Bis(trifluoromethylsulfonyl)imide-based frozen ionic liquid for the hollow-fiber solid-phase microextraction of dichlorodiphenyltrichloroethane and its main metabolites.

1-Hexadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is a solid-phase ionic organic material under ambient temperature and is considered as a kind of "frozen" ionic liquid. Because of their solid-state and ultra-hydrophobicity, "frozen" ionic liquids are able to be confined in the pores of hollow fiber, based on which a simple method was developed for the hollow-fiber solid-phase microextraction of dichlorodiphenyltrichloroethane and its main metabolites. Under optimized conditions, the proposed method results in good linearity (R2 > 0.9965) over the range of 0.5-50 µg/L, with low limits of detection and quantification in the range of 0.33-0.38 and 1.00-1.25 µg/L, respectively. Intra- and interday precisions evaluated by relative standard deviation were 3-6 and 1-6%, respectively. The spiked recoveries of dichlorodiphenyltrichloroethane and its main metabolites from real water samples were in the range of 64-113 and 79-112%, respectively, at two different concentration levels. The results suggest that "frozen" ionic liquids are promising for use as a class of novel sorbents.

Glycine functionalized multiwall carbon nanotubes as a novel hollow fiber solid-phase microextraction sorbent for pre-concentration of venlafaxine and o-desmethylvenlafaxine in biological and water samples prior to determination by high-performance liquid chromatography.

A hollow fiber solid-phase microextraction method for pre-concentration of venlafaxine and o-desmethylvenlafaxine in biological matrices is described for the first time. The functionalized MWCNTs with an amino acid, glycine, were synthesized and held in the pore of a hollow fiber by sol-gel technique. In order to extract venlafaxine and o-desmethylvenlafaxine from real samples, the hollow fiber was immersed into the sample solution under a magnetic stirring for 20 min. The extracted venlafaxine and o-desmethylvenlafaxine from the fibers were then desorbed with methanol by sonication and analyzed using high-performance liquid chromatography. Important microextraction parameters including pH of donor phase, donor phase volume, stirring rate, extraction time, and desorption conditions such as the type and volume of solvents and desorption time were thoroughly investigated and optimized. The optimized technique provides good repeatability (RSD of the intraday precision 3.7 and 3.4, interday precision of 5.8 and 5.4 %), linearity of (0.1-300 and 0.2-360 ng mL(-1)), low LODs of (0.03 and 0.07 ng mL(-1)), and high enrichment factor of (164 and 176) for venlafaxine and o-desmethylvenlafaxine, respectively. The analytical performance of Gly-MWCNTs as a new SPME sorbent was compared with MWCNTs and carboxylic MWCNTs. The results indicate that Gly-MWCNTs are quite effective for extraction of venlafaxine and o-desmethylvenlafaxine. Feasibility of the method was evaluated by analyzing human urine and real water samples. The results obtained in this work show a promising, simple, selective, and sensitive sample preparation and determination method for biological and water samples.

Keggin type phosphotungstic acid intercalated copper-chromium-layered double hydroxide reinforced porous hollow fiber as a sorbent for hollow fiber solid phase microextraction of selected chlorophenols besides their quantification via high performance liquid chromatography.

Herein, a copper-chromium-layered double hydroxide (Cu/Cr-LDH) was synthesized by the co-precipitation method. The Cu/Cr-LDH was intercalated to the Keggin-type polyoxometalate (H3PW12O40). The modified LDH accommodated in the pores of hollow fiber (HF), to prepare the extracting device for the HF-solid phase microextraction method (HF-SPME). The method was used for the extraction of 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6- trichlorophenol from tap water, river water, and tea sample. The extracted target analytes were quantified via high-performance liquid chromatography-UV detection. The figures of merit of the method such as, linear dynamic ranges (LDRs), limit of detections (LODs) and, limit of quantifications (LOQs), were determined based on the obtained optimum condition. Based on the results, the LDR was between 1 and 500 µg L - 1 and r2 higher than 0.9960. The LODs and LOQs were obtained in the ranges of 0.28-0.36 µg L - 1 and 0.92-1.1 µg L - 1, respectively. The relative standard deviations ((RSDs% for inter-and intra-day) of the method for the extraction of target analytes were calculated in two different concentrations of (2 and 10 µg L - 1) and (5 and 10 µg L - 1) between 3.70% - 5.30% and 3.50% - 5.70%-respectively. The enrichment factors were obtained between 57 and 61. In order to investigate the accuracy of the method, also the relative recovery was obtained, between 93 and 105%. Finally, the proposed method was used for the extraction of the selected analytes in different water and tea samples.

