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Selected papers from the latest issue:
Zero-valent iron/iron oxide-oxyhydroxide/graphene as a magnetic sorbent for the enrichment of polychlorinated biphenyls, polyaromatic hydrocarbons and phthalates prior to gas chromatography–mass spectrometry
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
A composite magnetic material consisting of zero-valent iron, iron oxide-oxyhydroxide and graphene was synthesized and used successfully as a sorbent for the micro solid-phase extraction of PAHs, PCBs and phthalic acid esters. The components endow the composite with multiple characteristics such as adsorption capability and facile removal due to its magnetic properties. Due to the π–π electrostatic stacking property of graphene, the high specific surface area and the adsorption capability of both components, the resulting black flaky Fe0/iron oxide-oxyhydroxide/graphene composite showed high extraction efficiency for the target analytes from water samples. Compared with the neat graphene, the composite material has improved properties in terms of microextraction capabilities as both the hydrophobic graphene and zero-valent iron participate in the adsorption of the hydrophobic molecules. The precision from the extraction of all three groups of compounds was lower than 7% and the recoveries were from 90 to 93% from a spiked lake water sample. The high recoveries in relation to the low final volume of the desorption solvent ensure high preconcentration efficiency and a promising sorbent for analytical applications.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
A composite magnetic material consisting of zero-valent iron, iron oxide-oxyhydroxide and graphene was synthesized and used successfully as a sorbent for the micro solid-phase extraction of PAHs, PCBs and phthalic acid esters. The components endow the composite with multiple characteristics such as adsorption capability and facile removal due to its magnetic properties. Due to the π–π electrostatic stacking property of graphene, the high specific surface area and the adsorption capability of both components, the resulting black flaky Fe0/iron oxide-oxyhydroxide/graphene composite showed high extraction efficiency for the target analytes from water samples. Compared with the neat graphene, the composite material has improved properties in terms of microextraction capabilities as both the hydrophobic graphene and zero-valent iron participate in the adsorption of the hydrophobic molecules. The precision from the extraction of all three groups of compounds was lower than 7% and the recoveries were from 90 to 93% from a spiked lake water sample. The high recoveries in relation to the low final volume of the desorption solvent ensure high preconcentration efficiency and a promising sorbent for analytical applications.
Highlights
► Synthesis and proper characterization of a magnetic sorbent. ► Expansion of the analytical capability of graphene and mainly of zero-valent iron. ► Analytical enrichment of several classes of organic pollutants. ► Magnetic micro solid-phase extraction by applying a convenient retrieval.Solvatochromic relationship: Prediction of distribution of ionic solutes in aqueous two-phase systems
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
Partition ratios of several ionic compounds in 20 different polymer/polymer aqueous two-phase systems (ATPS) containing 0.15M NaCl in 0.01M phosphate buffer, pH 7.4, were determined. The differences between the electrostatic properties of the phases in all the ATPS were estimated from partitioning of the homologous series of dinitrophenylated-amino acids. Also the solvatochromic solvent parameters characterizing the solvent dipolarity/polarizability (π*), solvent hydrogen-bond donor acidity (α), and solvent hydrogen-bond acceptor basicity (β) of aqueous media were measured in the coexisting phases of the ATPS. The solute-specific coefficients for the compounds examined were determined by the multiple linear regression analysis using the modified linear solvation energy relationship equation. The minimal number of ATPS necessary for determination of the coefficients was established and 10 ATPS were selected as a reference ATPS set. The solute-specific coefficients values obtained with this reference set of ATPS were used to predict the partition ratios for the compounds in 10 ATPS not included in the reference set. The predicted partition ratios values were compared to those determined experimentally and found to be in good agreement. It is concluded that the presented model of solute–solvent interactions as the driving force for solute partitioning in polymer/polymer ATPS describes experimental observations with 90–95% accuracy.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
Partition ratios of several ionic compounds in 20 different polymer/polymer aqueous two-phase systems (ATPS) containing 0.15M NaCl in 0.01M phosphate buffer, pH 7.4, were determined. The differences between the electrostatic properties of the phases in all the ATPS were estimated from partitioning of the homologous series of dinitrophenylated-amino acids. Also the solvatochromic solvent parameters characterizing the solvent dipolarity/polarizability (π*), solvent hydrogen-bond donor acidity (α), and solvent hydrogen-bond acceptor basicity (β) of aqueous media were measured in the coexisting phases of the ATPS. The solute-specific coefficients for the compounds examined were determined by the multiple linear regression analysis using the modified linear solvation energy relationship equation. The minimal number of ATPS necessary for determination of the coefficients was established and 10 ATPS were selected as a reference ATPS set. The solute-specific coefficients values obtained with this reference set of ATPS were used to predict the partition ratios for the compounds in 10 ATPS not included in the reference set. The predicted partition ratios values were compared to those determined experimentally and found to be in good agreement. It is concluded that the presented model of solute–solvent interactions as the driving force for solute partitioning in polymer/polymer ATPS describes experimental observations with 90–95% accuracy.
