Molecularly imprinted solid-phase extraction monolithic capillary column for selective extraction and sensitive determination of safranine T in wolfberry

A method was developed to sensitively determine safranine T in wolfberry by molecularly imprinted solid-phase extraction (MISPE) coupled with high-performance liquid chromatography and laser-induced fluorescence detection (HPLC-LIF). The MISPE capillary monolithic column was prepared by water-bath in situ polymerization, using safranine T, methacrylic acid (MAA), and ethylene dimethacrylate (EDMA) as template, functional monomer, and cross-linker, respectively. The properties of the homemade MISPE capillary monolithic column, including capacity and specificity, were investigated under optimized conditions and the morphologies of inner polymers were characterized by scanning electron microscopy (SEM). The mean recoveries of safranine T in wolfberry ranged from 91.2 % to 92.9 % and the intraday and interday relative standard deviation (RSD) values all ranged from 3.4 % to 4.2 %. Good linearity was obtained over 0.001–1.0 μg mL^–1 (r?=?0.9999) with a detection limit (S/N?=?3) of 0.4 ng g^–1. Under the selected conditions, enrichment factors of over 90-fold were obtained and the extraction on the monolithic column effectively cleaned up the wolfberry matrix. The results demonstrated that the proposed MISPE-HPLC-LIF method could be applied to sensitively determine safranine T in wolfberry.

A three phase dispersive liquid-liquid microextraction technique for the extraction of antibiotics in milk

We have developed a 3-phase method for dispersive liquid-liquid microextraction of ß-lactam antibiotics in milk. Chloroform and acetonitrile serve as the solvents for extraction and disperssion, respectively, where Aliquat 336 is the carrier. An experimental design based on Plackett-Burman and Central composite designs were applied for the screening and optimization of significant parameters in the extraction method. The experimental conditions for extraction were optimized, and the subsequent HPLC assay gave relative standard deviations and detection limits in the range of 4.3–8.5 % and 50–500 μg L^-1, respectively. Preconcentration factors are in the range of 80–125.

Magnetic molecular imprint-based extraction of sulfonylurea herbicides and their determination by capillary liquid chromatography

We have developed a simple method for the extraction of sulfonylurea herbicides (SUHs) from environmental water samples. It is based on a magnetic molecular imprint (MMIP) as a sorbent. The MMIP was prepared using metsulfuron-methyl as the template molecule, methacrylic acid as the functional monomer, trimethylolpropane trimethacrylate as the cross-linking agent, and magnetite as the magnetic component. Extraction can be carried out by blending and stirring water sample, extraction solvent and MMIP. Once the extraction is completed, the MMIP containing the SUHs can be separated from the sample matrix with a magnet. The SUHs desorbed from the polymers were then quantified by capillary liquid chromatography with diode array detection. The limits of quantification are in the range of 0.08 to 0.1 ng?mL^?1. Repeatabilities of peak areas and retention times range from 2.9 % to 4.0 % and from 0.1 % to 0.3 %, respectively. The method was successfully applied to the determination of the SUHs bensulfuron-methyl, metsulfuronmethyl, pyrazosulfuron-methyl, thifensulfuron-methyl, and triasulfuron in waste water samples. Recoveries range from 94.3 % to 102.3 %.

Fragment-imprinted microspheres for the extraction of sulfonamides

Fragment-imprinted microspheres (FIMs) were synthesized by suspension polymerization of 4-sulfa-6-chloropyrimidine (the template), methacrylic acid and styrene (the mixed functional monomers), divinylbenzene (the crosslinker), and azobisisobutyronitrile (the initiator). The optimum conditions were obtained by an orthogonal experiment. After removal of the templates, the microspheres serve as a material to fairly specifically bind sulfonamides, the absorption capacity being 6.32 mg g^–1, whereas the absorption by non-imprinted microspheres is 1.68 mg g^?1. A method was worked out for the simultaneous determination of five sulfonamides by solid phase extraction (using the FIMs) coupled to HPLC, and applied to analyze milk samples. The recoveries are within 87.6 and 96.5 %, with relative standard deviations between 1.25 and 2.89 %.

