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Rapid and sensitive solid phase extraction-large volume injection-gas chromatography for the analysis of mineral oil saturated and aromatic hydrocarbons in cardboard and dried foods
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Sabrina Moret, Laura Barp, Giorgia Purcaro, Lanfranco S. Conte
A rapid off-line solid phase extraction-large volume injection-gas chromatography-flame ionisation detection (SPE-LVI-GC-FID) method, based on the use of silver silica gel and low solvent consumption, was developed for mineral oil saturated hydrocarbon (MOSH) and mineral oil aromatic hydrocarbon (MOAH) determination in cardboard and dried foods packaged in cardboard. The SPE method was validated using LVI with a conventional on-column injector and the retention gap technique (which allowed to inject up to 50μL of the sample). Detector response was linear over all the concentration range tested (0.5–250μg/mL), recoveries were practically quantitative, repeatability was good (coefficients of variation lower than 7%) and limit of quantification adequate to quantify the envisioned limit of 0.15mg/kg proposed in Germany for MOAH analysis in food samples packaged in recycled cardboard. Rapid heating of the GC oven allowed to increase sample throughput (3–4 samples per hour) and to enhance sensitivity. The proposed method was used for MOSH and MOAH determination in selected food samples usually commercialised in cardboard packaging. The most contaminated was a tea sample (102.2 and 7.9mg/kg of MOSH and MOAH below n-C25, respectively), followed by a rice and a sugar powder sample, all packaged in recycled cardboard.
Source:Journal of Chromatography A, Volume 1243
Sabrina Moret, Laura Barp, Giorgia Purcaro, Lanfranco S. Conte
A rapid off-line solid phase extraction-large volume injection-gas chromatography-flame ionisation detection (SPE-LVI-GC-FID) method, based on the use of silver silica gel and low solvent consumption, was developed for mineral oil saturated hydrocarbon (MOSH) and mineral oil aromatic hydrocarbon (MOAH) determination in cardboard and dried foods packaged in cardboard. The SPE method was validated using LVI with a conventional on-column injector and the retention gap technique (which allowed to inject up to 50μL of the sample). Detector response was linear over all the concentration range tested (0.5–250μg/mL), recoveries were practically quantitative, repeatability was good (coefficients of variation lower than 7%) and limit of quantification adequate to quantify the envisioned limit of 0.15mg/kg proposed in Germany for MOAH analysis in food samples packaged in recycled cardboard. Rapid heating of the GC oven allowed to increase sample throughput (3–4 samples per hour) and to enhance sensitivity. The proposed method was used for MOSH and MOAH determination in selected food samples usually commercialised in cardboard packaging. The most contaminated was a tea sample (102.2 and 7.9mg/kg of MOSH and MOAH below n-C25, respectively), followed by a rice and a sugar powder sample, all packaged in recycled cardboard.
Highlights
► Rapid and sensitive off-line SPE-LVI-GC-FID method for MOSH and MOAH analysis. ► Large volume injection with PTV as an alternative to on-column injection. ► The validated method was proposed as an alternative to the on-line LC–GC method. ► The method was applied to different food extracts.Low-voltage electrically-enhanced microextraction as a novel technique for simultaneous extraction of acidic and basic drugs from biological fluids
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Shahram Seidi, Yadollah Yamini, Maryam Rezazadeh, Ali Esrafili
In the present work, for the first time a new set-up was presented for simultaneous extraction of acidic and basic drugs using a recent novel electrically-enhanced microextraction technique, termed electromembrane extraction at low voltages followed by high performance liquid chromatography with ultraviolet detection. Nalmefene (NAL) as a basic drug and diclofenac (DIC) as an acidic drug were extracted from 24mL aqueous sample solutions at neutral pH into 10μL of each acidified (HCl 50mM) and basic (NaOH 50mM) acceptor solution, respectively. Supported liquid membranes including 2-nitrophenyl octyl ether containing 5% di-(2-ethylhexyl) phosphate and 1-octanol were used to ensure efficient extraction of NAL and DIC, respectively. Low voltage of 40V was applied over the SLMs during 14min extraction time. The influences of fundamental parameters affecting the transport of target drugs were optimized using experimental design. Under optimal conditions, NAL and DIC were extracted with extraction recoveries of 12.5 and 14.6, respectively, which corresponded to preconcentration factors of 300 and 350, respectively. The proposed technique provided good linearity with correlation coefficient values higher than 0.9956 over a concentration range of 8–500μgL−1 and 12–500μgL−1 for NAL and DIC, respectively. Limits of detection and quantifications, and intra-day precisions (n =3) were less than 4μgL−1, 12μgL−1, and 10.1%, respectively. Extraction and determination of NAL and DIC in human urine samples were successfully performed. In light of the data obtained in the present work, this new set-up for EME with low voltages has a future potential as a simple, selective, and fast sample preparation technique for simultaneous extraction and determination of acidic and basic drugs in different complicated matrices.