Highlights
► Physico-chemical characterization of 20 aqueous two-phase systems. ► 10 ATPS selected to cover the whole range of physico-chemical features. ► Solute descriptors for eight ionic compounds obtained in those 10 ATPS. ► Partition ratios values for the compounds in the remaining 10 ATPS can be predicted.Determination of five booster biocides in seawater by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
Stir bar sorptive extraction (SBSE) and thermal desorption (TD)–gas chromatography–mass spectrometry (GC–MS) have been optimized for the determination of five organic booster biocides (Chlorothalonil, Dichlofluanid, Sea-Nine 211, Irgarol 1051 and TCMTB) in seawater samples. The parameters affecting the desorption and absorption steps were investigated using 10mL seawater samples. The optimised conditions consisted of an addition of 0.2gmL−1 KCl to the sample, which was extracted with 10mm length, 0.5mm film thickness stir bars coated with polydimethylsiloxane (PDMS), and stirred at 900rpm for 90min at room temperature (25°C) in a vial. Desorption was carried out at 280°C for 5min under 50mLmin−1 of helium flow in the splitless mode while maintaining a cryotrapping temperature of 20°C in the programmed-temperature vaporization (PTV) injector of the GC–MS system. Finally, the PTV injector was ramped to a temperature of 280°C and the analytes were separated in the GC and detected by MS using the selected-ion monitoring (SIM) mode. The detection limits of booster biocides were found to be in the range of 0.005–0.9μgL−1. The regression coefficients were higher than 0.999 for all analytes. The average recovery was higher than 72% (R.S.D.: 7–15%). All these figures of merit were established running samples in triplicate. This simple, accurate, sensitive and selective analytical method may be used for the determination of trace amounts of booster biocides in water samples from marinas.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
Stir bar sorptive extraction (SBSE) and thermal desorption (TD)–gas chromatography–mass spectrometry (GC–MS) have been optimized for the determination of five organic booster biocides (Chlorothalonil, Dichlofluanid, Sea-Nine 211, Irgarol 1051 and TCMTB) in seawater samples. The parameters affecting the desorption and absorption steps were investigated using 10mL seawater samples. The optimised conditions consisted of an addition of 0.2gmL−1 KCl to the sample, which was extracted with 10mm length, 0.5mm film thickness stir bars coated with polydimethylsiloxane (PDMS), and stirred at 900rpm for 90min at room temperature (25°C) in a vial. Desorption was carried out at 280°C for 5min under 50mLmin−1 of helium flow in the splitless mode while maintaining a cryotrapping temperature of 20°C in the programmed-temperature vaporization (PTV) injector of the GC–MS system. Finally, the PTV injector was ramped to a temperature of 280°C and the analytes were separated in the GC and detected by MS using the selected-ion monitoring (SIM) mode. The detection limits of booster biocides were found to be in the range of 0.005–0.9μgL−1. The regression coefficients were higher than 0.999 for all analytes. The average recovery was higher than 72% (R.S.D.: 7–15%). All these figures of merit were established running samples in triplicate. This simple, accurate, sensitive and selective analytical method may be used for the determination of trace amounts of booster biocides in water samples from marinas.
