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Selected papers from the latest issue:
Preparation and characterization of ceramic/carbon coated Fe3O4 magnetic nanoparticle nanocomposite as a solid-phase microextraction adsorbent
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Hassan Heidari, Habib Razmi, Abolghasem Jouyban
A novel solid-phase microextraction (SPME) fiber based on a glass tube coated with ceramic/carbon coated Fe3O4 magnetic nanoparticle nanocomposite (C–Fe3O4/C MNP) was prepared by sol–gel technique. The carbon coated Fe3O4 magnetic nanoparticles were synthesized by a simple hydrothermal reaction and the resultant powder was mixed with sol–gel precursors to prepare C–Fe3O4/C MNP. The prepared C–Fe3O4/C MNP was deposited on surface of glass tubes as new substrate with a simple method. The results revealed that this procedure was a simple and reproducible technique for the preparation of SPME fibers coated with magnetic nanoparticles. The scanning electron micrographs of the fiber surface revealed a three-dimensional structure which is suitable as SPME adsorbents. Some polycyclic aromatic hydrocarbons (PAHs) were selected as model compounds for evaluating performance of the designed SPME fiber. The analytes were extracted with SPME, and desorbed using acetonitrile via ultrasonication. The extracts were analyzed by high performance liquid chromatography (HPLC) with fluorescence detection. The results demonstrated that the proposed method based on the C–Fe3O4/C MNP fiber had wide dynamic linear range (0.01–350μgL−1) with good linearity (R 2 >0.990) and low detection limits (0.7–50pgmL−1). The relative standard deviation ranged from 6.9% to 12.2% for inter-day variations. These fibers were successfully used for the analysis of spiked water samples, which demonstrating the applicability of the home-made C–Fe3O4/C MNP fibers.
Source:Journal of Chromatography A, Volume 1245
Hassan Heidari, Habib Razmi, Abolghasem Jouyban
A novel solid-phase microextraction (SPME) fiber based on a glass tube coated with ceramic/carbon coated Fe3O4 magnetic nanoparticle nanocomposite (C–Fe3O4/C MNP) was prepared by sol–gel technique. The carbon coated Fe3O4 magnetic nanoparticles were synthesized by a simple hydrothermal reaction and the resultant powder was mixed with sol–gel precursors to prepare C–Fe3O4/C MNP. The prepared C–Fe3O4/C MNP was deposited on surface of glass tubes as new substrate with a simple method. The results revealed that this procedure was a simple and reproducible technique for the preparation of SPME fibers coated with magnetic nanoparticles. The scanning electron micrographs of the fiber surface revealed a three-dimensional structure which is suitable as SPME adsorbents. Some polycyclic aromatic hydrocarbons (PAHs) were selected as model compounds for evaluating performance of the designed SPME fiber. The analytes were extracted with SPME, and desorbed using acetonitrile via ultrasonication. The extracts were analyzed by high performance liquid chromatography (HPLC) with fluorescence detection. The results demonstrated that the proposed method based on the C–Fe3O4/C MNP fiber had wide dynamic linear range (0.01–350μgL−1) with good linearity (R 2 >0.990) and low detection limits (0.7–50pgmL−1). The relative standard deviation ranged from 6.9% to 12.2% for inter-day variations. These fibers were successfully used for the analysis of spiked water samples, which demonstrating the applicability of the home-made C–Fe3O4/C MNP fibers.
Highlights
► We reported C–Fe3O4/C MNP, for first time, as a new type of SPME adsorbent. ► C–Fe3O4/C MNP was deposited on glass tubes as new substrate. ► Fabricated fiber provided good fiber-to-fiber reproducibility. ► Disposable ability of the fibers eliminates possibility of sample carry-over. ► The results reveal that this method has advantages over other reports.Synthesis and characterization of the core–shell magnetic molecularly imprinted polymers (Fe3O4@MIPs) adsorbents for effective extraction and determination of sulfonamides in the poultry feed
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Xuan Kong, Ruixia Gao, Xiwen He, Langxing Chen, Yukui Zhang
In this study, we present a general method to prepare the core–shell magnetic molecularly imprinted polymers (MIPs) nanoparticles (NPs) for sulfamethazine (SMZ). The resulting Fe3O4@MIPs NPs possess a highly improved imprinting effect, fast adsorption kinetics and high adsorption capacity, and can be applied to extract sulfonamide in the poultry feed. In this protocol, the magnetite NPs were synthesized by co-precipitating Fe2+ and Fe3+ in an ammonia solution first. Silica was then coated on the Fe3O4 NPs using a sol–gel method to obtain silica shell magnetic NPs. Subsequently, the vinyl groups were grated onto silica-modified Fe3O4 surface by 3-methacryloyloxypropyltrimethoxysilane. Finally, the MIPs films were formed on the surface of Fe3O4@SiO2 by the copolymerization of vinyl end groups with functional monomer, methacrylic acid, cross-linking agent, ethylene glycol dimethacrylate, the initiator azo-bis-isobutyronitrile and template molecule, sulfamethazine. The morphology, magnetic, adsorption and recognition properties of Fe3O4@MIPs NPs were characterized using transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrometer, vibrating sample magnetometer (VSM) and re-binding experiments. The results showed that the binding sites of Fe3O4@MIPs were good accessibility, fast adsorption rate and the maximum adsorption capacity of Fe3O4@MIPs to SMZ was 344.8μgg−1. The selectivity of the obtained Fe3O4@MIPs NPs were elucidated by the different rebinding capability of SMZ and structural related sulfonamides in the mixed solution. The results indicated that the Fe3O4@MIPs had high imprinting factor 9.5 and significant selectivity. A method was developed for enrichment and determination of SMZ in the poultry feed samples with recoveries of duck and chicken feed ranging from 63.3 to 76.5% and 68.7 to 74.7%, respectively and the relative standard deviations (RSD) (<6.7%).
