Surfactant-Alumina-Coated Magnetic Nanoparticles as an Efficient Aldehydes Adsorbent Prior Their Determination by HPLC

Separation and determination of trace levels of low-molecular weight aldehydes are very important from water suppliers’ point of view. Modified magnetic nanoparticles can be used for this propose. Alumina-coated magnetic nanoparticles modified with sodium dodecyl sulfate (SDS/Al₂O₃/Fe₃O₄) are used for extraction of formaldehyde (FA) and acetaldehyde (AA) from drinking water samples. In this manner, the aldehydes were converted to their corresponding hydrazones by the reaction with 2,4-dinitrophenylhydrazine (DNPH). After preconcentration, the HPLC technique was used for the determination of the aldehydes and the results were compared with the commercial C₁₈ solid-phase extraction (SPE) columns. The results showed that the extraction with SDS/Al₂O₃/Fe₃O₄ is more efficient and faster than the commercial columns. A very good repeatability (RSD was 3.3 and 2.4% for FA and AA, respectively, n = 7, C = 50 ppb) was obtained. Linear regression analysis indicated that the responses for two investigated compounds were linear over about two orders of magnitude above the LOD (LOD was 3.6 ppb for FA and 3.2 ppb for AA), with correlation coefficients >0.9990. Determination of FA and AA in tap water and various brands of bottled waters were carried out using the modified nanoparticles. Based on the obtained results, the aldehyde content of the commercial bottled waters was particularly apparent after exposure to direct sunlight.