An optimized methodology for the determination of multiclass organic ultraviolet sunscreens and metabolites in human milk through chromatographic and chemometric resolution

Organic UV filters (UVFS) are used to mitigate the dermal effects associated with health risks from UV radiation, making them essential in personal care products. UVFS are frequently identified in environmental samples due to their high lipophilicity and persistence, underscoring the urgency of comprehensive assessments and regulatory measures aimed at safeguarding ecosystems and human health. The present study reports a multiclass analytical method for determining 16 UV sunscreens and metabolites in breast milk based on an ultrasound-assisted-dispersive liquid-liquid micro-extraction (UA-DLLME) with further chromatographic and chemometric resolution. The experimental conditions of the UA-DLLME were optimized through the implementation of the Design of Experiment tools. To model the responses, least-squares and artificial neural network methodologies were implemented. The optimal conditions were found by employing the desirability function. The samples were analyzed through reverse-phase liquid chromatographic separation, UV diode array, and fast-scanning fluorescence detection. The chromatographic analysis enabled the resolution of 16 analytes in a total time of 13.0 min. Multivariate curve resolution-alternating least-square (MCR-ALS) modelling was implemented to resolve analytes that were not fully resolved and to determine analytes that coeluted with endogenous components of the breast milk samples. An enrichment factor of 5-fold concentration was obtained with this methodology, reaching recoveries between 65 % and 105 % for 13 multiclass UV sunscreens and metabolites in breast milk samples with RSD % and REP % lower than 12 %.

Simultaneous Determination of Flavor Enhancers Inosine 5´-Monophosphate and Guanosine 5´-Monophosphate in Food Preparations by Derivative Spectrophotometry

A derivative spectrophotometry method was developed for the quantitative determination of 2 flavor enhancers, inosine 5´-monophosphate (IMP) and guanosine 5´monophosphate (GMP), in the presence of monosodium glutamate (MSG). Procedures for determining IMP and GMP singly and in binary mixtures are described. Overlapping absorption spectra of both compounds were resolved by using first-derivative spectrophotometry. By measuring the first-derivative signals of IMP and GMP at 253 and 248 nm, respectively, simultaneous determination was possible for IMP and GMP at 5–40 μg/mL, in the presence of up to 5000 μg/mL MSG. The method was satisfactorily used to determine IMP and GMP in several food preparations.

A novel analytical methodology for the determination of hydroxy polycyclic aromatic hydrocarbons in breast and cow milk samples

Hydroxy polycyclic aromatic hydrocarbons (OHPAHs) in biological fluids, such as milk, are considered as biomarkers of exposure to polycyclic aromatic hydrocarbons (PAHs) in organism. The presence of OHPAHs in milk samples indicates a potential contamination on human organisms and milk producing animals. In this way, infants can be contaminated by lactation through the consumption of milk of both, human and animal origins. In this paper, eight OHPAHs have been analyzed in commercial cow milks and in human breast milk using HPLC and fast scanning fluorimetric detection (FSFD). Extraction and cleaning procedures of OHPAHs from milk samples have been investigated, and the experimental results using two bibliographic protocols and a new proposed protocol have been compared. The new protocol using enzymatic hydrolysis, proteins precipitation and, solvent extraction using acetonitrile, was proposed as the most adequate for the determination of 2-hydroxyfluorene, 1-/9-, 2-/3- and 4-hydroxyphenanthrenes, 1-hydroxypyrene and 3-hydroxybenzo[a]pyrene. The method recoveries ranged from 80-102% and 75-91% for fresh cow milk and for human breast milk, respectively, for all components except for 3-OHBz[a] Py. Low recovery values were calculated for 3-hydroxybenzo[a]pyrene in all cases. No statistical difference in the method performance was observed between fresh cow milk and human breast milk.