In-situ synthesis of nanocubic cobalt oxide @ graphene oxide nanocomposite reinforced hollow fiber-solid phase microextraction for enrichment of non-steroidal anti-inflammatory drugs from human urine prior to their quantification via high-performance liquid chromatography-ultraviolet detection.

The in-situ synthesis and application of nanocubic Co3O4-coated graphene oxide (Co3O4@ GO) was introduced for the first time to present a cost-effective, stable and convenient operation and a simple device for hollow fiber solid-phase microextraction (HF-SPME) of four selected nonsteroidal anti-inflammatory drugs (NSAIDs) including diclofenac, mefenamic acid, ibuprofen and indomethacin. The extracted analytes were desorbed by an appropriate organic solvent and analyzed via high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The prepared sorbent was approved using different characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The variables effective on the Co3O4@GO-HF-SPME method including extraction time, desorption time, desorption solvent volume, sample pH, stirring rate and ionic strength were screened via Plackett-Burman design and then optimized by Box-Behnken design. Under optimal condition, the calibration curves were linear within the range of 1.0-200.0 µg L-1 of analyte concentration with detection limits of 0.18-1.1 µg L-1 and the relative standard deviations less than 10.1%. The limits of quantification (LOQs) were in the range of 0.60-3.67 µg L-1. Matrix effect was not observed with this method; therefore, standard addition is not necessary for quantification of target compounds. The enrichment factors were obtained in the range of 49-68. The relative recoveries of the urine sample analysis were calculated in the range of 93-102%. Finally, the presented method exhibited good sensitivity, excellent repeatability, high reusability and acceptable precision, which will be a promising method to analyze various nonsteroidal anti-inflammatory drugs in urine samples.

MIL-101 (Cr) @ graphene oxide-reinforced hollow fiber solid-phase microextraction coupled with high-performance liquid chromatography to determine diazinon and chlorpyrifos in tomato, cucumber and agricultural water.

An effective, sensitive, relatively-fast and cost-effective method was developed to determine two types of selected organophosphorus pesticides (OPPs) including diazinon and chlorpyrifos in tomato, cucumber and agricultural water samples through applying MIL-101@ graphene oxide-reinforced hollow fiber solid-phase microextraction (MIL-101@GO-HF-SPME). The extracted analytes were desorbed via organic solvent and analyzed through high-performance liquid chromatography-ultraviolet detection (HPLC-UV) after extraction. MIL-101@ GO sorbent which was previously prepared and characterized was first dispersed in methanol by ultrasonication and then immobilized into the pores of a hollow fiber (HF). Several factors involved in MIL-101@GO-HF-SPME experiment such as desorption volume, ionic strength, desorption time, sample pH, extraction time and stirring rate were screened via Plackett-Burman design and then optimized through Box-Behnken design with the purpose of reaching the highest extraction efficiency. The above method showed a good linear range (1-500 µg L-1) with coefficient of determination higher than 0.9948, low limits of determination (LODs, 0.21 and 0.27 µg L-1), acceptable limits of quantifications (LOQs, 0.72 and 0.91 µg L-1), good enrichment factors (EFs, 49 and 41), acceptable absolute recoveries (AR%, 49 and 41%) and good spiking recoveries (88-104%) under the optimized condition at three different spiked levels for chlorpyrifos and diazinon, respectively. It is worth mentioning that due to the clean-up function of HF, there is no time-consuming sample pretreatment procedure (e.g. filtration or centrifugation) prior to the microextraction. Therefore, the presented method took advantage of both excellent adsorption performance of MIL-101@GO and the clean-up function of HF. The results confirmed that the presented method would be promising for the analysis of various types of these pesticides in environmental and vegetable samples.

Potential application of amino acids in analytical toxicology.

The ability of extraction and preconcentration of small quantities of substances from biological samples is important in analytical sciences, particularly forensic medicine. In the present study, we evaluated the binding potential of amino acids to produce a new solid phase microextraction fiber based on carbon nanotube (CNTs) for extraction and preconcentration of small amount of morphine in urine sample. Raw CNTs were first carboxylated and then functionalized with 3 amino acids including glutamate, arginine, and cysteine. Functionalization was confirmed by FTIR analysis, Raman spectroscopy and SEM imaging. The functionalized CNTs were coated on polypropylene hollow fiber and used for preconcentration. The results of HPLC analysis in isocratic elution mode using acetonitrile-sodium acetate (10:90, v/v; pH 4; 0.01 M) as the mobile phase showed that amino acids are able to adsorb morphine and the prepared fiber could preconcentrate a very low concentration of morphine (0.25 ppb) in urine matrix. In addition, the fiber was successfully used for up to 30 times with no significant loss in the extraction efficiency. Lowest limit of detection (LOD) and limit of quantitation (LOQ) was 0.07 and 0.25, respectively. Also, the lowest and best recovery of the fiber was 87.8% and 139% at LOQ, which belonged to glutamate and arginine, respectively. The fibers based on amino acids can be used for the detection of a small amount of morphine in biological samples, which are not detectable by conventional methods. Simple mechanism of these fibers in preconcentrating morphine makes them a novel candidate for detection of other opiates and drugs of abuses in crime scene investigations and postmortem examinations several days after exposure.

