demonstrated excellent trapping efficiency with no impact on the derivatization. However, significant amounts of acetone and MEK were found in methanol and IPA making these solvents unsuitable for this application. The PFBHA derivatives were then extracted into toluene and analysed by GC-MS using selected ion monitoring (SIM) mode.
For e-liquids, a 0.5 g sample was diluted with water and derivatized with PFBHA using the same process as e-aerosols. However, for some flavoured e-liquids, up to 20 times more PFBHA was required to complete the derivatization of the unsaturated carbonyls and 2,3-butanedione (diacetyl). In order to ensure a sufficient amount of PFBHA had been added, fortified matrix test samples had to be prepared.
This method exhibited good linearity (R2>0.99) and specificity. The accuracy and precision of the method was evaluated using fortified commercial e-liquids and e-aerosols. For all investigated carbonyl compounds, recoveries ranged from 82 to 117% with precision between 2 and 16%. Most of the target compounds could be quantified to levels below 0.1 µg/g for e-liquids, and 1.0 µg/collection for e-aerosols.