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

Bond Elut C-18 solid-phase extraction cartridges were used for preconcentra tion and pre-column derivatization with 3,5-dinitrobenzoyl chloride (DNB) o f aliphatic amines in water. Conditions for analyte preconcentration and de rivatization (including the volume of sample, concentration of reagent, tim e of reaction and pH) were investigated, using ethylamine, isopropylamine a nd 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 th en derivatized and desorbed by drawing in succession the DNB solution and a cetonitrile. The collected extracts are subsequently chromatographed in a H ypersil ODS C-18 column using acetonitrile-water for elution. The DNB deriv atives are monitored at 230 nm. The method provides satisfactory reproducib ility and linearity within the 0.050-1.0 mg l(-1) concentration interval, t he limits of detection being 2-5 mug 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 wa s applied to the determination of ethylamine, isopropylamine and dimethylam ine in tap and river waters.