Source:Journal of Chromatography A, Volume 1245
Xuan Kong, Ruixia Gao, Xiwen He, Langxing Chen, Yukui Zhang
In this study, we present a general method to prepare the core–shell magnetic molecularly imprinted polymers (MIPs) nanoparticles (NPs) for sulfamethazine (SMZ). The resulting Fe3O4@MIPs NPs possess a highly improved imprinting effect, fast adsorption kinetics and high adsorption capacity, and can be applied to extract sulfonamide in the poultry feed. In this protocol, the magnetite NPs were synthesized by co-precipitating Fe2+ and Fe3+ in an ammonia solution first. Silica was then coated on the Fe3O4 NPs using a sol–gel method to obtain silica shell magnetic NPs. Subsequently, the vinyl groups were grated onto silica-modified Fe3O4 surface by 3-methacryloyloxypropyltrimethoxysilane. Finally, the MIPs films were formed on the surface of Fe3O4@SiO2 by the copolymerization of vinyl end groups with functional monomer, methacrylic acid, cross-linking agent, ethylene glycol dimethacrylate, the initiator azo-bis-isobutyronitrile and template molecule, sulfamethazine. The morphology, magnetic, adsorption and recognition properties of Fe3O4@MIPs NPs were characterized using transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrometer, vibrating sample magnetometer (VSM) and re-binding experiments. The results showed that the binding sites of Fe3O4@MIPs were good accessibility, fast adsorption rate and the maximum adsorption capacity of Fe3O4@MIPs to SMZ was 344.8μgg−1. The selectivity of the obtained Fe3O4@MIPs NPs were elucidated by the different rebinding capability of SMZ and structural related sulfonamides in the mixed solution. The results indicated that the Fe3O4@MIPs had high imprinting factor 9.5 and significant selectivity. A method was developed for enrichment and determination of SMZ in the poultry feed samples with recoveries of duck and chicken feed ranging from 63.3 to 76.5% and 68.7 to 74.7%, respectively and the relative standard deviations (RSD) (<6.7%).
Highlights
► We present a general method to prepare the core–shell magnetic MIPs nanoparticles (Fe3O4@MIPs) for sulfamethazine. ► The Fe3O4@MIPs possess a highly improved imprinting factor, fast adsorption kinetics and high adsorption capacity. ► The structure and affinity properties of the resulting Fe3O4@MIPs were characterized. ► We used Fe3O4@MIPs for enrichment and determination of SMZ in the poultry feed samples.Dispersive micro solid-phase extraction of triazines from waters using oxidized single-walled carbon nanohorns as sorbent
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Juan Manuel Jiménez-Soto, Soledad Cárdenas, Miguel Valcárcel
This article evaluates the usefulness of dispersed single-walled carbon nanohorns as sorbent for the isolation and preconcentration of triazines from waters. For this purpose, the carbon nanoparticles were oxidized to increase their solubility in aqueous media in order to obtain a stable dispersion that can be used as extractant of the selected pollutants. Then, 1mL of the dispersion containing the oxidized single-walled carbon nanohorns at a concentration of 0.2g/L was added to 10mL of sample and stirred for 2min using a vortex. Then, the whole volume was passed through a disposable 0.45μm Nylon filter which retained the nanoparticles enriched with the triazines. Further elution with methanol permitted the gas chromatographic analysis of the analytes and subsequent identification and quantification by mass spectrometry working under the selected ion monitoring mode (SIM). The limits of detection (LODs) were in low nanogram per liter level, which allowed the detection of the selected triazines at the concentration stated by legislation. The precision of the method, calculated as relative standard deviation, was acceptable in all instances. Finally, the recovery study carried out in different water samples provided average values between 87% and 94%. The results obtained revealed the applicability of oxidized single-walled carbon nanohorns for the proposed analytical problem.
Source:Journal of Chromatography A, Volume 1245
Juan Manuel Jiménez-Soto, Soledad Cárdenas, Miguel Valcárcel
This article evaluates the usefulness of dispersed single-walled carbon nanohorns as sorbent for the isolation and preconcentration of triazines from waters. For this purpose, the carbon nanoparticles were oxidized to increase their solubility in aqueous media in order to obtain a stable dispersion that can be used as extractant of the selected pollutants. Then, 1mL of the dispersion containing the oxidized single-walled carbon nanohorns at a concentration of 0.2g/L was added to 10mL of sample and stirred for 2min using a vortex. Then, the whole volume was passed through a disposable 0.45μm Nylon filter which retained the nanoparticles enriched with the triazines. Further elution with methanol permitted the gas chromatographic analysis of the analytes and subsequent identification and quantification by mass spectrometry working under the selected ion monitoring mode (SIM). The limits of detection (LODs) were in low nanogram per liter level, which allowed the detection of the selected triazines at the concentration stated by legislation. The precision of the method, calculated as relative standard deviation, was acceptable in all instances. Finally, the recovery study carried out in different water samples provided average values between 87% and 94%. The results obtained revealed the applicability of oxidized single-walled carbon nanohorns for the proposed analytical problem.
