A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:
Selective Isolation of G-Quadruplexes by Affinity Chromatography
16 February 2012, 21:36:46
Publication year: 2012
Source: Journal of Chromatography A, Available online 16 February 2012
Tianjun Chang, Xiangjun Liu, Xiaohong Cheng, Cui Qi, Hongcheng Mei, ...
G-quadruplex (G4) is a characteristic secondary structure of nucleic acids containing repetitive tandem guanines. G4-forming sequences are found prevalent in the human genome by bioinformatics analysis. Accumulating evidence has suggested that G4 s are involved in many biological processes. Selective isolation of G4 s would be an effective tool in the study of G4 s. In this paper, we prepared four affinity matrixes using hemin or a perylene derivative (N,N’-Bis-(2-(amino)ethyl)-3,4,9,10- perylenetetracarboxylic acid diimide, Pery01) as ligand, and investigated the retention behaviors of different G4 s on these matrixes. Our experimental results suggest that the π-π stacking interaction between ligand and G-tetrad plays a key role in the selective isolation of G4 s, whereas the electrostatic interaction between DNA and matrix causes the nonspecific binding. One matrix prepared by immobilizing Pery01 on polyglycidylmethacrylate (PGMA) beads through an aminocaproic acid spacer exhibits good selectivity for parallel structure G4 s and has been successfully used to directly isolate a spiked parallel G4 from plasma.
Source: Journal of Chromatography A, Available online 16 February 2012
Tianjun Chang, Xiangjun Liu, Xiaohong Cheng, Cui Qi, Hongcheng Mei, ...
G-quadruplex (G4) is a characteristic secondary structure of nucleic acids containing repetitive tandem guanines. G4-forming sequences are found prevalent in the human genome by bioinformatics analysis. Accumulating evidence has suggested that G4 s are involved in many biological processes. Selective isolation of G4 s would be an effective tool in the study of G4 s. In this paper, we prepared four affinity matrixes using hemin or a perylene derivative (N,N’-Bis-(2-(amino)ethyl)-3,4,9,10- perylenetetracarboxylic acid diimide, Pery01) as ligand, and investigated the retention behaviors of different G4 s on these matrixes. Our experimental results suggest that the π-π stacking interaction between ligand and G-tetrad plays a key role in the selective isolation of G4 s, whereas the electrostatic interaction between DNA and matrix causes the nonspecific binding. One matrix prepared by immobilizing Pery01 on polyglycidylmethacrylate (PGMA) beads through an aminocaproic acid spacer exhibits good selectivity for parallel structure G4 s and has been successfully used to directly isolate a spiked parallel G4 from plasma.
Highlights
► G-Quadruplexes are special secondary structure of nucleic acids ► Selective isolation of G-Quadruplexes is rarely reported ► Four affinity matrixes immobilized with hemin or a perylene derivative are prepared ► The factors that influence the selectivity are discussed ► G-Quadruplex spiked in plasma has been successfully isolated by direct injectionDetermination of nitrophenols using ultrahigh pressure liquid chromatography and a new manual shaking-enhanced, ultrasound-assisted emulsification microextraction method based on solidification of a floating organic droplet
16 February 2012, 21:36:46
Publication year: 2012
Source: Journal of Chromatography A, Available online 16 February 2012
Ren-Je Chung, Mei-I Leong, Shang-Da Huang
Nitrophenols are toxic compounds in the wastewater. In the proposed method, a new technique using a manual shaking-enhanced, ultrasound-assisted emulsification microextraction (MS-USAEME) method based on solidification of a floating organic droplet combined with ultrahigh pressure liquid chromatography (UHPLC) has been developed for the extraction and determination of nitrophenols in aqueous samples. In this method, the low toxicity extraction solvent 1-undecanol was used to extract the nitrophenols. After centrifugation, ice bath was used to solidify the floating extraction solvent, using microtubes to collect the floated extraction solvent and diluting with 30 μL of dimethyl sulfoxide, then injecting into the UHPLC for further analysis. The relative standard deviations (RSD) were 6-12%, enrichment factors (EFs) were 62-500, the relative recoveries (RR) of this method were 80-110% for spiked lake water samples. The detection limits of this method were 0.5–3.0 μg Lfor spiked lake water and 0.6–3.2 μg Lfor spiked agriculture water. The further performance of the proposed method was gauged by analyzing field samples.
