Determination of aliphatic amines in water by liquid chromatography using solid-phase extraction cartridges for preconcentration and derivatization

Abstract

Bond Elut C₁₈ solid-phase extraction cartridges were used for preconcentration and pre-column derivatization with 3,5-dinitrobenzoyl chloride (DNB) of aliphatic amines in water. Conditions for analyte preconcentration and derivatization (including the volume of sample, concentration of reagent, time of reaction and pH) were investigated, using ethylamine, isopropylamine and dimethylamine as model compounds. On the basis of these studies, a rapid and sensitive method for the determination of aliphatic amines in water is presented. The analytes are retained and purified on the cartridges and then derivatized and desorbed by drawing in succession the DNB solution and acetonitrile. The collected extracts are subsequently chromatographed in a Hypersil ODS C₁₈ column using acetonitrile–water for elution. The DNB derivatives are monitored at 230 nm. The method provides satisfactory reproducibility and linearity within the 0.050–1.0 mg l⁻¹ concentration interval, the limits of detection being 2–5 µg l⁻¹. Analyte recoveries were in the 70–102% range, whereas the conversion yields compared with those observed for the solution derivatization were in the 79–107% range. The total analysis time (sample treatment plus chromatography) was about 15 min. The method was applied to the determination of ethylamine, isopropylamine and dimethylamine in tap and river waters.