Highlights
► Optimization of SBSE–TD–GC–MS for booster biocides in natural seawater. ► The use of SBSE for the simultaneous extraction of booster biocides in seawater. ► Validation of SBSE–TD–GC–MS for booster biocides in seawater.New application of the QuEChERS methodology for the determination of volatile phenols in beverages by liquid chromatography
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
The QuEChERS methodology has been used for the determination of pesticides in solid samples. However, this technique can be equally useful for other applications, namely for liquid samples. This work presents a new application of QuEChERS to the analysis of important ageing markers in beverages, the volatile phenols, by liquid chromatography with fluorimetric and UV detection. The sample preparation methodology comprises two sequential steps: (1) salting-out liquid–liquid extraction and (2) dispersive solid-phase extraction for extract clean-up. The methodology showed good repeatability (ca. 3%) and reproducibility (ca. 6%) with recovery levels above 90% and limits of detection varied in the range of 0.001–0.055mgL−1. A variable amount of phenols was found in the analysed samples (beers, wines and fruit juices), being 4-ethylphenol and 4-ethylguaiacol the compounds found in higher amounts, varying in the range of 0.12–1.11mgL−1 and 0.13–1.23mgL−1, respectively.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
The QuEChERS methodology has been used for the determination of pesticides in solid samples. However, this technique can be equally useful for other applications, namely for liquid samples. This work presents a new application of QuEChERS to the analysis of important ageing markers in beverages, the volatile phenols, by liquid chromatography with fluorimetric and UV detection. The sample preparation methodology comprises two sequential steps: (1) salting-out liquid–liquid extraction and (2) dispersive solid-phase extraction for extract clean-up. The methodology showed good repeatability (ca. 3%) and reproducibility (ca. 6%) with recovery levels above 90% and limits of detection varied in the range of 0.001–0.055mgL−1. A variable amount of phenols was found in the analysed samples (beers, wines and fruit juices), being 4-ethylphenol and 4-ethylguaiacol the compounds found in higher amounts, varying in the range of 0.12–1.11mgL−1 and 0.13–1.23mgL−1, respectively.
Highlights
► A QuEChERS-based methodology for the analysis of phenols in beverages was developed. ► High degree of sample clean-up for liquid chromatographic analysis is achieved. ► Competitive alternative to other sample preparation methodologies such as SPE. ► Low solvent consumption and no special laboratory equipment are required.Dried blood spots: Liquid chromatography–mass spectrometry analysis of Δ9-tetrahydrocannabinol and its main metabolites
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
A sensitive and selective HPLC–MS/MS method has been developed for the first time for the analysis of Δ9-tetrahydrocannabinol (the most important active cannabinoid) and its hydroxylated and carboxylated metabolites in human Dried Blood Spots (DBSs). The simultaneous determination of Δ9-tetrahydrocannabinol and its two main metabolites allows assessing the time elapsed after the drug intake and distinguishing between acute or former consumption. This is an important information in specific contexts such as “on street” controls by police forces. DBSs have been chosen as the optimal biological matrix for this kind of testing, since they provide information on the actual state of intoxication, without storage and transportation problems usually associated with classical blood testing. The analysis is carried out on a C8 reversed phase column with a mobile phase composed of 0.1% formic acid in a water/methanol mixture and an electrospray ionisation (ESI) source, coupled to a triple quadrupole mass spectrometer. The method was validated according to international guidelines, with satisfactory results in terms of extraction yields, precision, stability and accuracy. Application to real DBS samples from Cannabis abusers gave reliable results, thus confirming the methodology suitability for roadside testing.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
A sensitive and selective HPLC–MS/MS method has been developed for the first time for the analysis of Δ9-tetrahydrocannabinol (the most important active cannabinoid) and its hydroxylated and carboxylated metabolites in human Dried Blood Spots (DBSs). The simultaneous determination of Δ9-tetrahydrocannabinol and its two main metabolites allows assessing the time elapsed after the drug intake and distinguishing between acute or former consumption. This is an important information in specific contexts such as “on street” controls by police forces. DBSs have been chosen as the optimal biological matrix for this kind of testing, since they provide information on the actual state of intoxication, without storage and transportation problems usually associated with classical blood testing. The analysis is carried out on a C8 reversed phase column with a mobile phase composed of 0.1% formic acid in a water/methanol mixture and an electrospray ionisation (ESI) source, coupled to a triple quadrupole mass spectrometer. The method was validated according to international guidelines, with satisfactory results in terms of extraction yields, precision, stability and accuracy. Application to real DBS samples from Cannabis abusers gave reliable results, thus confirming the methodology suitability for roadside testing.