Source: Journal of Chromatography A, Available online 16 February 2012
Ren-Je Chung, Mei-I Leong, Shang-Da Huang
Nitrophenols are toxic compounds in the wastewater. In the proposed method, a new technique using a manual shaking-enhanced, ultrasound-assisted emulsification microextraction (MS-USAEME) method based on solidification of a floating organic droplet combined with ultrahigh pressure liquid chromatography (UHPLC) has been developed for the extraction and determination of nitrophenols in aqueous samples. In this method, the low toxicity extraction solvent 1-undecanol was used to extract the nitrophenols. After centrifugation, ice bath was used to solidify the floating extraction solvent, using microtubes to collect the floated extraction solvent and diluting with 30 μL of dimethyl sulfoxide, then injecting into the UHPLC for further analysis. The relative standard deviations (RSD) were 6-12%, enrichment factors (EFs) were 62-500, the relative recoveries (RR) of this method were 80-110% for spiked lake water samples. The detection limits of this method were 0.5–3.0 μg Lfor spiked lake water and 0.6–3.2 μg Lfor spiked agriculture water. The further performance of the proposed method was gauged by analyzing field samples.
Highlights
► Only 12 μL of low toxic organic solvent is required. ► Low LODs, fast extraction. ► Manual shaking for 10 sec before ultrasound emulsification is essential. ► Method based on solidification of a floating organic droplet is used.Prediction of retention times in comprehensive two-dimensional gas chromatography using thermodynamic models
16 February 2012, 21:36:46
Publication year: 2012
Source: Journal of Chromatography A, Available online 16 February 2012
Teague M. McGinitie, James J. Harynuk
A method was developed to accurately predict both the primary and secondary retention times for a series of alkanes, ketones and alcohols in a flow-modulated GC × GC system. This was accomplished through the use of a three-parameter thermodynamic model where ΔH, ΔS, and ΔCpfor an analyte's interaction with the stationary phases in both dimensions are known. Coupling this thermodynamic model with a time summation calculation it was possible to accurately predict bothtrandtrfor all analytes. The model was able to predict retention times regardless of the temperature ramp used, with an average error of only 0.64% fortrand an average error of only 2.22% fortr. The model shows promise for the accurate prediction of retention times in GC × GC for a wide range of compounds and is able to utilize data collected from 1D experiments.
Source: Journal of Chromatography A, Available online 16 February 2012
Teague M. McGinitie, James J. Harynuk
A method was developed to accurately predict both the primary and secondary retention times for a series of alkanes, ketones and alcohols in a flow-modulated GC × GC system. This was accomplished through the use of a three-parameter thermodynamic model where ΔH, ΔS, and ΔCpfor an analyte's interaction with the stationary phases in both dimensions are known. Coupling this thermodynamic model with a time summation calculation it was possible to accurately predict bothtrandtrfor all analytes. The model was able to predict retention times regardless of the temperature ramp used, with an average error of only 0.64% fortrand an average error of only 2.22% fortr. The model shows promise for the accurate prediction of retention times in GC × GC for a wide range of compounds and is able to utilize data collected from 1D experiments.
Highlights
► Thermodynamic prediction of retention time applied to GC × GC separations ► Under GC × GC conditions, thermodynamic model is superior to retention index inD ► New model offers easy prediction forD, unlike retention index which is cumbersomeEvaluation of sulfonated graphene sheets as sorbent for micro-solid-phase extraction combined with gas chromatography-mass spectrometry
16 February 2012, 21:36:46
Publication year: 2012
Source: Journal of Chromatography A, Available online 16 February 2012
Hong Zhang, Wei Ping Low, Hian Kee Lee
This report describes the use of sulfonated graphene sheets as sorbent in micro-solid-phase extraction (μ-SPE), together with gas chromatography-mass spectrometry, for the determination of polycyclic aromatic hydrocarbons (PAHs) in water. In this study, for the first time, graphene sheets were used as a sorbent material for this mode of microextraction. The modified graphene sheets were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and elemental analysis. μ-SPE parameters such as extraction time, desorption time and desorption solvent were optimized. The method showed good precision, reproducibility and linear response for PAH analysis over a concentration range of 0.05 - 100 μg/L for naphthalene and 0.01 - 100 μg/L for the remaining PAHs (acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene) with coefficient of determination (r) of higher than 0.992. Limits of detection of from 0.8 to 3.9 ng/L for 7 PAHs were achieved. The developed method was successfully applied to determine PAHs in river water samples.
