Carbon nanocones/disks as new coating for solid-phase microextraction

In this article, the potential of carbon nanocones/disks as coating for solid-phase microextraction has been evaluated for the first time. The nanostructures were immobilized on a stainless steel needle by means of an organic binder. The fiber coating obtained was ca. 50 μm of thickness and 35 mm in length. The evaluation of the sorbent capacity was carried out through the determination of toluene, ethylbenzene, xylene isomers and styrene in water samples following the headspace sampling modality (15 min, 30 °C). The fiber was then transferred to a 10 mL vial which was sealed and heated at 110 °C for 15 min in the headspace module of the instrument to achieve the thermal desorption of the analytes. Then 2.5 mL of the headspace generated were injected in the gas chromatograph-mass spectrometer for analytes separation and quantitation. The detection and quantitation limits obtained for 10 mL of sample were 0.15 and 0.5 ng mL⁻¹ (0.6 and 2 ng mL⁻¹ for toluene). The optimized procedure was applied to the determination of the selected volatile compounds in waters collected from different locations. The recovery values obtained (average recovery ca. 92%) demonstrated the usefulness of the carbon nanocones/disks as sorbent material in solid-phase microextraction.     

Selective trace enrichment of acidic pharmaceuticals in real water and sediment samples based on solid-phase extraction using multi-templates molecularly imprinted polymers

A novel multi-templates molecularly imprinted polymer (MIP), using acidic pharmaceuticals mixture (ibuprofen (IBP), naproxen (NPX), ketoprofen (KEP), diclofenac (DFC), and clofibric acid (CA)) as the template, was prepared as solid-phase extraction (SPE) material for the quantitative enrichment of acidic pharmaceuticals in environmental samples and off-line coupled with liquid chromatography–mass spectrometry (LC/MS/MS). Washing solvent was optimized in terms of kind and volume for removing the matrix constituents nonspecifically adsorbed on the MIP. When 1 L of water sample spiked at 1 μg/L was loaded onto the cartridge, the binding capacity of the MIP cartridge were 48.7 μg/g for KEP, 60.7 μg/g for NPX, 52 μg/g for CA, 61.3 μg/g for DFC and 60.7 μg/g for IBP, respectively, which are higher than those of the commercial single template MIP in organic medium (e.g. toluene) reported in the literature. Recoveries of the five acidic pharmaceuticals extracted from 1 L of real water samples such as lake water and wastewater spiked at 1 μg/L were more than 95%. The recoveries of acidic pharmaceuticals extracted from 10-g sediment sample spiked at the 10 ng/g level were in the range of 77.4–90.6%. To demonstrate the potential of the MIP obtained, a comparison with commercial C18 SPE cartridge was performed. Molecularly imprinted solid-phase extraction (MISPE) cartridge showed higher recoveries than commercial C18 SPE cartridge for acidic pharmaceuticals. These results showed the suitability of the MISPE method for the selective extraction of a group of structurally related compounds such as acidic pharmaceuticals.     

Evaluation of single-walled carbon nanohorns as sorbent in dispersive micro solid-phase extraction

A new dispersive micro solid-phase extraction method which uses single-walled carbon nanohorns (SWNHs) as sorbent is proposed. The procedure combines the excellent sorbent properties of the nanoparticles with the efficiency of the dispersion of the material in the sample matrix. Under these conditions, the interaction with the analytes is maximized. The determination of polycyclic aromatic hydrocarbons was selected as model analytical problem. Two dispersion strategies were evaluated, being the functionalization via microwave irradiation better than the use of a surfactant. The extraction was accomplished by adding 1 mL of oxidized SWHNs (o-SWNHs) dispersion to 10 mL of water sample. After extraction, the mixture was passed through a disposable Nylon filter were the nanoparticles enriched with the PAHs were retained. The elution was carried out with 100 μL of hexane. The limits of detection achieved were between 30 and 60 ng L⁻¹ with a precision (as repeatability) better than 12.5%. The recoveries obtained for the analytes in three different water samples were acceptable in all instances. The performance of o-SWNHs was favourably compared with that provided by carboxylated single-walled carbon nanotubes and thermally treated carbon nanocones.     

