Monitoring winemaking process using tyrosine influence in the excitation-emission matrices of wine.

Wine samples collected during the winemaking process have been analyzed employing a previously optimized UHPLC-FD method, determining their biogenic amines and amino acids profile. The results obtained have been submitted to a statistical analysis from which it was extracted that the most influential analyte was tyrosine. Thanks to its fluorescence, a method for its determination by excitation-emission matrices has been proposed. The accuracy of the method has been checked by means of Elliptical Joint Confidence Region test. The winemaking process has been monitored with this method, obtaining a faster and cheaper way to follow the process.

Automated chromatographic method with fluorescent detection to determine biogenic amines and amino acids. Application to craft beer brewing process.

The combined determination of biogenic amines and amino acids is a challenge for food scientists. In this research, a new methodology for the automatic on-line precolumn derivatization and determination of 8 biogenic amines and 9 precursor amino acids by Ultra-High Performance Liquid Chromatography with fluorescent detection has been developed. The method derivatized the analytes with o-phthaldialdehyde and achieved the separation of the 17 derivatives in less than 15 min, obtaining good quality parameters (limits of detection varied between 7.00 and 210 µg L-1, and RSD intraday ranged between 1.5 and 6.0%). The optimization of the derivatization procedure has been carried out employing an experimental design and the Surface Response Methodology. The method has been validated and applied to wine and beer, obtaining good recuperation percentages (72.3-138.4%). Also, samples collected during the fermentation of a craft beer, as well as a bottled sample of the same batch, have been analyzed, to monitor the changes in the profile of biogenic amines and amino acids.

Dispersive liquid-liquid microextraction for a rapid determination of glyoxal in alcoholic beverages.

Carbonyl compounds, like glyoxal, methylglyoxal, diacetyl or pentane-2,3-dione, among others, have been widely studied. Besides its endogenous origin, they are originated from foodstuffs and are related to sensorial characteristics in products such as wine and beer. Generally, for their determination, the analytes must be derivatised to adapt them for the detection system and this step takes long time. The main aim of this research was to develop a simultaneous derivatization and extraction method which takes place in only few minutes. 3,4-diaminopyridine, as derivatizing reagent, generate a fluorescent product. This reaction is selective for glyoxal. For this new dispersive liquid-liquid microextraction (DLLME) procedure combined with chromatographic determination of glyoxal, various parameters affecting the extraction were optimized and finally, a mixture of butan-1-ol as dispersant solvent and dichloromethane as extractant solvent were selected. Its chromatographic peak appears at 2.6min. Four Spanish wines and five Spanish beers have been analysed and the results showed that the levels of glyoxal are comprised between 2.8-9.5mgL-1. The proposed DLLME method drastically reduces the reaction time from 2 or 3-20min improving the methods found in the literature. The glyoxal concentration found in the wines and beers analysed do not suppose any health risk.

Novel HPLC--Fluorescence methodology for the determination of methylglyoxal and glyoxal. Application to the analysis of monovarietal wines "Ribera del Guadiana".

The determination and quantification of α-dicarbonyl compounds, glyoxal and methylglyoxal, in "Ribera del Guadiana" monovarietal wines (Extremadura, Spain) without sample clean-up has been carried out by HPLC with spectrofluorimetric detection (307/371 nm). For this purpose, a derivatization step with the new reagent 3,4-diaminopyridine at pH 2 during 120 min at 90 °C has been included. Afterwards, the sample could be injected in the chromatographic system with no clean-up, during a total run time of 4 min. Several monovarietal wines (white, rosé and red) have been analyzed and the levels of these compounds for white wines were between 0.4-1.0 mg L(-1) glyoxal and 0.8-1.3 mg L(-1) methylglyoxal; and between 0.8-3.0 mg L(-1) and 0.5-1.8 mg L(-1) of glyoxal and methylglyoxal respectively, in red wines.

Determination of chemotherapeutic drugs in human urine by capillary electrophoresis with UV and fluorimetric detection using solid-supported liquid-liquid extraction for sample clean-up.