Multiwall carbon nanotube- zirconium oxide nanocomposite hollow fiber solid phase microextraction for determination of polyaromatic hydrocarbons in water, coffee and tea samples.

The purpose of this study was to evaluate the application of hollow fiber solid-phase microextraction (HF-SPME) followed by HPLC-UV to determine the ultra-trace amounts of polycyclic aromatic hydrocarbons (PAHs) as model analytes in complex coffee and tea samples. HF-SPME can be effectively used as an alternative to the direct immersion SPME (DI-SPME) method in complex matrices. The DI-SPME method suffers from serious limitation in dirty and complicated matrices with low sample clean-up, while the HF-SPME method has high clean-up and selectivity due to the high porosity of hollow fiber that can pick out analyte from complicated matrices. As a hollow fiber sorbent, a novel multiwall carbon nanotube/zirconium oxide nanocomposite (MWCNT/ZrO2) was fabricated. The excellent adsorption of PAHs on the sorbent was attributed to the dominant roles of π-π stacking interaction and hydrophobic interaction. Under the optimized extraction conditions, the wide linear range of 0.1-200 µg L-1 with coefficients of determination better than 0.998 and low detection limits of 0.033-0.16 µg L-1 with satisfactory precision (RSD < 6.6%) were obtained. The relative recoveries obtained by spiking the PAHs in water, coffee and tea samples were in the range of 92.0-106.0%. Compared to other methods, MWCNT/ZrO2 hollow fiber solid phase microextraction demonstrated a good capability for determination of PAHs in complex coffee and tea samples.

N-doped carbon nanotubes-reinforced hollow fiber solid-phase microextraction coupled with high performance liquid chromatography for the determination of phytohormones in tomatoes.

A N-doped carbon nanotubes-reinforced hollow fiber solid-phase microextraction (N-doped CNTs-HF-SPME) method was developed for determination of two naphthalene-derived phytohormones, 1-naphthalene acetic acid (NAA) and 2-naphthoxyacetic acid (2-NOA), at trace levels in tomatoes. N-doped CNTs were dispersed in ultrapure water with the assistance of surfactant, and then immobilized into the pores of hollow fiber by capillary forces and sonification. The resultant N-doped CNTs-HF was wetted with 1-octanol, subsequently immersed into the tomato samples to extract the target analytes under a magnetic stirring, and then desorbed with methanol by sonication prior to chromatographic analysis. Compared with CNTs, the surface hydrophilicity of N-doped CNTs was improved owing to the doping of nitrogen atoms, and a uniform dispersion was formed, thus greatly simplifying the preparation process and reducing waste of materials. In addition, N-doped CNTs-HF exhibits a more effective extraction performance for NAA and 2-NOA on account of the introduction of Lewis-basic nitrogen. It is worth to mention that owing to the clean-up function of HF, there are not any complicated sample pretreatment procedures prior to the microextraction. To achieve the highest extraction efficiency, important microextraction parameters including the length and the concentration level of N-doped CNTs in surfactant solution, extraction time, desorption conditions such as the type and volume of solvents, pH value, stirring rate and volume of the donor phase were thoroughly investigated and optimized. Under the optimal conditions, the method showed 165- and 123-fold enrichment factors of NAA and 2-NOA, good inter-fiber repeatability and batch-to-batch reproducibility, good linearity with correlation coefficients higher than 0.9990, low limits of detection and quantification (at ng g-1 levels), and satisfactory recoveries in the range of 83.10-108.32% at three spiked levels. The proposed method taking advantages of both excellent adsorption performance of N-doped CNTs and the clean-up function of HF, was a simple, green, efficient and cost-effective enrichment procedure for the determination of trace NAA and 2-NOA in tomatoes.

Graphene oxide-silica composite coating hollow fiber solid phase microextraction online coupled with inductively coupled plasma mass spectrometry for the determination of trace heavy metals in environmental water samples.