Synthetic approaches to parabens molecularly imprinted polymers and their applications to the solid-phase extraction of river water samples

In this paper we describe the synthesis, characterisation and use of two distinct molecularly imprinted polymers (MIPs) prepared using esters of p-hydroxybenzoic acid (parabens) as templates: one MIP was synthesised by precipitation polymerisation using a semi-covalent molecularly imprinting strategy with methyl paraben as the template/target (MIP 1); the second MIP was prepared in monolithic form through a conventional non-covalent molecular imprinting strategy, with butyl paraben as the template (MIP 2). MIP 1 recognized methyl paraben, showed cross-selectivity for other parabens analytes used in the study and higher affinity towards these compounds than did a non-imprinted control polymer. Similarly, MIP 2 demonstrated higher affinity towards paraben analytes than a non-imprinted control polymer.For the analysis of environmental water samples, a solid-phase extraction (SPE) protocol was developed using MIP 2 as sorbent, and results were compared to a SPE using a commercial sorbent (Oasis HLB). With MIP 2 as sorbent and butyl paraben as target, when percolating 500 mL of river water spiked at 1 μg L⁻¹ through the SPE cartridge, and using 1 mL of isopropanol as cleaning solvent, a higher recovery of butyl 4-hydroxybenzoate (butyl paraben) and a cleaner chromatogram where achievable when using the MIP compared to the commercial sorbent.     

Determination of 16 polycyclic aromatic hydrocarbons in environmental water samples by solid-phase extraction using multi-walled carbon nanotubes as adsorbent coupled with gas chromatography–mass spectrometry

A solid-phase extraction (SPE) using multi-walled carbon nanotubes (MWCNTs) as adsorbent coupled with gas chromatography–mass spectrometry (GC–MS) method was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. Several condition parameters, such as extraction adsorbents, elution solvents and volumes, and sample loading flow rate and volume were optimized to obtain high SPE recoveries and extraction efficiency. 150 mg MWCNTs as sorbent presented high extraction efficiency of 16 PAHs due to the large specific surface area and high adsorption capacity of MWCNTs compared with the commercial C18 column (250 mg/2 mL). The calibration curves of 16 PAHs extracted were linear in the range of 20–5000 ng L⁻¹, with the correlation coefficients (r²) between 0.9848 and 0.9991. The method attained good precisions (relative standard deviation, RSD) from 1.2% to 12.1% for standard PAHs aqueous solutions; method recoveries ranged in 76.0–125.5%, 74.5–127.0%, and 70.0–122.0% for real spiked samples from river water, tap water and seawater, respectively. Limits of detection (LODs, S/N = 3) of the method were determined from 2.0 to 8.5 ng L⁻¹. The optimized method was successfully applied to the determination of 16 PAHs in real environmental water samples.     

Development and optimization of a method for the analysis of phenols and chlorophenols from aqueous samples by gas chromatography-mass spectrometry, after solid-phase extraction and trimethylsilylation