Highlights
► A new application of dispersive μ-SPE using o-SWNHs is presented. ► Triazines have been selected as target compounds. ► It has been applied to the analysis of water samples. ► The limits of detection are in the low nanogram per liter level.Minimisation of artefact formation of dimethyl disulphide during sampling and analysis of methanethiol in air using solid sorbent materials
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Kristin Barkve Andersen, Michael Jørgen Hansen, Anders Feilberg
Methanethiol (MT) is a potent odorant that can be difficult to measure due to its high volatility and reactivity; it easily reacts to form dimethyl disulphide (DMDS) during sampling and/or analysis. This paper focuses on finding an optimal method for sampling and measuring MT with minimum artefact formation using sorbent materials and a thermal desorption-gas chromatography–mass spectrometry method (TD-GC–MS). Experiments were conducted to identify suitable sorbent materials and tubes for analysis. Breakthrough, desorption rate, the effects of storage and desorption temperatures were investigated and different drying methods were established with respect to quantitative sampling and formation of DMDS. Proton-transfer-reaction mass spectrometry (PTR-MS) was used in the development of the method and was an especially useful tool for determination of breakthrough. The results show that glass tubes packed with silica gel for pre-concentration of MT before analysis with TD-GC–MS give the best results. In addition, a combination of Tenax TA and carbonised molecular sieve or Tenax TA cooled to ≤0°C gives acceptable results. 80°C was found to be the optimal desorption temperature. For all the sampling methods tested, storage conditions were observed to be very critical for transformation of MT. Room temperature storage should be limited to few minutes and, in general, tubes should be kept at 0°C or lower during storage.
Source:Journal of Chromatography A, Volume 1245
Kristin Barkve Andersen, Michael Jørgen Hansen, Anders Feilberg
Methanethiol (MT) is a potent odorant that can be difficult to measure due to its high volatility and reactivity; it easily reacts to form dimethyl disulphide (DMDS) during sampling and/or analysis. This paper focuses on finding an optimal method for sampling and measuring MT with minimum artefact formation using sorbent materials and a thermal desorption-gas chromatography–mass spectrometry method (TD-GC–MS). Experiments were conducted to identify suitable sorbent materials and tubes for analysis. Breakthrough, desorption rate, the effects of storage and desorption temperatures were investigated and different drying methods were established with respect to quantitative sampling and formation of DMDS. Proton-transfer-reaction mass spectrometry (PTR-MS) was used in the development of the method and was an especially useful tool for determination of breakthrough. The results show that glass tubes packed with silica gel for pre-concentration of MT before analysis with TD-GC–MS give the best results. In addition, a combination of Tenax TA and carbonised molecular sieve or Tenax TA cooled to ≤0°C gives acceptable results. 80°C was found to be the optimal desorption temperature. For all the sampling methods tested, storage conditions were observed to be very critical for transformation of MT. Room temperature storage should be limited to few minutes and, in general, tubes should be kept at 0°C or lower during storage.
Highlights
► Different sorbent tubes and packing materials for analysis of methanethiol. ► Investigated breakthrough and the effect of storage and desorption temperatures. ► Artefact formation of dimethyl disulphide was assessed under different conditions. ► Silanized glass tubes packed with silica gel gave the best recovery. ► Sorbent tubes should be kept at 0°C or lower during storage.Ionic liquids-based crosslinked copolymer sorbents for headspace solid-phase microextraction of polar alcohols
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Juanjuan Feng, Min Sun, Xusheng Wang, Xia Liu, Shengxiang Jiang
Halogen-based polymeric ionic liquid (PIL) fibers, which have proved efficient for solid-phase microextraction (SPME) of polar compounds, were with very limited fiber lifetimes. In this work, a novel crosslinked PIL sorbent with satisfactory stability and durability was prepared in situ via crosslinking polymerization processes on microstructured-silver coated stainless steel wire. 1,1′-(1,6-Hexanediyl)bis(1-vinylimidazolium) bibromide ionic liquid was synthesized and used as the crosslinking agent, with 1-vinyl-3-octylimidazolium bromide as monomer. Extraction properties of the fiber for polar alcohols in polar aqueous matrix were examined using headspace SPME (HS-SPME) coupled to gas chromatography-flame ionization detection (GC-FID). Under the optimized extraction and desorption conditions, the established method exhibited high extraction capacity. Wide linear ranges were obtained with correlation coefficients (R) ranging from 0.9947 to 0.9999. Limits of detection were in the range of 0.5–20μgL−1. Compared with the non-crosslinked PIL fiber, the proposed crosslinked PIL fiber was with higher thermal stability and durability and longer lifetime. Four different liquor beverages were analyzed as real samples and good results were obtained.
Source:Journal of Chromatography A, Volume 1245
Juanjuan Feng, Min Sun, Xusheng Wang, Xia Liu, Shengxiang Jiang
Halogen-based polymeric ionic liquid (PIL) fibers, which have proved efficient for solid-phase microextraction (SPME) of polar compounds, were with very limited fiber lifetimes. In this work, a novel crosslinked PIL sorbent with satisfactory stability and durability was prepared in situ via crosslinking polymerization processes on microstructured-silver coated stainless steel wire. 1,1′-(1,6-Hexanediyl)bis(1-vinylimidazolium) bibromide ionic liquid was synthesized and used as the crosslinking agent, with 1-vinyl-3-octylimidazolium bromide as monomer. Extraction properties of the fiber for polar alcohols in polar aqueous matrix were examined using headspace SPME (HS-SPME) coupled to gas chromatography-flame ionization detection (GC-FID). Under the optimized extraction and desorption conditions, the established method exhibited high extraction capacity. Wide linear ranges were obtained with correlation coefficients (R) ranging from 0.9947 to 0.9999. Limits of detection were in the range of 0.5–20μgL−1. Compared with the non-crosslinked PIL fiber, the proposed crosslinked PIL fiber was with higher thermal stability and durability and longer lifetime. Four different liquor beverages were analyzed as real samples and good results were obtained.
