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.

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.

Phenylalanine Photoinduced Fluorescence and Characterization of the Photoproducts by LC-MS.

Phenylalanine (Phe) is a direct precursor of tyrosine and several neurotransmitters. The accumulation of Phe in the brain generates serious and not recoverable pathologies in children. Early detection in newborns is fundamental to apply the appropriate therapy and avoid irreversible health problems.

Phenanthrene metabolites determination in human breast and cow milk by combining elution time-emission fluorescence data with multiway calibration.

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).

HPLC-fast scanning fluorimetric detection determination of risk exposure to polycyclic aromatics hydrocarbons biomarkers in human urine.

Aim: An HPLC method for the determination of 2-hydroxyfluorene (2-OHF), various hydroxyphenanthrene metabolites (1-, 2-, 3-, 4- and 9-hydroxyphenanthrene, OHPhs), 1-hydroxypyrene (1-OHPy) and 3-hydroxybenzo[a]pyrene (3-OHB[a]Py) in human urine, has been developed using fast scanning fluorimetric detection and gradient elution mode.

Materials & Methods: All reagents were of analytical grade. Standard solutions were prepared separately, by exact weighing or dilution with ultrapure acetonitrile, and were stored at 4 ºC in darkness.

HPLC determination of serum pteridine pattern as biomarkers.

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.

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.

A simple HPLC-ESI-MS method for the direct determination of ten pteridinic biomarkers in human urine.

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.

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.

Enhanced MCR-ALS modeling of HPLC with fast scan fluorimetric detection second-order data for quantitation of metabolic disorder marker pteridines in urine.

This work presents the development of a liquid chromatographic method based on modeling entire fast scan fluorimetric detection second-order data with the multivariate curve resolution alternating least squares algorithm, for the simultaneous determination of five marker pteridines in urine samples. The modeling strategy involves the building of a single MCR-ALS model composed of matrices augmented in the spectral mode, i.e.

Separation and determination of 11 marker pteridines in human urine by liquid chromatography and fluorimetric detection.

A simple liquid chromatographic method has been developed to achieve the complete separation and determination of a wide range of pteridinic compounds and creatinine (CREA) in urine samples, in just one run. The influences of mobile phase composition and buffer pH have been studied. The optimized mobile phase was composed of a Tris-HCl buffer (15 mmol/L) at pH 6.

Determination of marker pteridines in urine by HPLC with fluorimetric detection and second-order multivariate calibration using MCR-ALS.

A liquid chromatographic method has been developed, in combination with the multivariate curve resolution-alternating least squares algorithm (MCR-ALS), for the simultaneous determination of marker pteridines in urine samples. A central composite design has been applied to optimize the factors influencing the separation (buffer concentration, buffer pH, flow rate, oven temperature, mobile-phase composition). A set of 15 calibration samples were randomly prepared, in a concentration range of 0.

Determination of marker pteridins and biopterin reduced forms, tetrahydrobiopterin and dihydrobiopterin, in human urine, using a post-column photoinduced fluorescence liquid chromatographic derivatization method.

A liquid chromatographic method for the simultaneous analysis of marker pteridins and biopterin reduced forms, in urine samples is proposed. A Zorbax Eclipse XDB-C18 column was used for the chromatographic separation, using a 98/2 (v/v), citrate buffer (pH 5.5)-acetonitrile mobile phase, in isocratic mode.

Analysis of antibiotics in fish samples.

The use of antibiotics in food-producing animals has generated considerable interest because the widespread administration of these drugs may lead to the development of resistant human pathogens. A large increase in the demand for seafood products has occurred in the last century. This has led to a concomitant increase in high-intensity aquaculture methods, characterized by high stock density and volume, and the heavy use of formulated feeds containing antibiotics, among other substances.

Second-order multivariate calibration procedures applied to high-performance liquid chromatography coupled to fast-scanning fluorescence detection for the determination of fluoroquinolones.