A 3-step analytical procedure was developed and optimized for the simultaneous determination of 6 phenols (phenol, o-, m-, p-cresol, catechol and resorcinol) and 19 chlorophenols (all mono-, di-, tri-, and tetrachlorophenol isomers and pentachlorophenol) from environmental water samples. The analytical scheme consists of (1) solid-phase extraction (SPE) carried out on hypercrosslinked styrene-divinylbenzene (Isolute ENV+) cartridge; (2) derivatization with trimethylsilyl-N,N-dimethylcarbamate (TMSDMC); (3) analysis of the derivatives with capillary gas chromatography-mass spectrometry, in the selective ion monitoring mode. Ethyl acetate, ethyl acetate/acetic acid (5 v/v%) mixture, dichloromethane and acetonitrile were compared as to their ability to elute the phenols and chlorophenols from the ENV + sorbent in the smallest solvent volume possible. The optimized extraction step uses a minimal amount of organic solvent (4 mL ethyl acetate). Derivatization of the phenols and chlorophenols with TMSDMC was studied with respect to conversion, reagent excess, medium, temperature and the stability of the trimethylsilyl derivatives. If the reagent is applied in sufficient excess, the reaction takes place instantaneously at room temperature, and the derivatives remain stable for 24 h, making the procedure simple, fast and convenient. The overall method gave detection limits of 0.05-100 ng/L for all compounds except resorcinol which could not be retained on the SPE cartridge. The complete optimized analytical scheme was applied to ground water and river water samples collected in Hungary.     

Solid-phase extraction followed by dispersive liquid–liquid microextraction for the sensitive determination of selected fungicides in wine

A novel approach for the determination of seven fungicides (metalaxyl-M, penconazole, folpet, diniconazole, propiconazole, difenoconazole and azoxystrobin) in wine samples is presented. Analytes were extracted from the matrix and transferred to a small volume of a high density, water insoluble solvent using solid-phase extraction (SPE) followed by dispersive liquid–liquid microextraction (DLLME). Variables affecting the performance of both steps were thoroughly investigated (metalaxyl-M was not included in some optimisation studies) and their effects on the selectivity and efficiency of the whole sample preparation process are discussed. Under optimised conditions, 20 mL of wine were first concentrated using a reversed-phase sorbent and then target compounds were eluted with 1 mL of acetone. This extract was mixed with 0.1 mL of 1,1,1-trichloroethane (CH₃CCl₃) and the blend added to 10 mL of ultrapure water. After centrifugation, an aliquot (1–2 μL) of the settled organic phase was analyzed by gas chromatography (GC) with electron capture (ECD) and mass spectrometry (MS) detection. The method provided enrichment factors (EFs) around 200 times and an improved selectivity in comparison to use of SPE as single sample preparation technique. Moreover, the yield of the global process was similar for red and white wine samples and the achieved limits of quantification (LOQs) (from 30 to 120 ng L⁻¹ and from 40 to 250 ng L⁻¹, for GC–ECD and GC–MS, respectively) were low enough for the determination of target species in commercial wines. Among compounds considered in this work, metalaxyl-M and azoxystrobin were found in several wines at concentrations from 0.8 to 32 ng mL⁻¹.     

Determination of organic priority pollutants and emerging compounds in wastewater and snow samples using multiresidue protocols on the basis of microextraction by packed sorbents coupled to large volume injection gas chromatography–mass spectrometry analysis

This paper describes the development and validation of a new procedure for the simultaneous determination of 41 multi-class priority and emerging organic pollutants in water samples using microextraction by packed sorbent (MEPS) followed by large volume injection–gas chromatography–mass spectrometry (LVI–GC–MS). Apart from method parameter optimization the influence of humic acids as matrix components on the extraction efficiency of MEPS procedure was also evaluated. The list of target compounds includes polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalate esters (PEs), nonylphenols (NPs), bisphenol A (BPA) and selected steroid hormones. The performance of the new at-line microextraction-LVI–GC–MS protocol was compared to standard solid-phase extraction (SPE) and LVI–GC–MS analysis. LODs for 100 mL samples (SPE) ranged from 0.2 to 736 ng L⁻¹ were obtained. LODs for 800 μL of sample (MEPS) were between 0.2 and 266 ng L⁻¹. In the case of MEPS methodology even a sample volume of only 800 μL allowed to detect the target compounds. These results demonstrate the high sensitivity of both procedures which permitted to obtain good recoveries (>75%) for all cases. The precision of the methods, calculated as relative standard deviation (RSD) was below 21% for all compounds and both methodologies. Finally, the developed methods were applied to the determination of target analytes in various samples, including snow and wastewater.     

