Search

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 %., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The applicability of front-face excitation-emission fluorescence spectroscopy to compare grape water extracts of two consecutive sampling dates, corresponding with two maturation stages, and subjected to full irrigation and non-irrigation, was carried out. The decomposition of the obtained three way grape samples was initially analyzed by means of parallel factor analysis (PARAFAC). A tentative identification of fluorophores was done by matching PARAFAC score values with HPLC measurements. It was found that the first PARAFAC component was highly correlated with the sum of concentrations of catechin and epicatechin. The decomposition of the three way fluorescence data by linear discriminant analysis (LDA)-PARAFAC and LDA-unfolding partial least squares (U-PLS) allowed to discriminate between the first and the second maturation stage. The incorporation of an additional mode to the data, achieved by a diethyl ether extraction, giving rise to a four-way excitation-emission-solvent-samples data set, allowed to differentiate between irrigated and non-irrigated samples with the same assayed algorithms. As far as we know, the use of four-way data arrays for classification issues has been reported for the first time., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Phenanthrene is the most released polycyclic aromatic hydrocarbon into the environment by anthropogenic action. Because of the absorption and biotransformation pathways, this compound is metabolized and the most abundant metabolites are hydroxylated derivatives, such as 1-, 2-, 3-, 4- and 9-hydroxyphenanthrene, which are excreted through biological fluids, included mammals milk. For the resolution and quantitation of co-eluted analytes, elution time-emission fluorescence matrices were analysed with different second-order calibration algorithms: n-way and unfolded partial least squares, both coupled with residual bilinearization (N-PLS/RBL and U-PLS/RBL), and multivariate curve resolution-alternative least squares (MCR-ALS). Once optimized the chromatographic parameters, in isocratic mode, the elution time was of 5.5 min. The second-order data were obtained exciting at 250 nm, with an emission range from 330 to 430 nm, each 1 nm, and elution time from 0 to 5.5 min each 5.4 s. The ranges for the second-order multivariate methods in validation samples were from 1.0 to 9.0 ng mL -1 for 1-, 2-, 3- and 4-hydroxyphenanthrene, and from 5.0 to 45.0 ng mL -1 for 9-hydroxyphenanthrene. Root mean square errors of prediction between 0.45 and 1.82 ng mL -1 (relative errors of prediction 7-22%) were obtained. The optimized procedures were applied in the analysis of human breast milk and in whole and semi-skimmed commercial cow milk. N-PLS/RBL and U-PLS/RBL algorithms show satisfactory results for the five metabolites with recoveries ranging between 82% and 115%., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Within olive oils, extra virgin olive oil is the highest quality and, in consequence, the most expensive one. Because of that, it is common that some merchants attempt to take economic advantage by mixing it up with other less expensive oils, like olive oil or olive pomace oil. In consequence, the characterization and authentication of extra virgin olive oils is a subject of great interest, both for industry and consumers. This paper reports the potential of front-face total fluorescence spectroscopy combined with second-order chemometric methods for the detection of extra virgin olive oils adulteration with other olive oils. Excitation-emission matrices (EEMs) of extra virgin olive oils and extra virgin olive oils adulterated with olive oils or with olive pomace oils were recorded using front-face fluorescence spectroscopy. The full information content in these fluorescence images was analyzed with the aid of unsupervised parallel factor analysis (PARAFAC), PARAFAC supervised by linear discriminant analysis (LDA-PARAFAC), and discriminant unfolded partial least-squares (DA-UPLS). The discriminant ability of LDA-PARAFAC was studied through the tridimensional plots of the canonical vectors, defining a surface separating the established categories. For DA-UPLS, the discriminant ability was established through the bidimensional plots of predicted values of calibration and validation samples, in order to assign each sample to a given class. The models demonstrated the possibility of detecting adulterations of extra virgin olive oils with percentages of around 15% and 3% of olive and olive pomace oils, respectively. Also, UPLS regression was used to quantify the adulteration level of extra virgin olive oils with olive oils or with olive pomace oils., (Copyright © 2017 Elsevier B.V. All rights reserved.)

