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Selected papers from the latest issue:
Recent developments in the detailed characterization of polymers by multidimensional chromatography
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Anja Baumgaertel, Esra Altuntaş, Ulrich S. Schubert
Synthetic polymers as well as biopolymers reveal complex structures, such as variations in functionality, chain length and architecture. Therefore, combinations of different chromatographic techniques are a prerequisite for a detailed characterization. One possible approach is the combination of high performance liquid chromatography at critical conditions (LCCC) and size-exclusion chromatography, also named as two-dimensional chromatography, which allows the separation of the polymers according to different properties, like molar mass, chemical composition or functionality. In addition, LCCC hyphenated with different mass spectrometry techniques, e.g. MALDI-TOF or ESI-TOF, leads to additional information about molecular details of the polymeric structure. We summarize in this article the recent developments in two-dimensional chromatography of synthetic polymers and biopolymers since 2005.
Source:Journal of Chromatography A, Volume 1240
Anja Baumgaertel, Esra Altuntaş, Ulrich S. Schubert
Synthetic polymers as well as biopolymers reveal complex structures, such as variations in functionality, chain length and architecture. Therefore, combinations of different chromatographic techniques are a prerequisite for a detailed characterization. One possible approach is the combination of high performance liquid chromatography at critical conditions (LCCC) and size-exclusion chromatography, also named as two-dimensional chromatography, which allows the separation of the polymers according to different properties, like molar mass, chemical composition or functionality. In addition, LCCC hyphenated with different mass spectrometry techniques, e.g. MALDI-TOF or ESI-TOF, leads to additional information about molecular details of the polymeric structure. We summarize in this article the recent developments in two-dimensional chromatography of synthetic polymers and biopolymers since 2005.
Comparison of sample preparation approaches for phospholipids profiling in human serum by liquid chromatography–tandem mass spectrometry
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
C. Ferreiro-Vera, F. Priego-Capote, M.D. Luque de Castro
Fractionation of biological fluids for proper analysis by LC–MS of low-abundance metabolites in the presence of high-abundant endogenous metabolites is of interest, particularly when the latter cause undesirable phenomena such as ionization suppression, as is the case with phospholipids (PLs). An exhaustive study and comparison of different protocols for sample preparation based on deproteinization, liquid–liquid extraction (LLE) and solid-phase extraction (SPE) has been carried out with the main aim of implementing metabolomics analysis of PLs within a global metabolite profiling of serum. After selecting LLE and SPE as the best strategies for sample preparation, the fractions from each approach were analyzed by LC–TOF/MS in positive and negative ionization modes, and the highest number of molecular features was found by the latter strategy (2667 versus 1911 in the positive ionization mode). SPE also allows obtaining a clean elution of PLs which made possible tentative identification of these metabolites in both ionization modes by matching to the Human Metabolome Database. Confirmatory analysis to assess PLs identity was supported on MS/MS experiments at different collision energies.
Source:Journal of Chromatography A, Volume 1240
C. Ferreiro-Vera, F. Priego-Capote, M.D. Luque de Castro
Fractionation of biological fluids for proper analysis by LC–MS of low-abundance metabolites in the presence of high-abundant endogenous metabolites is of interest, particularly when the latter cause undesirable phenomena such as ionization suppression, as is the case with phospholipids (PLs). An exhaustive study and comparison of different protocols for sample preparation based on deproteinization, liquid–liquid extraction (LLE) and solid-phase extraction (SPE) has been carried out with the main aim of implementing metabolomics analysis of PLs within a global metabolite profiling of serum. After selecting LLE and SPE as the best strategies for sample preparation, the fractions from each approach were analyzed by LC–TOF/MS in positive and negative ionization modes, and the highest number of molecular features was found by the latter strategy (2667 versus 1911 in the positive ionization mode). SPE also allows obtaining a clean elution of PLs which made possible tentative identification of these metabolites in both ionization modes by matching to the Human Metabolome Database. Confirmatory analysis to assess PLs identity was supported on MS/MS experiments at different collision energies.
Selective extraction of genotoxic impurities and structurally alerting compounds using polymeric ionic liquid sorbent coatings in solid-phase microextraction: Alkyl halides and aromatics
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Tien D. Ho, Manishkumar D. Joshi, Mark A. Silver, Jared L. Anderson
A series of polymeric ionic liquids (PILs) possessing varied chemical makeup and composition were applied as selective solid-phase microextraction (SPME) sorbent coatings for the analysis of genotoxic impurities (GTIs) and related structurally alerting compounds, namely, alkyl halides and aromatics. In addition to exploiting two previously synthesized PILs as selective coatings, two new PILs, namely, N,N-didecyl-N-methyl-d-glucaminium poly(2-methyl-acrylic acid 2-[1-(3-{2-[2-(3-trifluoromethanesulfonylamino-propoxy)-ethoxy]-ethoxy}-propylamino)-vinylamino]-ethyl ester) (poly([DDMGlu][MTFSI])), and poly(1-vinyl-3-propylphenylimidazolium) chloride (poly([VPPIM][Cl])), were designed, synthesized, and their selectivity examined in the extraction of the selected analytes. The glucaminium-based coating was developed to exploit the hydrogen bond-acidic hydroxyl groups within the carbohydrate moiety of the PIL in addition to dispersive capabilities resulting from the cation and anion. The poly([VPPIM][Cl]) coating was tailored to possess π–π interaction capabilities through the phenyl functionality while also containing the hydrogen bond-basic chloride anion. Calibration studies were performed via headspace extraction to determine the sensitivity and limit of detection (LOD) for all analytes with respect to each PIL-based sorbent coating and compared to the polyacrylate (PA) and polydimethylsiloxane (PDMS) sorbent coatings. PILs containing the chloride anion exhibited high selectivity for aniline-based compounds. The glucaminium-based PIL exhibited good sensitivity for larger aliphatic alkyl halides. The poly(1-4-vinylbenzyl-3-hexadecylimidazolium) bis[(trifluoromethyl)sulfonyl] imide (poly([VBHDIM][NTf2])) PIL coating demonstrated superior selectivity for larger aliphatic/aromatic analytes. The LODs of both commercial and PIL-based coatings for the two classes of GTIs ranged from low part-per-billion (ppb) to mid part-per-trillion (ppt) levels. Recovery studies were performed at two concentration levels within the linear range in order to validate the accuracy of the technique. Scanning electron micrographs were obtained for three PIL-based coatings following approximately 70 extraction/desorption steps, wherein the fiber coatings were observed to be largely smooth and intact.
