Analysis of aldehydes in human exhaled breath condensates by in-tube SPME-HPLC

In this paper, polypyrrole/graphene (PPy/G) composite coating was prepared by a facile electrochemical polymerization strategy on the inner surface of a stainless steel (SS) tube. Based on the coating tube, a novel online in-tube solid-phase microextraction -high performance liquid chromatography (IT-SPME-HPLC) was developed and applied for the extraction of aldehydes in the human exhaled breath condensates (EBC). The hybrid PPy/G nanocomposite exhibits remarkable chemical and mechanical stability, high selectivity, and satisfactory extraction performance toward aldehyde compounds. Moreover, the proposed online IT-SPME-HPLC method possesses numerous superiorities, such as time and cost saving, process simplicity, high precision and sensitivity. Some parameters related to extraction efficiency were optimized systematically. Under the optimal conditions, the recoveries of the aldehyde compounds at three spiked concentration levels varied in the range of 85%–117%. Good linearity was obtained with excellent correlation coefficients (R²) being larger than 0.994. The relative standard deviations (n = 5) of the method ranged from 1.8% to 11.3% and the limits of detection were between 2.3 and 3.3 nmol L⁻¹. The successful application of the proposed method in human EBC indicated that it is a promising approach for the determination of trace aldehyde metabolites in complex EBC samples.     

Electrospun polystyrene nanofibers as a novel adsorbent to transfer an organic phase from an aqueous phase

The aim of this work is to develop a simple phase‐transfer method for dispersive liquid–liquid microextraction. For this purpose, a polystyrene nanofiber was prepared by a facile electrospinning strategy and used for the first time as an adsorbent to transfer the organic phase in dispersive liquid–liquid microextraction procedure. The fiber was characterized and its chemical stability and excellent hydrophobicity enable it to selectively adsorb the organic solvent in an aqueous sample. High porosity and specific surface area provide a large adsorption capacity. Under the optimal conditions, the developed dispersive liquid–liquid microextraction with high‐performance liquid chromatography method was successfully applied to the analysis of aldehydes in environmental water samples. The merits of this approach are that it is easy‐to‐operate, low‐cost, time‐saving, and has satisfactory sensitivity. It provides an alternative way for fast and convenient phase transfer of the hydrophobic organic solvent from the aqueous phase.     

Polydopamine-sheathed electrospun nanofiber as adsorbent for determination of aldehydes metabolites in human urine

In this paper, a novel polydopamine modified polystyrene/graphene electrospun nanofiber membrane (PS/G@PDA) was fabricated on the surface of filter paper and used for thin film microextraction (TFME) for the first time. Benefiting from the hydrophilic polydopamine (PDA) coating and the porous fibrous structure, the PS/G@PDA membrane exhibited large surface area, high extraction efficiency, rapid extraction equilibrium, special selectivity and excellent biocompatibility. A thin film microextraction-high performance liquid chromatography method was developed and applied for the analysis of six aldehyde metabolites in human urine samples. Under the optimal conditions, the recoveries of the aldehyde compounds varied in the range of 83%–115%, with the relative standard deviation values lower than 14.5% (n = 5). Moreover, satisfactory sensitivities with the limits of detection in the range of 2.3–6.5 nmol L⁻¹ and good linearity with excellent correlation coefficients (R²) being larger than 0.9936 had also been achieved. In general, a fast, convenient, sensitive, high-efficient and matrix-free method was successfully proposed and expected becoming a promising approach for the determination of trace aldehyde metabolites in complex biological samples.     

