Adsorptive stripping square wave voltammetry (Ad-SSWV) accomplished with second-order multivariate calibration determination of fenitrothion and its metabolites in river water samples

A method, using stripping square wave voltammetry (Ad-SSWV), for the simultaneous determination of fenitrothion (FEN) and its metabolites: fenitrooxon (OXON) and 3-methyl-4-nitrophenol (3-MET) in environmental samples is reported. All three compounds produce, at mercury electrode (HMDE), an electrochemical signal due to an adsorptive-reductive process. The electrochemical approach shows a very high overlap degree for FEN and OXON voltammograms, however the adsorption kinetic profile could be used as an additional differential variable between both analytes. Second-order multivariate calibration has been tested to solve the mixture of the three compounds. The second-order assayed methods were parallel factor analysis (PARAFAC), unfolded partial least squares (U-PLS), multidimensional partial least squares (N-PLS) and the latest ones were used in combination with the residual bilinearization procedure RBL. U-PLS/RBL model was stated as the best second-order algorithm for the simultaneous determination of these three compounds up to 50 ng mL⁻¹ for each analyte. The detection limits and recovery values were 1.6 ng mL⁻¹ and 92 ± 7% for FEN; 3.7 ng mL⁻¹ and 101 ± 9% for OXON and 0.6 ng mL⁻¹ and 97 ± 8% for 3-MET.     

Multi-way partial least-squares and residual bi-linearization for the direct determination of monohydroxy-polycyclic aromatic hydrocarbons on octadecyl membranes via room-temperature fluorescence excitation emission matrices

Multi-way partial least-squares (N-PLS) is combined to the residual bi-linearization procedure (RBL) for the direct analysis of metabolites of polycyclic aromatic hydrocarbons in urine samples. Metabolite analysis is carried out via a two-step experimental procedure based on solid-phase extraction and room temperature fluorescence spectroscopy. Excitation-emission matrices are recorded from octadecyl (C18) membranes that serve as solid substrates for sample extraction and spectroscopic measurements. Excellent metabolite recoveries were obtained in all cases, which varied from 96.2 ± 1.35% (9-hydroxyphenanthrene) to 99.7 ± 0.49% (3-hydroxybenzo[a]pyrene). Background correction of extraction membranes is carried out with a new alternating least-squares (ALS) procedure adapted to second order data. The performance of N-PLS/RBL is compared to the well-established multivariate curve resolution-alternating least-squares (MCR-ALS) algorithm. Both algorithms provided similar analytical figures of merit, including their ability to handle unknown interference in urine samples. With only 10 mL of sample, the limits of detection varied between 0.06–0.08 ng mL⁻¹ (1-hydroxypyrene) and 0.016–0.018 ng mL⁻¹ (2-hydroxyfluorene). When compared to previously reported univariate calibration data, the limits of detection via N-PLS/RBL and MCR-ALS are approximately one order of magnitude higher. This was somehow expected due to the effect of unexpected components in multivariate figures of merit, i.e. a more realistic approach to the analysis of metabolites in human urine samples.     

Multivariate curve-resolution analysis of pesticides in water samples from liquid chromatographic-diode array data

Liquid chromatographic-diode array detection data recorded for aqueous mixtures of 11 pesticides show the combined presence of strongly coeluting peaks, distortions in the time dimension between experimental runs, and the presence of potential interferents not modeled by the calibration phase in certain test samples. Due to the complexity of these phenomena, data were processed by a second-order multivariate algorithm based on multivariate curve resolution and alternating least-squares, which allows one to successfully model both the spectral and retention time behavior for all sample constituents. This led to the accurate quantitation of all analytes in a set of validation samples: aldicarb sulfoxide, oxamyl, aldicarb sulfone, methomyl, 3-hydroxy-carbofuran, aldicarb, propoxur, carbofuran, carbaryl, 1-naphthol and methiocarb. Limits of detection in the range 0.1-2 μg mL⁻¹ were obtained. Additionally, the second-order advantage for several analytes was achieved in samples containing several uncalibrated interferences. The limits of detection for all analytes were decreased by solid phase pre-concentration to values compatible to those officially recommended, i.e., in the order of 5 ng mL⁻¹.     

