Y. Moliner-Martínez

Analysis of 18 perfluorinated compounds in river waters: Comparison of high performance liquid chromatography–tandem mass spectrometry, ultra-high-performance liquid chromatography–tandem mass spectrometry and capillary liquid chromatography–mass spectrometry ☆

In this work, the performance of ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and capillary liquid chromatography-mass spectrometry (CLC-MS) has been studied for the analysis of eighteen perfluorinated compounds in water samples. UHPLC-MS/MS and CLC-MS analysis were carried out using a Zorbax C-18 column (50 mm × 2.1 mm, 1.8 μm) and a Zorbax SB-C18 column (150 mm × 0.5 mm, 3.5 μm), respectively, in gradient elution mode with a mobile phase of ammonium formate and methanol. Both techniques were compared with conventional LC-MS/MS in terms of speed, sensitivity, selectivity and resolution. Water samples were extracted by solid phase extraction (SPE). Mean absolute recoveries at two concentration levels, 6 and 60 ng L⁻¹, calculated from the eighteen compounds were: 77 ± 12(s) and 82 ± 12(s), respectively. Relative standard deviation (RSD) was lower than 16% for each perfluorinated compound. The results obtained showed that UHPLC-MS/MS and CLC-MS allow the determination of perfluorinated compounds in water samples with satisfactory sensitivity and resolution and reduced analysis time. Therefore, both techniques were employed for the analysis of water samples to determine the target analytes at low concentration levels and with lower analysis times than using HPLC-MS/MS. Similar statistical values were obtained from both techniques at 95% confidence level. Several compounds have been detected, but perfluorooctanoic acid (PFOA) (171 ng L⁻¹ and 148 ng L⁻¹ by UHPLC-MS/MS and CLC-MS, respectively) showed the highest concentration.

Peptide Metal–Organic Frameworks for Enantioselective Separation of Chiral Drugs

We report the use of a chiral Cu(II) 3D metal-organic framework (MOF) based on the tripeptide Gly-l-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine. Monte Carlo simulations suggest that chiral recognition is linked to preferential binding of one of the enantiomers as a result of either stronger or additional H-bonds with the framework that lead to energetically more stable diastereomeric adducts. Solid-phase extraction of a racemic mixture by using Cu(GHG) as the extractive phase permits isolating >50% of the (+)-ephedrine enantiomer as target compound in only 4 min. To our knowledge, this represents the first example of a MOF capable of separating chiral polar drugs.

Preconcentration of emerging contaminants in environmental water samples by using silica supported Fe3O4 magnetic nanoparticles for improving mass detection in capillary liquid chromatography

A magnetic material based on Fe(3)O(4) magnetic nanoparticles incorporated in a silica matrix by using a sol-gel procedure has been used to extract and preconcentrate emerging contaminants such as acetylsalicylic acid, acetaminophen, diclofenac and ibuprofen from environmental water samples prior to the analysis with Capillary LC-MS. The use of the proposed silica supported Fe(3)O(4) magnetic nanoparticles enables surfactant free extracts for the analysis with MS detection without interferences in the ionisation step. Under the optimum conditions, we demonstrated the reusability of the magnetic sorbent material during 20 uses without loss in the extraction efficiency. In addition, no cleanup was necessary. The preconcentration factor was 100 and the detection limits were between 50 and 150 ng/L. The proposed procedure has been applied to the analysis of water samples obtaining recoveries between 80 and 110% and RSD values lower than 12%. Concentrations of the target analytes over the range 1.7 and 0.1 μg/L have been found in different water samples.

Miniaturized matrix solid phase dispersion procedure and solid phase microextraction for the analysis of organochlorinated pesticides and polybrominated diphenylethers in biota samples by gas chromatography electron capture detection

This work has developed a miniaturized method based on matrix solid phase dispersion (MSPD) using C18 as dispersant and acetonitrile-water as eluting solvent for the analysis of legislated organochlorinated pesticides (OCPs) and polybrominated diphenylethers (PBDEs) in biota samples by GC with electron capture (GC-ECD). The method has compared Florisil-acidic Silica and C18 as dispersant for samples as well as different solvents. Recovery studies showed that the combination of C18-Florisil was better when using low amount of samples (0.1 g) and with low volumes of acetonitrile-water (2.6 mL). The use of SPME for extracting the analytes from the solvent mixture before the injection resulted in detection limits between 0.3 and 7.0 microg kg(-1) (expressed as wet mass). The miniaturized procedure was easier, faster, less time consuming than the conventional procedure and reduces the amounts of sample, dispersant and solvent volume by approximately 10 times. The proposed procedure was applied to analyse several biota samples from different parts of the Comunidad Valenciana.