Highlights
► Dicationic IL was used as crosslinking agent to prepare copolymeric ILs SPME fiber. ► Durability of fibers was improved greatly by in situ crosslinking polymerization. ► Aliphatic alcohols in liquors were quantified by the HS-SPME–GC method.Preparation of aqueous two-phase systems composed of two pH-response polymers and liquid–liquid extraction of demeclocycline
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Bo Yan, Xuejun Cao
Aqueous two-phase systems have potential applications for separation and purification of bioproducts in bio-industry. However, a key problem is the recovery of the polymers forming aqueous two-phase systems. In this study, two novel random copolymers (PADB and PADBA) were synthesized using acrylic acid, dimethylamino-ethyl methacrylate, butyl methacrylate and allyl alcohol as monomers and used to form pH response aqueous two-phase systems. The recoveries of PADB and PADBA are 97.18% and 98.87% and the pI of PADB and PADBA are 2.79 and 4.01, respectively. Demeclocycline was partitioned in the PADB/PADBA aqueous two-phase systems and the partition coefficient reached 0.085, in the presence of MgSO4 (60mmol/L) at pH 5.28.
Source:Journal of Chromatography A, Volume 1245
Bo Yan, Xuejun Cao
Aqueous two-phase systems have potential applications for separation and purification of bioproducts in bio-industry. However, a key problem is the recovery of the polymers forming aqueous two-phase systems. In this study, two novel random copolymers (PADB and PADBA) were synthesized using acrylic acid, dimethylamino-ethyl methacrylate, butyl methacrylate and allyl alcohol as monomers and used to form pH response aqueous two-phase systems. The recoveries of PADB and PADBA are 97.18% and 98.87% and the pI of PADB and PADBA are 2.79 and 4.01, respectively. Demeclocycline was partitioned in the PADB/PADBA aqueous two-phase systems and the partition coefficient reached 0.085, in the presence of MgSO4 (60mmol/L) at pH 5.28.
Highlights
► Two novel pH-response copolymers PADB and PADBA are synthesized. ► Novel aqueous two-phase systems are constructed by PADB and PADBA. ► Polymers are recovered by adjusting pH of their solutions and have high recovery. ► Demeclocycline is partitioned in the PADB/PADBA aqueous two-phase systems.Development of a liquid chromatography tandem mass spectrometry method for trace analysis of trisiloxane surfactants in the aqueous environment: An alternative strategy for quantification of ethoxylated surfactants
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Amandine Michel, Heinz-Jürgen Brauch, Eckhard Worch, Frank T. Lange
Trisiloxane surfactants, often referred to as superspreaders or superwetters, are added to pesticides to enhance the activity and the rainfastness of the active substance by promoting rapid spreading over hydrophobic surfaces. To fill the lack of data on the environmental occurrence of these compounds, we have developed and validated a method for their trace analysis in the aqueous environment. The method is based on liquid–liquid extraction followed by liquid chromatography and tandem mass spectrometry. The oligomeric distribution of trisiloxane surfactant in a reference solution was determined by a theoretical calculation and by experimental measurements. Based on these results, the quantification was performed by comparison with a calibration made with a single homologue instead of a mixture of homologues. This approach avoids a time-consuming synthesis of pure homologues and reduces the risk of wrong estimation of the concentration because of different response factors of the sample and the standard. Such an approach could be applied to the quantification of other ethoxylated surfactants following a similar distribution. The validation was performed from 2 to 250ng/L (total surfactant concentration) in deionized water, tap water, and river water (Rhine water). Knowing the oligomeric distribution of the polymer in the reference solution, the corresponding calibration ranges were estimated for individual homologues. Limits of quantification were found to be between 0.37ng/L and 15ng/L. The total recovery of sample preparation was between 77% and 116%. Matrix effects were lower than 10% with river water and the relative standard deviation evaluated over ten identical samples of spiked river water was below 12%.
Source:Journal of Chromatography A, Volume 1245
Amandine Michel, Heinz-Jürgen Brauch, Eckhard Worch, Frank T. Lange
Trisiloxane surfactants, often referred to as superspreaders or superwetters, are added to pesticides to enhance the activity and the rainfastness of the active substance by promoting rapid spreading over hydrophobic surfaces. To fill the lack of data on the environmental occurrence of these compounds, we have developed and validated a method for their trace analysis in the aqueous environment. The method is based on liquid–liquid extraction followed by liquid chromatography and tandem mass spectrometry. The oligomeric distribution of trisiloxane surfactant in a reference solution was determined by a theoretical calculation and by experimental measurements. Based on these results, the quantification was performed by comparison with a calibration made with a single homologue instead of a mixture of homologues. This approach avoids a time-consuming synthesis of pure homologues and reduces the risk of wrong estimation of the concentration because of different response factors of the sample and the standard. Such an approach could be applied to the quantification of other ethoxylated surfactants following a similar distribution. The validation was performed from 2 to 250ng/L (total surfactant concentration) in deionized water, tap water, and river water (Rhine water). Knowing the oligomeric distribution of the polymer in the reference solution, the corresponding calibration ranges were estimated for individual homologues. Limits of quantification were found to be between 0.37ng/L and 15ng/L. The total recovery of sample preparation was between 77% and 116%. Matrix effects were lower than 10% with river water and the relative standard deviation evaluated over ten identical samples of spiked river water was below 12%.
Highlights
► Silicone surfactant as agricultural adjuvants. ► Selective and sensitive method for trace analysis in the aqueous environment. ► Oligomer composition by Poisson distribution and single mass spectrometry.Alkaline-stable peptide ligand affinity adsorbents for the purification of biomolecules
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Stefano Menegatti, Amith D. Naik, Patrick V. Gurgel, Ruben G. Carbonell
A strategy of modification of resin surface chemistry is presented to produce hydrophilic peptide-based alkaline-stable affinity adsorbents for the purification of biopharmaceuticals from complex media. In this work, the peptide-based affinity adsorbent HWRGWV-Toyopearl resin for the purification of IgG is presented as an example. When prepared by direct peptide synthesis on the chromatographic matrix, the peptide-based resin showed lability under alkaline conditions. In fact, the regeneration with aqueous 0.1M NaOH caused the leaching of 40% of the peptide ligand, resulting in a decrease of IgG yield from 85% to 23%. It was found that the ligand leaching was caused by the coupling of a significant amount of peptide by alkaline-labile ester bonds. A method was designed to prevent the formation of ester bonds and allow the synthesis of the ligand exclusively on alkaline-stable bonds. The method consists in activating the hydrophilic base resin, blocking the hydroxyl groups responsible for alkaline lability and performing the peptide synthesis exclusively via alkaline-stable amide bonds. Repeated cycles of IgG purification from a cell culture medium were performed, each followed by cleaning with aqueous NaOH (0.1M, 0.5M and 1M). The IgG yield decreased from 91% to 85% after 200 purification cycles with 0.1M NaOH. However, the IgG purity remained almost constant at around 95% based on SDS-PAGE analysis. The procedure presented is rapid, efficient and inexpensive and does not require any equipment other than the conventional instrumentation for peptide synthesis. The method also has a broad application since it is valid for any peptide ligand identified for the purification of a biopharmaceutical target.