Highlights
► First method simultaneously analysing THC, THC-OH and THC-COOH in DBS. ► DBS: alternative matrix to the use of whole blood and plasma to monitor Cannabis intoxication. ► Method fully validated on standard solutions and “blank” DBS samples. ► Application to real DBS from Cannabis abusers. ► Reliable results confirming the methodology suitability for roadside testing.Direct determination of chlorophenols in water samples through ultrasound-assisted hollow fiber liquid–liquid–liquid microextraction on-line coupled with high-performance liquid chromatography
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
In this study we on-line coupled hollow fiber liquid–liquid–liquid microextraction (HF-LLLME), assisted by an ultrasonic probe, with high-performance liquid chromatography (HPLC). In this approach, the target analytes – 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 2,6-dichlorophenol (2,6-DCP), and 3,4-dichlorophenol (3,4-DCP) – were extracted into a hollow fiber (HF) supported liquid membrane (SLM) and then back-extracted into the acceptor solution in the lumen of the HF. Next, the acceptor solution was withdrawn on-line into the HPLC sample loop connected to the HF and then injected directly into the HPLC system for analysis. We found that the chlorophenols (CPs) could diffuse quickly through two sequential extraction interfaces – the donor phase – SLM and the SLM – acceptor phase – under the assistance of an ultrasonic probe. Ultrasonication provided effective mixing of the extracted boundary layers with the bulk of the sample and it increased the driving forces for mass transfer, thereby enhancing the extraction kinetics and leading to rapid enrichment of the target analytes. We studied the effects of various parameters on the extraction efficiency, viz. the nature of the SLM and acceptor phase, the compositions of the donor and acceptor phases, the fiber length, the stirring rate, the ion strength, the sample temperature, the sonication conditions, and the perfusion flow rate. This on-line extraction method exhibited linearity (r 2 ≥0.998), sensitivity (limits of detection: 0.03–0.05μgL−1), and precision (RSD%≤4.8), allowing the sensitive, simple, and rapid determination of CPs in aqueous solutions and water samples with a sampling time of just 2min.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
In this study we on-line coupled hollow fiber liquid–liquid–liquid microextraction (HF-LLLME), assisted by an ultrasonic probe, with high-performance liquid chromatography (HPLC). In this approach, the target analytes – 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 2,6-dichlorophenol (2,6-DCP), and 3,4-dichlorophenol (3,4-DCP) – were extracted into a hollow fiber (HF) supported liquid membrane (SLM) and then back-extracted into the acceptor solution in the lumen of the HF. Next, the acceptor solution was withdrawn on-line into the HPLC sample loop connected to the HF and then injected directly into the HPLC system for analysis. We found that the chlorophenols (CPs) could diffuse quickly through two sequential extraction interfaces – the donor phase – SLM and the SLM – acceptor phase – under the assistance of an ultrasonic probe. Ultrasonication provided effective mixing of the extracted boundary layers with the bulk of the sample and it increased the driving forces for mass transfer, thereby enhancing the extraction kinetics and leading to rapid enrichment of the target analytes. We studied the effects of various parameters on the extraction efficiency, viz. the nature of the SLM and acceptor phase, the compositions of the donor and acceptor phases, the fiber length, the stirring rate, the ion strength, the sample temperature, the sonication conditions, and the perfusion flow rate. This on-line extraction method exhibited linearity (r 2 ≥0.998), sensitivity (limits of detection: 0.03–0.05μgL−1), and precision (RSD%≤4.8), allowing the sensitive, simple, and rapid determination of CPs in aqueous solutions and water samples with a sampling time of just 2min.