In this work, a novel graphene oxide-silica (GO-silica) composite coating was prepared for hollow fiber solid phase microextraction (HF-SPME) of trace Mn, Co, Ni, Cu, Cd and Pb followed by on-line inductively coupled plasma mass spectrometry (ICP-MS) detection. The structure of the prepared graphene oxide and GO-silica composite was studied and elucidated by atomic force microscopy (AFM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The GO-silica composite coated hollow fiber was characterized by scanning electron microscope (SEM), and the results show that the GO-silica composite coating possessed a homogeneous and wrinkled structure. Various experimental parameters affecting the extraction of the target metal ions by GO-silica composite coated HF-SPME have been investigated carefully. Under the optimum conditions, the limits of detection (LODs, 3σ) for Mn, Co, Ni, Cu, Cd and Pb were 7.5, 0.39, 20, 23, 6.7 and 28 ng L(-1) and the relative standard deviations (RSDs, c(Mn, Co, Cd)=0.05 µg L(-1), c(Ni, Cu, Pb)=0.2 µg L(-1), n=7) were 7.2, 7.0, 5.6, 7.3, 7.8 and 4.6%, respectively. The accuracy of the proposed method was validated by the analysis of Certified Reference Material of GSBZ 50009-88 environmental water and the determined values were in a good agreement with the certified values. The proposed method has been successfully applied for the determination of trace metals in real environmental water samples with recoveries ranging from 85 to 119%.

Sol-gel-derived magnetic SiO2/TiO2 nanocomposite reinforced hollow fiber-solid phase microextraction for enrichment of non-steroidal anti-inflammatory drugs from human hair prior to high performance liquid chromatography.

Hollow fiber-solid phase micro-extraction (HF-SPME) technique containing sol-gel-derived Fe3O4/SiO2/TiO2 core-double shell nanocomposite as a novel high efficiency sorbent, coupled with high performance liquid chromatography was used to extraction and determination of six non-steroidal anti-inflammatory drugs; acetylsalicylic acid, naproxen, piroxicam, diclofenac, indomethacin and mefenamic acid, in hair samples. First, magnetite nanoparticles (Fe3O4-NPs) were synthesized by chemical co-precipitation of Fe(II) and Fe(III) ions (where the ratio of Fe(II) to Fe(III) is 1:2 and a non-oxidizing environment), in alkaline medium to produce magnetite particles. Subsequently, surface of Fe3O4-NPs was modified with SiO2 and TiO2 using layer-by-layer chemical technique. A core-shell structure of Fe3O4/SiO2/TiO2 composite was prepared by coating magnetite core particles with silica and titania layers. In the proposed method, NSAIDs were extracted by the synthesized nanocomposite and analyzed by HPLC. The parameters affecting the efficiency of magnetic nanoparticle (MNPs) assisted HF-SPME were investigated and optimized. The method validation was included and satisfying results with high pre-concentration factors (405 up to 2450) were obtained. It owes large surface area and porosity of the nano-adsorbent. Under the optimal conditions, the method detection limits (S/N=3) were in the range of 0.01-0.10µgml-1 and the limits of quantification (S/N=10) between 0.04 and 0.30µgml-1. Relative standard deviations were 3.09-6.61%. Eventually, the method was successfully applied to human hair after administration of NSAIDs.

Carbon nanotubes reinforced hollow fiber solid phase microextraction for the determination of strychnine and brucine in urine.

A mixed matrix membrane (MMM), based on carbon nanotubes (CNTs) and hollow fiber (HF), was prepared and combined with solid phase microextraction (SPME) mode to determine strychnine and brucine in urine. This MMM was prepared by dispersing CNTs in water via surfactant assistance, and then immobilizing CNTs into the pores of HF by capillary forces and sonification. The prepared carbon nanotubes reinforced hollow fiber (CNTs-HF) was subsequently wetted by a few microliters of organic solvent (1-octanol), and then applied to extract the target analytes in direct immersion sampling mode. After extraction, analytes were desorbed via ultrasonic-assisted effect, and then detected via high-performance liquid chromatography (HPLC). To achieve the highest extraction efficiency, main extraction parameters such as the type and amount of surfactant, the diameter and doping level of CNTs, extraction time, desorption condition, pH value, stirring rate and volume of the donor phase were optimized. Under the optimum extraction conditions, the method showed good linearity ranges with correlation coefficients higher than 0.9990, good repeatability and batch-to-batch reproducibility with relative standard deviations (RSDs) less than 6% and 5% for strychnine and brucine, respectively, and low limits of detection (0.7 and 0.9 µg L(-1) for strychnine and brucine, respectively). The recoveries were in the range of 83.81-116.14% at three spiked levels. The developed method was successfully applied to real urine sample with mean relative recoveries of 94.28% and 91.30% for strychnine and brucine, respectively. The developed method shows comparable results against reference methods and is a simple, green, and cost-effective microextraction technique.