Liquid chromatography with diode array detection and multivariate curve resolution for the selective and sensitive quantification of estrogens in natural waters

Following the green analytical chemistry principles, an efficient strategy involving second-order data provided by liquid chromatography (LC) with diode array detection (DAD) was applied for the simultaneous determination of estriol, 17β-estradiol, 17α-ethinylestradiol and estrone in natural water samples. After a simple pre-concentration step, LC–DAD matrix data were rapidly obtained (in less than 5 min) with a chromatographic system operating isocratically. Applying a second-order calibration algorithm based on multivariate curve resolution with alternating least-squares (MCR-ALS), successful resolution was achieved in the presence of sample constituents that strongly coelute with the analytes. The flexibility of this multivariate model allowed the quantification of the four estrogens in tap, mineral, underground and river water samples. Limits of detection in the range between 3 and 13 ng L⁻¹, and relative prediction errors from 2 to 11% were achieved.     

Spectrofluorimetry in organized media coupled to second-order multivariate calibration for the determination of galantamine in the presence of uncalibrated interferences

The present article describes the spectrofluorimetric determination of galantamine, a widely used acetylcholinesterase inhibitor, through excitation-emission fluorescence matrices and second-order calibration. With the purpose of enhancing the fluorescence intensity of this substance, the effect of different organized assemblies was evaluated. Although the interaction of galantamine with different cyclodextrins is weak, it was corroborated that the fluorescence intensity of this pharmaceutical in the presence of α-cyclodextrin is increased by a twofold factor. Among the studied micellar media, the anionic surfactant sodium dodecyl sulfate produced the largest signals for the compound of interest (sixfold enhancement), and was selected as auxiliary reagent for the subsequent determinations. The developed approach enabled the determination of galantamine at the ng mL⁻¹ level without the necessity of applying separation steps, and in the presence of uncalibrated interferences. The applied second-order chemometric tools were parallel factor analysis (PARAFAC), unfolded partial least-squares coupled to residual bilinearization (U-PLS/RBL), and multidimensional partial least-squares coupled to residual bilinearization (N-PLS/RBL). The ability of U-PLS/RBL to successfully overcome spectral interference problems is demonstrated. The quality of the proposed method was established with the determination of galantamine in both artificial and natural water samples.     

Chemometrics assisted spectrophotometric determination of pyridine in water and wastewater

The paper reports a direct method for the determination of pyridine in water and wastewater samples based on ultraviolet spectrophotometric measurements using multi-way modeling techniques. Parallel factor analysis (PARAFAC) and multi-way partial least squares (N-PLS) regression methods were employed for the decomposition of spectra and quantification of pyridine. The study was carried out in the pH range of 1.0-12.0 and concentration range of 0.67-51.7 μg mL⁻¹ of pyridine. Both the three-way PARAFAC and tri-PLS1 models successfully predicted the concentration of pyridine in synthetic (spiked) river water and field wastewater samples. The mean recovery obtained from PARAFAC regression model were 97.39% for the spiked and 99.84% for the field wastewater samples, respectively. The sensitivity and precision of the method for pyridine determination were 0.58% and 5.95%, respectively. The N-PLS regression model yielded mean recoveries of 99.29% and 100.18% for the spiked and field wastewater samples, respectively. The prediction accuracy of the methods was evaluated through the root mean square error of prediction (RMSEP). For PARAFAC, it was 0.65 and 0.82 μg mL⁻¹ for spiked river water and field wastewater samples, respectively, while for N-PLS, it was 0.25 and 0.37 μg mL⁻¹, respectively. Both the PARAFAC and N-PLS methods, thus, yielded satisfactory results for the prediction of pyridine concentration in water and wastewater samples.     