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., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Pteridinic derivatives are important biomolecules considered as biomarkers for several diseases, especially in cancer and infectious pathologies. A new fluorimetric-HPLC method for the analysis of nine pteridines in human serum has been reported. Two analytical columns composed by C18 porous and fused core particles were assayed and the results compared. Fused core particle column allows us adequate separation, in only one run and in 15 min. Acid precipitation step of the proteins and clean-up process with an Isolute ENV+ (hydroxylated polystyrene-divinylbenzene copolymer) cartridge of the serum samples have been optimized. Analytes were determined by fluorimetric detection, exciting at 272 nm and measuring the fluorescence emission at 410 nm for isoxanthopterin, at 465 nm for xanthopterin, and at 445 nm for the analysis of the other pteridines. Detection limits between 0.07 and 0.61 ng mL(-1) were calculated according to Clayton criterium. Intraday precision varied from 1.2 to 5.3 and interday precision between 1.2 and 7.4, both expressed as RSD (%). External standard and standard addition calibrations were compared in the analysis of serum samples. The pteridine amounts in serum (expressed as ng mL(-1) ± confidence interval) were 3.69 ± 1.78; 1.35 ± 0.24; 0.46 ± 0.14; 0.54 ± 0.24; 0.84 ± 0.55; 2.10 ± 0.51 and 0.23 ± 0.11 for XAN, NEO, MON, ISO, BIO and 6HMPT, respectively, using the external standard method. Comparable results were obtained by the standard addition method. It is noticeable that 7BIO was not detected in the healthy serum samples analyzed., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Pteridines are important biomarkers metabolites related to several biochemical pathways such as activation of the cell-mediated immune system, biosynthesis of neurotransmitters, etc. The level of pteridinic compounds in urine is considered as an important clinic criterion. In this work, a new liquid chromatography-mass spectrometry (LC-MS) method is proposed to determine several pteridinic biomarkers in urine samples using 6-methylpterin as internal standard (I.S.). Matrix effect was evaluated and several dilutions of urine were tested in order to study the evolution of signal suppression. Sample preparation was limited to 10-fold dilution of the filtered urine followed by injection onto a reversed-phase column. The signal was recorded in selected ion monitoring mode. The lowest limit of detection was found for pterin (values ranged from 1.70 to 3.88 ng mL(-1)) whereas the highest limit was for xanthopterin (values ranged from 10.5 to 49.9 ng mL(-1)) for healthy volunteers between 17 and 51 years old., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The aim of this paper is to study the applicability of second-order multivariate methods in the simultaneous determination of two therapeutic drugs in human urine samples. The studied drugs, irinotecan and thalidomide, are used in the treatment of malignant tumours. Irinotecan (CPT-11) is used to treat colon cancer; recent studies have shown the benefits of using thalidomide in combination with CPT-11 in the treatment of this disease. CPT-11 is highly fluorescent, but the native fluorescence of thalidomide is very weak. The second-order methods assayed were parallel factor analysis (PARAFAC), unfolded partial least-squares (U-PLS) and multidimensional partial least-squares (N-PLS), both combined with the residual bilinearization procedure (RBL). The excitation-emission matrices (EEMs) of the samples were recorded as analytical signal. The accuracy and precision of the algorithms were evaluated through the root mean square error of prediction (RMSEP) and the elliptical joint confidence region test (EJCR), obtaining better results with PARAFAC, which was successfully applied to the determination of thalidomide and CPT-11 in human urine samples, after a previous liquid-liquid extraction with chloroform., (Copyright © 2011 Elsevier B.V. All rights reserved.)

It has been carried out the determination of trans-resveratrol and trans-piceid in red wine samples by using room temperature synchronous fluorescence, sensitized through their retention on nylon membranes, in front-face mode. These compounds are weakly fluorescent in solution but their retention allows using the native fluorescence of these compounds as analytical signal, due to the increase in the medium rigidity. To determine these compounds in red wine, a previous liquid-liquid extraction is necessary and in the case of trans-resveratrol it is also necessary a previous cleanup stage using C18 cartridges. Diethylether and ethyl acetate are the selected extractant solvents for trans-resvertarol and trans-piceid, respectively. The retention on nylon membranes was carried out by immersion of the membranes in solutions of these compounds. Variables involved in the retention and measurement processes were optimized, and the analytical figures of merit were obtained under optimal conditions. Ethanol:water 10:90 v:v and ethyl acetate were the solvents used for the retention of trans-resveratrol and trans-piceid, respectively and, for each case a immersion time of 300 and 600s was selected. Satisfactory linear relation between fluorescence intensity and concentration was found in the intervals 0.040 and 0.242mgL(-1) of trans-resvertarol and 0.009 and 0.288mgL(-1) of trans-piceid. Concentration of 1.08±0.21mgL(-1) for trans-resveratrol and 1.49±0.36mgL(-1) for trans-piceid were found in a wine sample obtained from a pool of commercial red wines., (Copyright © 2010 Elsevier B.V. All rights reserved.)

In this work four spectrofluorimetric methods for the determination of irinotecan (CPT-11) in human urine and pharmaceuticals have been developed. Initially, the fluorescent characteristics of irinotecan (CPT-11) have been studied in both acidic and basic media. Later, the fluorescence emission generated by the oxidation of CPT-11 with several agents was studied. A quenching of fluorescence could be observed in the presence of Ce(IV) and I(2)/I(-). Also, the reaction between several divalent and trivalent metal ions with CPT-11 was studied, and one method in presence of Fe(3+) was developed since it was the only metal ion that changes the fluorescence of the analyte. The proposed methods present limit of detection comprises between 0.46 and 2.57ngmL(-1). The spectrofluorimetric methods were applied to human urine. No pre-treatment of the sample was necessary, only a dilution 1:20 with water was made. No interference of the matrix was observed in the conditions used. Recoveries were comprises between 100.0 and 104.3%. Also, pharmaceuticals preparations were analyzed with recoveries between 106.7 and 119.7%. The proposed spectrofluorimetric methods were validated by RP-HPLC, obtaining that the oxidation with iodine is the best method to analyze urine samples, while than, the fluorimetric method developed at acidic pH value is the best for the analysis of pharmaceuticals.

