Second-order advantage with excitation–emission photoinduced fluorimetry for the determination of the antiepileptic carbamazepine in environmental waters

Abstract

A photochemically induced fluorescence system combined with second-order chemometric analysis for the determination of the anticonvulsant carbamazepine (CBZ) is presented. CBZ is a widely used drug for the treatment of epilepsy and is included in the group of emerging contaminant present in the aquatic environment. CBZ is not fluorescent in solution but can be converted into a fluorescent compound through a photochemical reaction in a strong acid medium. The determination is carried out by measuring excitation-emission photoinduced fluorescence matrices of the products formed upon ultraviolet light irradiation in a laboratory-constructed reactor constituted by two simple 4 W germicidal tubes. Working conditions related to both the reaction medium and the photoreactor geometry are optimized by an experimental design. The developed approach enabled the determination of CBZ at trace levels without the necessity of applying separation steps, and in the presence of uncalibrated interferences which also display photoinduced fluorescence and may be potentially present in the investigated samples. Different second-order algorithms were tested and successful resolution was achieved using multivariate curve resolution-alternating least-squares (MCR-ALS). The study is employed for the discussion of the scopes and yields of each of the applied second-order chemometric tools. The quality of the proposed method is probed through the determination of the studied emerging pollutant in both environmental and drinking water samples. After a pre-concentration step on a C18 membrane using 50.0 mL of real water samples, a prediction relative error of 2% and limits of detection and quantification of 0.2 and 0.6 ng mL(-1) were respectively obtained.

Green analytical determination of emerging pollutants in environmental waters using excitation–emission photoinduced fluorescence data and multivariate calibration

“…As previously reported [15], CBZ is not fluorescent, but emits fluorescence upon UV irradiation in acid media, with excitation and emission maxima at 308 and 410 nm respectively ( Fig. 1A).…”

“…The corresponding volumes of the aqueous standard solutions of each analyte were transferred into 2.00 mL volumetric flasks and 2 mol L -1 HCl was added to the mark. These solutions were transferred to a 1.0 cm quartz cell, and irradiated during 20 min in a laboratory-constructed reactor described in a previous work [15]. Finally, solutions were cooled to 20 ºC and their EEPIFMs were recorded in the conditions described in Section 2.2.…”

“…MCR-ALS, which proved to be the best algorithm for determining CBZ in natural waters by a similar EEPIFM approach [15], was also applied. Since a significant overlapping among the studied analytes occurs in excitation and emission spectra, both augmentation modes were checked, e.g.…”

“…In the present work, three emerging pollutants, representative of different groups of therapeutic drugs, were investigated: the anticonvulsant carbamazepine (CBZ), the antibacterial fluoroquinolone ofloxacin (OFL), and the non-steroidal anti-inflammatory piroxicam (PX) (Scheme 1), because they are frequently found in environmental waters. They Recently, our research group quantified CBZ, as a single analyte, in environmental waters using the PIF signals after UV irradiation of acidic solutions in a simple laboratoryconstructed reactor [15]. The lack of selectivity was overcome by the second-order advantage of multi-way calibration [16] and pollutant was quantitated in the presence of unknown sample constituents.…”

Application Example

“…The number of components in the test samples, selected as indicated above, was also two (Figure 12.14). 11,12 Both quantitation and statistical analysis in test samples were performed, following the same procedure described above for validation samples. This behavior has been observed in other complex analytical systems.…”