A naked-eye based strategy for semiquantitative immunochromatographic assay

It is critical to develop a cost-effective quantitative/semiquantitative assay for rapid diagnosis and on-site detection of toxic or harmful substances. Here, a naked-eye based semiquantitative immunochromatographic strip (NSI-strip) was developed, on which three test lines (TLs, TL-I, TL-II and TL-III) were dispensed on a nitrocellulose membrane to form the test zone. Similar as the traditional strip assay for small molecule, the NSI-strip assay was also based on the competitive theory, difference was that the analyte competed three times with the capture reagent for the limited number of antibody binding sites. After the assay, the number of TLs developed in the test zone was inversely proportional to the analyte concentration, thus analyte content levels could be determined by observing the appeared number of TLs. Taking aflatoxin B₁ as the model analyte, visual detection limit of the NSI-strip was 0.06 ng mL⁻¹ and threshold concentrations for TL-I–III were 0.125, 0.5, and 2.0 ng mL⁻¹, respectively. Therefore, according to the appeared number of TLs, the following concentration ranges would be detectable by visual examination: 0–0.06 ng mL⁻¹ (negative samples), and 0.06–0.125 ng mL⁻¹, 0.125–0.5 ng mL⁻¹, 0.5–2.0 ng mL⁻¹ and >2.0 ng mL⁻¹ (positive samples). That was to say, compared to traditional strips the NSI-strip could offer more parameter information of the target analyte content. In this way, the NSI-strip improved the qualitative presence/absence detection of traditional strips by measuring the content (range) of target analytes semiquantitatively.     

Chromatographic analysis of serotonin, 5-hydroxyindolacetic acid and homovanillic acid in dried blood spots and platelet poor and rich plasma samples

An isocratic high-performance liquid chromatographic method has been developed for the measurement of serotonin, 5-hydroxyindolacetic and homovanillic acids in dried blood spots and in platelet poor and rich plasma samples. Analyses were carried out on a C18 reversed-phase column using a mobile phase composed of 13% methanol and 87% aqueous citrate buffer, containing octanesulfonic and ethylendiaminotetracetic acids. Coulometric detection was used, setting the guard cell at +0.100 V, the first analytical cell at −0.200 V and the second analytical cell at +0.400 V. For the pre-treatment of biological samples a novel solid-phase extraction procedure, based on mixed-mode reversed-phase – strong anion exchange Oasis cartridges, was implemented. Extraction yields of the analytes from all these matrices were satisfactory, being always higher than 89.0%. The calibration curve was linear over the on-column concentration range of 0.1–22.5 ng mL⁻¹ for serotonin and 5-hydroxyindolacetic acid and of 0.25–22.5 ng mL⁻¹ for homovanillic acid. The sensitivity was good with a limit of detection of 0.05 ng mL⁻¹ for serotonin and 5-hydroxyindolacetic acid and 0.12 ng mL⁻¹ for homovanillic acid. Results were also satisfactory in terms of precision, selectivity and accuracy. The analytical method was successfully applied to human platelet poor and rich plasma samples and to dried blood spots from volunteers and psychiatric patients.     

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.     

High-performance liquid chromatography with fluorescence detection and ultra-performance liquid chromatography with electrospray tandem mass spectrometry method for the determination of indoleamine neurotransmitters and their metabolites in sea lamprey plasma