Source:Journal of Chromatography A, Volume 1243
Shahram Seidi, Yadollah Yamini, Maryam Rezazadeh, Ali Esrafili
In the present work, for the first time a new set-up was presented for simultaneous extraction of acidic and basic drugs using a recent novel electrically-enhanced microextraction technique, termed electromembrane extraction at low voltages followed by high performance liquid chromatography with ultraviolet detection. Nalmefene (NAL) as a basic drug and diclofenac (DIC) as an acidic drug were extracted from 24mL aqueous sample solutions at neutral pH into 10μL of each acidified (HCl 50mM) and basic (NaOH 50mM) acceptor solution, respectively. Supported liquid membranes including 2-nitrophenyl octyl ether containing 5% di-(2-ethylhexyl) phosphate and 1-octanol were used to ensure efficient extraction of NAL and DIC, respectively. Low voltage of 40V was applied over the SLMs during 14min extraction time. The influences of fundamental parameters affecting the transport of target drugs were optimized using experimental design. Under optimal conditions, NAL and DIC were extracted with extraction recoveries of 12.5 and 14.6, respectively, which corresponded to preconcentration factors of 300 and 350, respectively. The proposed technique provided good linearity with correlation coefficient values higher than 0.9956 over a concentration range of 8–500μgL−1 and 12–500μgL−1 for NAL and DIC, respectively. Limits of detection and quantifications, and intra-day precisions (n =3) were less than 4μgL−1, 12μgL−1, and 10.1%, respectively. Extraction and determination of NAL and DIC in human urine samples were successfully performed. In light of the data obtained in the present work, this new set-up for EME with low voltages has a future potential as a simple, selective, and fast sample preparation technique for simultaneous extraction and determination of acidic and basic drugs in different complicated matrices.
Highlights
► A new set-up of electromembrane extraction at low voltages was designed. ► The set-up was applied for simultaneous extraction of acidic and basic drugs. ► Acidic and basic drugs were extracted into anode and cathode lumens, respectively. ► HPLC–UV was applied for separation and determination of the drugs. ► Determination of the drugs in human urine samples was successfully performed.Electro membrane extraction followed by low-density solvent based ultrasound-assisted emulsification microextraction combined with derivatization for determining chlorophenols and analysis by gas chromatography–mass spectrometry
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Liang Guo, Hian Kee Lee
A highly efficient and simple two-step method, electro membrane extraction (EME) followed by low-density solvent based ultrasound-assisted emulsification microextraction (EME–LDS-USAEME) combined with derivatization and analysis by gas chromatography–mass spectrometry (GC–MS), was developed for the determination of trace level chlorophenols in environmental water samples. In the first step, the analytes were extracted, under electrical potential, from the sample solution into the acceptor solution, which was held in a polypropylene membrane sheet with 1-octanol as the supported liquid membrane. The acceptor solution from the first step was then employed as the sample solution for the second step of LDS-USAEME. In this step, the target analytes were extracted into a solvent with lower density than water that was dispersed in the sample solution with the assistance of ultrasound. The extract was separated from the sample solution by centrifugation and collected as the upper layer. Finally, the extract with a derivatization reagent were injected into a GC–MS system for analysis. Six chlorophenols, 2-chlorophenol, 4-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol were selected here as model compounds for developing and evaluating the method. Several factors influencing the extraction and derivatization were investigated. With the EME–LDS-USAEME procedure, high enrichment factors of up to 2198 were achieved. Under the most favorable conditions, good limits of detection (down to 0.005μg/L), linearity (from 0.05–10 to 0.2–10μg/L, depending on the analytes), and repeatability of extraction (RSDs below 9.7%, n =5) were obtained. The proposed method was applied to determine chlorophenols in drainwater samples.