Front-face fluorescence spectroscopy combined with second-order multivariate algorithms for the quantification of polyphenols in red wine samples

The potential of front-face fluorescence spectroscopy combined with second-order chemometric methods was investigated for the quantification of the main polyphenols present in wine samples. Parallel factor analysis (PARAFAC) and unfolded-partial least squares coupled to residual bilinearization (U-PLS/RBL) were assessed for the quantification of catechin, epicatechin, quercetin, resveratrol, caffeic acid, gallic acid, p-coumaric acid, and vanillic acid in red wines. Excitation-emission matrices of different red wine samples, without pretreatment, were obtained in front-face mode, recording emission between 290 and 450 nm, exciting between 240 and 290 nm, for the analysis of epicatechin, catechin, caffeic acid, gallic acid, and vanillic acid; and excitation and emission between 300-360 and 330-400nm, respectively, for the analysis of resveratrol. U-PLS/RBL algorithm provided the best results and this methodology was validated by an optimized liquid chromatographic coupled to diode array and fluorimetric detectors procedure, obtaining a very good correlation for vanillic acid, caffeic acid, epicatechin and resveratrol.

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.

Usefulness of fluorescence excitation-emission matrices in combination with PARAFAC, as fingerprints of red wines

The possibility of using front-face fluorescence spectroscopy to characterize red wines was investigated, and a tentative identification of their main fluorescent components was attempted. Fifty-seven red wine samples from different origins were included in the present study. Their fluorescence excitation-emission matrices (EEMs) were registered directly on 3-mL aliquots of untreated samples. The assayed excitation and emission ranges were 245-340 and 300-500 nm, respectively. The set of 57 EEMs was analyzed by means of parallel factor analysis (PARAFAC). Thus, the spectral excitation and emission profiles of possible "pure" fluorescence components (PARAFAC loadings) and the relative contribution of each component to the individual EEMs (PARAFAC scores) were obtained. The red wine system contained four main fluorescence components, and the excitation and emission loadings had maxima at the wavelength pairs 260/380, 275/323, 330/410, and 280/364 nm, respectively. A tentative identification of fluorophores was done by matching PARAFAC score values with HPLC measurements on the same 57 samples, as well as fluorescence measurements on pure compounds typically present in red wine. It was found that the third component was highly correlated with concentrations of catechin and epicatechin. When the PARAFAC score values were plotted against each other, they did to some extent discriminate the wines according to origin (country) and grape variety.

High-performance liquid chromatographic determination of glyoxal and methylglyoxal in urine by prederivatization to lumazinic rings using in serial fast scan fluorimetric and diode array detectors

Glyoxal and methylglyoxal are two important markers of oxidative stress and both are involved in the evaluation of several diseases. A new HPLC method for determining glyoxal and methylglyoxal in urine was developed. The method is based on the reaction of alpha-dialdehydes, glyoxal and methylglyoxal, with 5,6-diamino-2,4-hydroxypyrimidine sulfate in basic medium to form highly fluorescent lumazine derivatives. Creatinine was also included in the method even though it does not react with the reagent. The derivatives and creatinine are separated on a C(18) reversed-phase column with a mobile phase consisting of acetonitrile:citrate buffer, pH 6.0 (3:97 v/v). The flow rate was 1.0mLmin(-1) and the effluent was monitored photometrically at 250 nm for determination of creatinine and fluorimetrically at 500 nm (exciting at 330 nm) for determination of glyoxal and methylglyoxal derivatives. Recording time of the separation is less than 10 min. Determination of the analytes is performed in urine after incubation of the sample, with the reagent in alkaline medium, for 30 min at 60 degrees C. Urinary levels of glyoxal and methylglyoxal, expressed as glyoxal/creatinine and methylglyoxal/creatinine ratios, in healthy young women and men were determined. For women, values of 0.80+/-0.37 and 0.60+/-0.22 microg/mg of creatinine were found for glyoxal and methylglyoxal, respectively. For men, values of 0.63+/-0.15 and 0.49+/-0.05 microg/mg of creatinine were found for glyoxal and methylglyoxal, respectively. These results were also related to the body mass index of each individual.