Source:Journal of Chromatography A, Volume 1240
Tien D. Ho, Manishkumar D. Joshi, Mark A. Silver, Jared L. Anderson
A series of polymeric ionic liquids (PILs) possessing varied chemical makeup and composition were applied as selective solid-phase microextraction (SPME) sorbent coatings for the analysis of genotoxic impurities (GTIs) and related structurally alerting compounds, namely, alkyl halides and aromatics. In addition to exploiting two previously synthesized PILs as selective coatings, two new PILs, namely, N,N-didecyl-N-methyl-d-glucaminium poly(2-methyl-acrylic acid 2-[1-(3-{2-[2-(3-trifluoromethanesulfonylamino-propoxy)-ethoxy]-ethoxy}-propylamino)-vinylamino]-ethyl ester) (poly([DDMGlu][MTFSI])), and poly(1-vinyl-3-propylphenylimidazolium) chloride (poly([VPPIM][Cl])), were designed, synthesized, and their selectivity examined in the extraction of the selected analytes. The glucaminium-based coating was developed to exploit the hydrogen bond-acidic hydroxyl groups within the carbohydrate moiety of the PIL in addition to dispersive capabilities resulting from the cation and anion. The poly([VPPIM][Cl]) coating was tailored to possess π–π interaction capabilities through the phenyl functionality while also containing the hydrogen bond-basic chloride anion. Calibration studies were performed via headspace extraction to determine the sensitivity and limit of detection (LOD) for all analytes with respect to each PIL-based sorbent coating and compared to the polyacrylate (PA) and polydimethylsiloxane (PDMS) sorbent coatings. PILs containing the chloride anion exhibited high selectivity for aniline-based compounds. The glucaminium-based PIL exhibited good sensitivity for larger aliphatic alkyl halides. The poly(1-4-vinylbenzyl-3-hexadecylimidazolium) bis[(trifluoromethyl)sulfonyl] imide (poly([VBHDIM][NTf2])) PIL coating demonstrated superior selectivity for larger aliphatic/aromatic analytes. The LODs of both commercial and PIL-based coatings for the two classes of GTIs ranged from low part-per-billion (ppb) to mid part-per-trillion (ppt) levels. Recovery studies were performed at two concentration levels within the linear range in order to validate the accuracy of the technique. Scanning electron micrographs were obtained for three PIL-based coatings following approximately 70 extraction/desorption steps, wherein the fiber coatings were observed to be largely smooth and intact.
Dispersive microextraction based on water-coated Fe3O4 followed by gas chromatography–mass spectrometry for determination of 3-monochloropropane-1,2-diol in edible oils
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Qin Zhao, Fang Wei, Neng Xiao, Qiong-Wei Yu, Bi-Feng Yuan, Yu-Qi Feng
In the present work, we developed a novel dispersive microextraction technique by combining the advantages of liquid-phase microextraction (LPME) and magnetic solid-phase extraction (MSPE). In this method, trace amount of water directly absorbed on bare Fe3O4 to form water-coated Fe3O4 (W-Fe3O4) and rapid extraction can be achieved while W-Fe3O4 dispersed in the sample solution. The analyte adsorbed W-Fe3O4 can be easily collected and isolated from sample solution by application of a magnet. It was worth noting that in the proposed method water was used as extractant and Fe3O4 served as the supporter and retriever of water. The performance of the method was evaluated by extraction of 3-monochloropropane-1,2-diol (3-MCPD) from edible oils. The extracted 3-MCPD was then derived by a silylanization reagent (1-trimethylsilylimidazole) before gas chromatography–mass spectrometry (GC–MS) analysis. Several parameters that affected the extraction and derivatization efficiency were investigated. Our results showed that the limit of detection for 3-MCPD was 1.1ng/g. The recoveries in spiked oil samples were in the range of 70.0–104.9% with the RSDs less than 5.6% (intra-day) and 6.4% (inter-day). Taken together, the simple, rapid and cost-effective method developed in current study, offers a potential application for the extraction and preconcentration of hydrophilic analytes from complex fatty samples.
Source:Journal of Chromatography A, Volume 1240
Qin Zhao, Fang Wei, Neng Xiao, Qiong-Wei Yu, Bi-Feng Yuan, Yu-Qi Feng
In the present work, we developed a novel dispersive microextraction technique by combining the advantages of liquid-phase microextraction (LPME) and magnetic solid-phase extraction (MSPE). In this method, trace amount of water directly absorbed on bare Fe3O4 to form water-coated Fe3O4 (W-Fe3O4) and rapid extraction can be achieved while W-Fe3O4 dispersed in the sample solution. The analyte adsorbed W-Fe3O4 can be easily collected and isolated from sample solution by application of a magnet. It was worth noting that in the proposed method water was used as extractant and Fe3O4 served as the supporter and retriever of water. The performance of the method was evaluated by extraction of 3-monochloropropane-1,2-diol (3-MCPD) from edible oils. The extracted 3-MCPD was then derived by a silylanization reagent (1-trimethylsilylimidazole) before gas chromatography–mass spectrometry (GC–MS) analysis. Several parameters that affected the extraction and derivatization efficiency were investigated. Our results showed that the limit of detection for 3-MCPD was 1.1ng/g. The recoveries in spiked oil samples were in the range of 70.0–104.9% with the RSDs less than 5.6% (intra-day) and 6.4% (inter-day). Taken together, the simple, rapid and cost-effective method developed in current study, offers a potential application for the extraction and preconcentration of hydrophilic analytes from complex fatty samples.