Source:Journal of Chromatography A, Volume 1243
Liang Guo, Hian Kee Lee
A highly efficient and simple two-step method, electro membrane extraction (EME) followed by low-density solvent based ultrasound-assisted emulsification microextraction (EME–LDS-USAEME) combined with derivatization and analysis by gas chromatography–mass spectrometry (GC–MS), was developed for the determination of trace level chlorophenols in environmental water samples. In the first step, the analytes were extracted, under electrical potential, from the sample solution into the acceptor solution, which was held in a polypropylene membrane sheet with 1-octanol as the supported liquid membrane. The acceptor solution from the first step was then employed as the sample solution for the second step of LDS-USAEME. In this step, the target analytes were extracted into a solvent with lower density than water that was dispersed in the sample solution with the assistance of ultrasound. The extract was separated from the sample solution by centrifugation and collected as the upper layer. Finally, the extract with a derivatization reagent were injected into a GC–MS system for analysis. Six chlorophenols, 2-chlorophenol, 4-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol were selected here as model compounds for developing and evaluating the method. Several factors influencing the extraction and derivatization were investigated. With the EME–LDS-USAEME procedure, high enrichment factors of up to 2198 were achieved. Under the most favorable conditions, good limits of detection (down to 0.005μg/L), linearity (from 0.05–10 to 0.2–10μg/L, depending on the analytes), and repeatability of extraction (RSDs below 9.7%, n =5) were obtained. The proposed method was applied to determine chlorophenols in drainwater samples.
Highlights
► Electro membrane extraction followed by ultrasound emulsification microextraction is reported. ► Flexible pipette allows convenient retrieval of lower density extract in USAEME. ► On-column derivatization avoids separate derivatization and expedites the procedure. ► High extraction efficiency for chlorophenols from aqueous samples obtained. ► The approach is fast and gives low LODs, good linearity and repeatability.Mass spectrometric identification and characterization of new clomiphene metabolites in human urine by liquid chromatography–quadrupole time-of-flight tandem mass spectrometry
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Jianghai Lu, Genye He, Xiaobing Wang, Youxuan Xu, Yun Wu, Ying Dong, Zhenwen He, Xin Liu, Tao Bo, Gangfeng Ouyang
Clomiphene, a selective estrogen receptor modulator, is prohibited by World Anti Doping Agency (WADA) out-of-competition and in-competition. As it is extensively metabolized, further investigation of clomiphene metabolic profile will be essential to routine anti-doping analysis. The metabolic pathway and the different metabolites of clomiphene in human urine collected from three healthy volunteers during 1week were studied by liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOFMS) based on accurate mass measurement. Seven unreported metabolites were identified and characterized, and all of the newly found urinary metabolites belonged to a new metabolic pathway (hydrogenation). An approach for the metabolism study of clomiphene and its analogs by LC–QTOFMS was presented. Two metabolites, 3,4-dihydroxy-dihydro-clomiphene (m/z 440.1991) and 3,4-dihydroxy-dihydro-deethyl-clomiphne (m/z 412.1674), are the potential biomarkers for monitoring oral administration of clomiphene in doping control.
Source:Journal of Chromatography A, Volume 1243
Jianghai Lu, Genye He, Xiaobing Wang, Youxuan Xu, Yun Wu, Ying Dong, Zhenwen He, Xin Liu, Tao Bo, Gangfeng Ouyang
Clomiphene, a selective estrogen receptor modulator, is prohibited by World Anti Doping Agency (WADA) out-of-competition and in-competition. As it is extensively metabolized, further investigation of clomiphene metabolic profile will be essential to routine anti-doping analysis. The metabolic pathway and the different metabolites of clomiphene in human urine collected from three healthy volunteers during 1week were studied by liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOFMS) based on accurate mass measurement. Seven unreported metabolites were identified and characterized, and all of the newly found urinary metabolites belonged to a new metabolic pathway (hydrogenation). An approach for the metabolism study of clomiphene and its analogs by LC–QTOFMS was presented. Two metabolites, 3,4-dihydroxy-dihydro-clomiphene (m/z 440.1991) and 3,4-dihydroxy-dihydro-deethyl-clomiphne (m/z 412.1674), are the potential biomarkers for monitoring oral administration of clomiphene in doping control.