Poly(vinylidene fluoride) membrane based thin film microextraction for enrichment of benzoylurea insecticides from water samples followed by their determination with HPLC

Thin-film microextraction(TFME),a new geometry for solid-phase microextraction,has become an attractive sample-preparation technique.Compared to other microextraction approaches,the sensitivity of this technique was enhanced without sacrificing the sampling time due to the high surface area-tovolume ratio together with the increase of extraction-phase volume.In this paper,a new TFME method based on poly(vinylidene fluoride) membrane was developed for the extraction of benzoylurea insecticides(diflubenzuron,triflumuron,hexaflumuron and teflubenzuron) from water samples followed by their determination with high performance liquid chromatography-diode array detection.Under the optimal conditions,good linearity was observed over the concentration range of 0.5-100.0 ng/mL with correlation coefficient greater than 0.9994.The limits of detection(S/N = 3) of the method for the target analytes were 0.1 ng/mL.Mean recoveries ranged from 87.7% to 103.9% with relative standard deviations lower than 6.5%.The results indicated that the developed TFME method is simple,efficient,and cost effective.     

Development of a novel monolith frit-based solid-phase microextraction method for determination of hexanal and heptanal in human serum samples

In this paper, a polypropylene frit with porous network structure and high area-to-thickness ratio (4.8 mm diameter, 1.6 mm thickness, 20 mm pore size) was utilized as a mould of monolith. Poly(methacrylic acid-ethlyene glycol dimethacrylate) (MAA-EGDMA) monolith was in situ synthesized in the micro-channel of frit by photopolymerization. A monolith frit-based solid-phase microextraction method (SPME) was developed for the determination of hexanal and heptanal in serum samples by combining with high-performance liquid chromatography. 2,4-Dinitrophenylhydrazine (DNPH) as the derivatizing reagent was absorbed on a monolith frit, then its derivatization reaction with aldehydes and the absorption of formed hydrazones on the monolith disk occurred simultaneously. The condition parameters for polymerization, derivatization and extraction were optimized systematically. Under the optimum conditions, rigid structure, low back-pressure and high column capacity were achieved for the monolith frit. The limits of detection for hexanal and heptanal were 1.86 and 1.38 nmol/L, respectively. The inter- and intra-day relative standard deviations were less than 7.7% (n = 6). This method was applied successfully to aldehydes analysis in human serum samples. The method possesses advantages such as simplicity, efficiency, low cost and good biocompatibility. It provides an alternative approach for quantification of aldehydes in complex biological samples.     

Rapid determination of atrazine in environmental water samples by a novel liquid phase microextraction

A novel method was described for the rapid determination of atrazine using dispersive liquid phase microextraction in combination with high performance liquid chromatography （HPLC）. Possible impact parameters such as sample pH, extraction and disperser solvents, salting-out effect, and extraction time were investigated. The experimental results indicated that proposed method possessed an excellent analytical performance, The linear range, detection limit, and precision （R.S.D.） were 0.1- 50 ng mL- 1 （R2 = 0.9955）, 0.601 ng mL- 1 and 6,4%, respectively. The proposed method was validated with the real water samples, and the spiked recoveries were in the range of 69.9-89.8%, respectively. These results indicated that the established method with high enrichment factor, short extraction time was an excellent alternative for the routine analysis of atrazine in environmental samples. 2007 Qing Xiang Zhou. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Electrospun metal‐organic framework/polyacrylonitrile composite nanofibrous mat as a microsorbent for the extraction of tetracycline residue in human blood plasma

A new composite nanofiber of polyacrylonitrile doped with copper benzene‐1,3,5‐tricarboxylate metal‐organic framework was fabricated by electrospinning and used as a microsorbent in the solid‐phase extraction of trace tetracycline. The chemical structure of the adsorbent was studied by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area analysis, and Barrett‐Joyner‐Halenda pore size and volume analysis techniques. The significant parameters of the method including desorption solvent kind and volume, adsorbent mass, pH, and salt percentage were investigated. At the optimized conditions, the linear range was 8–1000 μg/L with a determination coefficient (R²) of 0.9954. The limits of detection and quantification were 2.40 and 8.00 μg/L, respectively. The inter‐ and intraday precisions were 4.7 and 3.4%, respectively. The developed extraction method was followed by high‐performance liquid chromatography and applied for the determination of tetracycline in human blood plasma, and good relative recoveries (97.3‐104.5%) were obtained.     

