Solid-phase extraction with C18 silica gel modified with 2,4-dinitrophenylhydrazine and HPLC-UV determination of benzaldehyde and furfural in beverages

Aliphatic and aromatic aldehydes and ketones are used in organic synthesis, in the production of medicines, pesticides, short-chain ketones are used as organic solvents. Carbonyl compound impurities can be present in polymeric materials, environmental objects, pharmaceuticals, food products, and wood products, and aldehydes and ketones can also be present in biological fluids. Carbonyl compounds have harmful effects on the environment and living organisms; some of them, namely, formaldehyde and acrolein, are carcinogens. Therefore, an important task is the development and improvement of methods for sample preparation and quantitative determination of carbonyls. A method of solid-phase extraction (SPE) of aromatic aldehydes, in combination with HPLC/UV determination, has been developed for the analysis of soft drinks. A SPE cartridge was filled with C18 silica gel impregnated with 2,4-dinitrophenylhydrazine (DNPH). The developed method includes the steps of sorption, derivatization, and elution of carbonyl compounds, which were carried out sequentially in dynamic mode. The following parameters were optimized: type of sorbent, mineral acid and its concentration, concentration of DNPH on the sorbent, and volume of aqueous sample. When an aqueous solution of aldehydes was passed through the SPE cartridge, aromatic aldehydes were sorbed on the sorbent and converted into DNPH-hydrazones, then the derivatives were eluted with acetonitrile and determined by HPLC/UV. The limit of detection using the 3s-criterion was 1-2 mg/L for 2-furaldehyde and benzaldehyde. 2-furaldehyde was determined in ground and instant coffee. The method of standard additions was applied to eliminate the matrix effects. The relative standard deviation did not exceed 2,5%. The advantages of the sample preparation method of aromatic aldehydes are rapidity, simplicity, small amount of initial sample, economy of toxic organic solvents, and sufficiently high selectivity of determination.