Highlights
► The metabolic pathway and metabolites of clomiphene in human urine were studied. ► Seven unreported metabolites were identified and characterized by LC–QTOFMS. ► Two newly found metabolites are potential biomarkers in doping control analysis.Three-dimensional cell bioreactor coupled with high performance liquid chromatography–mass spectrometry for the affinity screening of bioactive components from herb medicine
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Zhao-Li Mou, Xiao-Ni Qi, Rui-Lin Liu, Jing Zhang, Zhi-Qi Zhang
An efficient and convenient method, three-dimensional (3-D) cell bioreactor coupled with high performance liquid chromatography–mass spectrometry was developed for affinity screening and analysis of multiple bioactive components from herbal medicines. Cancer cells were cultured on a porous scaffold to form a 3-D cell bioreactor. After interacting with live and fixed cells, the HPLC fingerprinting chromatograms of herbal medicine extract were compared to evaluate the binding properties of herbal components on cells. Model anticancer drugs (paclitaxel and resveratrol) and non-anticancer drugs (ketoprofen and penicillin G) were chosen to investigate the feasibility. When cell–drug interaction time was 30min, the binding degrees of paclitaxel and resveratrol (each 15μg/ml) were 82.2±7.2% and 66.1±4.1%, and for ketoprofen and penicillin G (each 15μg/ml) were less than 3%. This method was used to screen bioactive components from Polygonum cillinerve (Nakai) Ohwi (PCO) extract, and the binding degrees of two main components in PCO extract (10μg/ml), aristolochic acid A and aristolochic acid B, were 63.0±5.1% and 18.8±0.9%, respectively. These results demonstrated that this method was highly specific, efficient and convenient for affinity screening and analysis of bioactive components interacted with cells.
Source:Journal of Chromatography A, Volume 1243
Zhao-Li Mou, Xiao-Ni Qi, Rui-Lin Liu, Jing Zhang, Zhi-Qi Zhang
An efficient and convenient method, three-dimensional (3-D) cell bioreactor coupled with high performance liquid chromatography–mass spectrometry was developed for affinity screening and analysis of multiple bioactive components from herbal medicines. Cancer cells were cultured on a porous scaffold to form a 3-D cell bioreactor. After interacting with live and fixed cells, the HPLC fingerprinting chromatograms of herbal medicine extract were compared to evaluate the binding properties of herbal components on cells. Model anticancer drugs (paclitaxel and resveratrol) and non-anticancer drugs (ketoprofen and penicillin G) were chosen to investigate the feasibility. When cell–drug interaction time was 30min, the binding degrees of paclitaxel and resveratrol (each 15μg/ml) were 82.2±7.2% and 66.1±4.1%, and for ketoprofen and penicillin G (each 15μg/ml) were less than 3%. This method was used to screen bioactive components from Polygonum cillinerve (Nakai) Ohwi (PCO) extract, and the binding degrees of two main components in PCO extract (10μg/ml), aristolochic acid A and aristolochic acid B, were 63.0±5.1% and 18.8±0.9%, respectively. These results demonstrated that this method was highly specific, efficient and convenient for affinity screening and analysis of bioactive components interacted with cells.
Highlights
► A three-dimensional (3-D) cell bioreactor was fabricated. ► An affinity screen method was developed by coupling the bioreactor with HPLC/MS. ► The method was used to screen bioactive components in herbal medicine. ► Specific binding components with cells can be screened and analyzed.Rapid baseline-separation of all eight tocopherols and tocotrienols by reversed-phase liquid-chromatography with a solid-core pentafluorophenyl column and their sensitive quantification in plasma and liver
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Nadine Grebenstein, Jan Frank
Of the eight natural vitamin E congeners (α-, β-, γ-, and δ-tocopherol and α-, β-, γ-, and δ-tocotrienol), the non-α-tocopherol congeners have unique biological properties that may contribute to human health. Their study in vivo has been complicated by the lack of a simple analytical method that completely resolves and sensitively detects all eight natural tocopherols and tocotrienols in biological matrices. We thus developed and validated (according to the FDA guidelines for bioanalytical method validation) the first reversed-phase liquid chromatographic method for the baseline-separation and quantification of all eight tocopherols and tocotrienols. Analytes were extracted from human plasma or mouse liver and separated on a Phenomenex Kinetex PFP column (2.6μm, 150×4.6mm) by elution with methanol:water (85:15, vol/vol) at a flow rate of 0.8mL/min. The developed RP-LC method used a solid-core pentafluorophenyl stationary phase and achieved baseline separation of all eight vitamin E congeners within 15min at a backpressure of 23MPa, which is suitable for most conventional HPLC systems. The method was fast, linear, accurate, and precise with detection limits of 27–156pg and good recoveries (82–122%) for all analytes. In conclusion, we developed and validated the first RP-LC method for baseline resolution of all eight tocopherols and tocotrienols extracted from plasma and liver, which should be useful for the quantification of individual vitamin E congeners in large epidemiological studies and randomized controlled trials.