A simple QuEChERS-like extraction approach for molecular chemical characterization of organic aerosols: application to nitrated and oxygenated PAH derivatives (NPAH and OPAH) quantified by GC–NICIMS

An extraction procedure based on the Quick Easy Cheap Effective Rugged and Safe (QuEChERS) approach has been developed and used for analysis of particle-bound nitrated and oxygenated PAH derivatives (NPAH and OPAH, respectively). Several analytical conditions, for example GC injection temperature and MS detection settings, were optimized. This analytical procedure enabled simultaneous GC–NICIMS quantification of 32 NPAH and 32 OPAH (or other oxygenated compounds), including typical components of secondary organic aerosol (SOA) formed by photooxidation of PAH (e.g. 2-formyl-trans-cinnamaldehyde and 6H-dibenzo[b,d]pyran-6-one). The QuEChERS-like approach was optimized, including the nature of the extraction solvent, the sorbent used for clean-up, and extraction time. The final extraction procedure was based on brief mechanical agitation (vortex mixing for 1.5 min), with 7 mL acetonitrile as solvent. Because dispersive solid-phase extraction (d-SPE) did not provide satisfactory results, SPE using SiO₂ was selected for sample purification. Identical results were obtained when the QuEChERS-like and traditional pressurised solvent extraction (PLE) procedures were compared for analysis of fortified ambient air particle samples. The procedure was validated by analysis of two aerosol standard reference materials (NIST SRM 1649b (urban dust) and SRM 2787 (fine particulate matter, <10 μm)). For numerous NPAH and OPAH, this is the first report of their quantification in both SRMs. Compared with other extraction methods, including PLE, the QuEChERS-like procedure resulted in increased productivity and reduced extraction cost. This paper shows that QuEChERS-like extraction procedures can be suitably adapted for molecular chemical characterization of aerosol samples and could be extended to other categories of compound.

A molecular imprint-coated stirrer bar for selective extraction of caffeine, theobromine and theophylline

We have prepared a novel caffeine imprinted polymer on a stir bar that can be used for selective extraction of caffeine, theobromine and theophylline from beverages. The polymerization time and quantities of reagents (template, cross-linker, porogenic solvent) were optimized. The morphology of the molecularly imprinted polymer-coating was studied by scanning electron microscopy and Fourier transform IR spectroscopy. A rapid and sensitive method was worked out for the extraction of caffeine, theobromine and theophylline from beverages by using the molecularly imprinted stir bar followed by HPLC analysis. The effects of extraction solvent, stirring speed, desorption solvent, adsorption and desorption time were optimized. The method displays a linear response in the 5–150 μg L^?1 caffein concentration range, with a correlation coefficient of >0.9904. The recoveries for three analytes in tea, carbonated and functional beverages were 91–108 %, 90–110 % and 93–109 %, with relative standard deviations ranging from 3.6–5.7 %, 3.5–7.9 % and 3.2–7.9 %, respectively.

Development of monolith-based stir bar sorptive extraction and liquid chromatography tandem mass spectrometry method for sensitive determination of ten sulfonamides in pork and chicken samples

A highly sensitive method was developed for the simultaneous determination of ten sulfonamides in pork and chicken samples by monolith-based stir bar sorptive extraction (SBSE) coupled to high-performance liquid chromatography tandem mass spectrometry. The samples were freeze-dried and extracted by acetonitrile, then enriched and further extracted by SBSE which was based on poly(vinylphthalimide-co-N,N-methylenebisacrylamide) monolith (SBSE-VPMB) as coating. To achieve optimum extraction performance of SBSE for sulfonamides, several parameters, including pH value and ionic strength in the sample matrix and extraction and desorption time, were investigated in detail. Under the optimal conditions, the limits of detection (S/N?=?3) for target sulfonamides were 1.2–6.1 ng/kg in pork and 2.0–14.6 ng/kg in chicken, respectively. Real samples spiked at the concentration of 0.5 and 5.0 μg/kg showed recoveries above 55 % and relative standard deviations below 12 %. At the same time, the extraction performances of target sulfonamides on SBSE-VPMB were compared with other SBSE based on porous monolith and commercial SBSE.

Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene by using three electroneutral receptors

From extraction experiments and $ \gamma $ -activity measurements, the extraction constants corresponding to the general equilibrium Eu³⁺(aq) + 3 A^?(aq) + L(nb) $ \Leftrightarrow $ EuL³⁺(nb) + 3A^?(nb) taking place in the two-phase water–nitrobenzene system ( $ {\text{A}}^{ - } = {\text{CF}}_{ 3} {\text{SO}}_{3}^{ - } $ ; L = electroneutral receptors denoted by 1, 2, and 3 – see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL³⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the series of 3 < 2 < 1.