Poly(methyltetradecylsiloxane) immobilized onto silica for extraction of multiclass pesticides from surface waters

A new material based on poly(methyltetradecylsiloxane) (PMTDS) thermally immobilized onto a silica support has been tested as a sorbent for the solid-phase extraction (SPE) from water of several pesticides used in soybean cultivation. The SPE methodology was developed and validated for six of these pesticides (imazethapyr, imazaquin, metsulfuron-methyl, bentazone, chlorimuron-ethyl and tebuconazole) according to the International Conference on Harmonization directives and the results were compared with those obtained with a commercial C18 SPE cartridge. The PMTDS-based sorbent gives results similar to the commercial sorbent with recoveries and precisions in agreement with directives for residue analysis. The quantification limits, after concentration, of all the pesticides evaluated were 1.0 μg L⁻¹, below the levels imposed by the principal regulatory agencies. The PMTDS-based sorbent preparation is fast, easy and reproducible and the cartridges are less expensive than similar commercial SPE materials.     

One step carbon nanotubes-based solid-phase extraction for the gas chromatographic–mass spectrometric multiclass pesticide control in virgin olive oils

This article presents a novel application of carbon nanotubes for the determination of pesticides (chlortoluron, diuron, atrazine, simazine, terbuthylazin-desethyl, dimetoathe, malathion and parathion) in virgin olive oil samples. For this purpose, two carbon nanotubes, multi-walled and carboxylated single-walled, were evaluated, the later being the most appropriate for the aim of the work. The sorbent (30 mg) was packed in 3-mL commercial cartridge and the virgin olive oil samples diluted (20%, v/v) in hexane were passed through it. After a washing step with 3 mL of hexane to remove the sample matrix, the pesticides were eluted with 500 μL of ethyl acetate. In order to achieve lower detection limits, the eluent was evaporated under a nitrogen stream and the residue reconstituted in 50 μL of the same solvent. Aliquots of 2 μL of the extract were directly injected into the GC–MS system for analysis. The low limits of detection achieved, between 1.5 and 3.0 μg L⁻¹, permit the application of the method to control the presence of these pollutants in very restrictive samples such as the ecological virgin olive oil. In addition to the sensitivity enhancement, the solid-phase extraction procedure is rather simple as it involves a single preconcentration–elution step, which allows sample processing in less than 8 min. Moreover, the cartridge can be reused at least 100 times without losing performance. The method was applied to the determination of the pesticides in two monovarietal and one ecologic commercial extra virgin olive oil samples. Two pesticides were detected in each of the monovarietal virgin olive oils while the ecological sample resulted to be a pesticide-free one.     

On-line trace enrichment of phenolic compounds from water using a pyrrole-based polymer as the solid-phase extraction sorbent coupled with high-performance liquid chromatography

A pyrrole-based conductive polymer was prepared and applied as new sorbent for on-line solid-phase extraction (SPE) of phenol and chlorophenols from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in non-aqueous solution. The efficiency of this polymer for extraction of phenol and chlorophenols was evaluated using 35 mg of PPy as the sorbent in an on-line SPE system coupled to reversed-phase liquid chromatography with UV detection. The mobile phase were mixture of phosphate buffer-acetonitrile and compounds were eluted by the mobile phase using a six-port switching valve. High volumes of water, up to 160 ml, could be preconcentrated without the loss of phenols, except for the more polar ones. The R.S.D. for a river water sample spiked with phenol and chlorophenols at sub-ppb level was lower than 7% (n=5) and detection limits of 15-100 and 35-150 ng l⁻¹ for tap and river water were obtained, respectively.     