Source:Journal of Chromatography A, Volume 1243
Nadine Grebenstein, Jan Frank
Of the eight natural vitamin E congeners (α-, β-, γ-, and δ-tocopherol and α-, β-, γ-, and δ-tocotrienol), the non-α-tocopherol congeners have unique biological properties that may contribute to human health. Their study in vivo has been complicated by the lack of a simple analytical method that completely resolves and sensitively detects all eight natural tocopherols and tocotrienols in biological matrices. We thus developed and validated (according to the FDA guidelines for bioanalytical method validation) the first reversed-phase liquid chromatographic method for the baseline-separation and quantification of all eight tocopherols and tocotrienols. Analytes were extracted from human plasma or mouse liver and separated on a Phenomenex Kinetex PFP column (2.6μm, 150×4.6mm) by elution with methanol:water (85:15, vol/vol) at a flow rate of 0.8mL/min. The developed RP-LC method used a solid-core pentafluorophenyl stationary phase and achieved baseline separation of all eight vitamin E congeners within 15min at a backpressure of 23MPa, which is suitable for most conventional HPLC systems. The method was fast, linear, accurate, and precise with detection limits of 27–156pg and good recoveries (82–122%) for all analytes. In conclusion, we developed and validated the first RP-LC method for baseline resolution of all eight tocopherols and tocotrienols extracted from plasma and liver, which should be useful for the quantification of individual vitamin E congeners in large epidemiological studies and randomized controlled trials.
Highlights
► A reversed-phase HPLC method for all 8 vitamin E congeners was developed. ► Baseline-separation was achieved on a solid-core pentafluorophenyl column. ► All tocopherols and tocotrienols were resolved in <15min with a LOD of 27–156pg. ► The method was validated for human plasma and mouse liver tissue. ► Reversed-phase separation of all vitamin E congeners is reported for the first time.Determination of CMPO using HPLC–UV
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Gracy Elias, Gary S. Groenewold, Bruce J. Mincher, Stephen P. Mezyk
Octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) is an extractant proposed for selective separation of radionuclide metals from used nuclear fuel solutions using solvent extraction. Radiolysis reactions can degrade CMPO and reduce separation performance and hence methods for measuring the concentration of CMPO are needed. A novel high performance liquid chromatography (HPLC) method was developed for measuring CMPO in dodecane that featured a low pH buffer, octanol as a co-solvent with 2-propanol, and ultraviolet (UV) detection. Validation data indicated that the HPLC–UV method for CMPO determination provided good linearity, sensitivity, accuracy and precision. Method performance was evaluated using CMPO samples that had undergone radiolysis, and the results showed a decrease in CMPO concentration and the appearance of degradation products. The degradation products were identified using electrospray ionization mass spectrometry, which also showed formation of CMPO–nitric acid complexes that account for the apparent loss of CMPO in an acidic environment, independent of irradiation.
Source:Journal of Chromatography A, Volume 1243
Gracy Elias, Gary S. Groenewold, Bruce J. Mincher, Stephen P. Mezyk
Octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) is an extractant proposed for selective separation of radionuclide metals from used nuclear fuel solutions using solvent extraction. Radiolysis reactions can degrade CMPO and reduce separation performance and hence methods for measuring the concentration of CMPO are needed. A novel high performance liquid chromatography (HPLC) method was developed for measuring CMPO in dodecane that featured a low pH buffer, octanol as a co-solvent with 2-propanol, and ultraviolet (UV) detection. Validation data indicated that the HPLC–UV method for CMPO determination provided good linearity, sensitivity, accuracy and precision. Method performance was evaluated using CMPO samples that had undergone radiolysis, and the results showed a decrease in CMPO concentration and the appearance of degradation products. The degradation products were identified using electrospray ionization mass spectrometry, which also showed formation of CMPO–nitric acid complexes that account for the apparent loss of CMPO in an acidic environment, independent of irradiation.
