Bárbara Socas-Rodríguez

Hollow-fiber liquid-phase microextraction for the determination of natural and synthetic estrogens in milk samples

In this work, a group of nine estrogens, four of them being natural (estriol, 17β-estradiol, 17α-estradiol and estrone), four being synthetic (17α-ethynylestradiol, diethylstibestrol, dienestrol and hexestrol) and one metabolite (2-hydroxyestradiol) have been extracted and preconcentrated from milk samples with different fat content (whole, semi-skimmed and skimmed). After protein precipitation with acetonitrile containing acetic acid, evaporation of the supernatant and reconstitution of the residue in water, hollow-fiber liquid-phase microextraction (HF-LPME) using 1-octanol as extraction solvent was applied to further preconcentrate the analytes. Separation, determination and quantification were achieved by high-performance liquid chromatography coupled to a diode array detector and a fluorescence detector set in series. Deproteinization conditions, as well as parameters affecting the extraction efficiency in HF-LPME (pH of the sample, ionic strength, extraction time, stirring speed, temperature and desorption conditions) were investigated and optimized. Calibration, precision and accuracy studies were carried out to validate the methodology in different types of milk providing LODs in the low μg/L range.

Core-shell polydopamine magnetic nanoparticles as sorbent in micro-dispersive solid-phase extraction for the determination of estrogenic compounds in water samples prior to high-performance liquid chromatography-mass spectrometry analysis.

In this work, core-shell Fe3O4@poly(dopamine) magnetic nanoparticles (m-NPs) were prepared and characterized in our laboratory and applied as sorbents for the magnetic-micro solid phase extraction (m-μSPE) of twelve estrogenic compounds of interest (i.e. 17α-estradiol, 17β-estradiol, estrone, hexestrol, 17α-ethynylestradiol, diethylstibestrol, dienestrol, zearalenone, α-zearalanol, β-zearalanol, α-zearalenol and β-zearalenol) from different water samples. Separation, determination and quantification were achieved by high-performance liquid chromatography coupled to ion trap mass spectrometry with electrospray ionization. NPs@poly(dopamine) were synthesized by a chemical coprecipitation procedure and characterized by different surface characterization techniques (X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, transmission and scanning electron microscopy, infrared and Raman spectroscopy, vibrating sample magnetometry, microelectrophoresis and adsorption/desorption isotherms). Parameters affecting the extraction efficiency of m-μSPE (i.e. polymerization time, pH of the sample, extraction and elution conditions) were studied and optimized. The methodology was validated for Milli-Q, mineral, tap and wastewater using 2-methoxyestradiol as internal standard, obtaining recoveries ranging from 70 to 119% with relative standard deviation values lower than 20% and limits of quantification in the range 0.02-1.1 μg/L.

Determination of estrogens in environmental water samples using 1,3‐dipentylimidazolium hexafluorophosphate ionic liquid as extraction solvent in dispersive liquid–liquid microextraction

In this work, the potential of a symmetric dialkyl‐substituted ionic liquid (IL), 1,3‐dipenthylimidazolium hexafluorophosphate ([PPIm][PF6]), as extraction solvent in dispersive liquid–liquid microextraction (DLLME) has been studied for the analysis of a group of three natural (estriol, 17β‐estradiol, and 17α‐estradiol) and four synthetic (17α‐ethynylestradiol, diethylstibestrol, dienestrol, and hexestrol) estrogenic compounds as well as one mycotoxin with estrogenic activity (zearalenone) in different types of water samples (Milli‐Q, mineral, and wastewater). Separation, determination, and quantification were developed by HPLC‐DAD and a fluorescence detector (FD) connected in series. Factors influencing the IL‐DLLME procedure (sample pH, amount of IL, type and volume of disperser solvent, ionic strength, and assistance of vortex agitation) were investigated and optimized by means of a step‐by‐step approach. Once the optimum extraction conditions were established (10 mL of water at pH 8, 60 mg of [PPIm][PF6], 500 μL of ACN as disperser solvent and vortex agitation for 1 min), the calibration curves of the whole method (IL‐DLLME‐HPLC‐DAD/FD) were obtained and precision and accuracy were evaluated. It was demonstrated that the developed methodology was repeatable, accurate, and selective with limits of detection in the 0.30–0.57 μg/L and 13.8–37.1 μg/L range for FD and DAD, respectively. Relative recovery values were higher than 85% for the different types of water samples and the Students t test demonstrated that there were not significant differences between the added and the found concentration.