Highlights
► The method employs an ultrasonication technique to accelerate mass transfer. ► A push/pull perfusion technique has been applied in HF-LLLME for the first time. ► The UA-HF-LLLME technique is suitable for on-line HPLC coupling. ► Only 2min is required for on-line sampling of the model analytes.Hybridization of commercial polymeric microparticles and magnetic nanoparticles for the dispersive micro-solid phase extraction of nitroaromatic hydrocarbons from water
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
In this article, the combination of commercial polymeric microparticles (OASIS MCX) and cobalt ferrite nanoparticles is evaluated in dispersive micro-solid phase extraction (D-μSPE) for the determination of six nitroaromatic hydrocarbons in water. The high affinity of the polymeric material toward the target analytes as well as the magnetic behavior of cobalt ferrite nanoparticles are combined in a synergic way to developed an efficient and simple D-μSPE approach. The sorptive performance of the hybrid material is compared with that most usual sorbents and the effect of its synthesis steps on the extraction capability is also evaluated in depth. After the optimization of selected variables, D-μSPE method was assessed in terms of linearity, sensitivity, precision and accuracy. The new extraction method allows the determination of the target compounds with limits of detection in the range from 0.12 to 1.26μg/L and relative standard deviations lower than 9.6%. The recovery study was performed in two different water samples obtaining percentages from 71 to 103%, which demonstrated the applicability of the hybrid sorbent for the selected analytical problem.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
In this article, the combination of commercial polymeric microparticles (OASIS MCX) and cobalt ferrite nanoparticles is evaluated in dispersive micro-solid phase extraction (D-μSPE) for the determination of six nitroaromatic hydrocarbons in water. The high affinity of the polymeric material toward the target analytes as well as the magnetic behavior of cobalt ferrite nanoparticles are combined in a synergic way to developed an efficient and simple D-μSPE approach. The sorptive performance of the hybrid material is compared with that most usual sorbents and the effect of its synthesis steps on the extraction capability is also evaluated in depth. After the optimization of selected variables, D-μSPE method was assessed in terms of linearity, sensitivity, precision and accuracy. The new extraction method allows the determination of the target compounds with limits of detection in the range from 0.12 to 1.26μg/L and relative standard deviations lower than 9.6%. The recovery study was performed in two different water samples obtaining percentages from 71 to 103%, which demonstrated the applicability of the hybrid sorbent for the selected analytical problem.