The reactions of 4-chloro-7-nitrobenzofurazan (NBD-Cl) with glyphosate (GLY) and with its main metabolite, aminomethylphosphonic acid (AMPA), have been studied. The resolution of binary mixtures of glyphosate and aminomethylphosphonic acid has been accomplished by partial least squares (PLS) multivariate calibration. The method of determination is based on the fluorescence emission of the derivatives formed in presence of NBD-Cl at 90 degrees C, in methanol and in basic medium. The dynamic ranges of the methods were comprised between 10 and 150mugl(-1) for GLY and between 10 and 200mugl(-1) for AMPA, being the detection limits 2 and 5.4mugl(-1) for GLY and AMPA, respectively. The total luminiscence information of the derivatives has been used to optimize the spectral data set to perform the calibration, by analysis of the three-dimensional excitation-emission matrices. A comparison between the predictive ability of the multivariate calibration method, partial least squares type 1 (PLS-1), on two spectral data sets, emission and synchronous spectra, has been performed. The PLS-1 method, applied to the emission spectra, has been selected as optimum. The proposed method has been applied to the simultaneous determination of GLY and AMPA in river water. For concentrations ranging from 100 to 600mugl(-1) of each compound in the samples, analytical recoveries range from 83 to 94% for GLY and from 104 to 120% for AMPA.

Leucovorin (LV) and methotrexate (MTX) were determined in human blood serum samples by using a model based in the net analytical signal concept. The calibration method used is a variation of the original hybrid linear analysis (HLA) method, developed by Goicoechea and Olivieri (HLA/GO). The calibration set was composed by nine serum samples with different amounts of LV and MTX in the range of 0-10 mugml(-1). The selection of the optimum wavelength range involved the calculation of the net analyte signal regression plot for each test sample, in conjunction with the calculation of the minimum error indicator. Relative errors of prediction (REP, %) of 3.0 and 5.3% were calculated for LV and MTX, respectively. Only two factors were necessary to optimize the proposed HLA/GO model. Sensitivity, selectivity, analytical sensitivity and limit of detection of the proposed procedure were calculated. Detection limits of 0.34 and 0.93 mugml(-1) for LV and MTX were determined. The proposed model was tested in the analysis of serum samples, without previous separation steps, obtaining recovery values between 96 and 99%, and between 92 and 103% for LV and MTX, respectively.

In this study a kinetic fluorimetric method for the determination of folinic acid (leucovorin, LV) in human urine has been developed. The fluorescence emission generated by the oxidation reaction between LV and potassium permanganate in alkaline medium has been monitored at 360nm (excitation wavelength 290nm). The effect of instrumental and experimental variables on the reaction was investigated and a 0.17M sodium hydroxide, 3.3x10(-5)M KMnO(4) concentration and a temperature of 70 degrees C were selected for the reaction. The concentration range has been optimized between 10 and 700ngml(-1) of LV. The correlation coefficient was 0.9989. The sensitivity of the proposed method is 9.5ngml(-1) (expressed as limit of detection in accordance with the Clayton criterion). The determination time per sample is smaller than 200s. The proposed kinetic fluorimetric method has been applied to the direct determination of this compound in human urine. Recovery values from urine samples, containing LV, range from 82 to 110% (mean 96%).

The resolution of binary mixtures of nalidixic acid (NA) and 7-hydroxymethylnalidixic acid (OH-NA) has been accomplished by partial least squares (PLS) and principal component regression (PCR) multivariate calibration. The method of determination is based on the fluorescence emission of these compounds in the presence of gamma-cyclodextrin (gamma-CD). The formation of the inclusion compounds gives rise to an increase of the fluorescence emission compared to aqueous solution. The total luminescence information of the compounds has been used to optimize the spectral data set to perform the calibration. A comparison between the predictive ability of three multivariate calibration methods, PLS-1, PLS-2 and PCR, on three spectral data sets, excitation, emission and synchronous spectra has been performed. The PLS-1 method, applied to the emission spectra, has been selected as optimum. The proposed method has been applied to the simultaneous determination of NA and OH-NA in urine. Recovery values from urine samples containing (NA) and (OH-NA) range from 91 to 103% (mean 97%), and from 92 to 105% (mean 99%), respectively.

The simultaneous determination of salicylic acid and diflunisal in human serum has been accomplished by synchronous fluorimetry, in combination with partial least-squares multivariate calibration. The total luminescence information of the analytes has been used to optimize the spectral data set for the calibration, by analysis of the three-dimensional excitation-emission matrices. The synchronous spectrum, maintaining a constant difference of Deltalambda = 128 nm between the emission and excitation wavelengths, has been selected as optimum to perform the determination. The method is based on the fluorescence of these compounds in chloroform containing 1% (v/v) acetic acid. Serum samples are treated with trichloroacetic acid to remove the proteins, and both analytes are extracted into chloroform-1% (v/v) acetic acid prior to the determination. For concentrations ranging from 60-240 mug ml(-1) of each drug, analytical recoveries range from 96% to 103% for salicylic acid and from 97% to 105% for diflunisal.