Dual cloud point extraction coupled with hydrodynamic-electrokinetic two-step injection followed by micellar electrokinetic chromatography for simultaneous determination of trace phenolic estrogens in water samples

A dual cloud point extraction (dCPE) off-line enrichment procedure coupled with a hydrodynamic–electrokinetic two-step injection online enrichment technique was successfully developed for simultaneous preconcentration of trace phenolic estrogens (hexestrol, dienestrol, and diethylstilbestrol) in water samples followed by micellar electrokinetic chromatography (MEKC) analysis. Several parameters affecting the extraction and online injection conditions were optimized. Under optimal dCPE–two-step injection–MEKC conditions, detection limits of 7.9–8.9 ng/mL and good linearity in the range from 0.05 to 5 μg/mL with correlation coefficients R ²?≥?0.9990 were achieved. Satisfactory recoveries ranging from 83 to 108 % were obtained with lake and tap water spiked at 0.1 and 0.5 μg/mL, respectively, with relative standard deviations (n?=?6) of 1.3–3.1 %. This method was demonstrated to be convenient, rapid, cost-effective, and environmentally benign, and could be used as an alternative to existing methods for analyzing trace residues of phenolic estrogens in water samples.

Magnetic titanium oxide nanoparticles for hemimicelle extraction and HPLC determination of organophosphorus pesticides in environmental water

We report on a method for the extraction of organophosphorus pesticides (OPPs) from water samples using mixed hemimicelles and magnetic titanium dioxide nanoparticles (Fe₃O₄@TiO₂) modified by cetyltrimethylammonium. Fe₃O₄@TiO₂ nanoparticles were synthesized by a hydrothermal process and then characterized by scanning electron microscopy and Fourier transform IR spectrometry. The effects of the quantity of surfactant, extraction time, desorption solvent, pH value, extraction volume and reuse of the sorbent were optimized with respect to the extraction of OPPs including chlorpyrifos, dimethoate, and trichlorfon. The extraction method was applied to analyze OPPs in environmental water using HPLC along with UV detection. The method has a wide linear range (100–15,000 ng L^?1), good linearity (r?>?0.999), and low detection limits (26–30 ng L^?1). The enrichment factor is ~1,000. The recoveries (at spiked levels of 100, 1,000 and 10,000 ng L^?1) are in the range of 88.5–96.7 %, and the relative standard deviations range from 2.4 % to 8.7 %.

Solid phase ligand-less extraction of cadmium(II) using a silica gel modified with an amino-functionalized ionic liquid

A method was developed for the determination of cadmium(II) by ligand-less solid phase extraction that is based on the direct retention of Cd(II) in a mini-column filled with a silica gel modified with an amino-functionalized ionic liquid. The effects of pH, sample volume and its flow rate, eluent concentration and its volume, the flow rate of eluent, and of potential interferences on extraction and desorption were optimized. Following its determination by electrothermal atomic absorption spectrometry, the detection limit for Cd(II) is 8.9 ng L^?1, and the relative standard deviation is 2.3 % (at 1.0 ng mL^?1; for n?=?5). The method was applied to the analysis of Cd(II) in a certified reference material (laver; GBW10023), and the recoveries ranged from 97.0 to104.0 %

Nickel-aluminum layered double hydroxide as a nano-sorbent for the solid phase extraction of selenium, and its determination by continuous flow HG-AAS

We have used a nano-structured nickel-aluminum layered double hydroxide (Ni-Al LDH) for the extraction of trace levels of selenium prior to its determination by continuous-flow hydride generation atomic absorption spectrometry. Extraction is based on the adsorption of Se(IV) anions on the Ni-Al-nitrate LDH, and/or their exchange with the nitrate anions in the LDH interlayer. The effects of pH value, amount of nanosorbent, eluent type and concentration, sample volume and flow rate were optimized. No appreciable matrix effects were observed. Under optimum conditions, the limit of detection (defined as three times the standard deviation of the blank signal divided by the slope of the calibration plot) is 10 pg?mL^?1, and the relative standard deviation is 2.8 %. The sorption capacity and preconcentration factor are 10 mg?g^?1 and 33, respectively. The method was successfully applied to the determination of Se(IV) in tap water, river water, well water, wastewater and oyster tissue (certified reference material, CRM 1566b).

Micro-solid phase extraction of ochratoxin A, and its determination in urine using capillary electrophoresis

We describe a simple, environmentally friendly and selective technique for the determination of ochratoxin A (OTA) in urine. It involves (a) the use of a molecularly imprinted polymer as a sorbent in micro-solid-phase extraction in which the sorbent is contained in a propylene membrane envelope, and (b) separation and detection by capillary electrophoresis (CE). Under optimized conditions, response is linear in the range between 50 and 300 ng mL^?1 (with a correlation coefficient of 0.9989), relative standard deviations range from 4 to 8 %, the detection limit for OTA in urine is 11.2 ng mL^?1 (with a quantification limits of 32.5 ng mL^?1) which is lower than those of previously reported methods for solid-phase extraction combined with CE. The recoveries of OTA from urine spiked at levels of 50, 150 and 300 ng mL^?1 ranged from 93 to 97 %.