Highlights
► Commercial polymeric microparticles and magnetic nanoparticles are combined. ► The influence of the synthetic steps on the sorption was studied. ► The hybrid material is used for the nitroaromatic compounds determination in water. ► The developed extraction method was assessed.Determination of ultraviolet filters in environmental water samples by temperature-controlled ionic liquid dispersive liquid-phase microextraction
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
In the present study, a rapid, highly efficient and environmentally friendly sample preparation method named temperature-controlled ionic liquid dispersive liquid-phase microextraction (TC-IL-DLPME), followed by high performance liquid chromatography (HPLC) was developed for the extraction, preconcentration and determination of four benzophenone-type ultraviolet (UV) filters (viz. benzophenone (BP), 2-hydroxy-4-methoxybenzophenone (BP-3), ethylhexyl salicylate (EHS) and homosalate (HMS)) from water samples. An ultra-hydrophobic ionic liquid (IL) 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]), was used as the extraction solvent in TC-IL-DLPME. Temperature served two functions here, the promotion of the dispersal of the IL to the aqueous sample solution to form infinitesimal IL drops and increase the interface between them and the target analytes (at high temperature), and the facilitation of mass transfer between the phases, and achievement of phase separation (at low temperature). Due to the ultra-hydrophobic feature and high density of the extraction solvent, complete phase separation could be effected by centrifugation. Moreover, no disperser solvent was required. Another prominent feature of the procedure was the combination of extraction and centrifugation in a single step, which not only greatly reduced the total analysis time for TC-IL-DLPME but also simplified the sample preparation procedure. Various parameters that affected the extraction efficiency (such as type and volume of extraction solvent, temperature, salt addition, extraction time and pH) were evaluated. Under optimal conditions, the proposed method provided good enrichment factors in the range of 240–350, and relative standard deviations (n =5) below 6.3%. The limits of detection were in the range of 0.2–5.0ng/mL, depending on the analytes. The linearities were between 1 and 500ng/mL for BP, 5 and 1000ng/mL for BP-3, 10 and 1000ng/mL for HMS and 5 and 1000ng/mL for EHS. Finally, the proposed method was successfully applied to the determination of UV filters in swimming pool and tap water samples and acceptable relative recoveries over the range of 88.0–116.0% were obtained.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
In the present study, a rapid, highly efficient and environmentally friendly sample preparation method named temperature-controlled ionic liquid dispersive liquid-phase microextraction (TC-IL-DLPME), followed by high performance liquid chromatography (HPLC) was developed for the extraction, preconcentration and determination of four benzophenone-type ultraviolet (UV) filters (viz. benzophenone (BP), 2-hydroxy-4-methoxybenzophenone (BP-3), ethylhexyl salicylate (EHS) and homosalate (HMS)) from water samples. An ultra-hydrophobic ionic liquid (IL) 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]), was used as the extraction solvent in TC-IL-DLPME. Temperature served two functions here, the promotion of the dispersal of the IL to the aqueous sample solution to form infinitesimal IL drops and increase the interface between them and the target analytes (at high temperature), and the facilitation of mass transfer between the phases, and achievement of phase separation (at low temperature). Due to the ultra-hydrophobic feature and high density of the extraction solvent, complete phase separation could be effected by centrifugation. Moreover, no disperser solvent was required. Another prominent feature of the procedure was the combination of extraction and centrifugation in a single step, which not only greatly reduced the total analysis time for TC-IL-DLPME but also simplified the sample preparation procedure. Various parameters that affected the extraction efficiency (such as type and volume of extraction solvent, temperature, salt addition, extraction time and pH) were evaluated. Under optimal conditions, the proposed method provided good enrichment factors in the range of 240–350, and relative standard deviations (n =5) below 6.3%. The limits of detection were in the range of 0.2–5.0ng/mL, depending on the analytes. The linearities were between 1 and 500ng/mL for BP, 5 and 1000ng/mL for BP-3, 10 and 1000ng/mL for HMS and 5 and 1000ng/mL for EHS. Finally, the proposed method was successfully applied to the determination of UV filters in swimming pool and tap water samples and acceptable relative recoveries over the range of 88.0–116.0% were obtained.
