In-tube Solid-phase Microextraction Method Research Articles

Novel synthesized attapulgite nanoparticles-based hydrophobic monolithic column for in-tube solid-phase microextraction of thiosildenafil, pseudovardenafil, and norneosildenafil in functional foods.

In this study, a novel method which involved in-tube solid-phase microextraction (SPME) using an attapulgite (ATP) nanoparticles-based hydrophobic monolithic column was successfully developed. It was coupled with high-performance liquid chromatography-ultraviolet detection for the determination of three phosphodiesterase-5 (PDE-5) inhibitors, including thiosildenafil, pseudovardenafil, and norneosildenafil, in functional foods. The monolithic column was prepared by one-step polymerization, using 3-trimethoxysilylpropyl methacrylate-modified ATP nanoparticles and 1-butyl-3-vinylimidazolium bromide (VBIMBr) as the functional monomers, and ethylene glycol dimethacrylate (EDMA) as the cross-linker. The obtained poly(ATP-VBIMBr-EDMA) monolith was characterized by scanning electron microscopy equipped with energy-dispersive analysis of X-ray, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. The adsorption capacity, up to 2.00μg/cm calculated by the Langmuir isotherm model, was about six times that of the poly(VBIMBr-EDMA) monolith. Crucial factors affecting the extraction efficiency, including sample solvent, elution solvent, flow rates of sampling loading and elution, sample loading volume, and elution volume, were investigated in details. Under the optimal in-tube SPME conditions, the proposed method showed good reproducibility with run-to-run, column-to-column, and batch-to-batch relative standard deviations less than 7.2%, and low limits of detection of 0.5-0.9ng/mL in real samples. Thiosildenafil was detected in four types of functional foods with the contents of 1.30-4.78μg/g. This newly proposed in-tube SPME method based on poly(ATP-VBIMBr-EDMA) monolith may provide a simple, efficient, and promising alternative to daily monitoring of PDE-5 inhibitors in functional foods.

Determination of ultra-trace amounts of chlorophenols in rain, tap and river water by an electrochemically controlled in-tube solid phase microextraction method

A nanostructured copolymer coating consisting of PPy doped with Naf was electrochemically synthesized on the inner surface of a stainless steel capillary tube. It was utilized to extract trace pollutants from water samples.

Graphene oxide based in‐tube solid‐phase microextraction combined with liquid chromatography tandem mass spectrometry for the determination of triazine herbicides in water

J. Sep. Sci. 2015, 38, 2312–2319. DOI: 10.1002/jssc.201500070 Monolayer graphene oxide sheets were covalently modified onto the inner wall of a fusedsilica capillary to prepare a graphene oxide coating with 30 nm thickness and porous wrinkled-membrane-like structure, which was used as an extraction column for in-tube solid phase microextraction. The coating showed enough stability and high extraction efficiency to triazine compounds due to π-π stacking and hydrogen bonding interactions between graphene oxide and triazine molecules. The proposed in-tube solid phase microextraction method was applied to simultaneous analysis of trace triazine herbicides in environmental samples, with good recoveries and repeatability.

Electroplating of nanostructured polyaniline–polypyrrole composite coating in a stainless-steel tube for on-line in-tube solid phase microextraction

In this work, a novel and efficient on-line in-tube solid phase microextraction method followed by high performance liquid chromatography was developed for preconcentration and determination of trace amounts of parabens. A nanostructured polyaniline–polypyrrole composite was electrochemically deposited on the inner surface of a stainless steel tube and used as the extraction phase. Several important factors that influence the extraction efficiency, including type of solid-phase coating, extraction and desorption times, flow rates of the sample solution and eluent, pH, and ionic strength of the sample solution were investigated and optimized. Under the optimal conditions, the limits of detection were in the range of 0.02–0.04μgL−1. This method showed good linearity for parabens in the range of 0.07–50μgL−1, with coefficients of determination better than 0.998. The intra- and inter-assay precisions (RSD%, n=3) were in the range of 5.9–7.0% and 4.4–5.7% at three concentration levels of 2, 10, and 20μgL−1, respectively. The extraction recovery values for the spiked samples were in the acceptable range of 80.3–90.2%. The validated method was successfully applied for analysis of methyl-, ethyl-, and propyl parabens in some water, milk, and juice samples.