Capillary electrophoresis was used for the rapid determination of three chemotherapeutic drugs employed to treat colorectal cancer: irinotecan, tegafur, and leucovorin, and their main metabolites (7-ethyl-10-hydroxycamptothecin and 5-fluorouracil), in human urine samples. A phosphate buffer (pH 11.34; 20 mM) was selected as the background electrolyte. A hydrodynamic injection (9 s, 30 mbar) was applied and the separation was carried out using a separation temperature and voltage of 25°C and 25 kV, respectively. A capillary with two detection windows for serial online UV and fluorescence detection was satisfactorily employed. A solid-supported liquid-liquid extraction procedure was optimized for the clean-up of the urine samples and the extraction of the analytes. Matrix effects were assessed and signal suppression was observed for three of the analytes, thus, matrix-matched calibration was used for compensating residual matrix effects on these analytes. The proposed method allows the separation and quantification of the chemotherapeutics in less than 6 min. Detection limits range between 0.01 and 0.30 mg/L. The method was satisfactorily applied to the determination of the target compounds in human urine samples, with recoveries of 92.4-107.7%.

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

An eco-friendly strategy for the simultaneous quantification of three emerging pharmaceutical contaminants is presented. The proposed analytical method, which involves photochemically induced fluorescence matrix data combined with second-order chemometric analysis, was used for the determination of carbamazepine, ofloxacin and piroxicam in water samples of different complexity without the need of chromatographic separation. Excitation-emission photoinduced fluorescence matrices were obtained after UV irradiation, and processed with second-order algorithms. Only one of the tested algorithms was able to overcome the strong spectral overlapping among the studied pollutants and allowed their successful quantitation in very interferent media. The method sensitivity in superficial and underground water samples was enhanced by a simple solid-phase extraction with C18 membranes, which was successful for the extraction/preconcentration of the pollutants at trace levels. Detection limits in preconcentrated (1:125) real water samples ranged from 0.04 to 0.3 ng mL(-1). Relative prediction errors around 10% were achieved. The proposed strategy is significantly simpler and greener than liquid chromatography-mass spectrometry methods, without compromising the analytical quality of the results.

Evaluation of liquid chromatographic behavior of lumazinic derivatives, from α-dicarbonyl compounds, in different C18 columns: application to wine samples using a fused-core column and fluorescence detection.

Several C18 columns, packed with totally porous particles of different sizes and shell thicknesses, have been compared for simultaneous determination of α-dicarbonyl compounds, previous derivatization to lumazinic derivatives. Chromatographic conditions for the separation have been optimized for each column, and chromatographic parameters have been calculated and exhaustively compared. A core-shell C18 column provided the best results, and a HPLC method with fluorimetric detection has been proposed. The developed method has been validated in terms of linearity, precision, and sensitivity. Detection and quantification limits obtained were comprised between 0.02 and 0.30 and 0.07 and 1.0 ng mL(-1), respectively, while RSD values obtained were lower than 6% and 5% in intraday and interday repeatability studies, respectively. The method has been applied to analysis of the α-dicarbonyl compounds in different types of wines. The higher levels of the total α-dicarbonyl compounds were found in sweet wines and the lower levels in white wines.

Development of a method for the determination of advanced glycation end products precursors by liquid chromatography and its application in human urine samples.

A liquid chromatographic method with fluorimetric detection has been developed to determine the most abundant α-dicarbonyl compounds, generated as intermediates in the Maillard's reaction, previous derivatization to high fluorescent pteridinic derivatives. Hence, the biomarkers D-glucosone, 3-deoxyglucosone, glyoxal, methylglyoxal, diacetyl, 2,3-pentanedione, and phenylglyoxal were quantified using a gradient elution mode. The experimental conditions of the derivatization reaction and mobile phase composition were optimized. Linearity ranges (peak area versus α-dicarbonyl compound concentration) from 1.0 to 100.0 ng mL(-1) were obtained. Detection limits were comprised between 0.3 and 11.0 ng mL(-1). The high sensitivity of the method allows the determination of α-dicarbonyl compounds present in human urine, such as D-glucosone, 3-deoxyglucosone, glyoxal, and methylglyoxal, that are used as biomarkers, in order to investigate their roles in several diseases, with special emphasis in diabetes mellitus. With the aim of avoiding the interferences due to pteridinic compounds present in urine, a cleanup step with an ISOLUTE ENV+ cartridge was carried out. The concentrations of these urinary biomarkers have been reported as a normalized ratio to urinary creatinine, and determined in healthy and in diabetic volunteers, of different ages and sex. In all urine samples, standard addition and external calibration procedures were applied and compared.