Different second-order multivariate calibration algorithms, namely parallel factor analysis (PARAFAC), N-dimensional partial least-squares (N-PLS) and multivariate curve resolution-alternating least-squares (MCR-ALS) have been compared for the analysis of four fluoroquinolones in aqueous solutions, including some human urine samples (additional four fluoroquinolones were simultaneously determined by univariate calibration). Data were measured in a short time with a chromatographic system operating in the isocratic mode. The detection system consisted of a fast-scanning spectrofluorimeter, which allows one to obtain second-order data matrices containing the fluorescence intensity as a function of retention time and emission wavelength.

Determination of fluoroquinolones in urine and serum by using high performance liquid chromatography and multiemission scan fluorimetric detection.

A high performance liquid chromatography (HPLC) method has been developed for the simultaneous determination of four fluoroquinolones. The studied compounds have been enoxacin (ENO), norfloxacin (NOR), ofloxacin (OFLO) and enrofloxacin (ENRO). An isocratic elution method, using a mixture of tetrahydrofuran (8%) and phosphate buffer (pH 3.

Strategies for solving matrix effects in the analysis of sulfathiazole in honey samples using three-way photochemically induced fluorescence data.

A widely employed compound for honey treatment, sulfathiazole (ST), was determined in commercial honey samples, employing a combination of photochemically induced fluorescence excitation-emission matrices (EEMs) and chemometric processing of the recorded second-order data. Parallel Factor Analysis (PARAFAC) and Self-Weighted Alternating Trilinear Decomposition (SWATLD) methods were used for calibration. An appropriately designed calibration with a set of standards composed of 18 samples, coupled to the use of the second-order advantage offered by the applied chemometric techniques, allowed quantitation of sulfathiazole in spiked commercial honey samples.

Partial least squares multicomponent fluorimetric determination of fluoroquinolones in human urine samples.

Ternary mixtures of fluoroquinolones, with a 7-piperazinyl substituted group have been simultaneously determined in human urine samples by application of a multivariate calibration partial least squares (PLS) model. The calibration set was designed with 15 urine samples containing different concentrations of the three fluoroquinolones and 16 blank urine samples. The concentration range for the fluoroquinolones were up to 25ngml(-1) for norfloxacin (NOR), 80ngml(-1) for ofloxacin (OFLO) and 300ngml(-1) for enoxacin (ENO).

Determination of carbendazim, thiabendazole and fuberidazole using a net analyte signal-based method.

The net analyte signal (NAS)-based method HLA/GO, modification of the original hybrid linear analysis (HLA) method, has been used to determine carbendazim, fuberidazole and thiabendazole in water samples. This approach was used after a solid-phase extraction (SPE) step, using the native fluorescence emission spectra of real samples, previously standardized by piecewise direct standardization (PDS). The results obtained show that the modification of HLA performs in a similar way that partial least-squares method (PLS-1).

Determination of antitubercular drugs in urine and pharmaceuticals by LC using a gradient flow combined with programmed diode array photometric detection.

The simultaneous determination of the antitubercular drugs rifampicin, pyrazinamide, isoniazid and the acetylisoniazid metabolite has been accomplished by LC, using a C-18 analytical column. The assayed drugs are usually administered together in the treatment of tuberculosis. Creatinine was also included in the chromatographic determination, in order to establish the curve of excretion of the drugs in urine.

Selection of the wavelength range and spectrophotometric determination of leucovorin and methotrexate in human serum by a net analyte signal based method.

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).

Stopped-flow fluorimetric determination of amoxycillin and clavulanic acid by partial least-squares multivariate calibration.

Mixtures of amoxycillin and clavulanic acid were determined by using kinetic data in combination with partial least-squares multivariate calibration. The reaction of oxidation of these compounds with cerium(IV) in sulfuric acid medium has been monitored fluorimetrically. To follow the kinetics of the reaction, the stopped-flow mixing technique was used.

Kinetic fluorimetric study of the oxidation reaction of folinic acid (leucovorin) with potassium permanganate. Determination in human urine.

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.