Multiway Partial Least-Squares Coupled to Residual Trilinearization: A Genuine Multidimensional Tool for the Study of Third-Order Data. Simultaneous Analysis of Procaine and Its Metabolitep-Aminobenzoic Acid in Equine Serum

A new third-order multivariate calibration approach, based on the combination of multiway-partial least-squares with a separate procedure called residual trilinearization (N-PLS/RTL), is presented and applied to multicomponent analysis using third-order data. The proposed chemometric algorithm is able to predict analyte concentrations in the presence of unexpected sample components, which require strict adherence to the second-order advantage. Results for the determination of procaine and its metabolite p-aminobenzoic acid in equine serum are discussed, based on kinetic fluorescence excitation-emission four-way measurements and application of the newly developed multiway methodology. Since the analytes are also the reagent and product of the hydrolysis reaction followed by fast-scanning fluorescence spectroscopy, the classical approach based on parallel factor analysis is challenged by strong linear dependencies and multilinearity losses. In comparison, N-PLS/RTL appears an appealing genuine multiway alternative that avoids the latter complications, yielding analytical results that are statistically comparable to those rendered by related unfolded algorithms, which are also able to process four-way data. Prediction was made on validation samples with a qualitative composition similar to the calibration set and also on test samples containing unexpected equine serum components.

Comparison of different fluorimetric signals for the simultaneous multivariate determination of tocopherols in vegetable oils

This paper deals with the simultaneous determination of the quaternary mixture of tocopherols (alpha-, beta-, gamma-, and delta-T) performed using fluorimetric techniques and partial least squares (PLS-1) multivariate analysis. In this study, PLS-1 was applied to matrices made up of fluorescence excitation and emission spectra (EEM) and with fluorescence excitation, emission, and synchronous spectra (EESM) of tocopherols dissolved in hexane: diethyl ether (70:30 v/v). A calibration set of 55 samples based in a central composite plus a full factorial plus a fractionated factorial design was constructed. When synthetic samples were analyzed, recoveries around 100% were obtained and detection limits were calculated using EEM and EESM. For the analysis of the oils, the samples, diluted in hexane, were cleaned in silica cartridges and tocopherols were eluted with hexane: diethyl ether (90:10 v/v). The developed method was applied to different edible oils. The results are satisfactory for alpha-, beta-, and gamma-, but they are worse for delta-T.

Second-Order Advantage Achieved with Four-Way Fluorescence Excitation−Emission−Kinetic Data Processed by Parallel Factor Analysis and Trilinear Least-Squares. Determination of Methotrexate and Leucovorin in Human Urine

Four-way fluorescence data recorded by following the kinetic evolution of excitation-emission fluorescence matrices (EEMs) have been analyzed by parallel factor analysis and trilinear least-squares algorithms. These methodologies exploit the second-order advantage of the studied data, allowing analyte concentrations to be estimated even in the presence of an uncalibrated fluorescent background. They were applied to the simultaneous determination of the components of the anticancer combination of methotrexate and leucovorin in human urine samples. Both analytes were converted into highly fluorescent compounds by oxidation with potassium permanganate, and the kinetics of the reaction was continuously monitored by recording full EEM of the samples at different reaction times. A commercial fast scanning spectrofluorometer has been used for the first time to measure the four-way EEM kinetic data. The rapid scanning instrument allows the acquisition of a complete EEM in 12 s at a wavelength scanning speed of 24 000 nm/min. The emission spectra were recorded from 335 to 490 nm at 5-nm intervals, exciting from 255 to 315 nm at 6-nm intervals. Ten successive EEMs were measured at 72-s intervals, to follow the fluorescence kinetic evolution of the mixture components. Good recoveries were obtained in synthetic binary samples and also in spiked urine samples. The excitation, emission, and kinetic time profiles recovered by both chemometric techniques are in good agreement with experimental observations.

Simultaneous determination of pteridines in multicomponent mixtures using derivative spectrophotometry and partial least-squares calibration

Simple binary mixtures composed of very similar pteridines (neopterin and pterin) have been resolved by derivative spectrophotometry. Detection limits of 0.30 microgram ml-1 and 0.12 microgram ml-1 for pterin and neopterin, respectively, have been calculated. Also, different mixtures of pteridines considered as disease markers, such as pterin, neopterin, xanthopterin and isoxanthopterin, have been determined by using a partial least-squares (PLS-2) model. Calibration set containing 0-7 micrograms ml-1 for each component was used. The resolution of several mixtures and single determination was tested in artificial samples.