Development of a novel stirrerliquid/solid microextraction method for the separation and enrichment of trace levels of active compounds in traditional Chinese medicine

A novel stirrer‐liquid/solid microextraction method was developed for the separation and enrichment of trace levels of curcumin, bisdemethoxycurcumin, and demethoxycurcumin in Rhizoma Curcumae Longae, Radix Curcumae, and Rhizoma Curcumae before their analysis by high‐performance liquid chromatography with ultraviolet detection. In the proposed approach, a magnetic stirrer was immersed in decanol to coat its surface completely with decanol, which was used as an extraction platform. The stirrer coated with decanol is not only a power to agitate the sample solution to constantly update the sample on the stirrer surface but also it can adsorb and extract the target analytes. Some effective parameters, including suitable superficial area of stirrer, extraction solvent, sample phase pH, NaCl concentration, stirring rate, extraction time, sample phase volume, were analyzed and selected. Under the optimal conditions, the linearities are 0.0044–2.20 μg/mL, detection limits are 0.3–0.6 ng/mL, and the extraction content per unit length and enrichment factors of the target analytes are 6.24–9.71/mm and 589–917, respectively. Also, the stirrer‐liquid/solid microextraction mechanism for the extraction and enrichment of the target analytes was analyzed and expounded. The results showed that stirrer‐liquid/solid microextraction is a simple, rapid sample pretreatment approach with a high enrichment factor.     

A novel sorptive extraction method based on polydimethylsiloxane frit for determination of lung cancer biomarkers in human serum

In this study, a porous polypropylene frit was coated with polydimethylsiloxane (PDMS) as extraction medium, based on the home-made PDMS-frit, a rapid, simple and sensitive sorptive extraction method was established for analysis of potential biomarkers of lung cancer (hexanal and heptanal) in human serum samples. In the method, derivatization and extraction occurred simultaneously on the PDMS-frit, then the loaded frit was ultrasonically desorbed in acetonitrile. Polymerization, derivatization–extraction and desorption conditions were optimized. Under the optimal conditions, satisfactory results were gained, a wide linear application range was obtained in the range of 0.002–5.0 μmol L⁻¹ (R > 0.997) for two aldehydes, the detection limits (S N⁻¹ = 3) were 0.5 nmol L⁻¹ for hexanal and 0.4 nmol L⁻¹ for heptanal. The relative standard deviations (RSDs, n = 5) of the method were below 7.9% and the recoveries were above 72.7% for the spiked serum. All these results hint that the proposed method is potential for disease markers analysis in complex biological samples.     

The use of graphene-based magnetic nanoparticles as adsorbent for the extraction of triazole fungicides from environmental water

A graphene-based magnetic nanocomposite (graphene-ferriferrous oxide; G-Fe(3) O(4) ) was synthesized and used as an effective adsorbent for the preconcentration of some triazole fungicides (myclobutanil, tebuconazole, and hexaconazole) in environmental water samples prior to high-performance liquid chromatography-ultraviolet detection. The method, which takes the advantages of both nanoparticle adsorption and magnetic phase separation from the sample solution, could avoid the time-consuming experimental procedures commonly involved in the traditional solid phase extraction such as centrifugation and filtrations. Various experimental parameters affecting the extraction efficiencies such as the amount of the magnetic nanocomposite, extraction time, the pH values of the sample solution, salt concentration, and desorption conditions were investigated. Under the optimum conditions, the enrichment factors of the method for the three analytes were 5824, 3600, and 4761, respectively. A good linearity was observed in the range of 0.1-50 ng/mL for tebuconazole and 0.05-50 ng/mL for myclobutanil and hexaconazole, respectively, with the correlation coefficients ranging from 0.9992 to 0.9996. The limits of detection (S/N = 3) of the method were between 0.005 and 0.01 ng/mL. The results indicated that as a magnetic solid-phase extraction adsorbent, the graphene-ferriferrous oxide (G-Fe(3) O(4) ) has a great potential for the preconcentration of some compounds from liquid samples.     

