Preconcentration and dansylation of aliphatic amines using C18 solid-phase packings. Application to the screening analysis in environmental water samples

Precolumn preconcentration and derivatization on solid sorbents (Bond Elut C18 solid-phase extraction cartridges) of low-molecular-mass aliphatic amines in water samples have been performed using dansyl chloride (Dns-Cl) as derivatization reagent. Conditions for analyte preconcentration and derivatization such as volume sample, reagent concentration, time, pH and temperature reaction were optimised. On the basis of these studies a rapid and sensitive method for screening of aliphatic amines in waters is presented. Up to volumes of 5 ml, samples are drawn through the sorbent, the analytes retained are dansylated at basic pH, at 100 degrees C for 10 min or 85 degrees C for 15 min. The derivatized analytes are desorbed with 0.5 ml of acetonitrile. Twenty microl of the collected extracts are chromatographed in a Hypersyl ODS C18 column using an acetonitrile-imidazole (pH 7) gradient for elution. Seven amines and ammonium were separated within 9 min. The Dns derivatives were monitored at 333 nm with UV detection and at lambda(excitation) = 350 nm and lambda(emission) = 530 nm with fluorescence detection. The different signals are compared. Dynamic ranges from 10 to 250 microg/l and limits of detection at the microgram-per-litre level and relative standard deviations from 2 to 15% were obtained for all the amines. The total analysis time (sample treatment plus chromatography) was less than 25 min. The method was applied to determination and screening analysis of these analytes in real environmental water samples.