Lipidomic analysis of polyunsaturated fatty acids and their oxygenated metabolites in plasma by solid-phase extraction followed by LC-MS

The present work describes the development of a robust and sensitive targeted analysis platform for the simultaneous quantification in blood plasma of lipid oxygenated mediators and fatty acids using solid-phase extraction (SPE) and high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). The concurrent analysis of these lipid mediators is challenging because of their instability, differences in solubility, and the frequent occurrence of isobaric forms with similar fragmentation patterns. Results demonstrated that the reduction of SPE temperature to 4 °C is a critical parameter for preserving the hydroperoxy derivatives. Polymeric HLB cartridges increased 40–50 % ARA, EPA, and DHA sensitivity compared to C18 sorbent and also provided higher global performance for most hydroxides and other oxidation products. The proposed method for the two tested mass analyzers yields high sensitivity, good linearity, and reproducibility, with detection limits ranging 0.002–7 ng/mL and global recoveries as high as 85–112 %. However, the additional advantage of the linear ion trap (LIT) mass analyzer working in full scan product ion mode, compared to the triple quadrupole (QqQ) operating in multiple reaction monitoring (MRM), should be noted: the full scan product ion mode provides the full fragmentation spectra of compounds that allowed the discrimination of coeluting isomers and false positive identifications without additional chromatography development. The proposed lipidomic procedure demonstrates a confident, simple, and sensitive method to profile in plasma a wide range of lipid eicosanoid and docosanoid mediators, including innovatively the analysis of hydroperoxy congeners and nonoxidized PUFA precursors.

Simulation of Rarefied Gas Flows in Atmospheric Pressure Interfaces for Mass Spectrometry Systems

The understanding of the gas dynamics of the atmospheric pressure interface is very important for the development of mass spectrometry systems with high sensitivity. While the gas flows at high pressure (>1 Torr) and low pressure (<10^–3 Torr) stages are relatively well understood and could be modeled using continuum and molecular flows, respectively, the theoretical modeling or numeric simulation of gas flow through the transition pressure stage (1 to 10^–3 Torr) remains challenging. In this study, we used the direct simulation Monte Carlo (DMSC) method to develop the gas dynamic simulations for the continuous and discontinuous atmospheric pressure interfaces (API), with different focuses on the ion transfer by gas flows through a skimmer or directly from the atmospheric pressure to a vacuum stage, respectively. The impacts by the skimmer location in the continuous API and the temporal evolvement of the gas flow with a discontinuous API were characterized, which provide a solid base for the instrument design and performance improvement.

Dithizone-modified nanoporous fructose as a novel sorbent for solid-phase extraction of ultra-trace levels of heavy metals

We are introducing nanoporous fructose (np-F) modified with dithizone as a new solid-phase for extraction of heavy metals ions including cadmium(II), copper(II), nickel(II) and lead(II). Effects of pH value, flow rates, type, concentration and volume of the eluent, breakthrough volume, and of other ions were studied. Under optimized conditions, the extraction efficiency is >97 %, and the limits of detection are 0.025, 0.15, 0.5 and 1.2 ng mL^?1 for the ions of cadmium, copper, nickel, and lead, respectively, and the adsorption capacities for these ions are 101, 81, 74 and 178 mg g^?1. The modified np-F sorbent was characterized by thermogravimetric analysis, differential thermal analysis, transmission electron microscopy, Fourier transform infrared spectrometry, X-ray diffraction, and nitrogen adsorption surface area (BET) measurements.

Validation of chlordecone analysis for native and remediated French West Indies soils with high organic matter content

An analytic method was developed and validated for the analysis of chlordecone in the three main types of French West Indies soils: Ferralsol, Andosol and Nitisol with and without the addition of Daramend® and compost amendment used in a remediation process. The method consists in analysis by gas chromatography coupled with triple quadrupole mass spectrometry after pressurised liquid extraction. The high natural content of organic matter in the soils coupled with the additional exogenous organic matter from the amendments tested lead to a complex extract. Trans-nonachlor was used as surrogate to correct the results for extraction efficiency, and ¹³C chlordecone was added as internal standard to mimic as closely as possible the behaviour of chlordecone and suppress possible side effects during its analysis. The key parameters of the method (linearity, repeatability, interday precision, specificity, extraction efficiency and limit of quantification) were validated in accordance with the NF T 90-210 standard method. The limit of quantification is 0.03 mg/kg. Uncertainty (k?=?2) was 40 % for concentrations lower than or equal to 1 mg/kg, and 30 % for concentrations greater than 1 mg/kg.