The investigation of electrospun polymer nanofibers as a solid-phase extraction sorbent for the determination of trazodone in human plasma

A novel micro-extraction procedure was developed through the use of an electrospun polymer nanofiber as a solid-phase extraction (SPE) sorbent to directly extract trazodone from human plasma. The target compound was then monitored by a high performance liquid chromatography with ultraviolet detector (HPLC-UV) system. Parameters of influencing the extraction efficiency, such as fiber diameter, fiber packing amount, eluted solvent, pH and ionic strength were investigated. Under the optimized conditions, a linear response for trazodone over the range of 20-2000 ng mL⁻¹ was achieved with a γ² value of 0.9996. The precision of the method was examined with relative standard deviations of 5.7, 2.7, 2.2% corresponding to 50, 200, and 500 ng mL⁻¹, respectively, of trazodone spiked into 0.1 mL of plasma samples. The extraction recoveries of 58.3-75.2% and the relative recoveries of 94.6-105.5% were obtained. The limit of detection (LOD) was determined to be 8 ng mL⁻¹. A 15 min of HPLC gradient was successfully applied to determine trazodone from human plasma. Due to its simplicity, selectivity and sensitivity, the method may be applied to pharmacokinetic and pharmacodynamic studies of drugs.     

A review on solid phase microextraction-high performance liquid chromatography as a novel tool for the analysis of toxic metal ions

This paper reviews the practical applications of solid phase microextraction-High performance liquid chromatography in the analysis of toxic metal species as these are important contaminants and are carcinogenic. Their determination in formulations, in feed and food, and in complex environmental matrices (e.g., waste water and industrial effluents) often requires analytical methods capable of high efficiency, unique selectivity, and high sensitivity. Solid phase microextraction (SPME) requires low solvent consumption and is quick in use. SPME is used for extraction and online desorption of analytes with the mobile phase of HPLC and subsequent detection by UV, ICP-MS or ESI-MS as detectors. Different SPME-HPLC methods are summarized in this article to demonstrate the usefulness of this technique for metallic species of As, Cr, Pb, Hg and Se.     

Molecularly imprinted polymer as a novel solid‐phase microextraction coating for the selective enrichment of trace imidazolinones in rice,peanut, and soil

The development and application of an imazethapyr molecularly imprinted polymer‐based solid‐phase microextraction coating were investigated. A novel molecularly imprinted polymer coating with imazethapyr as template was firstly prepared by a one‐step in situ polymerization method, and demonstrated specific selectivity to imidazolinone herbicides in complicated samples. The structural characteristics and extraction performance of the imazethapyr molecularly imprinted polymer coating were studied. The molecularly imprinted polymer coating was homogeneous, dense, and heat and solvent resistant. Adsorption capacity experiments showed that the molecularly imprinted polymer coating could selectively extract imazethapyr and its structural analogs, and the maximum adsorption capacity was 2.5 times as much as that of the nonimprinted polymer coating. A method for the determination of five imidazolinones by imazethapyr molecularly imprinted polymer solid‐phase microextraction coupled with high‐performance liquid chromatography was developed. The linear range was 0.50–50 μg/L for imazameth, imazamox, imazapyr acid, and imazethapyr, and 1.0–100 μg/L for imazaquin acid, and the detection limits were within the range of 0.070–0.29 μg/L. The method was applied to simultaneous and multiresidual determinations of trace imidazolinones in rice, peanut, and soil samples with satisfactory recoveries of 60.6–99.5, 79.1–123, and 61.3–116%, respectively, and relative standard deviations of 0.40–10%, which indicated that this method was suitable for the trace analysis of imidazolinones in complex food and environmental samples.     