High-performance liquid chromatographic-fluorometric determination of glyoxal, methylglyoxal, and diacetyl in urine by prederivatization to pteridinic rings

A sensitive and simple liquid chromatographic method to determine glyoxal, methylglyoxal, and diacetyl is reported. The method is based on the conversion to the corresponding pteridin derivatives (pterin, 6-methylpterin, and 6,7-dimethylpterin). The proposed method using fluorometric detection has been applied to the determination of the three alpha-dicarbonyl compounds in human urine. Linearity (peak area vs concentration of alpha-dicarbonyl) was observed at least up to 43 microM. Detection limits of 32 pmol for glyoxal, 11 pmol for methylglyoxal, and 99 pmol for diacetyl were calculated (20 microliters was injected). Levels of 132 microM for glyoxal and 15 microM for methylglyoxal were determined in normal urine samples, while diacetyl was not detected.

Simultaneous fluorimetric determination of acetylsalicylic acid metabolites in urine by partial least squares multivariate calibration

A method is described for the simultaneous determination of the main urinary acetylsalicylic acid (aspirin) metabolites, salicyclic, salicyluric and gentisic acids, based on their native fluorescence. The urine was extracted into diethyl ether in acid medium, and back-extracted with glycine/sodium hydroxide buffer solution at pH 9.4. A comparative study of the results found using the excitation, the emission and the combination of the excitation plus the emission spectral data, as analytical signals, was performed. The data set, composed of the excitation plus the emission spectra, was selected as the analytical signal. The optimum wavelengths to record the excitation (lambda(em)=444 nm) and the emission spectra (lambda(ex)=323 nm) were selected to maximize the contribution from gentisic acid, which is the minor urinary metabolite. Partial least squares (PLS-1) multivariate calibration was then applied for the determination. Recovery values from urine samples spiked with salicyclic, salicyluric and gentisic acids varied from 90.1 to 97.6% (mean 93.6%), from 90.0 to 110% (mean 97.9%) and from 89.9 to 104.7% (mean 98.5%), respectively.

Simultaneous determination of flavor enhancers inosine 5'-monophosphate and guanosine 5'-monophosphate in food preparations by derivative spectrophotometry

A derivative spectrophotometric method was developed for the quantitative determination of 2 flavor enhancers, inosine 5'-monophosphate (IMP) and guanosine 5'-monophosphate (GMP), in the presence of monosodium glutamate (MSG). Procedures for determining IMP and GMP singly and in binary mixtures are described. Overlapping absorption spectra of both compounds were resolved by using first-derivative spectrophotometry. By measuring the first-derivative signals of IMP and GMP at 253 and 248 nm, respectively, simultaneous determination was possible for IMP and GMP at 5-40 micrograms/mL, in the presence of up to 5000 micrograms/mL MSG. The method was satisfactorily used to determine IMP and GMP in several food preparations.

Multicomponent determination of flavour enhancers in food preparations by partial least squares and principal component regression modelling of spectrophotometric data

Three multivariate calibration methods, partial least squares (PLS-1 and PLS-2) and principal component regression (PCR), were applied to the simultaneous determination of three flavour enhancers (inosine 5'-monophosphate, guanosine 5'-monophosphate and monosodium glutamate), in mixtures by ultraviolet/visible absorption spectrophotometry. The absorption and first- and second-derivative absorption spectra of the ternary mixtures were used to perform the optimization of the calibration matrices by the PLS and PCR methods. The results obtained by the application of the different chemometric approaches are discussed and compared. No significant advantages were found for the prior differentiation step. The proposed method was applied satisfactorily to the determination of inosine 5'-monophosphate and guanosine 5'-monophosphate in several food preparations, in the presence of monosodium glutamate.

Determination of salicylic acid and its metabolites in urine by derivative synchronous spectrofluorimetry

The simultaneous determination of salicylic acid in binary and/or ternary mixtures and its two main urinary metabolites is proposed. Mixtures of salicylic, salicyluric and gentisic acids are resolved by synchronous spectrofluorimetry, in combination with first-derivative measurements. The urine is extracted with diethyl ether in acid medium. Salicylic and salicyluric acids are re-extracted into glycine-sodium hydroxide buffer solution of pH 11.6 and determined at that pH, and salicylic and gentisic acids are re-extracted into boric acid-sodium hydroxide buffer solution of pH 8.5 and determined at pH 6.