Optimisation of an in-tube solid phase microextraction method coupled with HPLC for determination of some oestrogens in environmental liquid samples using different capillary columns

A simple on-line method for simultaneous determination of some oestrogens including oestriol (E3), norethisterone (NORE), ethynylestradiol (EE2), D-norgestrel (NORG) and bisphenol A (BPA), in environmental liquid samples was developed by coupling in-tube solid phase microextraction (in-tube SPME) to high-performance liquid chromatography with diode array (DAD) and fluorescence (FLD) detectors. Two capillary chromatographic columns (Supel-Q™ and Carboxen™ 1006 porous layer open tubular) were selected to develop this method. To achieve optimum extraction performance, several parameters were investigated including number of draw/eject cycles and the sample volume for each of the columns. Reproducibility was satisfactory for inter- and intra-day precision, yielding % RSDs of less than 10% and 7.6%, respectively. Limits of detection (LODs) and quantification (LOQs) for the proposed method using a DAD detector were achieved in the ranges of 0.04–0.63 ng mL−1 and 0.12–1.9 ng mL−1, depending of the capillary column used. Fluorescence detection improved these parameters for E3, BPA and EE2, obtaining LODs of 0.005–0.03 ng mL−1 and LOQs of 0.015–0.08 ng mL−1 using Supel-Q and LODs of 0.01–0.015 ng mL−1 and LOQs of 0.025–0.04 ng mL−1 using Carboxen. The proposed method was successfully applied to spiked environmental waters obtaining recoveries greater than 80%.

Determination of ochratoxins in nuts and grain samples by in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive method for the determination of ochratoxins A and B in nuts and grain samples was developed using an automated in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-mass spectrometry (LC-MS). Ochratoxins were separated within 5 min by high-performance liquid chromatography using an Inertsil ODS-3 column with 5mM anmonium acetate/acetonitrile (65/35, v/v) as the mobile phase. Electrospray ionization conditions in the positive ion mode were optimized for mass spectrometric detection of ochratoxins. The pseudo molecular ion [M+H](+) was used to detect ochratoxins with selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a Carboxen-1006 PLOT capillary column as an extraction device. The extracted ochratoxins were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME/LC-MS with SIM method, good linearities of the calibration curves (r=0.9993 for ochratoxin A and r=0.9989 for ochratoxin B) were obtained in the concentration range from 0.5 to 20 ng/mL. The detection limits (S/N=3) for ochratoxins A and B were 92 and 89 pg/mL, respectively. The in-tube SPME method showed above 15-19-fold greater sensitivity than the direct injection method (10 μL injection). The within-day and between-day precisions (relative standard deviations) were below 5.1% and 7.7% (n=6), respectively. This method was applied successfully to analysis of nuts and grain samples without interference peaks. The recoveries of ochratoxins spiked into extraction solution from nut samples were above 88%. Ochratoxins were detected at 0.7-8.8 ng/g levels in various nuts and grain samples.

Determination of polycyclic aromatic hydrocarbons in food samples by automated on-line in-tube solid-phase microextraction coupled with high-performance liquid chromatography-fluorescence detection

A simple and sensitive automated method, consisting of in-tube solid-phase microextraction (SPME) coupled with high-performance liquid chromatography-fluorescence detection (HPLC-FLD), was developed for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in food samples. PAHs were separated within 15 min by HPLC using a Zorbax Eclipse PAH column with a water/acetonitrile gradient elution program as the mobile phase. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a CP-Sil 19CB capillary column as an extraction device. Low- and high-molecular weight PAHs were extracted effectively onto the capillary coating from 5% and 30% methanol solutions, respectively. The extracted PAHs were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME HPLC-FLD method, good linearity of the calibration curve ( r > 0.9972) was obtained in the concentration range of 0.05–2.0 ng/mL, and the detection limits ( S/ N = 3) of PAHs were 0.32–4.63 pg/mL. The in-tube SPME method showed 18–47 fold higher sensitivity than the direct injection method. The intra-day and inter-day precision (relative standard deviations) for a 1 ng/mL PAH mixture were below 5.1% and 7.6% ( n = 5), respectively. This method was applied successfully to the analysis of tea products and dried food samples without interference peaks, and the recoveries of PAHs spiked into the tea samples were >70%. Low-molecular weight PAHs such as naphthalene and pyrene were detected in many foods, and carcinogenic benzo[ a]pyrene, at relatively high concentrations, was also detected in some black tea samples. This method was also utilized to assess the release of PAHs from tea leaves into the liquor.

Determination of aflatoxins in food samples by automated on-line in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive automated method for determination of aflatoxins (B1, B2, G1, and G2) in nuts, cereals, dried fruits, and spices was developed consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). Aflatoxins were separated within 8 min by high-performance liquid chromatography using a Zorbax Eclipse XDB-C8 column with methanol/acetonitrile (60/40, v/v): 5 mM ammonium formate (45:55) as the mobile phase. Electrospray ionization conditions in the positive ion mode were optimized for MS detection of aflatoxins. The pseudo-molecular ions [M+H] + were used to detect aflatoxins in selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted aflatoxins were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC–MS with SIM method, good linearity of the calibration curve ( r > 0.9994) was obtained in the concentration range of 0.05–2.0 ng/mL using aflatoxin M1 as an internal standard, and the detection limits (S/N = 3) of aflatoxins were 2.1–2.8 pg/mL. The in-tube SPME method showed >23-fold higher sensitivity than the direct injection method (10 μL injection volume). The within-day and between-day precision (relative standard deviations) at the concentration of 1 ng/mL aflatoxin mixture were below 3.3% and 7.7% ( n = 5), respectively. This method was applied successfully to analysis of food samples without interference peaks. The recoveries of aflatoxins spiked into nuts and cereals were >80%, and the relative standard deviations were <11.2%. Aflatoxins were detected at <10 ng/g in several commercial food samples.