We present a comparison of two sensitive methods, HPLC with fluorescence detector (HPLC/FLD) and UPLC with electrospray tandem mass spectrometry (UPLC/MS/MS), for the determination of indoleamine neurotransmitters (NTs) and their metabolites in sea lamprey plasma samples. Liquid–liquid extraction (LLE) and solid-phase extraction (SPE) were also tested for recovery and matrix effect. The recoveries of SPE determined by HPLC/FLD and UPLC/MS/MS ranged from 75 to 123% and 78 to 105%, respectively, while the recoveries of LLE ranged from 45 to 73% and 48 to 75%, respectively. SPE combined with HPLC/FLD and UPLC/MS/MS to determine the target analytes in plasma samples were validated of the sensitivity, reproducibility, accuracy and precision. Both methods exhibited excellent linearity in the range of 0.2–50 ng mL⁻¹ for all analytes. The limits of detection (LOD) varied from 0.04 ng mL⁻¹ to 0.13 ng mL⁻¹ for HPLC/FLD method and 0.003 ng mL⁻¹ to 0.02 ng mL⁻¹ for UPLC/MS/MS method. The inter-day accuracy ranged from 82.5 to 127.0% for HPLC/FLD and 93.0 to 113.0% for UPLC/MS/MS. The inter-day precision ranged from 9.9 to 32.3% for HPLC/FLD and 5.4 to 13.2% for UPLC/MS/MS. These results demonstrated that the values obtained by both methods were within the satisfactory range and the UPLC/MS/MS method provided more accurate and precise measurements than HPLC/FLD method. The comparison is of great importance to determine the available detectors, considering the complexity and expensiveness versus quality parameters. These two methods were applied to the analysis of four important indoleamine neurotransmitter analytes (5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, tryptamine and melatonin) in sea lamprey plasma samples.     

Air-assisted liquid–liquid microextraction method as a novel microextraction technique; Application in extraction and preconcentration of phthalate esters in aqueous sample followed by gas chromatography–flame ionization detection

A novel microextraction technique, air-assisted liquid–liquid microextraction (AALLME), which is a new version of dispersive liquid–liquid microextraction (DLLME) method has been developed for extraction and preconcentration of phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP), di-n-butyl phthalate (DNBP), and di-2-ethylhexyl phthalate (DEHP), from aqueous samples prior to gas chromatography–flame ionization detection (GC–FID) analysis. In this method, much less volume of an organic solvent is used as extraction solvent in the absence of a disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GC–FID. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.12–1.15 and 0.85–4 ng mL⁻¹, respectively. Enrichment factors (EFs) and extraction recoveries (ERs) were in the ranges of 889–1022 and 89–102%, respectively. The relative standard deviations (RSDs) for the extraction of 100 ng mL⁻¹ and 500 ng mL⁻¹ of each phthalate ester were less than 4% for intra-day (n = 6) and inter-days (n = 4) precision. Finally some aqueous samples were successfully analyzed using the proposed method and three analytes, DIBP, DNBP and DEHP, were determined in them at ng mL⁻¹ level.     

Determination and identification,according to European Union Decision 2002/657/EC,of malachite green and its metabolite in fish by liquid chromatography–tandem mass spectrometry using an optimized extraction procedure and three-way calibration

This paper reports a multiresponse optimization of an extraction procedure in the simultaneous determination of malachite green (MG) and its metabolite (leucomalachite green, LMG) in fish by liquid chromatography with triple quadrupole mass spectrometry (LC–MS/MS). Prior to optimization, the active factors of the extraction procedure were determined by a screening experimental design. Then, in the optimal experimental conditions of the extraction, MG and LMG have been determined by using a three-way calibration model based on parallel factor analysis (PARAFAC). The procedure fulfils the performance requirements for a confirmatory method established by the European Union Decision 2002/657/EC. This norm establishes maximum permitted tolerances for relative abundance of the precursor/product ion pairs. There is a reported contradiction in the literature related to the fact that there are standard samples whose concentration is greater than CCα but the maximum permitted tolerances are not fulfilled in the identification of the analytes. In this work, it is shown that with the information provided by PARAFAC this contradiction is avoided. The figures of merit for PARAFAC and univariate calibration procedures were evaluated under optimal conditions in the extraction step. The figures of merit obtained were in the range of 0.13–0.23 μg kg⁻¹ for the decision limit, CCα, (α = 0.01) and 0.22–0.39 μg kg⁻¹ for the detection capability, CCβ, (β = 0.05), whereas mean relative errors in absolute value were in the range of 2.8–4.6% for MG and LMG with PARAFAC calibration. The proposed optimized extraction procedure using a PARAFAC calibration was also applied in the determination of MG and LMG in gilthead bream samples: the decision limit was in the range of 0.45–0.55 μg kg⁻¹, the detection capability was in the range of 0.76–0.92 μg kg⁻¹ for MG and LMG. Trueness was likewise confirmed and the mean of the absolute values of relative errors were between 4.2% and 7.2%.     