Removal of potentially genotoxic acetamide and arylsulfonate impurities from crude drugs by molecular imprinting
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
György Székely, Emelie Fritz, Joao Bandarra, William Heggie, Börje Sellergren
The present study describes the synthesis and preliminary testing of molecularly imprinted polymers (MIPs) as scavenger resins for removal of the genotoxic impurities (GTI) acetamide and arylsulfonates from active pharmaceutical ingredients (API). The MIPs were synthesized as monoliths using acetamide or methyl tosylate respectively as templates. The polymers were crushed and subsequently tested in the batch and chromatographic mode for template recognition and potential removal efficiency. Both the acetamide and the tosylate MIPs exhibited a strong memory effect for their templates and selectivity with respect to model APIs. For instance the MIP for acetamide preferentially retained acetamide over other amides, such as formamide, acrylamide, methacrylamide, benzamide and N-tert-butylacrylamide. Moreover, passing model API crude contaminated with the acetamide through the MIPs led to the quantitative removal of acetamide.
Source:Journal of Chromatography A, Volume 1240
György Székely, Emelie Fritz, Joao Bandarra, William Heggie, Börje Sellergren
The present study describes the synthesis and preliminary testing of molecularly imprinted polymers (MIPs) as scavenger resins for removal of the genotoxic impurities (GTI) acetamide and arylsulfonates from active pharmaceutical ingredients (API). The MIPs were synthesized as monoliths using acetamide or methyl tosylate respectively as templates. The polymers were crushed and subsequently tested in the batch and chromatographic mode for template recognition and potential removal efficiency. Both the acetamide and the tosylate MIPs exhibited a strong memory effect for their templates and selectivity with respect to model APIs. For instance the MIP for acetamide preferentially retained acetamide over other amides, such as formamide, acrylamide, methacrylamide, benzamide and N-tert-butylacrylamide. Moreover, passing model API crude contaminated with the acetamide through the MIPs led to the quantitative removal of acetamide.
Full evaporation dynamic headspace and gas chromatography–mass spectrometry for uniform enrichment of odor compounds in aqueous samples
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Nobuo Ochiai, Kikuo Sasamoto, Andreas Hoffmann, Kazunori Okanoya
A method for analysis of a wide range of odor compounds in aqueous samples at sub-ngmL−1 to μgmL−1 levels was developed by full evaporation dynamic headspace (FEDHS) and gas chromatography–mass spectrometry (GC–MS). Compared to conventional DHS and headspace solid phase microextraction (HS-SPME), FEDHS provides more uniform enrichment over the entire polarity range for odor compounds in aqueous samples. FEDHS at 80°C using 3L of purge gas allows complete vaporization of 100μL of an aqueous sample, and trapping and drying it in an adsorbent packed tube, while providing high recoveries (85–103%) of the 18 model odor compounds (water solubility at 25°C: log0.54–5.65mgL−1, vapor pressure at 25°C: 0.011–3.2mmHg) and leaving most of the low volatile matrix behind. The FEDHS-GC–MS method showed good linearity (r 2 >0.9909) and high sensitivity (limit of detection: 0.21–5.2ngmL−1) for the model compounds even with the scan mode in the conventional MS. The feasibility and benefit of the method was demonstrated with analyses of key odor compounds including hydrophilic and less volatile characteristics in beverages (whiskey and green tea). In a single malt whiskey sample, phenolic compounds including vanillin could be determined in the range of 0.92–5.1μgmL−1 (RSD<7.4%, n =6). For a Japanese green tea sample, 48 compounds including 19 potent odorants were positively identified from only 100μL of sample. Heat-induced artifact formation for potent odorants was also examined and the proposed method does not affect the additional formation of thermally generated compounds. Eighteen compounds including 12 potent odorants (e.g. coumarin, furaneol, indole, maltol, and pyrazine congeners) were determined in the range of 0.21–110ngmL−1 (RSD<10%, n =6).
Source:Journal of Chromatography A, Volume 1240
Nobuo Ochiai, Kikuo Sasamoto, Andreas Hoffmann, Kazunori Okanoya
A method for analysis of a wide range of odor compounds in aqueous samples at sub-ngmL−1 to μgmL−1 levels was developed by full evaporation dynamic headspace (FEDHS) and gas chromatography–mass spectrometry (GC–MS). Compared to conventional DHS and headspace solid phase microextraction (HS-SPME), FEDHS provides more uniform enrichment over the entire polarity range for odor compounds in aqueous samples. FEDHS at 80°C using 3L of purge gas allows complete vaporization of 100μL of an aqueous sample, and trapping and drying it in an adsorbent packed tube, while providing high recoveries (85–103%) of the 18 model odor compounds (water solubility at 25°C: log0.54–5.65mgL−1, vapor pressure at 25°C: 0.011–3.2mmHg) and leaving most of the low volatile matrix behind. The FEDHS-GC–MS method showed good linearity (r 2 >0.9909) and high sensitivity (limit of detection: 0.21–5.2ngmL−1) for the model compounds even with the scan mode in the conventional MS. The feasibility and benefit of the method was demonstrated with analyses of key odor compounds including hydrophilic and less volatile characteristics in beverages (whiskey and green tea). In a single malt whiskey sample, phenolic compounds including vanillin could be determined in the range of 0.92–5.1μgmL−1 (RSD<7.4%, n =6). For a Japanese green tea sample, 48 compounds including 19 potent odorants were positively identified from only 100μL of sample. Heat-induced artifact formation for potent odorants was also examined and the proposed method does not affect the additional formation of thermally generated compounds. Eighteen compounds including 12 potent odorants (e.g. coumarin, furaneol, indole, maltol, and pyrazine congeners) were determined in the range of 0.21–110ngmL−1 (RSD<10%, n =6).
Effect of ionization modifiers on the simultaneous analysis of all classes of phospholipids by nanoflow liquid chromatography/tandem mass spectrometry in negative ion mode
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Dae Young Bang, Sangsoo Lim, Myeong Hee Moon
The effect of ionization modifiers added to the mobile phase of nanoflow liquid chromatography–tandem mass spectrometry (nLC-ESI–MS3) on the simultaneous analysis of all phospholipid (PL) classes in negative ion mode has been investigated. While MS analysis of most PL classes is carried out in negative ion mode, analysis of neutral polar (polar but electrically neutral) lipids like phosphatidylcholine (PC) and sphingomyelin (SM) is highly efficient in positive ion mode. Therefore, analysis of PL mixture samples often requires two separate runs in both positive and negative ion mode. In order to establish run conditions to carry out a single nLC-ESI–MS–MS for all PLs, the ionization efficiency of 13 different types of PL molecules in nLC-ESI–MS has been evaluated in negative ion mode by varying the modifiers and their concentrations. Experiments demonstrated that a mixture of 0.05% ammonium hydroxide and 1mM ammonium formate added to the mobile phase provided effective ionization for all classes of PLs. The optimized conditions were applied to the analysis of a phospholipid mixture extracted from a human urine sample, yielding the identification of a total of 85 PL species. Analysis of the same sample with dual nLC-ESI–MS2 runs in both positive and negative ion mode confirmed that nLC-ESI-MS3 with the mixed modifier run only in negative ion mode gave comparable results.