Determination of patulin in fruit juice and dried fruit samples by in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive method for the determination of patulin in fruit juice and dried fruit samples was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). Patulin was separated within 5 min by high-performance liquid chromatography using a Synergi MAX-RP 80A column and water/acetonitrile (80/20, v/v) as the mobile phase. Electrospray ionization conditions in the negative ion mode were optimized for MS detection of patulin. The pseudo-molecular ion [M−H] − was used to detect patulin in selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample using a Carboxen 1006 PLOT capillary column as an extraction device. The extracted patulin was readily desorbed from the capillary by passage of the mobile phase, and no carry-over was observed. Using the in-tube SPME LC–MS with SIM method, good linearity of the calibration curve ( r = 0.9996) was obtained in the concentration range of 0.5–20 ng/mL using 13C 3-patulin as an internal standard, and the detection limit (S/N = 3) of patulin was 23.5 pg/mL. The in-tube SPME method showed >83-fold higher sensitivity than the direct injection method (10 μL injection volume). The within-day and between-day precision (relative standard deviations) were below 0.8% and 5.0% ( n = 6), respectively. This method was applied successfully for the analysis of fruit juice and dried fruit samples without interference peaks. The recoveries of patulin spiked into apple juice were >92%, and the relative standard deviations were <4.5%. Patulin was detected at ng/mL levels in various commercial apple juice samples.

Analysis of abietic acid and dehydroabietic acid in food samples by in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive method for the determination of abietic acid and dehydroabietic acid in food samples was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC/MS). These compounds were separated within 5 min by HPLC using an ODS-3 column and 5 mM ammonium formate/acetonitrile (10/90, v/v). Electrospray ionization conditions in the negative ion mode were optimized for MS detection of abietic acid and dehydroabietic acid. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a Supel Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC/MS method, good linearity of the calibration curve ( r > 0.9998) was obtained in the concentration range from 0 to 50 ng/mL, and the detection limits (S/N = 3) of abietic acid and dehydroabietic acid were 2.9 and 2.1 pg/mL, respectively. The in-tube SPME method showed above 75-fold greater sensitivity than the direct injection method (5 μL injection). This method was applied successfully to analysis of food samples without interference peaks. The recoveries of abietic acid and dehydroabietic acid spiked into liquid samples were above 79%, and the relative standard deviations were below 6.6%. These compounds were detected at ng/mL or ng/g levels in various liquid or solid food samples contacted with paper.

Determination of fluoroquinolones in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography–tandem mass spectrometry

We developed a sensitive and useful method for the determination of five fluoroquinolones (FQs), enoxacin, ofloxacin, ciprofloxacin, norfloxacin, and lomefloxacin in environmental waters, using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC/MS/MS). These compounds were analysed within 7 min by high-performance liquid chromatography (HPLC) using a CAPCELL PAK C8 column and aqueous ammonium formate (pH 3.0, 5 mM)/acetonitrile (85/15, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the positive ion mode were optimized for MS/MS detection. In order to optimize the extraction of FQs, several in-tube SPME parameters were examined. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample at a flow-rate of 150 μL/min, using a Carboxen 1010 PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve ( r ≥ 0.997) was obtained in the concentration range from 0.1 to 10 ng/mL for all compounds examined. The limits of detection (S/N = 3) of the five FQs ranged from 7 to 29 pg/mL. The in-tube SPME method showed 60–94-fold higher sensitivity than the direct injection method (5 μL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface waters and wastewaters were collected from the area around Asahi River, and ofloxacin was detected in wastewater samples of a sewage treatment plant and other two hospitals at 17.5–186.2 pg/mL. The recoveries of FQs spiked into river water were above 81% for a 0.1 or 0.2 ng/mL spiking concentration, and the relative standard deviations were below 1.9–8.6%.