First-order multivariate calibration applied to the simultaneous fluorometric determination of the anticancer agents CPT-11 and SN-38 in serum and urine samples.

The first-order multivariate calibration method was used for the simultaneous determination of the camptothecin derivative, CPT-11 and its main metabolite, SN-38. The method is based on the fluorescence emission of these compounds in acidic media (acetate buffer, pH 4.75) and in the presence of ethanol (50%). The experimental calibration matrix was constructed with 12 samples using a central composite design. The cross-validation method was used for selecting the optimum number of factors. The results showed that simultaneous determination could be performed in the range 0.08 - 1.50 and 0.10 - 0.40 µg mL(-1) for CPT-11 and SN-38, respectively. The method was successfully applied to the simultaneous determination of both analytes in human urine and in serum samples previously extracted with chloroform.

Spectrofluorimetric determination of SN-38, a promising new anti-tumor agent, in the presence and absence of organized media.

This study focuses on the spectrofluorimetric behavior of the camptothecin derivative 7-ethyl-10-hydroxycamptothecin (SN-38) alone and in the presence of organized media and also on its potential analytical applications. SN-38 displays native fluorescence in both lactone and carboxylate form, which has been the base for development of two spectrofluorimetric methods, one for the lactone form (acidic media) and another for the carboxylate form (basic media). In an attempt to improve the understanding of SN-38, its interaction with several cyclodextrins and surfactants has been studied using spectrofluorimetry. Consequently, the optimal working conditions for the determination of SN-38 have been established in both the presence and the absence of organized media. The proposed methods were applied to human urine, using liquid-liquid extraction for clean-up of the samples, with satisfactory recoveries. No interference of the urine matrix was observed.

Fluorescent determination of Hg2+ in water and fish samples using a chemodosimeter based in a Rhodamine 6G derivative and a portable fiber-optic spectrofluorimeter.

A fluorimetric chemodosimeter (FC1), based on a Rhodamine 6G derivative, is proposed for the recognition of Hg(2+) ions in water and fish samples. The reagent shows a highly selective and sensitive reaction with Hg(2+), giving rise to strong fluorescence emission at 555 nm. The obvious color change of the solution from colorless to pink upon the addition of Hg(2+) demonstrates that FC1 can be used for "naked-eye" detection of Hg(2+) in water effluents. The fluorescence intensity is proportional to the amount of Hg(2+) at ng mL(-1) levels, and it is capable of distinguishing between safe and toxic levels of inorganic mercury in drinking water and fish samples. The procedure has been implemented in a portable instrument composed of a 515 nm light-emitting diode (LED) excitation source, two fiber optics, and a charge-coupled device (CCD) camera as detector, connected to a portable computer for data acquisition and analysis, intended for in situ determination of mercury, offering a viable alternative to a conventional spectrofluorimeter. The proposed method has been applied to different water and fish samples with satisfactory results.

Simultaneous fluorometric determination of chlorophylls a and B and pheophytins a and B in olive oil by partial least-squares calibration.

The resolution of quaternary mixtures of chlorophylls a and b and pheophytins a and b has been accomplished by partial least-squares (PLS) multivariate calibration, applied to the fluorescence signals of these pigments. The total luminescence information of the compounds has been used to optimize the spectral data set to perform the calibration. After preliminary studies, a method is described in acetone media, to avoid emulsions with the olive oil samples. Different scanning paths have been selected for each method. For the simultaneous determination of the pigments in olive oil samples, a comparative study of the results found by using excitation, emission, and synchronous spectral data, as analytical signal, was performed. The excitation spectra were selected as the better analytical signals for the determination of the pigments in olive oil samples. The optimum wavelength range to record the excitation spectra (lambda(em) = 662 nm) was selected to minimize the contribution of pheophytin a and to maximize the contribution of the other pigments, which are the minor constituents in olive oil. Determination of these pigments in olive oil samples was effected from the excitation spectra of dissolutions o suitable aliquots in acetone. Recovery values from olive oil, spiked with chlorophylls a and b and pheophytins a and b, were in the ranges of 70-112, 71-111, 76-105, and 82-109%, respectively.