Highlights
► CMPO is a ligand useful for radionuclides extraction in nuclear fuel solutions. ► Developed and applied a novel analytical technique with HPLC–UV for CMPO. ► LC/ESI-MS identified CMPO and a dominant radiolysis product. ► Direct infusion ESI-MS characterized CMPO–HNO3 coordination chemistry.Liquid chromatography coupled to tandem mass spectrometry for the residue determination of ethylenethiourea (ETU) and propylenethiourea (PTU) in water
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Cristina Ripollés, Juan V. Sancho, Francisco J. López, Félix Hernández
Ethylenethiourea (ETU) and propylenethiourea (PTU) are the main degradation products of dithiocarbamates fungicides, which are widely used in agriculture from several years ago. Their determination in water at low concentrations (e.g. sub-ppb levels) is highly problematic due to their polar character and low molecular size. In the present study, two analytical methodologies have been developed and compared for the selective and sensitive determination of ETU and PTU in various types of waters. Both approaches are based on liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) with electrospray ionization, using triple quadrupole analyzer. Whereas the first methodology used an on-line solid-phase extraction (SPE) step in order to reach the adequate sensitivity, the second one avoided sample treatment and was based on direct injection into an ultra high performance liquid chromatography (UHPLC–MS/MS) system, making use of a new-generation instrument in order to reach sub-ppb analyte levels in water. Strong matrix effects (typically leading to signal enhancement) were observed for most of the evaluated waters, especially when applying the on-line SPE method, surely due to the higher amount of sample injected into the system. The use of the own analyte (ETU-d4) as isotope-labelled internal standard (ILIS) allowed to compensate these effects and to achieve an accurate ETU quantification at low concentrations. Moreover, three simultaneous transitions, operating in selected reaction monitoring mode, were acquired for both ETU and ETU-d4. This fact together with the evaluation of their relative intensity ratios assured the reliable identification of the analyte in the water samples. The two optimized methodologies were validated by analysis of six different samples (two drinking water, two groundwater and two surface water), spiked at two levels (0.1 and 1.0μg/L), and analyzed each in quintuplicate. Satisfactory accuracy and precision, with recoveries ranging from 73 to 104% and RSDs lower than 20%, were obtained for ETU. Limits of detection for ETU were found to be 0.058μg/L and 0.027μg/L with direct injection and with the on-line methodology, respectively. No satisfactory recoveries were obtained, in general, for PTU despite using its own deuterium-labelled molecule for matrix effects correction. Notable differences in the chemical behaviour between PTU and PTU-d6 were observed, which lead to significant variation in their chromatographic retention time and ionization efficiency. Thus, no satisfactory correction of matrix effects could be reached illustrating that the use of deuterated ILIS can be problematic in some particular cases. Despite the poor correction, a semi-quantitative analysis would be feasible for PTU at sub-ppb levels in water. To the best of our knowledge, this is the first article reporting the use of LC–MS/MS for the trace level determination of these problematic analytes in water.
Source:Journal of Chromatography A, Volume 1243
Cristina Ripollés, Juan V. Sancho, Francisco J. López, Félix Hernández
Ethylenethiourea (ETU) and propylenethiourea (PTU) are the main degradation products of dithiocarbamates fungicides, which are widely used in agriculture from several years ago. Their determination in water at low concentrations (e.g. sub-ppb levels) is highly problematic due to their polar character and low molecular size. In the present study, two analytical methodologies have been developed and compared for the selective and sensitive determination of ETU and PTU in various types of waters. Both approaches are based on liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) with electrospray ionization, using triple quadrupole analyzer. Whereas the first methodology used an on-line solid-phase extraction (SPE) step in order to reach the adequate sensitivity, the second one avoided sample treatment and was based on direct injection into an ultra high performance liquid chromatography (UHPLC–MS/MS) system, making use of a new-generation instrument in order to reach sub-ppb analyte levels in water. Strong matrix effects (typically leading to signal enhancement) were observed for most of the evaluated waters, especially when applying the on-line SPE method, surely due to the higher amount of sample injected into the system. The use of the own analyte (ETU-d4) as isotope-labelled internal standard (ILIS) allowed to compensate these effects and to achieve an accurate ETU quantification at low concentrations. Moreover, three simultaneous transitions, operating in selected reaction monitoring mode, were acquired for both ETU and ETU-d4. This fact together with the evaluation of their relative intensity ratios assured the reliable identification of the analyte in the water samples. The two optimized methodologies were validated by analysis of six different samples (two drinking water, two groundwater and two surface water), spiked at two levels (0.1 and 1.0μg/L), and analyzed each in quintuplicate. Satisfactory accuracy and precision, with recoveries ranging from 73 to 104% and RSDs lower than 20%, were obtained for ETU. Limits of detection for ETU were found to be 0.058μg/L and 0.027μg/L with direct injection and with the on-line methodology, respectively. No satisfactory recoveries were obtained, in general, for PTU despite using its own deuterium-labelled molecule for matrix effects correction. Notable differences in the chemical behaviour between PTU and PTU-d6 were observed, which lead to significant variation in their chromatographic retention time and ionization efficiency. Thus, no satisfactory correction of matrix effects could be reached illustrating that the use of deuterated ILIS can be problematic in some particular cases. Despite the poor correction, a semi-quantitative analysis would be feasible for PTU at sub-ppb levels in water. To the best of our knowledge, this is the first article reporting the use of LC–MS/MS for the trace level determination of these problematic analytes in water.