Simple and Rapid Determination of Linear Alkylbenzene Sulfonates by In-Tube Solid-Phase Microextraction Coupled with Liquid Chromatography

A simple and rapid method for the determination of linear alkylbenzene sulfonates (LAS) in aqueous samples was developed by using in-tube solid-phase microextraction (SPME) coupled with liquid chromatography (LC). Introducing a short section of open-tubular gas chromatography column as the extraction device, in-tube SPME method has been developed by Pawliszyn et al. for an effective on-line coupling of sample preparation and LC separation. As an open tubular capillary column for the in-tube SPME, we used a porous-layer open-tabular (PLOT) column with a porous layer on the inner wall and a larger surface area. The separation of LAS was carried out by using a mobile phase containing 65% acetonitrile and 35% sodium perchlorate aqueous solution (287 mM) with a Wakopak® WS AS-Aqua column. LAS in the sample solution was enriched through the capillary sequentially by using a microsyringe pump equipped with a gastight syringe and analyzed by using high performance liquid chromatography with fluorescence detection. The fluorescence excitation and emission were fixed at λex = 221 nm and λem =284 nm. With the optimum conditions, linear calibration curves were obtained from 0.2 to 25 μg/l. The detection limits based on 3σ were between 0.02 and 0.10 μg/l and the relative standard deviations of the method were between 1.6 and 12% (n = 5). The method was successfully applied to the determination of LAS in natural water samples. This method was applied to the determination of LAS in some urban river waters where domestic wastewater was discharged.

Fully automated analysis of estrogens in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography–tandem mass spectrometry

A simple, rapid and sensitive method for the determination of five estrogens, estrone, 17β-estradiol, estriol, ethynyl estradiol, and diethylstilbestrol, was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC/MS/MS). These estrogens were separated within 8 min by HPLC using an XDB-C8 column and 0.01% ammonia/acetonitrile (60/40, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the negative ion mode were optimized for MS/MS detection of the estrogens. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve ( r ≥ 0.9996) was obtained in the concentration range from 10 to 200 pg/mL for all compounds examined. The limits of detection ( S/ N = 3) of the five estrogens examined ranged from 2.7 to 11.7 pg/mL. The in-tube SPME method showed 34–90-fold higher sensitivity than the direct injection method (5 μL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface water and wastewater samples were collected from the area around Asahi River, and estriol was detected at 35.7 pg/mL in the effluent of a sewage treatment plant. The recoveries of estrogens spiked into river waters were above 86%, except for estriol, and the relative standard deviations were below 0.9–8.8%.

Determination of camptothecin and 10-hydroxycamptothecin in human plasma using polymer monolithic in-tube solid phase microextraction combined with high-performance liquid chromatography

A biocompatible in-tube solid-phase microextraction (SPME) device was used for the direct and on-line extraction of camptothecin and 10-hydroxycamptothecin in human plasma. Biocompatibility was achieved through the use of a poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column for extraction. Coupled to high performance liquid chromatography (HPLC) with UV detection, this on-line in-tube SPME method was successfully applied to the simultaneous determination of camptothecin and 10-hydroxycamptothecin in human plasma. The calculated detection limits for camptothecin and 10-hydroxycamptothecin were found to be 2.62 and 1.79 ng/mL, respectively. The method was linear over the range of 10-1000 ng/mL. Excellent method reproducibility was achieved, yielding RSDs of 2.49 and 1.59%, respectively. The detection limit (S/N = 3) of camptothecin was found to reach 0.1 ng/mL using fluorescence detection. The proposed method was shown to cope robustly with the extraction and analysis of camptothecin and 10-hydroxycamptothecin in plasma samples.

On-line coupling of in-tube solid phase microextraction (SPME) to HPLC for analysis of carbamates in water samples: Comparison of two commercially available autosamplers

In-tube solid phase microextraction (SPME) is a new on-line sample preparation technique that is easily installed on a conventional high-performance liquid chromatography (HPLC) autosampler, and has previously been used with the LC Packings FAMOS autosampler without modification of the autosampler itself. This paper describes the on-line coupling of in-tube SPME to a Hewlett Packard (HP) model 1100 HPLC autosampler, and reports on several fundamental aspects of the technology. The extraction and desorption processes with this system were thoroughly studied for a group of carbamate pesticides in water samples. The similarities and differences of the in-tube SPME technique with the two different autosamplers, FAMOS and Hewlett Packard, were compared during method development. The optimized conditions were successfully applied to extract the carbamates of interest from spiked surface, well, and tap water samples, exhibiting excellent method precision. The % relative standard deviation (RSD) for all the carbamates studied in the different environmental water samples was between 0.8 and 6.0%. There was no noticeable extraction efficiency decrease relative to pure laboratory samples when the method was applied to spiked environmental water samples. The method was found to be linear between 2 and 20,000 μg/L with correlation coefficients in the range of 0.9791 to 0.9991. With respect to the different water samples, the limits of detection (LODs) for all the carbamates studied were in the range of 0.44–17 μg/L. For carbaryl, the LODs were between 0.44 and 0.67 μg/L, which were lower than those obtained using the in-tube SPME method with the FAMOS autosampler. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 125–134, 2000