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 25 ng ml⁻¹ for norfloxacin (NOR), 80 ng ml⁻¹ for ofloxacin (OFLO) and 300 ng ml⁻¹ for enoxacin (ENO). The method is based on the native fluorescence emission of these compounds in sodium dodecyl sulfate (SDS) medium, at pH 4.0, when exciting at 277 nm. A selection of the emission wavelength range used for the analysis was made for each component. Intraday and interday precision values were determined. Figures of merit as selectivity, sensitivity, limit of detection (LOD) and analytical sensitivity were also calculated. Using the standard addition methodology, five urine samples from five different persons, fortified with three concentration levels of the fluoroquinolones, were analyzed. The limits of detection in urine were 10.0, 0.5 and 0.8 ng ml⁻¹ for ENO, NOR and OFLO, respectively.     

Single-step extraction and cleanup of bisphenol A in soft drinks by hemimicellar magnetic solid phase extraction prior to liquid chromatography/tandem mass spectrometry

Hemimicelles of tetradecanoate chemisorbed onto magnetic nanoparticles (MNPs) are here proposed as a sorbent for the single-step extraction and cleanup of bisphenol A (BPA) in soft drinks. The purpose of this work was to develop a simple, rapid and low-cost sample treatment suitable to assess the human exposure to BPA from this type of high consumption food. The nanoparticles were easily coated by mixing commercially available magnetite of 20–30 nm mean particle diameter with tetradecanoate at 85 °C for 30 min. The extraction/cleanup procedure involved stirring the samples (3 mL) with 200 mg of tetradecanoate-coated MNPs for 20 min, isolating the sorbent with a Nd–Fe–B magnet and eluting BPA with methanol. The extraction efficiency was not influenced by salt concentrations up to 1 M and pH values over the range 4–9. No cleanup of the extracts was needed, and the method proved matrix-independent. The extracts were analyzed by liquid chromatography, electrospray ionization tandem mass spectrometry. Quantitation was performed by internal standard calibration using BPA-¹³C₁₂. The limit of quantitation obtained for the method, 0.03 ng mL⁻¹, was below the usual range of concentrations reported for BPA in soft drinks (0.1–3.4 ng mL⁻¹). The proposed method was successfully applied to the determination of BPA in different samples acquired from various supermarkets in southern Spain; the concentrations found ranged from 0.066 to 1.08 ng mL⁻¹. Recoveries from samples spiked with 0.33 ng mL⁻¹ of BPA ranged from 91% to 105% with relative standard deviations from 3% to 8%.     

Development and validation of an open screening method for diuretics,stimulants and selected compounds in human urine by UHPLC–HRMS for doping control

A new doping control screening method for the analysis of diuretics and stimulants using ultra high pressure liquid chromatography–high resolution Orbitrap mass spectrometry has been developed. The screening was performed in full scan MS with scan-to-scan polarity switching which allowed to detect more than 120 target analytes. Sample preparation was limited to 10-fold dilution of the urine into the internal standard solution followed by injection. Total run time per sample was 10 min. Validation of the method yielded detection limits for diuretics between 25 and 250 ng mL⁻¹ and for stimulants between 5 and 500 ng mL⁻¹. The screening method has been implemented in routine doping control.     