Source:Journal of Chromatography A, Volume 1240
Dae Young Bang, Sangsoo Lim, Myeong Hee Moon
The effect of ionization modifiers added to the mobile phase of nanoflow liquid chromatography–tandem mass spectrometry (nLC-ESI–MS3) on the simultaneous analysis of all phospholipid (PL) classes in negative ion mode has been investigated. While MS analysis of most PL classes is carried out in negative ion mode, analysis of neutral polar (polar but electrically neutral) lipids like phosphatidylcholine (PC) and sphingomyelin (SM) is highly efficient in positive ion mode. Therefore, analysis of PL mixture samples often requires two separate runs in both positive and negative ion mode. In order to establish run conditions to carry out a single nLC-ESI–MS–MS for all PLs, the ionization efficiency of 13 different types of PL molecules in nLC-ESI–MS has been evaluated in negative ion mode by varying the modifiers and their concentrations. Experiments demonstrated that a mixture of 0.05% ammonium hydroxide and 1mM ammonium formate added to the mobile phase provided effective ionization for all classes of PLs. The optimized conditions were applied to the analysis of a phospholipid mixture extracted from a human urine sample, yielding the identification of a total of 85 PL species. Analysis of the same sample with dual nLC-ESI–MS2 runs in both positive and negative ion mode confirmed that nLC-ESI-MS3 with the mixed modifier run only in negative ion mode gave comparable results.
On-line fractionated size exclusion chromatography–nuclear magnetic resonance of polymers with 1H and 2H nuclear magnetic resonance detection
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Wolf Hiller, Mathias Hehn, Thorsten Hofe, Kirsten Oleschko, Peter Montag
A new approach for on-line SEC–NMR is introduced. The method combines time slicing, fractionation with adjusted loop collection and automatic stop-flow NMR analysis. It will be called on-line fractionated SEC–NMR. This technique allows the precise determination of molar mass distributions for any polymer which can be detected by NMR. It is a significant improvement of sensitivity and accuracy compared to onflow SEC–NMR and exhibits a much easier experimental setup than off-line SEC–NMR fractionation. The new method was applied to protonated and deuterated block copolymers by using 1H NMR and for the first time also 2H NMR detection. In this case block copolymers can be correctly characterized according to their block length distributions. As the consequence very precise molar mass parameters M n and M w can be determined. The results of the on-line fractionated SEC–NMR are in very good agreement with the multi detector analysis. The new technique also proposes a method for separating the true copolymer and low molar mass fractions in the mixture, whose structures are confirmed by HPLC–FTIR and 2D chromatography.
Source:Journal of Chromatography A, Volume 1240
Wolf Hiller, Mathias Hehn, Thorsten Hofe, Kirsten Oleschko, Peter Montag
A new approach for on-line SEC–NMR is introduced. The method combines time slicing, fractionation with adjusted loop collection and automatic stop-flow NMR analysis. It will be called on-line fractionated SEC–NMR. This technique allows the precise determination of molar mass distributions for any polymer which can be detected by NMR. It is a significant improvement of sensitivity and accuracy compared to onflow SEC–NMR and exhibits a much easier experimental setup than off-line SEC–NMR fractionation. The new method was applied to protonated and deuterated block copolymers by using 1H NMR and for the first time also 2H NMR detection. In this case block copolymers can be correctly characterized according to their block length distributions. As the consequence very precise molar mass parameters M n and M w can be determined. The results of the on-line fractionated SEC–NMR are in very good agreement with the multi detector analysis. The new technique also proposes a method for separating the true copolymer and low molar mass fractions in the mixture, whose structures are confirmed by HPLC–FTIR and 2D chromatography.
Separation of unsaturated organic compounds using silver–thiolate chromatographic material
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
José C. Aponte, James T. Dillon, Rafael Tarozo, Yongsong Huang
Separation of organic compounds containing various numbers of double bonds (DB) can be readily achieved by using silver ion impregnated silica gel, often called silver-ion or argentation chromatography. However, the practical application of silver-ion liquid chromatography in analytical and preparative separations has been limited by the concerns about the stability and mobility of silver ions and the widespread use of reversed phase high performance liquid chromatography. Silver covalently anchored onto the thiol moiety of mercaptopropyl modified silica gel has been tested for the separation of polycyclic aromatic hydrocarbons by ring numbers, but has never been shown to separate mixtures of alkenes having different number of double bonds. We report here that silver–thiolate chromatographic material (AgTCM; including, but not limited to, silver(I) mercaptopropyl silica gel) is also highly efficient in liquid chromatographic separation of alkane/alkenes differing by one double bond. AgTCM displays exceptionally high selectivity for unsaturated compounds and high stability under extended heat and light exposure, while silver is virtually immobile during solvent elution. Compared to ionic silver, silver–thiolate interacts with double bonds less strongly, allowing AgTCM to efficiently separate olefins using less polar (and often less viscous and lower cost) solvents. The interaction energy between silver and ethylene is calculated using established computational methods and the results are in full agreement with our experimental results. Importantly, the exceptional stability of AgTCM gives rise to much higher compound recovery than conventional silver-ion silica gel during the chromatographic elution. Our results pave the way for the development of novel covalently bonded, transition metal-containing chromatographic materials.