At-line microextraction by packed sorbent-gas chromatography–mass spectrometry for the determination of UV filter and polycyclic musk compounds in water samples

An at-line analysis protocol is presented that allows the determination of four UV filters, two polycyclic musk compounds and caffeine in water at concentration level of ng L⁻¹. The fully automated method includes analytes enrichment by Microextraction by packed sorbent (MEPS) coupled directly to large volume injection-gas chromatography–mass spectrometry. Two common SPE phases, C8 and C18, were examined for their suitability to extract the target substances by MEPS. The analytes were extracted from small sample volumes of 800 μL with recoveries ranging from 46 to 114% for the C8-sorbent and 65–109% for the C18-sorbent. Limits of detection between 34 and 96 ng L⁻¹ enable the determination of the analytes at common environmental concentration levels. Both sorbents showed linear calibration curves for most of the analytes up to a concentration level of 20 ng mL⁻¹. Carryover was minimized by washing the sorbents 10 times with 100 μL methanol. After this thorough cleaning, the MEPS are re-used and up to 70 analyses can be performed with the same sorbent. The fully automated microextraction GC–MS protocol was evaluated for the influence of matrix substances typical for wastewater. Dilution of samples prior to MEPS is recommended when the polar caffeine is present at high concentration. Real water samples were analyzed by the MEPS-GC–MS method and compared to standard SPE.     

Sucralose screening in European surface waters using a solid-phase extraction-liquid chromatography–triple quadrupole mass spectrometry method

An analytical method was developed for the analysis of sucralose, a persistent chlorinated calorie-free sugar substitute, in surface waters. The method is based on solid-phase extraction (SPE) of 400 mL water using Oasis HLB (Waters) adsorber material, followed by negative electrospray ionization (ESI) triple quadrupole LC–MS–MS detection. Quantification was performed by external calibration, as well as by isotope dilution with deuterated sucralose d6 internal standard. Extraction with Oasis HLB, a polymeric adsorbent suited for polar compounds, was much more efficient at neutral pH than at pH 3; a recovery of 62 ± 9% (n = 6; determined at 1 μg/L) could be achieved. Strong ion suppression caused by matrix substances was observed for sucralose in the SPE extracts. The analysis of 120 river surface water samples from 27 European countries showed that sucralose, which is in use in Europe since beginning 2005, can be found in the aquatic environment, at concentrations up to 1 μg/L. Sucralose was predominately found in samples from the UK, Belgium, the Netherlands, France, Switzerland, Spain, Italy, Norway, and Sweden, suggesting an increased use of the substance in Western Europe.     

Solid phase extractive preconcentration coupled to gas chromatography-atomic emission detection for the determination of chlorophenols in water samples

Solid-phase extraction (SPE) followed by derivatization and gas chromatography-atomic emission detection (GC-AED) was evaluated for the determination of five chlorophenols (CPs) in water samples. The derivatization was based on the esterification of phenolic compounds with ferrocenecarboxylic acid. The determination of the derivatized phenols was performed by GC-AED in the iron selective detection mode at 302 nm. The described method was tested on spiked water samples.The overall method gave detection limits of 1.6-3.7 ng L⁻¹ and recoveries of 90.9-104.5% for the examined mono- to trichlorophenols in 10 mL water samples. The CPs extracted from a 10 mL water sample with SPE were concentrated into 100 μL of organic solvent, a preconcentration factor of 100. The method was applied to lake and tap water samples, and CP contents between 6 and 51 ng L⁻¹ in lake water and between below the detection limit and 8 ng L⁻¹ in tap water were found for different CPs. The method is quick, simple and gives excellent recoveries, limits of detection and standard deviations.     