Determination of hormones in milk by hollow fiber-based stirring extraction bar liquid–liquid microextraction gas chromatography mass spectrometry

The hollow fiber-based stirring extraction bar liquid–liquid microextraction was applied to the extraction of hormones, including 17-α-ethinylestradiol, 17-α-estradiol, estriol, 17-β-estradiol, estrone, 17-α-hydroxyprogesterone, medroxyprogesterone, progesterone and norethisterone acetate, in milk. The present method has the advantages of both hollow fiber-liquid phase microextraction and stirring bar sorptive extraction. The stirring extraction bar was used as both the stirring bar of microextraction, and extractor of the analytes, which can make extraction, clean-up and concentration be carried out in one step. When the extraction was completed, the stirring extraction bar was easy isolated from the extraction system with the magnet. Several experimental parameters, including the type of extraction solvent, the number of hollow stirring extraction bar, extraction time, stirring speed, ionic strength, and desorption conditions were investigated and optimized. The analytes in the extract were derived and determined by gas chromatography mass spectrometry. Under optimal experimental conditions, good linearity was observed in the range of 0.20–20.00 ng mL⁻¹. The limits of detection and quantification were in the range of 0.02–0.06 ng mL⁻¹ and 0.07–0.19 ng mL⁻¹, respectively. The present method was applied to the analysis of milk samples, and the recoveries of analytes were in the range of 93.6–104.6% with the relative standard deviations ranging from 1.6% to 6.2% (n = 5). The results showed that the present method was a rapid and feasible method for the determination of hormones in milk samples.     

Novel polyamide-based nanofibers prepared by electrospinning technique for headspace solid-phase microextraction of phenol and chlorophenols from environmental samples

A novel solid phase microextraction (SPME) fiber was fabricated by electrospinning method in which a polymeric solution was converted to nanofibers using high voltages. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three dimensional structure. Polyamide (nylon 6), due to its suitable characteristics was used to prepare the unbreakable SPME nanofiber. The scanning electron microscopy (SEM) images of this new coating showed a diameter range of 100–200 nm for polyamide nanofibers with a homogeneous and porous surface structure. The extraction efficiency of new coating was investigated for headspace solid-phase microextraction (HS-SPME) of some environmentally important chlorophenols from aqueous samples followed by gas chromatography–mass spectrometry (GC–MS) analysis. Effect of different parameters influencing the extraction efficiency including extraction temperature, extraction time, ionic strength and polyamide amount were investigated and optimized. In order to improve the chromatographic behavior of phenolic compounds, all the analytes were derivatized prior to the extraction process using basic acetic anhydride. The detection limits of the method under optimized conditions were in the range of 2–10 ng L⁻¹. The relative standard deviations (RSD) (n = 3) at the concentration level of 1.7–6.7 ng mL⁻¹ were obtained between 1 and 7.4%. The calibration curves of chlorophenols showed linearity in the range of 27–1330 ng L⁻¹ for phenol and monochlorophenols and 7–1000 ng L⁻¹ for dichloro and trichlorophenols. Also, the proposed method was successfully applied to the extraction of phenol and chlorophenols from real water samples and relative recoveries were between 84 and 98% for all the selected analytes except for 2,4,6 tricholophenol which was between 72 and 74%.     