Electrospun polyethylene terephthalate/graphene oxide nanofibrous membrane followed by HPLC for the separation and determination of tamoxifen in human blood plasma

An electrospun polyethylene terephthalate/graphene oxide nanofibrous mat was fabricated and used as an effective and novel membrane for the solid‐phase extraction of tamoxifen in human blood plasma samples before detection by high‐performance liquid chromatography. The membrane was characterized by some identification techniques, such as FTIR spectroscopy, X‐ray diffraction, and scanning electron microscopy. The effective variables of the extraction procedure including desorption condition (type and volume of the eluent), adsorbent dose, pH of sample solution, salt concentration, and sample loading time were investigated and their optimum values were obtained using one factor at a time methodology. Under the optimized conditions, the results showed wide linear concentration range of 5–2000 ng/mL with a determination coefficient of 0.992. The limits of detection and limits of quantification were 1.3 and 5.0 ng/mL, respectively. The intra‐day and inter‐day precisions were 3.4 and 4.6%, respectively. The method was successfully applied to determination of tamoxifen in the blood plasma samples and satisfactory relative recoveries (92.6–98.3 %) were achieved.     

Octadecylsilane/Nylon‐6 composite as a thin‐film microextraction sorbent for the determination of bisphenol A in water samples

We report on the fabrication of a thin‐film composite for the extraction of bisphenol A from aqueous solutions. Nylon‐6, C₁₈ particles, and polyethylene glycol were used to prepare the thin film sorbent. Bisphenol A was used as a model compound to evaluate the extraction efficiency of the sorbent. High‐performance liquid chromatography with UV detection was used for the analysis. The extraction yield of the sorbent was compared with other thin films fabricated using different sorbents including nanoclay, LiChrolut EN, and multiwalled carbon nanotubes. Experimental parameters affecting the extraction performance (extraction time, desorption condition, sample stirring, and ionic strength of the sample solution) were investigated. The detection limit and the dynamic range of the method were 0.05 and 0.15–50 μg/L, respectively. The relative standard deviation of the method at two concentration levels (0.5 and 20 μg/L) was less than 7.2%. Finally, a polycarbonate baby bottle, river water, and wastewater samples were analyzed by the method.     

A novel liquid-phase microextraction method combined with high performance liquid chromatography for analysis of phthalate esters in landfill leachates

A novel liquid-phase microextraction (LPME) method was presented in this paper. The most attractive feature of this method is using a polychloroprene rubber tube (PCR tube) instead of a microsyringe to load organic solvent. The PCR tube and sample vial were horizontally placed so that the selection of organic solvent was not affected by the density of extractant. Therefore, the stability of organic solvent increased and the available organic solvent was extended greatly. In this work, three phthalate esters (PAEs) (dimethyl phthalate (DMP), diethyl phthalate (DEP), and di-n-butyl phthalate (DnBP)) were chosen as model analytes to testify the feasibility of the new method. A series of extraction parameters have been investigated systematically. Under the optimized condition, the method showed linear response over four orders of magnitude, ranged from 0.005 mg L⁻¹ to 50 mg L⁻¹. The correlation coefficients (r) were better than 0.997 and the limits of detection (LOD) were 0.0012 mg L⁻¹ for DMP, 0.0014 mg L⁻¹ for DEP and 0.0022 mg L⁻¹ for DnBP. Good reproducibility of extraction was acquired, the inter-day and intra-day relative standard deviation (R.S.D.) were below 7.9% and 7.4%, respectively. Recoveries that ranged from 82.7% to 116.9% were gained when the new method was used to determine three phthalate esters in landfill leachates. The enrichment factors were 5–26 for the three PAEs. The novel LPME is promising to be an alternative sample preparation method for extracting target analytes in complex sample matrices because of the simplicity, low cost and short sample preparation time.     

Carrier-mediated liquid phase microextraction coupled with high performance liquid chromatography for determination of illicit drugs in human urine

A new method was developed for the analysis of illicit drugs in human urine by coupling carrier-mediated liquid phase microextraction (LPME) to high performance liquid chromatography (HPLC). By adding an appropriate carrier in organic phase, simultaneous extraction and enrichment of hydrophilic (morphine and ephedrine) and hydrophobic (pethidine) drugs were achieved. Effects of the types of organic solvents and carriers, the carrier concentration in the organic phase, the HCl concentration in the acceptor solution, the stirring rate, and the extraction time on the enrichment factor of analytes were investigated. Under the optimal experimental conditions, high enrichment factors (202-515) were obtained. The linear detection ranges were 0.1-10 mg L⁻¹ for the studied drugs. The limits of detection (LOD) at signal-to-noise ratio of 3 were 0.05 mg L⁻¹ for both morphine and ephedrine, and 0.02 mg L⁻¹ for pethidine. This method was successfully applied to analysis of ephedrine in real urine specimens, revealing that the determination of illicit drugs in urine was feasible.     

