Determination of ammonia and aliphatic amines in environmental aqueous samples utilizing pre-column derivatization to their phenylthioureas and high performance liquid chromatography

Abstract

Pre-column conversion of ammonia and a number of aliphatic amines into phenylthiourea or its derivatives by reaction with phenyl isothiocyanate, followed by HPLC, has been used for their determination in environmental waters. Optimum conversion was found when the reaction was carried out in sodium hydrogencarbonatecarbonate medium at 40 °C for 15 min. Well separated peaks were obtained on a C 18 column with an acetonitrile-water gradient (1 ml min 21 ) of 30% acetonitrile for an initial 5 min which was increased linearly to 100% over 15 min and then maintained isocratic for 5 min, the acetonitrile ratio finally being returned to 30% in 5 min. The derivatized analytes were subjected to off-line solid phase extraction on C 18 sorbent. A linear calibration graph was obtained for 0.01-10 mg l 21 analytes with a correlation coefficient of 0.9954 for ammonia and in the range 0.9982-0.9996 for amines. The limit of detection for ammonia was 0.2 mg l 21 and for amines in the range 0.3-0.6 mg l 21 . The method was applied to tap, underground, river and aquarium waters, the recovery being in the range 97-106% (RSD 1.8-4.5%). Many of the samples were found to contain more than the permissible limit of ammonia. Phenyl isothiocyanate is stable for long periods in aqueous medium over wide ranges of pH and temperature, and the resulting phenylthioureas have adequate retention on C 18 sorbent and strong UV absorption, making this reagent suitable for the determination of amines in water.

Liquid chromatographic determination of aliphatic amines in water using solid support assisted derivatization with 9-fluorenylmethyl chloroformate

“…The highest value corresponded to n-pentylamine, which is most probably due to the presence of one of the peaks produced by the reagent close to peak of the FMOC-n-pentylamine derivative. The values obtained indicated that the sensitivity of the proposed procedure is comparable (and sometimes better) to that reported by typical LC methods using derivatization followed by extraction/solvent evaporation operations [2,3]. The sensitivity is also better than that achieved by the solid-phase assisted derivatization method with the UV reagent DNB (the LODs obtained with the present procedure are of about one order of magnitude lower) [12].…”

“…In such a way, the quantification of aliphatic amines within the range 0.05 1.0mgL 1 is possible with satisfactory accuracy and reproducibility. This concentration range is adequate for monitoring aliphatic amines in tap and river water (the method can be adapted to the analysis of highly polluted samples by reducing the volume of sample) [2,3].…”

Solid‐phase extraction and residue determination of glyphosate in apple by ion‐pairing reverse‐phase liquid chromatography with pre‐column derivatization

“…However, for LC with conventional detection systems, such as UV-Vis or fluorescence detectors, glyphosate needs to be derivatized because of the lack of chromophore or fluorophore. For these reasons, chemical derivatization or labeling becomes a necessary procedure to transform the analytes into derivatives that can be more easily isolated, separated, and detected [22]. Thus many derivatization agents have been developed for sensitive determination of glyphosate, including 4-chloro-7-nitrobenzofurazan (NBD-Cl) [23], 2,2-dihydroxy-1H-indene-1,3-(2H)-dione (Ninhydrin) [24 -26], l-fluoro-2,4-dinitrobenzene (DNP) [27], 9-fluorenylmethyl chloroformate (FMOC-Cl) [10, 28 -37], o-phthalaldehyde -mercaptoethanol (OPA -MERC) [38,39], and p-toluenesulfonyl chloride (TsCl) [9,40].…”

Rapid determination of aliphatic amines in water samples by pressure‐assisted monolithic octadecylsilica capillary electrochromatography‐mass spectrometry

“…Aliphatic amines are often determined by liquid chromatography [10]. Because they have a low absorptivity, however, their determination requires their previous derivatization which can be done even with fluorescent reagents [11].…”