Multiresidue determination of pesticides from aquatic media using polyaniline nanowires network as highly efficient sorbent for microextraction in packed syringe

A simple, rapid and sensitive method based on microextraction in packed syringe (MEPS), in combination with gas chromatography–mass spectrometry (GC–MS) was developed. Polyaniline (PANI) nanowires network was synthesized and used as sorbent of MEPS for the multiresidue determination of selected analytes from triazine, organochlrorine and organophosphorous pesticides in aqueous samples. The PANI nanowires network was prepared using soft template technique and its characterization was studied by scanning electron microscopy (SEM). The presence of micelles in this methodology showed to be an important parameter in shaping the growing polymer. Hexadecyltrimethylammonium bromide (HTAB) was used as structure directing agent in PANI preparation procedure and this was led to the formation of nanowires with diameters ranging from 35 nm to 45 nm. The synthesized PANI nanowires network showed higher extraction capability in comparison with the bulk PANI. Important parameters influencing the extraction and desorption processes including desorption solvent, elution volume, draw–eject cycles of sample, draw–eject mode, pH effect and amount of sorbent were optimized. Limits of detection were in the range of 0.07–0.3 ng mL⁻¹ using time scheduled selected ion monitoring (SIM) mode. The linearity of method was in the range from 0.5–200 ng mL⁻¹ to 0.2–1000 ng mL⁻¹. The method precision (RSD %) with three replicates were in the range of 5.3–18.4% at the concentration level of 5 ng mL⁻¹. The developed method was successfully applied to the Zayandeh-rood river water samples and the matrix factor obtained for the spiked real water samples were in the range of 0.79–0.94.     

Chemometrics-assisted excitation–emission fluorescence spectroscopy on nylon-attached rotating disks. Simultaneous determination of polycyclic aromatic hydrocarbons in the presence of interferences

This work presents a green and very simple approach which enables the accurate and simultaneous determination of benzo[a]pyrene, dibenz[a,h]anthracene, benz[a]anthracene, and chrysene, concerned and potentially carcinogenic heavy-polycyclic aromatic hydrocarbons (PAHs) in interfering samples. The compounds are extracted from water samples onto a device composed of a small rotating Teflon disk, with a nylon membrane attached to one of its surfaces. After extraction, the nylon membrane containing the concentrated analytes is separated from the Teflon disk, and fluorescence excitation–emission matrices are directly measured on the nylon surface, and processed by applying parallel factor analysis (PARAFAC), without the necessity of a desorption step. Under optimum conditions and for a sample volume of 25 mL, the PAHs extraction was carried out in 20 min. Detection limits based on the IUPAC recommended criterion and relative errors of prediction were in the ranges 20–100 ng L⁻¹ and 5–7%, respectively. Thanks to the combination of the ability of nylon to strongly retain PAHs, the easy rotating disk extraction approach, and the selectivity of second-order calibration, which greatly simplifies sample treatment avoiding the use of toxic solvents, the developed method follows most green analytical chemistry principles.     

Ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction followed high-performance liquid chromatography for the determination of ultraviolet filters in environmental water samples

In the present study, a rapid, highly efficient and environmentally friendly sample preparation method named ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction (IL-USA-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for the extraction and preconcentration of four benzophenone-type ultraviolet (UV) filters (viz. benzophenone (BP), 2-hydroxy-4-methoxybenzophenone (BP-3), ethylhexyl salicylate (EHS) and homosalate (HMS)) from three different water matrices. The procedure was based on a ternary solvent system containing tiny droplets of ionic liquid (IL) in the sample solution formed by dissolving an appropriate amount of the IL extraction solvent 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]) in a small amount of water-miscible dispersive solvent (methanol). An ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution, which markedly increased the extraction efficiency and reduced the equilibrium time. Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvents, ionic strength, pH and extraction time) were evaluated. Under optimal conditions, the proposed method provided good enrichment factors in the range of 354–464, and good repeatability of the extractions (RSDs below 6.3%, n = 5). The limits of detection were in the range of 0.2–5.0 ng mL⁻¹, depending on the analytes. The linearities were between 1 and 500 ng mL⁻¹ for BP, 5 and 500 ng mL⁻¹ for BP-3 and HMS and 10 and 500 ng mL⁻¹ for EHS. Finally, the proposed method was successfully applied to the determination of UV filters in river, swimming pool and tap water samples and acceptable relative recoveries over the range of 71.0–118.0% were obtained.