Source:Journal of Chromatography A, Volume 1245
Stefano Menegatti, Amith D. Naik, Patrick V. Gurgel, Ruben G. Carbonell
A strategy of modification of resin surface chemistry is presented to produce hydrophilic peptide-based alkaline-stable affinity adsorbents for the purification of biopharmaceuticals from complex media. In this work, the peptide-based affinity adsorbent HWRGWV-Toyopearl resin for the purification of IgG is presented as an example. When prepared by direct peptide synthesis on the chromatographic matrix, the peptide-based resin showed lability under alkaline conditions. In fact, the regeneration with aqueous 0.1M NaOH caused the leaching of 40% of the peptide ligand, resulting in a decrease of IgG yield from 85% to 23%. It was found that the ligand leaching was caused by the coupling of a significant amount of peptide by alkaline-labile ester bonds. A method was designed to prevent the formation of ester bonds and allow the synthesis of the ligand exclusively on alkaline-stable bonds. The method consists in activating the hydrophilic base resin, blocking the hydroxyl groups responsible for alkaline lability and performing the peptide synthesis exclusively via alkaline-stable amide bonds. Repeated cycles of IgG purification from a cell culture medium were performed, each followed by cleaning with aqueous NaOH (0.1M, 0.5M and 1M). The IgG yield decreased from 91% to 85% after 200 purification cycles with 0.1M NaOH. However, the IgG purity remained almost constant at around 95% based on SDS-PAGE analysis. The procedure presented is rapid, efficient and inexpensive and does not require any equipment other than the conventional instrumentation for peptide synthesis. The method also has a broad application since it is valid for any peptide ligand identified for the purification of a biopharmaceutical target.
Highlights
► The paper shows the development of a peptide-based ligand with alkaline stability. ► The procedure allows the adsorbent to withstand high pH cleaning and regeneration. ► The ligand remains effective over a large number of regeneration cycles. ► An application is shown using a peptide ligand for purification of IgG.Reversed-phase ion-pair liquid chromatography electrospray ionization tandem mass spectrometry for separation, sequencing and mapping of sites of base modification of isomeric oligonucleotide adducts using monolithic column
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Vaneet K. Sharma, James Glick, Paul Vouros
In this manuscript, an efficient high resolution reversed phase-ion pairing-liquid chromatography electrospray ionization tandem mass spectrometry (RP-IP-LC–MS/MS) method for separation of isomeric modified oligonucleotides using a polymeric (styrene-divinylbenzene) monolithic capillary column is presented. The effects of different ion pairing reagents (IPR), their concentration, mobile phase additives and conditions were evaluated towards achieving the highest possible resolution and chromatographic separation of isomeric oligonucleotides. Ion pairing reagents and mobile phase conditions were evaluated using as model N-acetylaminofluorene [AAF] adducted ss-oligonucleotides (CCC CGA GCA ATC TCA AT). The optimized mobile phase conditions were then applied for the mapping of sites of base modification of AAF adducted 15-base pair oligonucleotide fragments containing codon 135 of the p53 gene and for profiling a complex synthetic oligonucleotide mixture. The optimized method utilizes a monolithic poly(styrene-divinylbenzene) capillary column, triethylammonium bicarbonate as ion pairing reagent and methanol as organic modifier to perform IP-RPLC–ESI-MS/MS separation. The results show that the method is simultaneously applicable not only to oligonucleotide fragments adducted separately by different carcinogens but also to the analysis of multiple adducts in the same oligonucleotide fragment in a single experiment. The method presents itself as a tool for the identification, characterization and mapping of oligonucleotide adducts as biomarkers for DNA damage from carcinogens.
Source:Journal of Chromatography A, Volume 1245
Vaneet K. Sharma, James Glick, Paul Vouros
In this manuscript, an efficient high resolution reversed phase-ion pairing-liquid chromatography electrospray ionization tandem mass spectrometry (RP-IP-LC–MS/MS) method for separation of isomeric modified oligonucleotides using a polymeric (styrene-divinylbenzene) monolithic capillary column is presented. The effects of different ion pairing reagents (IPR), their concentration, mobile phase additives and conditions were evaluated towards achieving the highest possible resolution and chromatographic separation of isomeric oligonucleotides. Ion pairing reagents and mobile phase conditions were evaluated using as model N-acetylaminofluorene [AAF] adducted ss-oligonucleotides (CCC CGA GCA ATC TCA AT). The optimized mobile phase conditions were then applied for the mapping of sites of base modification of AAF adducted 15-base pair oligonucleotide fragments containing codon 135 of the p53 gene and for profiling a complex synthetic oligonucleotide mixture. The optimized method utilizes a monolithic poly(styrene-divinylbenzene) capillary column, triethylammonium bicarbonate as ion pairing reagent and methanol as organic modifier to perform IP-RPLC–ESI-MS/MS separation. The results show that the method is simultaneously applicable not only to oligonucleotide fragments adducted separately by different carcinogens but also to the analysis of multiple adducts in the same oligonucleotide fragment in a single experiment. The method presents itself as a tool for the identification, characterization and mapping of oligonucleotide adducts as biomarkers for DNA damage from carcinogens.