Source:Journal of Chromatography A, Volume 1240
José C. Aponte, James T. Dillon, Rafael Tarozo, Yongsong Huang
Separation of organic compounds containing various numbers of double bonds (DB) can be readily achieved by using silver ion impregnated silica gel, often called silver-ion or argentation chromatography. However, the practical application of silver-ion liquid chromatography in analytical and preparative separations has been limited by the concerns about the stability and mobility of silver ions and the widespread use of reversed phase high performance liquid chromatography. Silver covalently anchored onto the thiol moiety of mercaptopropyl modified silica gel has been tested for the separation of polycyclic aromatic hydrocarbons by ring numbers, but has never been shown to separate mixtures of alkenes having different number of double bonds. We report here that silver–thiolate chromatographic material (AgTCM; including, but not limited to, silver(I) mercaptopropyl silica gel) is also highly efficient in liquid chromatographic separation of alkane/alkenes differing by one double bond. AgTCM displays exceptionally high selectivity for unsaturated compounds and high stability under extended heat and light exposure, while silver is virtually immobile during solvent elution. Compared to ionic silver, silver–thiolate interacts with double bonds less strongly, allowing AgTCM to efficiently separate olefins using less polar (and often less viscous and lower cost) solvents. The interaction energy between silver and ethylene is calculated using established computational methods and the results are in full agreement with our experimental results. Importantly, the exceptional stability of AgTCM gives rise to much higher compound recovery than conventional silver-ion silica gel during the chromatographic elution. Our results pave the way for the development of novel covalently bonded, transition metal-containing chromatographic materials.
Efficient liquid chromatographic analysis of mono-, di-, and triglycerols using silver thiolate stationary phase
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
James T. Dillon, José C. Aponte, Rafael Tarozo, Yongsong Huang
We show that the characterization of mono-, di- and triglycerols can be readily accomplished by high performance liquid chromatography (HPLC) with silver(I)-mercaptopropyl modified silica gel, or silver thiolate chromatographic material (AgTCM), which can be used with evaporative light scattering detection (ELSD) or atmospheric pressure chemical ionization mass spectroscopy (APCI-MS). Separation of triglycerols varying by degrees of unsaturation and cis/trans configuration in common oil samples can be achieved using a simple linear gradient of hexane and acetone. In addition to double bonds, AgTCM also displays major selectivity for compounds with different levels of polarity, allowing for efficient separation between mono-, di- and triglycerols. In comparison to conventional reversed phase columns, AgTCM produces simple chromatograms for rapid assessment of degrees of unsaturation and the amount of trans fats in triglycerides, which are central issues to food quality determination. In comparison to previous silver-ion based HPLC separations, AgTCM–HPLC based column offers greatly enhanced stability, inertness, durability, and reproducibility allowing routine coupling of the HPLC with a mass spectrometer for detection.
Source:Journal of Chromatography A, Volume 1240
James T. Dillon, José C. Aponte, Rafael Tarozo, Yongsong Huang
We show that the characterization of mono-, di- and triglycerols can be readily accomplished by high performance liquid chromatography (HPLC) with silver(I)-mercaptopropyl modified silica gel, or silver thiolate chromatographic material (AgTCM), which can be used with evaporative light scattering detection (ELSD) or atmospheric pressure chemical ionization mass spectroscopy (APCI-MS). Separation of triglycerols varying by degrees of unsaturation and cis/trans configuration in common oil samples can be achieved using a simple linear gradient of hexane and acetone. In addition to double bonds, AgTCM also displays major selectivity for compounds with different levels of polarity, allowing for efficient separation between mono-, di- and triglycerols. In comparison to conventional reversed phase columns, AgTCM produces simple chromatograms for rapid assessment of degrees of unsaturation and the amount of trans fats in triglycerides, which are central issues to food quality determination. In comparison to previous silver-ion based HPLC separations, AgTCM–HPLC based column offers greatly enhanced stability, inertness, durability, and reproducibility allowing routine coupling of the HPLC with a mass spectrometer for detection.
High-performance liquid chromatography–mass spectrometry and evaporative light-scattering detector to compare phenolic profiles of muscadine grapes
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Qi You, Feng Chen, Julia L. Sharp, Xi Wang, Yuru You, Chuanji Zhang
Evaporative light scattering detector (ELSD) is considered as a universal detector able to detect almost any compound. This study successfully established a HPLC-ELSD method for the simultaneous determination of phenolic acids, flavonoids and anthocyanins in muscadine grape. Twenty-four phenolics, including 5 anthocyanins, were identified by HPLC–UV-MS, ten of them were selected to calibrate the ELSD. Results from the ELSD quantification suggested that gallic acid, proanthocyanidins, and ellagic acid were the main phenolics in muscadines. In addition, antioxidant tests suggested that the extracts of muscadine grapes possessed strong antioxidant activities. All extracts had a high total phenolic content (TPC). High total anthocyanins contents (TAC) were found in Noble muscadine, and high proanthocyanidins content (TPA) in the seed portion.
Source:Journal of Chromatography A, Volume 1240
Qi You, Feng Chen, Julia L. Sharp, Xi Wang, Yuru You, Chuanji Zhang
Evaporative light scattering detector (ELSD) is considered as a universal detector able to detect almost any compound. This study successfully established a HPLC-ELSD method for the simultaneous determination of phenolic acids, flavonoids and anthocyanins in muscadine grape. Twenty-four phenolics, including 5 anthocyanins, were identified by HPLC–UV-MS, ten of them were selected to calibrate the ELSD. Results from the ELSD quantification suggested that gallic acid, proanthocyanidins, and ellagic acid were the main phenolics in muscadines. In addition, antioxidant tests suggested that the extracts of muscadine grapes possessed strong antioxidant activities. All extracts had a high total phenolic content (TPC). High total anthocyanins contents (TAC) were found in Noble muscadine, and high proanthocyanidins content (TPA) in the seed portion.
Excess adsorption of binary aqueous organic mixtures on various reversed-phase packing materials
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
S. Buntz, M. Figus, Z. Liu, Y.V. Kazakevich
Excess adsorption isotherms of acetonitrile and methanol from water were measured on eight commercial columns. Columns used in this study represent latest examples in column development and include three different poroshell columns (Kinetex-C18, Acsentis-C18 and Halo-C18) as well as conventional columns with significantly different adsorbent geometry (Allure-C18, YMC-C18) and various hybrid-silica columns (Gemini-C18, Xterra-C18 and XBridge-C18). Comparison of the excess adsorption isotherms measured on all these columns and expressed in surface specific form demonstrated significant similarity of the adsorption properties of all columns, which allows us to introduce the “standard adsorption isotherm” for reversed-phase C18-type columns. The methodology of the evaluation of the total amount of adsorbent in the column and effective surface area of the C18 modified adsorbent is also discussed. These terms are critical for successful evaluation of surface specific parameters.
