Resolution of a multicomponent polycyclic aromatic hydrocarbon system in micellar media by linear variable angle fluorescence applying distinct chemometric techniques† J. Amador-Hernández, a A. Cladera, b J. M. Estela, b P. L. L´ opez-de-Alba a and V. Cerd` a* b a Instituto de Investigaciones Científicas, Universidad de Guanajuato, 36000 Guanajuato, Gto., Mexico b Department of Chemistry, Universitat de les Illes Balears, E-07071 Palma de Mallorca, Spain Received 3rd June 1998, Accepted 5th August 1998 The simultaneous spectrofluorimetric determination of aromatic polycyclic hydrocarbons of environmental interest, namely benzo[a]pyrene, benzo[e]pyrene, benzo[ghi]perylene, coronene, dibenzo[a,h]anthracene and indeno[1,2,3-cd]pyrene, in micellar media by using the non-ionic surfactant polyoxyethylene 10 lauryl ether (POLE) was investigated. In order to employ the highest sensitivity signals for the determination of each of the compounds in the mixture, the corresponding linear variable angle fluorescence spectra were recorded. Owing to the high spectral overlap observed, resolution of the multicomponent system was carried out by applying known algorithms such as multiple linear regression, partial least squares regression type 1 and artificial neural networks. The results obtained for both synthetic mixtures and water samples of two different origins spiked with known amounts of hydrocarbons of interest were satisfactory. Introduction Since the discovery of their carcinogenic properties, polycyclic aromatic hydrocarbons (PAHs) have become a topic of great interest and have been widely studied. 1–3 Owing to their occurrence during the incomplete combustion or pyrolysis of organic matter common in several natural or anthropogenic processes, these compounds are present in air, soil and water in different concentrations and international organizations such as the World Health Organization (WHO) and the US Environ- mental Protection Agency (EPA) have regulated the control of these compounds in the environment. Among the most commonly used instrumental techniques for the determination of these compounds are gas chromatography (GC) and high performance liquid chromatography (HPLC, 4–6 together with UV/VIS absorption spectrophotometry and spec- trofluorimetry; 3,7 however, conventional spectroscopic tech- niques require prior separation processes owing to the severe spectral interferences that occur. Synchronous fluorescence 8 has become a tool of great sensitivity and selectivity in multicomponent analysis and has been satisfactorily applied to the simultaneous determination of several PAHs. 9 Nevertheless, the high spectral overlap involving some hydrocarbons cannot be eliminated using this technique and alternatives are re- quired. Over the last few years, the introduction of computers in laboratories has allowed the automation of numerous in- strumental techniques. Thus, through the development of adequate software in fluorescence, fast and simple registration of spectra of variable angle is feasible without requiring hardware modification, increasing the possibilities of applica- tion of the former technique. 10 On the other hand, the development of software specialized for chemometric tech- niques allows the application of powerful mathematical algo- rithms to resolve complex chemical systems by using multiple analytical signals which, owing to the interferences present in the determination, deviations from linearity, noise, etc., cannot be directly resolved. 11,12 Among these algorithms are multiple linear regression (MLR), principal component regression (PCR), partial least squares regression (PLS) and artificial neural networks (ANN). 13–15 Variable angle fluorescence combined with multicomponent analysis chemometric tech- niques has allowed the development of sensitive analytical methods for the simultaneous determination of PAH mixtures with satisfactory results, without requiring prior separation processes. 16 The luminescence characteristics of various compounds change considerably in the presence of either ionic or non-ionic surfactants compared with an aqueous medium, giving rise to variations in the excitation and emisson spectra, increasing the fluorescence intensity and quenching effects, among others. 17 Through the adequate exploitation of the photophysical and/or photochemical phenomena that occur in micellar systems, the development of more sensitive and/or selective fluorimetric, phosphorimetric and chemoluminescent methods is feasible. 18 In this paper, the development of a spectroscopic method for the simultaneous determination of six PAHs of environmental interest is presented. This method is based on the linear variable angle fluorescence spectra obtained in a micellar medium with a non-ionic surfactant [polyoxyethylene 10 lauryl ether (POLE)]. The corresponding spectral interferences are resolved through the application of three different multivariate algo- rithms. Two of them (MLR and PLS) consider the linear relationship between the analytical property of interest (fluores- cence intensity) and the concentration of the analytes. The third algorithm (ANN) finds the relationship between the variables by means of training processes. This comparison was aimed at observing the predictive capacity of the methods studied in the resolution of a system with severe spectral interferences. † Presented at the VIIIth International Symposium on Luminescence Spectrometry in Biomedical and Environmental Analysis, Las Palmas de G.C., Spain, May 26–29, 1998. Analyst, 1998, 123, 2235–2241 2235