Highlights
► TC-IL-DLPME-HPLC-UV was for the first time applied to the determination of UV filters. ► High extraction efficiency with good enrichment factors of up to 350 were achieved. ► The new method did not need a disperser solvent. ► Extraction and centrifugation were combined into a single step. ► Simple and efficient method with low LODs, good repeatability and linearity.Scaling up of high-speed countercurrent chromatographic apparatus with three columns connected in series for rapid preparation of (−)-epicatechin
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
In the present study, compact high-speed countercurrent chromatographic apparatus was constructed with three columns connected in series. Two sets of columns were prepared from 10mm and 12mm I.D. tubing to form 12L and 15L capacities, respectively. Performance of these columns was compared for the separation of (−)-epicatechin gallate (ECG) from a tea extract by flash countercurrent chromatography (FCCC). In each separation, 200g of the tea extract in 1600mL of mobile phase was loaded onto the column. The 12L column gave 7.5L (35g of ECG) and the 15L column gave 9L (40g of ECG) of ECG solution without impurities. The ECG solution was directly hydrolyzed by tannase into (−)-epicatechin. The hydrolysate was purified by flash chromatography on AB-8 macroporous resin to give 52g of EC (purity 99.1%). This scaled up apparatus could be used for the industrial separation of natural products.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
In the present study, compact high-speed countercurrent chromatographic apparatus was constructed with three columns connected in series. Two sets of columns were prepared from 10mm and 12mm I.D. tubing to form 12L and 15L capacities, respectively. Performance of these columns was compared for the separation of (−)-epicatechin gallate (ECG) from a tea extract by flash countercurrent chromatography (FCCC). In each separation, 200g of the tea extract in 1600mL of mobile phase was loaded onto the column. The 12L column gave 7.5L (35g of ECG) and the 15L column gave 9L (40g of ECG) of ECG solution without impurities. The ECG solution was directly hydrolyzed by tannase into (−)-epicatechin. The hydrolysate was purified by flash chromatography on AB-8 macroporous resin to give 52g of EC (purity 99.1%). This scaled up apparatus could be used for the industrial separation of natural products.
Highlights
► High-speed countercurrent chromatography is scaled up with three columns in series. ► (−)-Epicatechin gallate is separated from a tea extract using this apparatus. ► (−)-Epicatechin gallate is hydrolyzed by tannase to (−)-epicatechin. ► Flash chromatography on AB-8 macroporous resin purifies (−)-Epicatechin. ► The scaled up apparatus could be used for industrial separation of natural products.Isolation of the retinal isomers from the isomerization of all-trans-retinal by flash countercurrent chromatography
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
The isolation of the retinal isomers from all-trans-retinal was performed by flash countercurrent chromatography. In each separation, isomerization reaction solution of 200mg all-trans-retinal could be loaded on a 1200mL of high-speed countercurrent chromatographic column with 5mm bore, eluted by a mobile phase flow rate of 25mL/min, resulting in 63mg of 11-cis-retinal, 24mg of 13-cis-retinal and 26mg of 9-cis-retinal with purities more than 95%. n-Hexane–acetonitrile (3:1) was used as the solvent system which possesses the advantages of simplicity, re-use of the solvent and multiple injections. This method could be used to prepare 13-cis-retinal, 11-cis-retinal and 9-cis-retinal for the photoisomerization investigation, such as the effect of 11-cis-retinal in the visual system.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
The isolation of the retinal isomers from all-trans-retinal was performed by flash countercurrent chromatography. In each separation, isomerization reaction solution of 200mg all-trans-retinal could be loaded on a 1200mL of high-speed countercurrent chromatographic column with 5mm bore, eluted by a mobile phase flow rate of 25mL/min, resulting in 63mg of 11-cis-retinal, 24mg of 13-cis-retinal and 26mg of 9-cis-retinal with purities more than 95%. n-Hexane–acetonitrile (3:1) was used as the solvent system which possesses the advantages of simplicity, re-use of the solvent and multiple injections. This method could be used to prepare 13-cis-retinal, 11-cis-retinal and 9-cis-retinal for the photoisomerization investigation, such as the effect of 11-cis-retinal in the visual system.
