Determination of aromatic amines by solid-phase microextraction and gas chromatography–mass spectrometry in water samples
Introduction
Aromatic amines, such as aniline and its substituted derivatives, are generally dangerous because of their toxicity and carcinogenicity 1, 2or else they can be converted into toxic N-nitroso compounds through reactions with nitrosylating agents in the environment [3]. These contaminants may be released as chemical residues of dyestuffs, cosmetics, medicines and rubber manufacture 3, 4, 5and also as by-products of energy technologies such as coal-conversion waste processing [1]. Chlorinated anilines such as p-chloroaniline and 3,4-dichloroaniline were also found as degradation products and intermediates of various phenylurea and phenylcarbamate pesticides 1, 3. In view of the importance of these compounds, a rapid and sensitive method of analysis is needed to detect them in the environment.
Aromatic amines have already been analysed in environmental water samples using a variety of analytical techniques such as gas chromatography (GC) coupled with different detectors 3, 6, 7, 8, high-performance liquid chromatography (HPLC) 10, 11, capillary zone electrophoresis (CZE) [12]and ultraviolet spectrophotometry [13]. GC–MS has been recognised as the method of choice in a wide series of environmental analyses, due to its superiority in selectivity and sensitivity 14, 15. However, in the case of polar compounds, such as aromatic amines 3, 7, 16, a derivatization step is often required to improve the gas chromatographic properties; other problems stem from the extraction of polar compounds from water samples.
The purpose of this study was to optimise an analytical method for the GC–MS analysis of some aromatic amines in water samples, achieving free amine detection without chemical derivatization and using solid-phase microextraction (SPME) to reduce the sample preparation time and increase the extraction efficiency.
SPME is a fast, simple, solvent-free extraction technique that can be easily automated, reduces analyte loss during extraction and requires only small water samples 8, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28. Organic pollutants are extracted by the stationary phase from an aqueous or gaseous matrix until equilibrium is achieved. More details about this technique are given in Section 2.
Parameters for development of the extractive method, such as linearity, sensitivity, equilibration time profile, precision, pH and salt effects, were investigated. The aniline derivatives analysed, presented in Fig. 1, are o-toluidine, p-chloroaniline, 2,4-dichloroaniline, 2,5-dichloroaniline, 3,4-dichloroaniline and 3,5-dichloroaniline. To our knowledge, the SPME method has been applied to this class of pollutants only in a few cases 8, 9.
Section snippets
Materials
Standard solutions of o-toluidine, p-chloroaniline, 2,4-dichloroaniline, 2,5-dichloroaniline, 3,4-dichloroaniline and 3,5-dichloroaniline were purchased from Aldrich (Steiheim, Germany), with purities >98%. The SPME holders for manual sampling and the coating fibers were supplied by Supelco (Bellefonte, PA, USA). Groundwater for real sample analysis was collected by USSL 67 (Garbagnate, Milan, Italy) from the Limbiate area, north of Milan, Italy.
Instrumental analysis
GC–MS analysis was carried out using a Hewlett
Results
Standard solutions of the aromatic amines in methanol were used in scan mode to obtain the mass spectra and to set up the chromatographic conditions. Fig. 2 shows the total ion GC–MS chromatogram of pure water samples spiked with standard solutions of the aromatic amines. The two isomers, 2,4- and 2,5-dichloroaniline, coelute as one peak, with the column and the chromatographic conditions employed. Since each isomer contributes equally to the peak area, as demonstrated by preliminary separate
Conclusions
The analytical method optimised in this study, based on SPME combined with GC–MS, for the detection of some dangerous environmental pollutants, such as the aromatic amines, proved to be simple, rapid, precise and sensitive.
It detects these polar compounds even in trace amounts, without derivatization, in water samples. The analytical method is applicable to real environmental samples with matrix effects.
In view of the interest in this class of pollutants and the satisfying results obtained with
Acknowledgements
Financial support for this work was provided by the Commission of the European Communities (Project ENV4-CT95-0020). E.F. is the recipient of a fellowship from Fondazione Lombardia per l'Ambiente, Milan, Italy. L.M. is the recipient of a fellowship from Banca Commerciale Italiana. Thanks to Prof. G. Gini, Politecnico of Milan (Italy), for the use of HazardExpert 2.0. We are grateful to USSL 67 (Garbagnate, Milan, Italy) for providing groundwater samples and to Supelco for technical support.
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