Analysis of oestrogenic compounds in dairy products by hollow-fibre liquid-phase microextraction coupled to liquid chromatography.

In this work, the potential of a hollow-fibre liquid-phase microextraction (LPME)-based method has been studied and validated for the extraction of a group of nine oestrogenic compounds four of them being natural (oestriol, 17β-oestradiol, 17α-oestradiol and oestrone), four being synthetic (17α-ethynyloestradiol, diethylstilbestrol, dienestrol and hexestrol) and one metabolite (2-hydroxyoestradiol) in different dairy products (whole and skimmed natural yogurt, a probiotic yogurt-type drink and cheese). The methodology includes a prior protein precipitation with acidified acetonitrile for all samples and an additional defatting step with n-hexane for cheese, the matrix with the highest fat content. Later separation, determination and quantification were done by high-performance liquid chromatography coupled to a diode array detector and a fluorescence detector set in series. Calibration, sensitivity, precision and accuracy of the method were carried out in the selected matrices, providing good linearity, LODs in the low μg/kg or μg/L range, good precision and appropriate accuracy.

Evaluation of two molecularly imprinted polymers for the solid-phase extraction of natural, synthetic and mycoestrogens from environmental water samples before liquid chromatography with mass spectrometry.

In this work, we have compared the selectivity of two commercial molecularly imprinted polymers (AFFINIMIP®SPE Estrogens and AFFINIMIP®SPE Zearalenone) for the extraction of 12 estrogenic compounds of interest (i.e. 17α-estradiol, 17β-estradiol, estrone, hexestrol, 17α-ethynylestradiol, diethylstibestrol, dienestrol, zearalenone, α-zearalanol, β-zearalanol, α-zearalenol and β-zearalenol) from different water samples. High-performance liquid chromatography coupled with ion trap mass spectrometry with electrospray ionization was used for their determination. Results showed that although both molecularly imprinted polymeric cartridges were specifically designed for different groups of analytes (natural estrogens like estradiol in the first case and zearalenone derivatives in the second) they nearly have the same extraction performance (with recovery values in the range 65-101%) for the same analytes in Milli-Q water because of the cross-reactivity of the polymer. However, when more complex water samples were analyzed, it was clear that the behavior was different and that the AFFINIMIP®SPE Estrogens showed less cross-reactivity than the other cartridge. Validation of the proposed methodology with both cartridges revealed that the extraction was reproducible and that the final limits of detection of the proposed method were in the low ng/L range.

Core-shell poly(dopamine) magnetic nanoparticles for the extraction of estrogenic mycotoxins from milk and yogurt prior to LC-MS analysis.

In this work, core-shell poly(dopamine) magnetic nanoparticles synthesized in our laboratory have been applied as dispersive solid-phase extraction (dSPE) sorbent for the extraction of a group of six mycotoxins of interest including zearalenone, α-zearalanol, β-zearalanol, α-zearalenol, β-zearalenol and zearalanone, from complex matrices such as milk (whole and skimmed cow milk and semi-skimmed goat milk) and yogurt (an unsweetened natural yogurt) prior to their LC-MS analysis. 17β-estradiol-D5 was used as internal standard. The procedure includes a deproteinization step prior to the extraction procedure. Matrix-matched calibration and a recovery study were carried out in the selected matrices, providing good linearity, relative recovery values in the range 70-120% with RSDs lower than 16% and LODs between 0.21 and 4.77μg/L for milk samples and between 0.29 and 4.54μg/kg for yogurt samples.

Determination of phthalic acid esters in water samples using core-shell poly(dopamine) magnetic nanoparticles and gas chromatography tandem mass spectrometry