Source:Journal of Chromatography A, Volume 1240
S. Buntz, M. Figus, Z. Liu, Y.V. Kazakevich
Excess adsorption isotherms of acetonitrile and methanol from water were measured on eight commercial columns. Columns used in this study represent latest examples in column development and include three different poroshell columns (Kinetex-C18, Acsentis-C18 and Halo-C18) as well as conventional columns with significantly different adsorbent geometry (Allure-C18, YMC-C18) and various hybrid-silica columns (Gemini-C18, Xterra-C18 and XBridge-C18). Comparison of the excess adsorption isotherms measured on all these columns and expressed in surface specific form demonstrated significant similarity of the adsorption properties of all columns, which allows us to introduce the “standard adsorption isotherm” for reversed-phase C18-type columns. The methodology of the evaluation of the total amount of adsorbent in the column and effective surface area of the C18 modified adsorbent is also discussed. These terms are critical for successful evaluation of surface specific parameters.
Extension of the liquid chromatography/quantitative structure–property relationship method to assess the lipophilicity of neutral, acidic, basic and amphotheric drugs
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Juan M. Pallicer, Carme Calvet, Adriana Port, Martí Rosés, Clara Ràfols, Elisabeth Bosch
A reported chromatographic method to determine the 1-octanol/water partition coefficient (log P o/w) has been used to estimate the lipophilicity of 33 drugs with diverse structures and functionalities, including neutral, acid, basic, and amphoteric compounds. The applicability of the chromatographic method has been extended to the UHPLC technique, and the results obtained were compared to those obtained from conventional HPLC. No significant difference between the results obtained by both techniques is noticed. Thus, the suitability of UHPLC, which involves shorter run times, for lipophilicity assessment is demonstrated. In order to show the consistency of this chromatographic method, the log P o/w values of those drugs which have acid–base properties have been also determined by potentiometry, and the final results have been compared with both values derived from the chromatographic method and the ones from the literature.
Source:Journal of Chromatography A, Volume 1240
Juan M. Pallicer, Carme Calvet, Adriana Port, Martí Rosés, Clara Ràfols, Elisabeth Bosch
A reported chromatographic method to determine the 1-octanol/water partition coefficient (log P o/w) has been used to estimate the lipophilicity of 33 drugs with diverse structures and functionalities, including neutral, acid, basic, and amphoteric compounds. The applicability of the chromatographic method has been extended to the UHPLC technique, and the results obtained were compared to those obtained from conventional HPLC. No significant difference between the results obtained by both techniques is noticed. Thus, the suitability of UHPLC, which involves shorter run times, for lipophilicity assessment is demonstrated. In order to show the consistency of this chromatographic method, the log P o/w values of those drugs which have acid–base properties have been also determined by potentiometry, and the final results have been compared with both values derived from the chromatographic method and the ones from the literature.
Enantioseparation of omeprazole—Effect of different packing particle size on productivity
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Martin Enmark, Jörgen Samuelsson, Patrik Forssén, Torgny Fornstedt
Enantiomeric separation of omeprazole has been extensively studied regarding both product analysis and preparation using several different chiral stationary phases. In this study, the preparative chiral separation of omeprazole is optimized for productivity using three different columns packed with amylose tris (3,5-dimethyl phenyl carbamate) coated macroporous silica (5, 10 and 25μm) with a maximum allowed pressure drop ranging from 50 to 400bar. This pressure range both covers low pressure process systems (50–100bar) and investigates the potential for allowing higher pressure limits in preparative applications in a future. The process optimization clearly show that the larger 25μm packing material show higher productivity at low pressure drops whereas with increasing pressure drops the smaller packing materials have substantially higher productivity. Interestingly, at all pressure drops, the smaller packing material result in lower solvent consumption (L solvent/kg product); the higher the accepted pressure drop, the larger the gain in reduced solvent consumption. The experimental adsorption isotherms were not identical for the different packing material sizes; therefore all calculations were recalculated and reevaluated assuming identical adsorption isotherms (with the 10μm isotherm as reference) which confirmed the trends regarding productivity and solvent consumption.
Source:Journal of Chromatography A, Volume 1240
Martin Enmark, Jörgen Samuelsson, Patrik Forssén, Torgny Fornstedt
Enantiomeric separation of omeprazole has been extensively studied regarding both product analysis and preparation using several different chiral stationary phases. In this study, the preparative chiral separation of omeprazole is optimized for productivity using three different columns packed with amylose tris (3,5-dimethyl phenyl carbamate) coated macroporous silica (5, 10 and 25μm) with a maximum allowed pressure drop ranging from 50 to 400bar. This pressure range both covers low pressure process systems (50–100bar) and investigates the potential for allowing higher pressure limits in preparative applications in a future. The process optimization clearly show that the larger 25μm packing material show higher productivity at low pressure drops whereas with increasing pressure drops the smaller packing materials have substantially higher productivity. Interestingly, at all pressure drops, the smaller packing material result in lower solvent consumption (L solvent/kg product); the higher the accepted pressure drop, the larger the gain in reduced solvent consumption. The experimental adsorption isotherms were not identical for the different packing material sizes; therefore all calculations were recalculated and reevaluated assuming identical adsorption isotherms (with the 10μm isotherm as reference) which confirmed the trends regarding productivity and solvent consumption.