Novel polymeric monolith materials with a β‐cyclodextrin‐graphene composite for the highly selective extraction of methyl jasmonate

A novel polymeric monolith column with a  β‐cyclodextrin‐graphene composite was prepared for extraction of methyl jasmonate. A simple, sensitive, and effective polymeric monolith microextraction with high‐performance liquid chromatography method has been presented for the determination. To carry out the best microextraction efficiency, several parameters such as sample flow rate, sample volume, and sample pH value were systematically optimized. In addition, the method validation showed a wide linear range of 5–2000 ng/mL, with a good linearity and low limits of detection for methyl jasmonate. The proposed method was successfully applied for the determination of methyl jasmonate in wintersweet flowers with recoveries of 90.67%. The result was confirmed by high‐performance liquid chromatography with mass spectrometry.     

Development of a novel ultrasound-assisted surfactant-enhanced emulsification microextraction method and its application to the analysis of eleven polycyclic aromatic hydrocarbons at trace levels in water

A novel ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) technique has been proposed by using low-density extraction solvents. In the proposed technique, Tween 80 and cyclohexane were injected into 5-mL glass test tubes with conical bottoms, containing 5.00 mL of a water sample that was located inside the ultrasonic bath. When the extraction process was finished, the glass test tube was sealed with a rubber plug and then placed upside down in a centrifuge. The finely dispersed droplets of cyclohexane collected at the conical bottom of test tube because the density of cyclohexane is less than of water, and the PAHs were concentrated in the cyclohexane. Next, 5 μL of the cyclohexane that collected at the conical bottom was removed using a 10-μL microsyringe and injected into high performance liquid chromatography coupled with fluorescence detection (HPLC-FLD) for analysis. The proposed method avoided the use of chlorinated solvents, which have been widely used as extraction solvents in a normal UASEME assay. Parameters that affected the extraction efficiency, such as the type and volume of the extraction solvent, the type and concentration of the surfactant, and the ultrasound emulsification time and salt addition, were investigated and optimised for the method. Under the optimum conditions, the enrichment factors ranged between 90 and 247. The limits of detection of the method were 0.6-62.5 ng L(-1). Good recoveries and repeatability of the method for the eleven PAHs were also obtained. The proposed UASEME technique has been demonstrated to be simple, practical and environmentally friendly for the determination of PAH residues in real water samples.     

New oil‐in‐salt liquid‐phase microextraction on permutite for the extraction and concentration of alkaloids in Coptis chinensis

A novel oil‐in‐salt liquid‐phase microextraction was developed and introduced for the extraction and concentration of the trace levels of active alkaloids in Coptis chinensis prior to being analyzed by high‐performance liquid chromatography with ultraviolet detection. Also, the oil‐in‐salt extraction mechanism was analyzed, the enrichment factor and extraction recovery were redefined, and the proposed method was compared with other methods. In the approach, the mixed solvent of pentanol/octanol (6:4, v/v) and NaCl (20% w/v) are immobilized on the permutite surface in turn to form oil‐in‐salt double membranes, through which the target analytes can be molecularized though salting‐out effect and be extracted by organic solvent. The main parameters affecting the approach were investigated and optimized. Under the optimized conditions, the enrichment factors of the analytes were 30–117, the linear ranges were 0.002–2 μg/mL for jatrorrhizine, coptisine, and palmatine, and 0.001–3 μg/mL for berberine (r ² ≥ 0.9923). The limits of detection were less than 1 ng/mL. Satisfactory recoveries (84.3%–120.3%) and precision (0.9%–7.5%) were also obtained. These results confirm that the approach is a simple and reliable sample pretreatment procedure and allows for the quantification of active alkaloids in C. chinensis at actual concentration levels.