Rapid extraction and determination of atrazine and its degradation products from microporous mineral sorbents using microwave-assisted solvent extraction followed by ultra-HPLC-MS/MS

We have evaluated three methods for the extraction of atrazine and six of its degradation products from microporous mineral sorbents. Soxhlet extraction and ultrasonic extraction, which work well on soils and sediments, recover only <15 % of the atrazine from a dealuminated Y zeolite. Closed-vessel microwave-assisted extraction, in contrast, gives much better recoveries. This is attributed to the accelerated mass transfer at elevated temperatures and the displacement by the solvent forced into the mineral micropores under elevated pressures. Under the optimized conditions, the recovery of atrazine from the hydrophilic Y zeolites (Si/Al ratios <8) is almost quantitative, and ～77 % for the more hydrophobic ones. The extraction efficiencies for the degradation products of atrazine in the hydrophilic zeolites (74.1–100 %) are also higher than those in the hydrophobic ones (22.3–44.2 %). The extracted compounds were quantified by a combination of ultra-HPLC and tandem MS and resulted in detection limits between 0.04 and 1.41 mg kg^?1 on a hydrophilic Y zeolite (Si/Al?=?2.55), and of 0.09–2.35 mg kg^?1 on a hydrophobic zeolite (Si/Al?=?15). The method was applied to study the degradation of atrazine sorbed on dealuminated Y zeolites.      

Quick supramolecular solvent-based microextraction for quantification of low curcuminoid content in food

There is a need to monitor the consumption of curcuminoids, an EU-permitted natural colour in food, to ensure that acceptable daily intakes are not exceeded, especially by young children. This paper describes a sensitive method able to quantify low contents of curcumin (CUR), demethoxycurcumin (DMC) and bis-demethoxycurcumin (BDMC) in foodstuffs. The method was based on a single-step extraction by use of a supramolecular solvent (SUPRAS) made up of reverse aggregates of decanoic acid, and direct analysis of the extract by use of liquid chromatography–photodiode array (PDA) detection. The extraction involved the stirring of 200 mg foodstuff with 600 μL SUPRAS for 15 min. No cleanup or concentration of the extracts was required. Curcuminoid solubilisation occurred via dispersion and hydrogen bonding. The method was used for the determination of curcuminoids in different types of foodstuff (snack, gelatine, yoghurt, mayonnaise, butter, candy and fish products) that encompassed a wide range of protein, fat, carbohydrate, sugar and water contents (0.85–11.04, 0–81.11, 0.06–75, 0.06–79.48, and 10.08–85.10 g, respectively, in each 100 g of food). Method quantification limits for the foodstuffs analysed were in the ranges 2.9–7.7, 2.8–11.2 and 3.3–9.0 μg kg^?1 for CUR, DMC and BDMC, respectively. The concentrations of curcuminoids detected in the foodstuffs and the recoveries obtained from fortified samples were in the ranges ND–284, ND–201 and ND–61.3 μg kg^?1, and 82–106, 89–106 and 90–102 %, for CUR, DMC and BDMC, respectively. The relative standard deviations were in the range 2–7 %. This method enabled quick and simple microextraction of curcuminoids with minimal solvent consumption, while delivering accurate and precise data.

Ultrasound-assisted emulsification–microextraction for the sensitive determination of ethyl carbamate in alcoholic beverages

A method based on ultrasound-assisted emulsification–microextraction (USAEME) was proposed in this contribution for the determination of ethyl carbamate (EC) in alcoholic beverages using gas chromatography coupled to triple quadrupole mass spectrometry. To achieve the determination of EC in alcoholic beverages, the influences on the extraction efficiency of type and volume of extraction solvent, temperature, ionic strength, alcohol content, and extraction time were studied, once the extraction solvent had been selected. The optimized conditions were 200.0 μL of chloroform at 30 °C during 5 min with 15 % (m/v) sodium chloride addition. The detection limit, relative standard deviations, linear range, and recoveries under the optimized conditions were 0.03 μg L^?1, 4.2–6.1 %, 0.1–50.0 μg L^?1, and 80.5–87.9 %, respectively. Moreover, the feasibility of the present method was also validated by real samples. To the best of our knowledge, this is the first time that USAEME has been applied to determine a strongly hydrophilic compound in alcoholic beverages.