Contrasting recovery patterns of 2, 4-dinitrophenylhydrazones (DNPH) derivative of carbonyls between liquid and gas phase standards using HPLC-based analysis

This study evaluates the relative recovery (RR) of five different carbonyls (CCs) (i.e., acetaldehyde, propionaldehyde, butyraldehyde, isovaleraldehyde, and valeraldehyde) following their reaction as 2, 4-dinitrophenylhydrazine (DNPH) derivatives when using gas phase and liquid phase standards. To this end, relative efficiency of CC-DNPH derivatization is compared between two liquid-phase standards (commercially available vs. lab made mixture) and between liquid and gas-phase standard. If the results are compared in terms of response factors (RF) derived for five carbonyls from all different standard phases, the recovery of gaseous CC standard was distinguished from that of liquid counterparts. The RR of the heavier carbonyls (propionaldehyde, butyraldehyde, isovaleraldehyde, and valeraldehyde) was approximately 60% low relative to their liquid counterparts; however, it was not the case for the lighter carbonyls (acetaldehyde) with the RR of ∼92%. This study thus suggests that the quantification of heavy carbonyls in ambient air, unless made by standards of the same matrix (i.e., gas phase) or compensated by the proper correction factor, may be subject to a large bias due to difference in derivatization reaction efficiency between matrix types. Hence, consideration of the matrix effect at the calibration stage is of particular importance to measure CC quantitatively.