Highlights
► Optimization of mobile phase conditions for efficient separation and sequencing of isomeric oligonucleotide adducts. ► Mapping of AAF adducted 15 mer long oligonucleotide containing codon 135 of p53 gene. ► Profiling of complex mixture comprising of unadducted, singly or multiple AAF adducted oligonucleotides of p53 gene fragments.Analysis of iodinated haloacetic acids in drinking water by reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry with large volume direct aqueous injection
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Yongtao Li, Joshua S. Whitaker, Christina L. McCarty
A large volume direct aqueous injection method was developed for the analysis of iodinated haloacetic acids in drinking water by using reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry in the negative ion mode. Both the external and internal standard calibration methods were studied for the analysis of monoiodoacetic acid, chloroiodoacetic acid, bromoiodoacetic acid, and diiodoacetic acid in drinking water. The use of a divert valve technique for the mobile phase solvent delay, along with isotopically labeled analogs used as internal standards, effectively reduced and compensated for the ionization suppression typically caused by coexisting common inorganic anions. Under the optimized method conditions, the mean absolute and relative recoveries resulting from the replicate fortified deionized water and chlorinated drinking water analyses were 83–107% with a relative standard deviation of 0.7–11.7% and 84–111% with a relative standard deviation of 0.8–12.1%, respectively. The method detection limits resulting from the external and internal standard calibrations, based on seven fortified deionized water replicates, were 0.7–2.3ng/L and 0.5–1.9ng/L, respectively.
Source:Journal of Chromatography A, Volume 1245
Yongtao Li, Joshua S. Whitaker, Christina L. McCarty
A large volume direct aqueous injection method was developed for the analysis of iodinated haloacetic acids in drinking water by using reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry in the negative ion mode. Both the external and internal standard calibration methods were studied for the analysis of monoiodoacetic acid, chloroiodoacetic acid, bromoiodoacetic acid, and diiodoacetic acid in drinking water. The use of a divert valve technique for the mobile phase solvent delay, along with isotopically labeled analogs used as internal standards, effectively reduced and compensated for the ionization suppression typically caused by coexisting common inorganic anions. Under the optimized method conditions, the mean absolute and relative recoveries resulting from the replicate fortified deionized water and chlorinated drinking water analyses were 83–107% with a relative standard deviation of 0.7–11.7% and 84–111% with a relative standard deviation of 0.8–12.1%, respectively. The method detection limits resulting from the external and internal standard calibrations, based on seven fortified deionized water replicates, were 0.7–2.3ng/L and 0.5–1.9ng/L, respectively.
Highlights
► A rapid, sensitive, and accurate LC/MS/MS method was reported for iodoacetic acids. ► Optimized LC conditions could separate the analytes from common inorganic anions. ► A divert valve technique was used to significantly reduce the matrix effects. ► The direct aqueous injection analysis achieved detection limits of 0.5–2.3ng/L. ► This method resulted in satisfactory recoveries and relative standard deviations.Cation separation and preconcentration using columns containing cyclen and cyclen–resorcinarene derivatives
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Na Li, Christopher English, Ammon Eaton, Austin Gillespie, T.C. Ence, Taylor J. Christensen, Adam Sego, Roger G. Harrison, John D. Lamb
The selectivity and separation of transition metal ions on two columns packed with cyclen-based macrocycles adsorbed onto 55% cross-linked styrene–divinylbenzene resin are presented. The N-cyclen and cyclen–resorcinarene stationary phases were made by adsorbing hydrophobically substituted N-cyclen or a cyclen–resorcinarene derivative (cyclenbowl) on the resin, respectively. The stability constants of cyclen with transition metal ions demonstrate that cyclen has selectivity for Cu2+ over other transition metal ions. Mn2+, Co2+, Ni2+, Cd2+, and Zn2+ ions were separated from Cu2+ using HNO3 eluent with the cyclenbowl column. The preconcentration of Cu2+ in parts per billion level from a high concentration matrix of Mn2+, Co2+, Ni2+, Cd2+, and Zn2+ ions was achieved in the cyclenbowl column using a nitric acid eluent gradient. Recovery of Cu2+ at >98% was obtained based on direct interaction of metal ion and cyclen. Although Mn2+, Co2+, Ni2+, Cd2+, and Zn2+ were not separated by HNO3 eluent, addition of oxalic acid yielded a very good separation. A retention mechanism is proposed for the latter system in which the protonated cyclen units attract negatively charged HC2O4 − ions that cooperate with cyclen sites in retaining transition metal ions.
Source:Journal of Chromatography A, Volume 1245
Na Li, Christopher English, Ammon Eaton, Austin Gillespie, T.C. Ence, Taylor J. Christensen, Adam Sego, Roger G. Harrison, John D. Lamb
The selectivity and separation of transition metal ions on two columns packed with cyclen-based macrocycles adsorbed onto 55% cross-linked styrene–divinylbenzene resin are presented. The N-cyclen and cyclen–resorcinarene stationary phases were made by adsorbing hydrophobically substituted N-cyclen or a cyclen–resorcinarene derivative (cyclenbowl) on the resin, respectively. The stability constants of cyclen with transition metal ions demonstrate that cyclen has selectivity for Cu2+ over other transition metal ions. Mn2+, Co2+, Ni2+, Cd2+, and Zn2+ ions were separated from Cu2+ using HNO3 eluent with the cyclenbowl column. The preconcentration of Cu2+ in parts per billion level from a high concentration matrix of Mn2+, Co2+, Ni2+, Cd2+, and Zn2+ ions was achieved in the cyclenbowl column using a nitric acid eluent gradient. Recovery of Cu2+ at >98% was obtained based on direct interaction of metal ion and cyclen. Although Mn2+, Co2+, Ni2+, Cd2+, and Zn2+ were not separated by HNO3 eluent, addition of oxalic acid yielded a very good separation. A retention mechanism is proposed for the latter system in which the protonated cyclen units attract negatively charged HC2O4 − ions that cooperate with cyclen sites in retaining transition metal ions.
