Determination of free- and bound-carbonyl compounds in airborne particles by ultra-fast liquid chromatography coupled to mass spectrometry.

This study presents the development and application of a new analytical methodology for determination of free- and bound-carbonyl compounds (CC) (as the CC themselves and as the hydroxyalkylsulfonic acids - HASA, respectively) in airborne particles. Free- and bound-CC determination were done through reaction with 2,4-dinitrophenylhydrazine (2,4-DNPH) and analysis by UFLC-MS. The method was successfully validated, showing good figures for linearity (R ≥ 0.9937), sensibility (3 fg ˂ LOD ˂ 20 fg for methacrolein and heptanal, respectively) and repeatability (5.9% ˂ RSD ˂ 13%). The proposed method was successfully applied in real samples of inhalable atmospheric particulate matter (PM) and urban dust certified reference material (SRM 1649 b). The main CC determined in the SRM 1649 b was formaldehyde (75.4 μg g in the free form, and 1898 μg g in the bound form). In addition, for the bound-CC form (HASA), concentrations were determined for acetaldehyde (60.3 μg g), acetone (20.5 μg g), acrolein (9.15 μg g), propionaldehyde (17.1 μg g) and valeraldehyde (12.2 μg g). For PM samples, formaldehyde (148 μg g) and acetaldehyde (28.9 μg g) were quantified as free aldehydes and as HASA (hydroxymethanelsulfonic acid and hydroxyethanesulfonic acid were 432 μg g and 211 μg g, respectively). Other bound-CC were, on average, within 19.2 μg g (acrolein) and 62.1 μg g (valeraldehyde). For all samples, acetone, acrolein, propionaldehyde and valeraldehyde were quantified only as HASA (bound-CC). Therefore, we could identify and quantify six carbonyl compounds using the proposed method. It is worth mentioning the hydrolysis step was crucial for the correct quantification of the HASAs. This was, in turn, what enabled the quantification of a greater number of analytes in the airborne samples. Hence, this procedure was found to be comprehensive, precise, accurate and suitable to be employed for determination of free-CC and HASA (bound-CC) in atmospheric particulate samples.