Highlights
► Dithiocarbamates degradation products ETU and PTU are determined at sub-ppb levels in water. ► Rapid ETU and PTU determination by direct injection in UHPLC–MS/MS QqQ (LOD 0.058μg/L). ► Alternative on-line SPE-LC–MS/MS can be used for ETU in water samples (LOD 0.027μg/L). ► Strong matrix effects observed are corrected for ETU using its own deuterated analyte as ILIS. ► Non satisfactory correction for PTU using PTU-d6 reveals that analyte ILIS may have different chemical behaviour.Analysis of electrophoretic soil humic acids fractions by reversed-phase high performance liquid chromatography with on-line absorbance and fluorescence detection
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
Oleg A. Trubetskoj, Claire Richard, Ghislain Guyot, Guillaume Voyard, Olga E. Trubetskaya
A combination of reversed-phase high performance liquid chromatography (RP HPLC) with on-line absorbance and fluorescence detection was used for analysis of chernozem soil humic acids (HAs) and their fractions A, B and C+D with different electrophoretic mobility (EM) and molecular size (MS). Samples were injected onto the column at the identical volume and absorbance. All chromatograms exhibit the resolution of seven peaks. The estimation of relative recovery of HAs and fractions from the reverse-phase column has been done. High MS fraction A, which possesses the low EM, is essentially more hydrophobic (73% of the fraction amount remained adsorbed on the column) and aliphatic than medium MS and EM fraction B (33% of the fraction amount remained adsorbed on the column). The most hydrophilic and aromatic properties belong to low MS fraction C+D, which possess the highest EM and practically was not adsorbed on the column. The hydrophobicity of the bulk HAs lies within the range of fractions hydrophobicity. The absorption spectra of bulk HAs, electrophoretic fractions A, B, C+D and corresponding RP HPLC peaks were featureless but had differences in the values of absorbance ratio at 300 and 400nm (A3/A4). For fractions A and B this ratio gradually decreased from peak 1 to 7 (from 3.05 to 2.80 and 3.00 to 2.40, respectively). This trend was less pronounced in HAs and practically absent in fraction C+D, where ratio A3/A4 varied within a small range. The strong relationship between fluorescence properties, EM, MS, polarity and aliphaticity/aromaticity of HAs fractions was found. Humic and protein-like fluorescence had different polarity nature. The protein-like fluorescence is located in humic material which irreversibly adsorbed on the reverse-phase column and not subjected to RP HPLC characterization. The humic-like fluorescence at Ex/Em 270/450nm is mostly located in the hydrophilic peak of low MS fraction C+D. Taking into account that high MS fraction A consisted mainly of aliphatic components it is reasonable to suggest that these associations are capable of organizing into micellar structures. These data could be of great environmental importance, because the different fractions might reflect different soil physical–chemical properties.