Source: Journal of Chromatography A, Available online 16 February 2012
Hong Zhang, Wei Ping Low, Hian Kee Lee
This report describes the use of sulfonated graphene sheets as sorbent in micro-solid-phase extraction (μ-SPE), together with gas chromatography-mass spectrometry, for the determination of polycyclic aromatic hydrocarbons (PAHs) in water. In this study, for the first time, graphene sheets were used as a sorbent material for this mode of microextraction. The modified graphene sheets were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and elemental analysis. μ-SPE parameters such as extraction time, desorption time and desorption solvent were optimized. The method showed good precision, reproducibility and linear response for PAH analysis over a concentration range of 0.05 - 100 μg/L for naphthalene and 0.01 - 100 μg/L for the remaining PAHs (acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene) with coefficient of determination (r) of higher than 0.992. Limits of detection of from 0.8 to 3.9 ng/L for 7 PAHs were achieved. The developed method was successfully applied to determine PAHs in river water samples.
Immuno-magnetic beads-based extraction-capillary zone electrophoresis-deep UV laser-induced fluorescence analysis of erythropoietin
16 February 2012, 21:36:46
Publication year: 2012
Source: Journal of Chromatography A, Available online 14 February 2012
Heye Wang, Peng Dou, Chenchen Lü, Zhen Liu
Erythropoietin (EPO) is an important glycoprotein hormone. Recombinant human EPO (rhEPO) is an important therapeutic drug and can be also used as doping reagent in sports. The analysis of EPO glycoforms in pharmaceutical and sports areas greatly challenges analytical scientists from several aspects, among which sensitive detection and effective and facile sample preparation are two essential issues. Herein, we investigated new possibilities for these two aspects. Deep UV laser-induced fluorescence detection (deep UV-LIF) was established to detect the intrinsic fluorescence of EPO while an immuno-magnetic beads-based extraction (IMBE) was developed to specifically extract EPO glycoforms. Combined with capillary zone electrophoresis (CZE), CZE-deep UV-LIF allows high resolution glycoform profiling with improved sensitivity. The detection sensitivity was improved by one order of magnitude as compared with UV absorbance detection. An additional advantage is that the original glycoform distribution can be completely preserved because no fluorescent labeling is needed. By combining IMBE with CZE-deep UV-LIF, the overall detection sensitivity was 1.5 × 10 mol/L, which was enhanced by two orders of magnitude relative to conventional CZE with UV absorbance detection. It is applicable to the analysis of pharmaceutical preparations of EPO, but the sensitivity is insufficient for the anti-doping analysis of EPO in blood and urine. IMBE can be straightforward and effective approach for sample preparation. However, antibodies with high specificity were the key for application to urine samples because some urinary proteins can severely interfere the immuno-extraction.
Source: Journal of Chromatography A, Available online 14 February 2012
Heye Wang, Peng Dou, Chenchen Lü, Zhen Liu
Erythropoietin (EPO) is an important glycoprotein hormone. Recombinant human EPO (rhEPO) is an important therapeutic drug and can be also used as doping reagent in sports. The analysis of EPO glycoforms in pharmaceutical and sports areas greatly challenges analytical scientists from several aspects, among which sensitive detection and effective and facile sample preparation are two essential issues. Herein, we investigated new possibilities for these two aspects. Deep UV laser-induced fluorescence detection (deep UV-LIF) was established to detect the intrinsic fluorescence of EPO while an immuno-magnetic beads-based extraction (IMBE) was developed to specifically extract EPO glycoforms. Combined with capillary zone electrophoresis (CZE), CZE-deep UV-LIF allows high resolution glycoform profiling with improved sensitivity. The detection sensitivity was improved by one order of magnitude as compared with UV absorbance detection. An additional advantage is that the original glycoform distribution can be completely preserved because no fluorescent labeling is needed. By combining IMBE with CZE-deep UV-LIF, the overall detection sensitivity was 1.5 × 10 mol/L, which was enhanced by two orders of magnitude relative to conventional CZE with UV absorbance detection. It is applicable to the analysis of pharmaceutical preparations of EPO, but the sensitivity is insufficient for the anti-doping analysis of EPO in blood and urine. IMBE can be straightforward and effective approach for sample preparation. However, antibodies with high specificity were the key for application to urine samples because some urinary proteins can severely interfere the immuno-extraction.