Ultra-high-pressure liquid chromatography–tandem mass spectrometry for the analysis of six resorcylic acid lactones in bovine milk

This work reports a rapid, reliable and sensitive multi-residue method for the simultaneous determination of six resorcylic acid lactones in bovine milk by ultra-high-pressure liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS). The resorcylic acid lactones were extracted, purified, and concentrated from milk samples in one step using a solid-phase extraction (SPE) cartridge that contained a polymeric mixed-mode anion-exchange sorbent. The analysis was performed on a Waters Acquity BEH C₁₈ column utilizing a gradient elution profile. Each LC run was completed in 3.5 min. The analytes were detected by multiple reaction monitoring (MRM) using electrospray ionization (ESI) negative mode. Mean recoveries from fortified samples ranged from 92.6% to 112.5%, with relative standard deviations lower than 11.4%. Using 5 mL bovine milk, the limits of detection and quantification for resorcylic acid lactones were in the ranges of 0.01–0.05 and 0.05–0.2 μg/L, respectively. The application of this newly developed method was demonstrated by analyzing bovine milk samples from markets.     

Solid-phase extraction combined with headspace single-drop microextraction of chlorophenols as their methyl ethers and analysis by high-performance liquid chromatography-diode array detection

Solid-phase extraction (SPE) of phenol and chlorophenols, their derivatization to methyl ethers, headspace single-drop microextraction (HS-SDME) of methyl ethers using 1-butanol as extraction solvent, and direct transfer of the drop into the injector for high performance liquid chromatography with diode array detection (HPLC-DAD) have been reported. A flanged-end polytetrafluoroethylene sleeve, 3 mm × 0.5 mm, placed at the tip of the syringe needle, allowed the use of 10 μL solvent drop for extraction. The procedure has been optimized for variables involved in SPE and HS-SDME. A rectilinear relationship was obtained between the amount of chlorophenols and peak area ratio of their methyl ethers/internal standard (4-methoxyacetophenone) in the range 0.01-10 mg L⁻¹, correlation coefficient in the range 0.9956-0.9996, and limit of detection in the range 1.5-3.9 μg L⁻¹ when HS-SDME alone was used for sample preparation. When using coupled SPE and HS-SDME, the linear range obtained was 0.1-500 μg L⁻¹, correlation coefficient in the range 0.9974-0.9998, and the limit of detection in the range 0.04-0.08 μg L⁻¹. Spiked real samples have been analyzed with adequate accuracy, and application of the method has been demonstrated for the analysis of chlorophenols formed upon bamboo pulp bleaching.     

High performance liquid chromatography–tandem mass spectrometry for the analysis of 10 pesticides in water: A comparison between membrane-assisted solvent extraction and solid phase extraction

This work describes the application of two sample preparation methods: membrane-assisted solvent extraction (MASE) and solid phase extraction (SPE) in combination with high performance liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) for the determination of 10 pesticides in surface and ground water. Optimal extraction conditions for MASE were 60 min extraction time at 30 °C with a solvent volume of 100 μL toluene. 5 μL of the toluene extract were directly injected in the HPLC–MS–MS system. Concerning SPE, two materials were tested and C18 was superior to Oasis HLB. Complete desorption was ensured by desorbing the SPE (C18) cartridge with 3 mL of an acetonitrile/methanol mixture (1:1). After evaporation, the extract was injected in the analytical system. Analyte breakthrough was not found for the investigated compounds. For both methods, high extraction yields were achieved, in detail 71% (metalaxyl) till 105% (linuron) for MASE and 52% (ethiofencarb) till 77% (prometryne) for SPE (C18). Detection limits were in the low ng/L range for both methods and precision, expressed as the relative standard deviation (RSD) of the peak areas was below 13%. Five real water samples were analyzed applying both extraction methods. The results were in good agreement and standard addition proved that no matrix effects (such as ion suppression) occurred. In this comparison SPE has the potential of larger sensitivity whereas faster analysis and slightly better recoveries were achieved with MASE. MASE shows potential to be a promising alternative to the conventional off-line SPE concerning low to medium polar compounds.     