Source:Journal of Chromatography A, Volume 1243
Oleg A. Trubetskoj, Claire Richard, Ghislain Guyot, Guillaume Voyard, Olga E. Trubetskaya
A combination of reversed-phase high performance liquid chromatography (RP HPLC) with on-line absorbance and fluorescence detection was used for analysis of chernozem soil humic acids (HAs) and their fractions A, B and C+D with different electrophoretic mobility (EM) and molecular size (MS). Samples were injected onto the column at the identical volume and absorbance. All chromatograms exhibit the resolution of seven peaks. The estimation of relative recovery of HAs and fractions from the reverse-phase column has been done. High MS fraction A, which possesses the low EM, is essentially more hydrophobic (73% of the fraction amount remained adsorbed on the column) and aliphatic than medium MS and EM fraction B (33% of the fraction amount remained adsorbed on the column). The most hydrophilic and aromatic properties belong to low MS fraction C+D, which possess the highest EM and practically was not adsorbed on the column. The hydrophobicity of the bulk HAs lies within the range of fractions hydrophobicity. The absorption spectra of bulk HAs, electrophoretic fractions A, B, C+D and corresponding RP HPLC peaks were featureless but had differences in the values of absorbance ratio at 300 and 400nm (A3/A4). For fractions A and B this ratio gradually decreased from peak 1 to 7 (from 3.05 to 2.80 and 3.00 to 2.40, respectively). This trend was less pronounced in HAs and practically absent in fraction C+D, where ratio A3/A4 varied within a small range. The strong relationship between fluorescence properties, EM, MS, polarity and aliphaticity/aromaticity of HAs fractions was found. Humic and protein-like fluorescence had different polarity nature. The protein-like fluorescence is located in humic material which irreversibly adsorbed on the reverse-phase column and not subjected to RP HPLC characterization. The humic-like fluorescence at Ex/Em 270/450nm is mostly located in the hydrophilic peak of low MS fraction C+D. Taking into account that high MS fraction A consisted mainly of aliphatic components it is reasonable to suggest that these associations are capable of organizing into micellar structures. These data could be of great environmental importance, because the different fractions might reflect different soil physical–chemical properties.
Highlights
► RP-UPLC with on-line absorbance and fluorescence of soil humic acids and fractions. ► Relative recovery of humic acid and fractions from the reverse-phase column. ► Relationship between fluorescence, absorbance, polarity and aliphaticity in fractions.High temperature gas chromatography–time-of-flight-mass spectrometry (HTGC–ToF-MS) for high-boiling compounds
30 May 2012,
09:17:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1243
P.A. Sutton, S.J. Rowland
High temperature gas chromatography (HTGC) is a routine technique for the analysis of high boiling compounds which are eluted from the column with oven cycling up to >400°C. In contrast, the coupling of HTGC with mass spectrometry (HTGC–MS) has received relatively little attention. This may be due to the availability of GC columns, mass spectrometers and accessories that are able to withstand constant high temperature cycling. We have assembled a HTGC–time of flight-MS (HTGC–ToF-MS) system from readily available products that is capable of rapid (<25min) analysis of ∼C10–100 hydrocarbon boiling equivalents and full mass spectral data recording up to m/z 1850. Here we report initial results from the analysis of diverse substrates including:long-chain (>C60) n-alkanes, n-acid methyl esters up to C64, triacylglycerides (TAGs) with molecular and fragment ions in a single analysis, intact wax esters from C40–64, C80 glycerol alkyl glycerol tetraethers (GDGTs), and C33–44 metallated porphyrins. Mass spectrometry at 430°C was achievable on a routine basis without significant thermal degradation of analytes. The method is applicable to analysis of a wide range of industrial, environmental, biological, geochemical and other samples where high molecular weight analytes are of interest.
Source:Journal of Chromatography A, Volume 1243
P.A. Sutton, S.J. Rowland
High temperature gas chromatography (HTGC) is a routine technique for the analysis of high boiling compounds which are eluted from the column with oven cycling up to >400°C. In contrast, the coupling of HTGC with mass spectrometry (HTGC–MS) has received relatively little attention. This may be due to the availability of GC columns, mass spectrometers and accessories that are able to withstand constant high temperature cycling. We have assembled a HTGC–time of flight-MS (HTGC–ToF-MS) system from readily available products that is capable of rapid (<25min) analysis of ∼C10–100 hydrocarbon boiling equivalents and full mass spectral data recording up to m/z 1850. Here we report initial results from the analysis of diverse substrates including:long-chain (>C60) n-alkanes, n-acid methyl esters up to C64, triacylglycerides (TAGs) with molecular and fragment ions in a single analysis, intact wax esters from C40–64, C80 glycerol alkyl glycerol tetraethers (GDGTs), and C33–44 metallated porphyrins. Mass spectrometry at 430°C was achievable on a routine basis without significant thermal degradation of analytes. The method is applicable to analysis of a wide range of industrial, environmental, biological, geochemical and other samples where high molecular weight analytes are of interest.
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