On line photochemically induced excitation-emission-kinetic four-way data. Analytical application for the determination of folic acid and its two main metabolites in serum by N-PLS/Residual Trilinearization (RTL) calibration

ALEJANDRO CESAR OLIVIERI; MUÑOZ DE LA PEÑA, ARSENIO; JIMENEZ GIRON, ANA; DURAN MERAS, ISABEL; ESPINOSA MANSILLA, ANUNCIACIÓN

Montepellier

Congreso; 11 Conferencia Internacional de Quimiometria en Quimica Analitica; 2008

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin-top:5.65pt; margin-right:0cm; margin-bottom:0cm; margin-left:0cm; margin-bottom:.0001pt; text-align:justify; mso-pagination:widow-orphan; mso-hyphenate:none; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:FR; mso-fareast-language:AR-SA;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Folate derivatives act as co-enzymes in several enzymatic reactions giving rise to methyl and formyl transfer in the biosynthesis of amino and nucleic acids. Folate deficiency may be linked to several pathological alterations such as pregnancy complications, neural tube defects and other numerous well established pathologies [1, 2]. Folic acid (FA) is administered to counteract the toxic effects of antitumoral drugs such as methotrexate [3]. Tetrahydrofolic (THF) and 5-methyl-tetrahydrofolic acid (5MTHF) are the most important FA metabolites involved in several biochemical routes in the human organism.   FA is a photosensitive compound and is degraded to various products in aqueous solution by ultraviolet and visible light and also by direct sun light. It has been demonstrated that the excited heterocyclic moiety is involved in the photochemical reaction [4]. Although the conventional way to generate fluorescent pteridin rings from tetrahydro- and dihydrofolates employed chemical oxidation [5, 6], the photoirradiation may be a more simple and efficient mode to develop a differential analytical methodology, by using chemometric tools in conjunction with kinetic spectral information. The variation of the luminescent properties of a folate derivative, monitored as its excitation-emission (EEM) fluorescent matrix during the photoirradiation process (a third-order signal), may produce a selective information for both substituted and non substituted folate.  Third-order data for several samples can be arranged into four-way arrays, which have been recently proposed for the resolution of mixtures of components in complex samples. They provide the opportunity of introducing an additional dimension to second-order data (which form three-way data sets), allowing for a theoretical increase in the predictive ability of the models. They also exploit, in some cases, the second-order advantage. As a precedent on the use of photochemically-induced four-way data arrays, Kim et al [7] described the analysis of photocatalytically enhanced fluorescence EEMs with parallel factor analysis (PARAFAC). The time-dependent photocatalytic degradation of polycyclic aromatic hydrocarbons (benzo[a]anthracene, benzo[k]fluoranthene and dibenzo[a,h]anthracene) has been employed to create an additional analytical dimension. It was demonstrated that the subsequent four-dimensional degradation-EEM data arrays had greater selectivity for each PAH than the three-dimension EEM data alone. Two recent reviews on multiway calibration [8,9] described modern advances and applications in this field, with emphasis on analytical work. Usually, the time evolution of the analytical signal (i.e., EEMs) is introduced to obtain the third dimension. A new algorithm, multi-dimensional partial least-squares (N-PLS) coupled to residual trilinearization (RTL), was recently proposed by our group, and applied to the determination of procaine and its metabolite, p-aminobenzoic acid, in equine serum, by analysing four-way data based on recording the kinetic evolution of fluorescence excitation-emission matrices  [10]. In the present work, the simultaneous determination of folic acid and its two main metabolites is proposed and applied to serum samples. The analytical performances of several multi-dimensional algorithms were compared and the best results were found with the N-PLS/RTL combination.