Highlights
► A deep UV-LIF approach was established for sensitive detection of EPO glycoforms. ► An extraction approach was developed for specific extraction of EPO glycoforms. ► Combined with 1 and 2, a CZE method was developed for analysis of EPO glycoforms.Comparative evaluation of post-column free radical scavenging and ferric reducing antioxidant power assays for screening of antioxidants in strawberries
16 February 2012, 21:36:46
Publication year: 2012
Source: Journal of Chromatography A, Available online 14 February 2012
Raimondas Raudonis, Lina Raudone, Valdas Jakstas, Valdimaras Janulis
ABTS and FRAP post-column techniques evaluate the antioxidant characteristics of HPLC separated compounds with specific reagents. ABTS characterize their ability to scavenge free radicals by electron-donating antioxidants, resulting in the absorbance decrease of the chromophoric radical. FRAP–is based on the reduction of Fe(III)–tripyridyltriazine complex to Fe(II)–tripyridyltriazine at low pH by electron-donating antioxidants, resulting in an absorbance increase. Both post-column assays were evaluated and compared according to the following validation parameters: specificity, precision, limit of detection (LoD), limit of quantitation (LoQ) and linearity. ABTS and FRAP post-column assays were specific, repeatable and sensitive and thus can be used for the evaluation of antioxidant active compounds. Antioxidant active compounds were quantified according to TEAC for each assay and ABTS/FRAP ratio was derived. No previous records of antioxidative activity of leaves and fruits of strawberries (Fragaria viridis, Fragaria moschata) research have been found. The reasearch results confirm the reliability of ABTS and FRAP post-column assays for screening of antioxidants in complex mixtures and the determination of radical scavenging and ferric reducing ability by their TEAC values.
Source: Journal of Chromatography A, Available online 14 February 2012
Raimondas Raudonis, Lina Raudone, Valdas Jakstas, Valdimaras Janulis
ABTS and FRAP post-column techniques evaluate the antioxidant characteristics of HPLC separated compounds with specific reagents. ABTS characterize their ability to scavenge free radicals by electron-donating antioxidants, resulting in the absorbance decrease of the chromophoric radical. FRAP–is based on the reduction of Fe(III)–tripyridyltriazine complex to Fe(II)–tripyridyltriazine at low pH by electron-donating antioxidants, resulting in an absorbance increase. Both post-column assays were evaluated and compared according to the following validation parameters: specificity, precision, limit of detection (LoD), limit of quantitation (LoQ) and linearity. ABTS and FRAP post-column assays were specific, repeatable and sensitive and thus can be used for the evaluation of antioxidant active compounds. Antioxidant active compounds were quantified according to TEAC for each assay and ABTS/FRAP ratio was derived. No previous records of antioxidative activity of leaves and fruits of strawberries (Fragaria viridis, Fragaria moschata) research have been found. The reasearch results confirm the reliability of ABTS and FRAP post-column assays for screening of antioxidants in complex mixtures and the determination of radical scavenging and ferric reducing ability by their TEAC values.
Highlights
► Post-column assays evaluate the antioxidant features of HPLC separated compounds ► ABTS characterize radical scavengers; FRAP is based on ferric reducing abilities ► Online assays were evaluated and compared according to validation parameters ► Fingerprinting of herbal materials, phytopreparations are the area of applicationHYPHENATED LIQUID CHROMATOGRAPHY-GAS CHROMATOGRAPHY TECHNIQUE: RECENT EVOLUTION AND APPLICATIONS
16 February 2012, 21:36:46
Publication year: 2012
Source: Journal of Chromatography A, Available online 14 February 2012
Giorgia Purcaro
Liquid chromatography (LC) hyphenated with gas chromatography (GC) was first presented in 1979. Since then an intensive study has been carried out to explore different types of interfaces both for coupling normal-phase (NP) and reverse-phase (RP) LC with GC. The present review focuses on the technical progress and applications presented in the last decade, and it describes the most used interfaces. In fact, more flexible interfaces have been studied to improve the use of LC-GC, in particular the use of a programmed temperature vaporiser (PTV) injector as the interface. An intensive effort has also been devoted to optimizing the coupling of reverse-phase LC for analysis of water-based samples. A brief overview of comprehensive approaches (LC × GC) is discussed along with prespective for further improvement of the technique.
Source: Journal of Chromatography A, Available online 14 February 2012
Giorgia Purcaro
Liquid chromatography (LC) hyphenated with gas chromatography (GC) was first presented in 1979. Since then an intensive study has been carried out to explore different types of interfaces both for coupling normal-phase (NP) and reverse-phase (RP) LC with GC. The present review focuses on the technical progress and applications presented in the last decade, and it describes the most used interfaces. In fact, more flexible interfaces have been studied to improve the use of LC-GC, in particular the use of a programmed temperature vaporiser (PTV) injector as the interface. An intensive effort has also been devoted to optimizing the coupling of reverse-phase LC for analysis of water-based samples. A brief overview of comprehensive approaches (LC × GC) is discussed along with prespective for further improvement of the technique.
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