Determination of carbonyl compounds in waters using triazine-based hydrazine reagents and liquid chromatography

Abstract

Triazine-based hydrazine reagents have been developed and applied for the determination of aldehydes in waters. N-Methyl-4-N′,N′-dimethylamino-6-(4 ′-methoxy-1′-naphthyl)-1,3,5-triazine-2-hydrazine (MDMNTH) and 4-N,N-dimethylamino-6-(4′-methoxy-1′-naphthyl)-1,3,5- triazine-2-hydrazine (DMNTH) react with these carbonyl compounds with very high yields under the formation of the respective hydrazones, which are separated by reversed-phase liquid chromatography with binary gradients of acetonitrile and water. Organic modifiers are added to obtain improved peak shapes. UV/vis as well as fluorescence detection has been applied successfully to quantify the hydrazones. The derivatization of aqueous solutions of the aldehydes has been optimized. Limits of detection are in the range between 0.1 μM and 1.0 μM depending on the analyte and the reagent used for derivatization. Although calibration via external standards is possible for higher analyte concentrations, best results are obtained by calibration via the derivatization reaction. Compared to the US EPA method 8315A, the newly developed method is characterized by very easy sample preparation, lower limits of detection without enrichment and excellent reproducibility with an average RSD of 1.5% with DMNTH as reagent and 3.5% with MDMNTH as reagent for a formaldehyde concentration of 1.0 ×10⁻⁵ mol L⁻¹. Aldehyde-spiked mineral water samples were analyzed successfully with the new method.