Highlights
► Cyclen-based ligands were used for IC separations. ► Cyclenbowl column showed higher capacity and efficiency than N-cyclen column. ► Preconcentration of Cu2+ is achieved using the cyclenbowl column. ► Both anion and cation separations are achieved with the cyclenbowl column. ► Five transition metal ions are well separated by oxalic acid/HNO3 gradient.The influence of the organic modifier in hydro-organic mobile phase on separation selectivity of steroid hormones separation using cholesterol-bonded stationary phases
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Szymon Bocian, Jan Soukup, Maria Matyska, Joseph Pesek, Pavel Jandera, Bogusław Buszewski
Chromatographic properties of four cholesterol bonded phases with different structures were studied. The columns used were packed with a stationary phase containing a cholesterol molecule attached to the silica surface using different types of linkage molecules. Columns were compared according to the retention and separation selectivity of steroid hormones. The measurements were done using binary hydro-organic mobile phases with methanol, ethanol and acetonitrile as an organic modifier. The presented results show that the coverage density of the bonded ligands and the type of organic modifier strongly influence the retention mechanism and separation selectivity of steroid hormones on cholesterol-containing adsorbents.
Source:Journal of Chromatography A, Volume 1245
Szymon Bocian, Jan Soukup, Maria Matyska, Joseph Pesek, Pavel Jandera, Bogusław Buszewski
Chromatographic properties of four cholesterol bonded phases with different structures were studied. The columns used were packed with a stationary phase containing a cholesterol molecule attached to the silica surface using different types of linkage molecules. Columns were compared according to the retention and separation selectivity of steroid hormones. The measurements were done using binary hydro-organic mobile phases with methanol, ethanol and acetonitrile as an organic modifier. The presented results show that the coverage density of the bonded ligands and the type of organic modifier strongly influence the retention mechanism and separation selectivity of steroid hormones on cholesterol-containing adsorbents.
Highlights
► Separation of steroid hormones on cholesterol-phases were performed. ► The influence of the organic modifier on separation selectivity were investigated. ► Steroid retention depends on coverage density of cholesterol moiety. ► Cholesterol-bonded phases allow to separate estradiol isomers.The effect of temperature and mobile phase composition on separation mechanism of flavonoid compounds on hydrosilated silica-based columns
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Jan Soukup, Pavel Jandera
We investigated the effects of mobile phase composition on the retention of flavones on four different hydrosilated C silica-based columns in buffered aqueous acetonitrile. Cogent UDC cholesterol™ and Cogent bidentate C18™ columns show significant dual reversed-phase/normal-phase retention behavior, while Cogent Diamond hydride™ and Cogent Silica hydride™ columns show negligible retention in the reversed-phase mode. The effect of the aqueous acetate buffer concentration on retention factors of flavones over the full mobile phase composition range, including both aqueous normal-phase (ANP) and reversed-phase mechanisms, can be described by a four-parameter equation for dual-retention mechanism. At increasing temperature, the retention factors and peak widths decrease both in the aqueous normal phase and in the reversed phase mobile phase range. In agreement with van’t Hoff model, linear ln k versus 1/T plots were observed, showing a single retention mechanism in the highly organic normal-phase and in highly aqueous reversed-phase mobile phase ranges. From among the stationary phases tested, Cogent UDC cholesterol™ column has high temperature stability (up to 100°C) and provides most selective and efficient separations of flavones both in the ANP and in the RP modes with almost reversed elution order.
Source:Journal of Chromatography A, Volume 1245
Jan Soukup, Pavel Jandera
We investigated the effects of mobile phase composition on the retention of flavones on four different hydrosilated C silica-based columns in buffered aqueous acetonitrile. Cogent UDC cholesterol™ and Cogent bidentate C18™ columns show significant dual reversed-phase/normal-phase retention behavior, while Cogent Diamond hydride™ and Cogent Silica hydride™ columns show negligible retention in the reversed-phase mode. The effect of the aqueous acetate buffer concentration on retention factors of flavones over the full mobile phase composition range, including both aqueous normal-phase (ANP) and reversed-phase mechanisms, can be described by a four-parameter equation for dual-retention mechanism. At increasing temperature, the retention factors and peak widths decrease both in the aqueous normal phase and in the reversed phase mobile phase range. In agreement with van’t Hoff model, linear ln k versus 1/T plots were observed, showing a single retention mechanism in the highly organic normal-phase and in highly aqueous reversed-phase mobile phase ranges. From among the stationary phases tested, Cogent UDC cholesterol™ column has high temperature stability (up to 100°C) and provides most selective and efficient separations of flavones both in the ANP and in the RP modes with almost reversed elution order.
