Reduced solvent and reagent amounts: effect on carbonyl dinitrophenylhydrazone measurements at low concentrations

This work aims to advance towards a more affordable laboratory procedure for sample treatment to determine carbonyl compounds by derivatization with 2,4-dinitrophenylhydrazine (DNPH). The proposal is based on reducing the amount of DNPH and solvents. A simple addition of standard carbonyls in a solution containing DNPH to prepare hydrazone standards is described and evaluated. Tedious recrystallization steps are avoided. Formaldehyde, acetaldehyde, acetone, tolualdehyde and hexanal, as carbonyl models, were quantified using a DNPH concentration of 400 μg mL^-1 and 3.8 mM H₂SO₄ and by keeping for 24 hours at room temperature. Analytical coefficients of variation between 10 and 25% were found from the analysis of blanks under intermediate conditions (two different devices, very different concentrations of DNPH and analysis on two days). From these values of relative standard deviations and background levels, quantification limits were estimated between 15 and 40 ng mL^-1. The reduction of reagent amounts allows the operator to better control the background levels in the use of DNPH, as well as making the method more cost-effective and easy to use. In short, it leads to a more sustainable adaptation of the classical method. The versatility in analytical application was tested to estimate the levels of formaldehyde, acetaldehyde and acetone in very different types of environmental samples. In particular, outdoor and indoor samples were collected in filters and impregnated cartridges, respectively. Moreover, tars in 2-propanol and particulate matter from gasification processes were also tested.