In-tube solid-phase microextraction coupled by in valve mode to capillary LC-DAD: Improving detectability to multiresidue organic pollutants analysis in several whole waters.

A simple and fast capillary chromatographic method has been developed to identify and quantify organic pollutants at sub-ppb levels in real water samples. The major groups of pesticides (organic halogens, organic phosphorous, and organic nitrogen compounds), some hydrocarbons (polycyclic aromatic hydrocarbons), phthalates and some phenols such as phenol and bisphenol A (endocrine disruptors) were included in this study. The procedure was based on coupling, in-tube solid-phase microextraction (IT-SPME) by using a conventional GC capillary column (95% methyl-5% phenyl substituted backbone, 80cmx0.32mm i.d., 3microm film thickness) in the injection valve to capillary liquid chromatography with diode array detection. A comparative study between the IT-SPME manifold and a column-switching device using a C(18) column (35mmx0.5mm i.d., 5microm particle size) has been performed. The IT-SPME procedure was optimal, it allows reaching limits of detection (LODs) between 0.008 and 0.2microg/L. No matrix effect was found and recoveries between 70 and 116% were obtained. The precision of the method was good, and the achieved intra- and inter-day variation coefficients were between 2 and 30%. This procedure has been applied to the screening analysis of 28 compounds in whole waters from several points of the Mediterranean coast (Valencia Community, Spain).

Magnetic In-Tube Solid Phase Microextraction

We report a new in-tube solid phase microextraction approach named magnetic in-tube solid phase microextraction, magnetic-IT-SPME. Magnetic-IT-SPME has been developed, taking advantage of magnetic microfluidic principles with the aim to improve extraction efficiency of IT-SPME systems. First, a magnetic hybrid material formed by Fe(3)O(4) nanoparticles supported on SiO(2) was synthesized and immobilized in the surface of a bared fused silica capillary column to obtain a magnetic adsorbent extraction phase. The capillary column was placed inside a magnetic coil that allowed the application of a variable magnetic field. Acetylsalicylic acid, acetaminophen, atenolol, diclofenac, and ibuprofen were tested as target analytes. The application of a controlled magnetic field resulted in quantitative extraction efficiencies of the target analytes between 70 and 100%. These results demonstrated that magnetic forces solve the low extraction efficiency (10-30%) of IT-SPME systems, which is one of their main drawbacks.

Capillary electrophoresis method for the characterization and separation of CdSe quantum dots.

This paper presents a simple and rapid methodology to separate and characterize free CdSe quantum dots (QDs) in aqueous medium by capillary electrophoresis (CE). First, we describe a controlled derivatization procedure to obtain water-soluble QDs through noncovalent interactions. This derivatization methodology was based on the formation of a complex between the QDs and several types of surfactants to enhance the hydrophilicity and stability of the CdSe QDs. The surfactants used to achieve the surface functionalization were trioctylphosphine oxide/trioctylphosphine (TOPO/TOP) and sodium dodecyl sulfate (SDS). Different CdSe QDs core sizes were synthesized as function of the nanocrystals growing time and then subjected to controlled coating. These free QDs were separated by capillary zone electrophoresis (CZE) based on the differences in the charge-to-mass ratio of the QDs-TOPO/TOP-SDS complexes, and the detection was carried out with UV-vis and laser-induced fluorescence (LIF) techniques obtaining detection limits 5 times lower with CE-LIF. Under the optimal working conditions, four different-sized QDs were successfully separated whose average sizes were 3.1, 3.6, 4.3, and 4.9 nm, and the size distribution was less than 7% for all of them [calculated from the full width at half-maximum (fwhm) of the fluorescence spectra and confirmed by high-resolution transmission electron microscopy (HTEM)]. Therefore, we were able to separate QDs that differ in only 0.5 nm in diameter and 19 nm in fluorescence emission maximum. This corresponds to the better resolution achieved in the analysis of these kinds of nanoparticles. Finally, a correlation between the migration times plus or minus peak width and the core sizes plus or minus size distribution was established.