Development and comparison of three liquid chromatography–atmospheric pressure chemical ionization/mass spectrometry methods for determining vitamin D metabolites in human serum
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Mary Bedner, Karen W. Phinney
Liquid chromatographic methods with atmospheric pressure chemical ionization mass spectrometry were developed for the determination of the vitamin D metabolites 25-hydroxyvitamin D2 (25(OH)D2), 25-hydroxyvitamin D3 (25(OH)D3), and 3-epi-25-hydroxyvitamin-D3 (3-epi-25(OH)D3) in the four Levels of SRM 972, Vitamin D in Human Serum. One method utilized a C18 column, which separates 25(OH)D2 and 25(OH)D3, and one method utilized a CN column that also resolves the diastereomers 25(OH)D3 and 3-epi-25(OH)D3. Both methods utilized stable isotope labeled internal standards for quantitation of 25(OH)D2 and 25(OH)D3. These methods were subsequently used to evaluate SRM 909c Human Serum, and 25(OH)D3 was the only vitamin D metabolite detected in this material. However, SRM 909c samples contained matrix peaks that interfered with the determination of the [2H6]-25(OH)D3 peak area. The chromatographic conditions for the C18 column were modified to remove this interference, but conditions that separated the matrix peaks from [2H6]-25(OH)D3 on the CN column could not be identified. The alternate internal standard [2H3]-25(OH)D3 did not suffer from matrix interferences and was used for quantitation of 25(OH)D3 in SRM 909c. During the evaluation of SRM 909c samples, a third method was developed using a pentafluorophenylpropyl column that also separates the diastereomers 25(OH)D3 and 3-epi-25(OH)D3. The 25(OH)D3 was measured in SRM 909c using all three methods, and the results were compared.
Source:Journal of Chromatography A, Volume 1240
Mary Bedner, Karen W. Phinney
Liquid chromatographic methods with atmospheric pressure chemical ionization mass spectrometry were developed for the determination of the vitamin D metabolites 25-hydroxyvitamin D2 (25(OH)D2), 25-hydroxyvitamin D3 (25(OH)D3), and 3-epi-25-hydroxyvitamin-D3 (3-epi-25(OH)D3) in the four Levels of SRM 972, Vitamin D in Human Serum. One method utilized a C18 column, which separates 25(OH)D2 and 25(OH)D3, and one method utilized a CN column that also resolves the diastereomers 25(OH)D3 and 3-epi-25(OH)D3. Both methods utilized stable isotope labeled internal standards for quantitation of 25(OH)D2 and 25(OH)D3. These methods were subsequently used to evaluate SRM 909c Human Serum, and 25(OH)D3 was the only vitamin D metabolite detected in this material. However, SRM 909c samples contained matrix peaks that interfered with the determination of the [2H6]-25(OH)D3 peak area. The chromatographic conditions for the C18 column were modified to remove this interference, but conditions that separated the matrix peaks from [2H6]-25(OH)D3 on the CN column could not be identified. The alternate internal standard [2H3]-25(OH)D3 did not suffer from matrix interferences and was used for quantitation of 25(OH)D3 in SRM 909c. During the evaluation of SRM 909c samples, a third method was developed using a pentafluorophenylpropyl column that also separates the diastereomers 25(OH)D3 and 3-epi-25(OH)D3. The 25(OH)D3 was measured in SRM 909c using all three methods, and the results were compared.
Investigation of porous graphitic carbon for triterpenoids and natural resinous materials analysis by high performance liquid chromatography hyphenated to mass spectrometry
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
B. Rhourri-Frih, P. Chaimbault, D. Dequeral, P. André, M. Lafosse
Natural resinous materials are mainly composed of pentacyclic triterpenes which exhibit a large number of interesting medicinal activities. However, the presence of numerous isomers within the active substances makes their screening by HPLC very challenging. Porous graphitic carbon was investigated as stationary phase to achieve triterpenes isomers separation. The influence of various parameters (temperature, formic acid concentration and mobile phase composition) on the retention was considered. A usual decrease of the retention of triterpenes was observed with the increase of the temperature. Therefore, separation in resinous materials was performed at 25°C. Acetonitrile–isopropanol mixture was chosen as mobile phase in gradient elution and leads to the best compromise between efficiency and high resolution. The lack of chromophore groups in the pentacyclic triterpenes structures required the use of mass spectrometry detection. Moreover, atmospheric pressure photo-ionisation mass spectrometry prevents compounds fragmentation which was helpful for spectra interpretation and compounds identification.
Source:Journal of Chromatography A, Volume 1240
B. Rhourri-Frih, P. Chaimbault, D. Dequeral, P. André, M. Lafosse
Natural resinous materials are mainly composed of pentacyclic triterpenes which exhibit a large number of interesting medicinal activities. However, the presence of numerous isomers within the active substances makes their screening by HPLC very challenging. Porous graphitic carbon was investigated as stationary phase to achieve triterpenes isomers separation. The influence of various parameters (temperature, formic acid concentration and mobile phase composition) on the retention was considered. A usual decrease of the retention of triterpenes was observed with the increase of the temperature. Therefore, separation in resinous materials was performed at 25°C. Acetonitrile–isopropanol mixture was chosen as mobile phase in gradient elution and leads to the best compromise between efficiency and high resolution. The lack of chromophore groups in the pentacyclic triterpenes structures required the use of mass spectrometry detection. Moreover, atmospheric pressure photo-ionisation mass spectrometry prevents compounds fragmentation which was helpful for spectra interpretation and compounds identification.
Identification and quantification of potential metabolites of Gd-based contrast agents by electrochemistry/separations/mass spectrometry
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Lena Telgmann, Helene Faber, Sandra Jahn, Daniel Melles, Hannah Simon, Michael Sperling, Uwe Karst
Oxidative and potentially metabolic pathways of the five most frequently used contrast agents for magnetic resonance imaging (MRI) based on gadolinium (Gd) are examined. The oxidation of gadopentetate (Gd-DTPA) was studied with a focus on electrochemical oxidation coupled to analytical separation methods and mass spectrometric detection. Mass voltammograms generated with online electrochemistry/electrospray ionization mass spectrometry (EC/ESI-MS) gave a first overview of oxidation products. Two potential metabolites could be detected, with the major metabolite originating from an N-dealkylation (M1). Four other Gd complexes used as MRI contrast agents showed similar reactions in the EC/ESI-MS set-up. To obtain more information about the properties and the quantity of the generated products, a wide range of separation and detection techniques was applied in further experiments. Gd-DTPA and its N-dealkylation product were successfully separated by capillary electrophoresis (CE) and detected by ESI-MS and inductively coupled plasma (ICP)-MS, respectively. CE experiments indicated that the second oxidation product (M2) detected in the mass voltammogram is unstable and decomposes to M1. Employing EC/CE/ICP-MS, the quantification of the metabolites could be achieved. Under the employed conditions, 8.8% of Gd-DTPA was oxidized. Online experiments with high performance liquid chromatography (HPLC) coupled to ESI-MS confirmed the decomposition of M2. Time-resolved measurements showed a decrease of M2 and a simultaneous increase in M1 within only a few minutes, confirming the conclusion that M2 degrades to M1, while EC/LC/ICP-MS measurements provided quantitative evidence as well. The EC/MS simulation shows that a metabolic transformation should not be disregarded in further research regarding the trigger of nephrogenic systemic fibrosis (NSF), a disease exclusively observed for several hundred dialysis patients after delivery of Gd-based MRI contrast agents with linear structure. Furthermore, the used methods may allow the prediction of options for the oxidative removal of these contrast agents from wastewaters.