Highlights
► Isomerization of all-trans-retinal produces cis-retinal isomers. ► Flash countercurrent chromatography can isolate the cis-retinal isomers. ► In each separation, 3 cis-retinal monomers are obtained. ► This separation is simple and provides excellent recovery. ► This method provides 3 cis-retinal monomers in a scale of 10-mg.pH-zone-refining counter-current chromatography: Origin, mechanism, procedure and applications
03 January 2013,
00:10:55
4 January 2013
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
Since 1980, high-speed counter-current chromatography (HSCCC) has been used for separation and purification of natural and synthetic products in a standard elution mode. In 1991, a novel elution mode called pH-zone refining CCC was introduced from an incidental discovery that an organic acid in the sample solution formed the sharp peak of an acid analyte. The cause of this sharp peak formation was found to be bromoacetic acid present in the sample solution which formed a sharp trailing border to trap the acidic analyte. Further studies on the separation of DNP-amino acids with three spacer acids in the stationary phase revealed that increased sample size resulted in the formation of fused rectangular peaks, each preserving high purity and zone pH with sharp boundaries. The mechanism of this phenomenon was found to be the formation of a sharp trailing border of an acid (retainer) in the column which moves at a lower rate than that of the mobile phase. In order to facilitate the application of the method, a new method was devised using a set of retainer and eluter to form a sharp retainer rear border which moves through the column at a desired rate regardless of the composition of the two-phase solvent system. This was achieved by adding the retainer in the stationary phase and the eluter in the mobile phase at a given molar ratio. Using this new method the hydrodynamics of pH-zone-refining CCC was diagrammatically illustrated by three acidic samples. In this review paper, typical pH-zone-refining CCC separations were presented, including affinity separations with a ligand and a separation of a racemic mixture using a chiral selector in the stationary phase. Major characteristics of pH-zone-refining CCC over conventional HSCCC are as follows: the sample loading capacity is increased over 10 times; fractions are highly concentrated near saturation level; yield is improved by increasing the sample size; minute charged compounds are concentrated and detected at the peak boundaries; and elution peaks are monitored with a pH flow meter for compounds with no chromophore. Since 1994, over 70 research papers on pH-zone-refining CCC have been published with the trends increasing in the recent years.
Publication year: 2013
Source:Journal of Chromatography A, Volume 1271, Issue 1
Since 1980, high-speed counter-current chromatography (HSCCC) has been used for separation and purification of natural and synthetic products in a standard elution mode. In 1991, a novel elution mode called pH-zone refining CCC was introduced from an incidental discovery that an organic acid in the sample solution formed the sharp peak of an acid analyte. The cause of this sharp peak formation was found to be bromoacetic acid present in the sample solution which formed a sharp trailing border to trap the acidic analyte. Further studies on the separation of DNP-amino acids with three spacer acids in the stationary phase revealed that increased sample size resulted in the formation of fused rectangular peaks, each preserving high purity and zone pH with sharp boundaries. The mechanism of this phenomenon was found to be the formation of a sharp trailing border of an acid (retainer) in the column which moves at a lower rate than that of the mobile phase. In order to facilitate the application of the method, a new method was devised using a set of retainer and eluter to form a sharp retainer rear border which moves through the column at a desired rate regardless of the composition of the two-phase solvent system. This was achieved by adding the retainer in the stationary phase and the eluter in the mobile phase at a given molar ratio. Using this new method the hydrodynamics of pH-zone-refining CCC was diagrammatically illustrated by three acidic samples. In this review paper, typical pH-zone-refining CCC separations were presented, including affinity separations with a ligand and a separation of a racemic mixture using a chiral selector in the stationary phase. Major characteristics of pH-zone-refining CCC over conventional HSCCC are as follows: the sample loading capacity is increased over 10 times; fractions are highly concentrated near saturation level; yield is improved by increasing the sample size; minute charged compounds are concentrated and detected at the peak boundaries; and elution peaks are monitored with a pH flow meter for compounds with no chromophore. Since 1994, over 70 research papers on pH-zone-refining CCC have been published with the trends increasing in the recent years.
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