Silica supported Fe(3)O(4) magnetic nanoparticles for magnetic solid-phase extraction and magnetic in-tube solid-phase microextraction: application to organophosphorous compounds.

This work demonstrates the application of silica supported Fe3O4 nanoparticles as sorbent phase for magnetic solid-phase extraction (MSPE) and magnetic on-line in-tube solid-phase microextraction (Magnetic-IT-SPME) combined with capillary liquid chromatography–diode array detection (CapLC-DAD) to determine organophosphorous compounds (OPs) at trace level. In MSPE, magnetism is used as separation tool while in Magnetic-IT-SPME, the application of an external magnetic field gave rise to a significant improvement of the adsorption of OPs on the sorbent phase. Extraction efficiency, analysis time, reproducibility and sensitivity have been compared. This work showed that Magnetic-IT-SPME can be extended to OPs with successful results in terms of simplicity, speed, extraction efficiency and limit of detection. Finally, wastewater samples were analysed to determine OPs at nanograms per litre.

Multiresidue analysis of organic pollutants by in-tube solid phase microextraction coupled to ultra-high performance liquid chromatography–electrospray-tandem mass spectrometry

In this work, in-tube solid phase microextraction (IT-SPME) coupling with ultra-high-pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) multiresidue analytical method has been proposed for the first time for on-line enrichment of 9 analytes included in Water Frame Directive 2000/60/EC (WFD). The device was equipped with a GC TRB-5 capillary column, used as pre-concentration loop, and two conventional six-port injection valves. Water sample and desorption solvent volumes were tested. The optimum conditions were 4mL of processed sample followed by elution with 40μL of methanol. The analytes were detected with a mass spectrometer after being ionized positively using an electrospray ionization (ESI) source. The method presents good linearity over the range assayed, 0.025-2.5μg/L for chlorpyriphos and 0.25-25μg/L for the other tested compounds and LODs between 0.025μg/L and 2.5μg/L. Enrichment factors ranged from 2.5 to 10. Intra and inter-day variation coefficients were <26 and 31.6% respectively. Once validated, the method was applied to several water samples from different sources demonstrating that it achieves the on-line enrichment of the analytes with the advantage of minimum sample manipulation, and the identification and quantification of some organic pollutants in water samples in the range of low parts-per-billion. The method provided similar analytical characteristics as those obtained in the established couple IT-SPME-Capillary Liquid Chromatography (CapLC).

Advantages of monolithic over particulate columns for multiresidue analysis of organic pollutants by in-tube solid-phase microextraction coupled to capillary liquid chromatography

The performance of a monolithic C(18) column (150 mm×0.2 mm i.d.) for multiresidue organic pollutants analysis by in-tube solid-phase microextraction (IT-SPME)-capillary liquid chromatography has been studied, and the results have been compared with those obtained using a particulate C(18) column (150 mm×0.5 mm i.d., 5 μm). Chromatographic separation has been carried out under isocratic elution conditions, and for detection and identification of the analytes a UV-diode array detector has been employed. Several compounds of different chemical structure and hydrophobicity have been used as model compounds: simazine, atrazine and terbutylazine (triazines), chlorfenvinphos and chlorpyrifos (organophosphorous), diuron and isoproturon (phenylureas), trifluralin (dinitroaniline) and di(2-ethylhexyl)phthalate. The results obtained revealed that the monolithic column was clearly advantageous in the context of multiresidue organic pollutants analysis for a number of reasons: (i) the selectivity was considerably improved, which is of particular interest for the most polar compounds triazines and phenyl ureas that could not be resolved in the particulate column, (ii) the sensitivity was enhanced, and (iii) the time required for the chromatographic separation was substantially shortened. In this study it is also proved that the mobile-phase flow rates used for separation in the capillary monolithic column are compatible with the in-valve IT-SPME methodology using extractive capillaries of dimensions similar to those used in conventional scale liquid chromatography (LC). On the basis of these results a new method is presented for the assessment of pollutants in waters, which permits the characterization of whole samples (4 mL) in less than 30 min, with limits of detection in the range of 5-50 ng/L.