Source:Journal of Chromatography A, Volume 1240
Lena Telgmann, Helene Faber, Sandra Jahn, Daniel Melles, Hannah Simon, Michael Sperling, Uwe Karst
Oxidative and potentially metabolic pathways of the five most frequently used contrast agents for magnetic resonance imaging (MRI) based on gadolinium (Gd) are examined. The oxidation of gadopentetate (Gd-DTPA) was studied with a focus on electrochemical oxidation coupled to analytical separation methods and mass spectrometric detection. Mass voltammograms generated with online electrochemistry/electrospray ionization mass spectrometry (EC/ESI-MS) gave a first overview of oxidation products. Two potential metabolites could be detected, with the major metabolite originating from an N-dealkylation (M1). Four other Gd complexes used as MRI contrast agents showed similar reactions in the EC/ESI-MS set-up. To obtain more information about the properties and the quantity of the generated products, a wide range of separation and detection techniques was applied in further experiments. Gd-DTPA and its N-dealkylation product were successfully separated by capillary electrophoresis (CE) and detected by ESI-MS and inductively coupled plasma (ICP)-MS, respectively. CE experiments indicated that the second oxidation product (M2) detected in the mass voltammogram is unstable and decomposes to M1. Employing EC/CE/ICP-MS, the quantification of the metabolites could be achieved. Under the employed conditions, 8.8% of Gd-DTPA was oxidized. Online experiments with high performance liquid chromatography (HPLC) coupled to ESI-MS confirmed the decomposition of M2. Time-resolved measurements showed a decrease of M2 and a simultaneous increase in M1 within only a few minutes, confirming the conclusion that M2 degrades to M1, while EC/LC/ICP-MS measurements provided quantitative evidence as well. The EC/MS simulation shows that a metabolic transformation should not be disregarded in further research regarding the trigger of nephrogenic systemic fibrosis (NSF), a disease exclusively observed for several hundred dialysis patients after delivery of Gd-based MRI contrast agents with linear structure. Furthermore, the used methods may allow the prediction of options for the oxidative removal of these contrast agents from wastewaters.
Gas chromatography–mass spectrometry with chemometric analysis for determining 12C and 13C labeled contributions in metabolomics and 13C flux analysis
04 May 2012,
11:54:34
Publication year:
2012
Source:Journal of Chromatography A, Volume 1240
Song Yang, Jeremy S. Nadeau, Elizabeth M. Humston-Fulmer, Jamin C. Hoggard, Mary E. Lidstrom, Robert E. Synovec
A novel method for the analysis of nearly co-eluting 12C and 13C isotopically labeled metabolites has been developed and evaluated for gas chromatography coupled to mass spectrometry (GC–MS) data. The method utilizes parallel factor analysis (PARAFAC) with two-dimensional GC–MS data when sample replicates are aligned and stacked in series to create a three-dimensional data cube for mathematical peak deconvolution and 12C and 13C contribution isolation, with the intent of increasing the accuracy and precision of quantitative metabolomics and 13C flux analysis. The platform is demonstrated with 13C-labeled metabolite extracts, generated via biosynthesis, added as an internal standard to unlabeled 12C metabolites extracted from the methanol-utilizing bacterium Methylobacterium extorquens AM1. Eleven representative metabolites that are common targets for flux analysis were chosen for validation. Good quantitative accuracy and precision were acquired for a 5.00μM known metabolite concentration (for the 11 metabolites), with an average predicted concentration of 5.07μM, and a RSD range of 1.2–13.0%. This study demonstrates the ability to reliably deconvolute 12C-unlabeled and 13C-labeled contributions for a given metabolite. Additionally, using this chemical analysis platform, a dynamic flux experiment is presented in which the incorporation of 13C-labeled cell extract can be detected in the methane-utilizing bacterium Methylosinus trichosporium OB3b and measured temporally.
Source:Journal of Chromatography A, Volume 1240
Song Yang, Jeremy S. Nadeau, Elizabeth M. Humston-Fulmer, Jamin C. Hoggard, Mary E. Lidstrom, Robert E. Synovec
A novel method for the analysis of nearly co-eluting 12C and 13C isotopically labeled metabolites has been developed and evaluated for gas chromatography coupled to mass spectrometry (GC–MS) data. The method utilizes parallel factor analysis (PARAFAC) with two-dimensional GC–MS data when sample replicates are aligned and stacked in series to create a three-dimensional data cube for mathematical peak deconvolution and 12C and 13C contribution isolation, with the intent of increasing the accuracy and precision of quantitative metabolomics and 13C flux analysis. The platform is demonstrated with 13C-labeled metabolite extracts, generated via biosynthesis, added as an internal standard to unlabeled 12C metabolites extracted from the methanol-utilizing bacterium Methylobacterium extorquens AM1. Eleven representative metabolites that are common targets for flux analysis were chosen for validation. Good quantitative accuracy and precision were acquired for a 5.00μM known metabolite concentration (for the 11 metabolites), with an average predicted concentration of 5.07μM, and a RSD range of 1.2–13.0%. This study demonstrates the ability to reliably deconvolute 12C-unlabeled and 13C-labeled contributions for a given metabolite. Additionally, using this chemical analysis platform, a dynamic flux experiment is presented in which the incorporation of 13C-labeled cell extract can be detected in the methane-utilizing bacterium Methylosinus trichosporium OB3b and measured temporally.
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