Application of sulfur microparticles for solid-phase extraction of polycyclic aromatic hydrocarbons from sea water and wastewater samples

The application of sulfur microparticles as efficient adsorbents for the solid-phase extraction (SPE) and determination of trace amounts of 10 polycyclic aromatic hydrocarbons (PAHs) was investigated in sea water and wastewater samples using high performance liquid chromatography coupled with an ultraviolet detector (HPLC–UV). Parameters influencing the preconcentration of PAHs such as the amount of sulfur, solution flow rate and volume, elution solvent, type and concentration of organic modifier, and salt effect were examined. The results showed that at a flow rate of 10 mL min⁻¹ for the sample solutions (100 mL), the PAHs could be adsorbed on the sulfur microparticles and then eluted by 2.0 mL of acetonitrile. For HPLC–UV analysis of extracted PAHs, the calibration curves were linear in the range of 0.05–80.0 μg L⁻¹; the coefficients of determinations (r²) were between 0.9934 and 0.9995. The relative standard deviations (RSDs) for eight replicates at two concentration levels (0.5 and 4.0 μg L⁻¹) of PAHs were lower than 7.3%, under optimized conditions. The limits of detection (LODs, <!-- no-mfc -->S/N<!-- /no-mfc --> = 3) of the proposed method for the studied PAHs were 0.007–0.048 μg L⁻¹. The recoveries of spiked PAHs (0.5 and 4 μg L⁻¹) in the wastewater and sea water samples ranged from 78% to 108%. The simplicity of experimental procedure, high extraction efficiency, short sample analysis, and using of low cost sorbent demonstrate the potential of this approach for routine trace PAH analysis in water and wastewater samples.     

Comparison of several sorbents for continuous in situ derivatization and preconcentration of low-molecular mass aldehydes prior to liquid chromatography–tandem mass spectrometric determination in water samples

A comparative study of six SPE conventional and non-conventional sorbent materials (silica RP-C₁₈, LiChrolut EN, Amberlite XAD-2, C₆₀ fullerene, multiwall carbon nanotubes and graphitized carbon black) was carried out for the in situ derivatization/preconcentration of eight aldehydes with 2,4-dinitrophenylhydrazine. Although two of the sorbents, LiChrolut EN and RP-C₁₈, turned out to be the most suitable for ultratrace analysis of the aldehydes, LiChrolut EN showed higher capacity for 2,4-dinitrophenylhydrazine trapping (higher efficiency for the in situ derivatization reaction) and superior performance in terms of sensitivity (likely a result of its increased sample breakthrough volume). The LiChrolut EN-based method combined with LC–MS/MS allowed the determination of aldehydes over the linear range of 0.02–15 μg l⁻¹, with limits of detection at 6–24 ng l⁻¹ and precision of 3.2–7.2%. The method was applied to determine low-molecular mass aldehydes in water samples. These results indicate that the method proposed is a straightforward and sensitive tool for the determination of these aldehydes in water samples providing better results than those LC–MS/MS reported alternatives in terms of the limit of detection, sample requirements for analysis and cost.     

Hybridization of commercial polymeric microparticles and magnetic nanoparticles for the dispersive micro-solid phase extraction of nitroaromatic hydrocarbons from water

In this article, the combination of commercial polymeric microparticles (OASIS MCX) and cobalt ferrite nanoparticles is evaluated in dispersive micro-solid phase extraction (D-μSPE) for the determination of six nitroaromatic hydrocarbons in water. The high affinity of the polymeric material toward the target analytes as well as the magnetic behavior of cobalt ferrite nanoparticles are combined in a synergic way to developed an efficient and simple D-μSPE approach. The sorptive performance of the hybrid material is compared with that most usual sorbents and the effect of its synthesis steps on the extraction capability is also evaluated in depth. After the optimization of selected variables, D-μSPE method was assessed in terms of linearity, sensitivity, precision and accuracy. The new extraction method allows the determination of the target compounds with limits of detection in the range from 0.12 to 1.26 μg/L and relative standard deviations lower than 9.6%. The recovery study was performed in two different water samples obtaining percentages from 71 to 103%, which demonstrated the applicability of the hybrid sorbent for the selected analytical problem.