In this work, the first application of core-shell poly(dopamine) magnetic nanoparticles as sorbent for the extraction of a group of eleven phthalic acid esters of interest (i.e. diethyl phthalate (DEP), dipropyl phthalate (DPP), dibutyl phthalate (DBP), bis-isopentyl phthalate (DIPP), bis-n-pentyl phthalate (DNPP), benzylbutyl phthalate (BBP), dicyclohexyl phthalate (DCHP), di-(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP)) and one adipate (bis (2-ethylhexyl) adipate, DEHA) from different water samples (Milli-Q, mineral, tap, pond and waste water) is proposed. Analysis were carried out by gas chromatography triple quadrupole tandem mass spectrometry. Parameters that affect the extraction performance were optimized following a step by step approach, being the optimum conditions the extraction of water at pH 6, with 60mg of sorbent and the elution with 6mL of dichloromethane. The methodology was validated for the five selected water samples using DBP-d4 as internal standard. Determination coefficients of matrix-matched calibration curves were above 0.9904 in all cases while relative recovery values ranged between 71 and 120%, with relative standard deviation values below 19%. The limits of quantification of the method ranged between 9 and 20ng/L. Matrix effects were found for most analytes and water samples. Real water samples were also analyzed, finding DEP and DBP at concentrations below 4.20 and 1.23μg/L, respectively, in mineral, tap and waste water. DCHP, DEHP and BBP were also found in some of the samples at concentrations below the LOQs of the method.

Dissipation kinetics of organophosphorus pesticides in milled toasted maize and wheat flour (gofio) during storage

The dissipation/degradation of the pesticides dimethoate, terbufos, disulfoton, and pirimiphos-methyl were evaluated in milled toasted maize and wheat flour (gofio) during three months of storage. Their dissipation kinetics and residual levels were determined, as well as their possible decomposition into some of their main transformation products (disulfoton sulfoxide, terbufos sulfone and disulfoton sulfone). For this purpose, pesticide-free milled toasted maize and wheat samples were spiked with the pesticides, and they were then stored in the darkness at ambient temperature in a closed container to simulate current storage conditions of such packed food. A multiresidue analysis based on the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method was performed for the simultaneous determination of these pesticides and their metabolites. After three months of storage, the dissipation of residues ranged between 34% (pirimiphos-methyl) and 86% (disulfoton) for maize gofio and between 69% (terbufos) and 92% (disulfoton and pirimiphos-methyl) for wheat gofio. The results demonstrated that the degradation was slower in gofio than in wheat gofio and that none of the selected metabolites were detected in any of the samples. Dissipation curves of all studied pesticides fitted to a first-order decay curve in both types of cereals.

Recent applications of nanomaterials in capillary electrophoresis

Nanomaterials have found an important place in Analytical Chemistry and, in particular, in Separation Science. Among them, metal‐organic frameworks, magnetic and non‐magnetic nanoparticles, carbon nanotubes and graphene, as well as their combinations, are the most important nanomaterials that have been used up to now. Concerning capillary electromigration techniques, these nanomaterials have also been used as both pseudostationary phases in electrokinetic chromatography (EKC) and as stationary phases in microchip capillary electrophoresis (CE) and capillary electrochromatography (CEC), as a result of their interesting and particular properties. This review article pretends to provide a general and critical revision of the most recent applications of nanomaterials in this field (period 2010–2017).

Multiresidue determination of estrogens in different dairy products by ultra-high-performance liquid chromatography triple quadrupole mass spectrometry

In this work, a simple and fast methodology has been validated and applied for the analysis of a group of 22 estrogenic compounds including eight phytoestrogens (i.e. daidzein, enterodiol, glycitein, enterolactone, genistein, formononetin, prunetin, biochanin A), six mycotoxins (β-zearalanol, β-zearalenol, α-zearalanol, α-zearalenol, zearalanone, zearalenone) as well as four synthetic (i.e. ethynylestradiol, diethylstilbestrol, dienestrol, hexestrol) and four natural estrogens (i.e. estriol, 17β-estradiol, 17α-estradiol, estrone) in different dairy products. Extraction was carried out using the QuEChERS method while separation, determination and quantification of the target analytes were achieved by ultra-high-performance liquid chromatography coupled to triple quadrupole mass spectrometry with an electrospray ionization interface. The methodology was validated for four dairy product samples with relevant interest for the population including skimmed and whole cheese and goat and cow kefir, using 17β-estradiol-2,4,16,16,17-d5 as internal standard for natural and synthetic estrogens and β-zeralanol-10,10,11,12,12-d5 as internal standard for mycotoxins and phytoestrogens. Recovery ranged from 70 to 119% for the four types of matrices with RSD values lower than 14% and the limits of quantification of the method achieved were in the range 0.025-2.50μg/kg for all samples. Finally, the analysis of commercially available products was carried out finding the presence of daidzein, glycitein enterolactone and genistein in some of the studied samples.