Highlights
► Flavonoid compounds were separated on four hydrosilated columns. ► Flavonoids show dual ANP–RP mode retention mechanism. ► Flavonoid glycosides and aglycones show different retention behavior. ► Increasing temperature decreases the retention of flavonoid compounds. ► Entropic and enthalpic contributions to the retention were determined.Unbiased metabolite profiling by liquid chromatography–quadrupole time-of-flight mass spectrometry and multivariate data analysis for herbal authentication: Classification of seven Lonicera species flower buds
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Wen Gao, Hua Yang, Lian-Wen Qi, E-Hu Liu, Mei-Ting Ren, Yu-Ting Yan, Jun Chen, Ping Li
Plant-based medicines become increasingly popular over the world. Authentication of herbal raw materials is important to ensure their safety and efficacy. Some herbs belonging to closely related species but differing in medicinal properties are difficult to be identified because of similar morphological and microscopic characteristics. Chromatographic fingerprinting is an alternative method to distinguish them. Existing approaches do not allow a comprehensive analysis for herbal authentication. We have now developed a strategy consisting of (1) full metabolic profiling of herbal medicines by rapid resolution liquid chromatography (RRLC) combined with quadrupole time-of-flight mass spectrometry (QTOF MS), (2) global analysis of non-targeted compounds by molecular feature extraction algorithm, (3) multivariate statistical analysis for classification and prediction, and (4) marker compounds characterization. This approach has provided a fast and unbiased comparative multivariate analysis of the metabolite composition of 33-batch samples covering seven Lonicera species. Individual metabolic profiles are performed at the level of molecular fragments without prior structural assignment. In the entire set, the obtained classifier for seven Lonicera species flower buds showed good prediction performance and a total of 82 statistically different components were rapidly obtained by the strategy. The elemental compositions of discriminative metabolites were characterized by the accurate mass measurement of the pseudomolecular ions and their chemical types were assigned by the MS/MS spectra. The high-resolution, comprehensive and unbiased strategy for metabolite data analysis presented here is powerful and opens the new direction of authentication in herbal analysis.
Source:Journal of Chromatography A, Volume 1245
Wen Gao, Hua Yang, Lian-Wen Qi, E-Hu Liu, Mei-Ting Ren, Yu-Ting Yan, Jun Chen, Ping Li
Plant-based medicines become increasingly popular over the world. Authentication of herbal raw materials is important to ensure their safety and efficacy. Some herbs belonging to closely related species but differing in medicinal properties are difficult to be identified because of similar morphological and microscopic characteristics. Chromatographic fingerprinting is an alternative method to distinguish them. Existing approaches do not allow a comprehensive analysis for herbal authentication. We have now developed a strategy consisting of (1) full metabolic profiling of herbal medicines by rapid resolution liquid chromatography (RRLC) combined with quadrupole time-of-flight mass spectrometry (QTOF MS), (2) global analysis of non-targeted compounds by molecular feature extraction algorithm, (3) multivariate statistical analysis for classification and prediction, and (4) marker compounds characterization. This approach has provided a fast and unbiased comparative multivariate analysis of the metabolite composition of 33-batch samples covering seven Lonicera species. Individual metabolic profiles are performed at the level of molecular fragments without prior structural assignment. In the entire set, the obtained classifier for seven Lonicera species flower buds showed good prediction performance and a total of 82 statistically different components were rapidly obtained by the strategy. The elemental compositions of discriminative metabolites were characterized by the accurate mass measurement of the pseudomolecular ions and their chemical types were assigned by the MS/MS spectra. The high-resolution, comprehensive and unbiased strategy for metabolite data analysis presented here is powerful and opens the new direction of authentication in herbal analysis.
Highlights
► A comprehensive metabolomic strategy was developed for herbal authentication. ► Non-targeted compounds were analyzed in minutes by molecular feature extraction. ► Multivariate statistical analysis showed good prediction performance. ► Totally 82 markers were obtained from 33-batch samples covering 7 Lonicera species.A sensitive and accurate liquid chromatography–tandem mass spectrometry method for quantitative determination of the novel hepatitis C NS5A inhibitor BMS-790052 (daclastasvir) in human plasma and urine
15 June 2012,
17:27:41
Publication year:
2012
Source:Journal of Chromatography A, Volume 1245
Hao Jiang, Jianing Zeng, Hamza Kandoussi, Yifei Liu, Xiaodong Wang, Marc Bifano, Laura Cojocaru, John Ryan, Mark E. Arnold
A liquid–liquid extraction (LLE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) methods have been developed and validated for the quantification of BMS-790052 (daclastasvir) in human plasma and urine. The samples were extracted with methyl-t-butyl ether (MTBE) before analyzing by an API 4000 mass spectrometer which was operated in a multiple reaction monitoring (MRM) mode for detection of positively charged ions of BMS-790052 and its internal standard, 13C10-BMS-790052. The standard curves ranged from 0.050 to 50.0ng/mL for BMS-790052 in human plasma, and 1.00–1000ng/mL in human urine. The intra-assay precision (%CV), based on four levels of analytical QCs (low, geometric mean, mid and high), was within 8.6%; inter-assay precision (%CV) was within 6.7% for both plasma and urine methods, and the mean assay accuracy (%Dev) was within ±3.0% for both plasma and urine methods. The ruggedness of this accurate, precise, and selective LLE–LC–MS/MS method has been demonstrated in the successful analysis of several thousand clinical study samples.
Source:Journal of Chromatography A, Volume 1245
Hao Jiang, Jianing Zeng, Hamza Kandoussi, Yifei Liu, Xiaodong Wang, Marc Bifano, Laura Cojocaru, John Ryan, Mark E. Arnold
A liquid–liquid extraction (LLE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) methods have been developed and validated for the quantification of BMS-790052 (daclastasvir) in human plasma and urine. The samples were extracted with methyl-t-butyl ether (MTBE) before analyzing by an API 4000 mass spectrometer which was operated in a multiple reaction monitoring (MRM) mode for detection of positively charged ions of BMS-790052 and its internal standard, 13C10-BMS-790052. The standard curves ranged from 0.050 to 50.0ng/mL for BMS-790052 in human plasma, and 1.00–1000ng/mL in human urine. The intra-assay precision (%CV), based on four levels of analytical QCs (low, geometric mean, mid and high), was within 8.6%; inter-assay precision (%CV) was within 6.7% for both plasma and urine methods, and the mean assay accuracy (%Dev) was within ±3.0% for both plasma and urine methods. The ruggedness of this accurate, precise, and selective LLE–LC–MS/MS method has been demonstrated in the successful analysis of several thousand clinical study samples.
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