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Selected papers from the latest issue:
Gas chromatographic-mass spectrometric investigation of volatile and extractable compounds of crude royal jelly
31 December 2011, 21:55:15
Publication year: 2011
Source: Journal of Chromatography B, Available online 30 December 2011
V.A. Isidorov, S. Bakier, I. Grzech
Using headspace solid-phase microextraction (HS-SPME) followed by diethyl ether and methanol extraction, it was possible to isolate as many as 185 organic compounds out of 17 samples of crude royal jelly (RJ). Of the above compound number, 169 compounds were positively identified by means of gas chromatography–mass spectrometry. The volatile fraction of RJ consists of 25 different compounds where approximately 47% of the total ion current (TIC) of volatile compound chromatograms were composed of substances characterized by bactericidal (phenols) and repelling (octanoic acid and 2-heptanone) activities. Preliminary investigations have shown that RJ stored for 10 months at -18 °C and 4 °C keeps its composition of volatile compounds unchanged, however, at the same time at room temperature RJ phenol contents is decreased twice, whereas the fraction of aliphatic acids is increased 2.8 times due to the presence of both acetic and butyric acids. The chromatogram of RJ ether extracts showed 85 different compounds, however about 88% of TIC consisted exclusively of 8 compounds, i.e. 10-hydroxy-2-decenoic, 10-hydroxydecanoic, 3,10-dihydroxydecanoic, 8-hydroxyoctanoic, 2-decene-1,10-dioc and (Z)-9-hydroxy-2-decenoic acids. Nine aliphatic acids, which were detected for the first time, are the homologues of hydroxy- and oxo-acids identified earlier in RJ. In the RJ methanol extracts 82 compounds were identified, mainly carbohydrates and their derivatives. Approximately 87% of TIC consisted of fructose, glucose and sucrose. Special attention was paid to discrepancies between obtained and literature data concerning the presence of free amino acids in RJ. It was suggested that these inconsistencies can be explained by the differences in the methods of RJ collection and/or sample preparation.
Source: Journal of Chromatography B, Available online 30 December 2011
V.A. Isidorov, S. Bakier, I. Grzech
Using headspace solid-phase microextraction (HS-SPME) followed by diethyl ether and methanol extraction, it was possible to isolate as many as 185 organic compounds out of 17 samples of crude royal jelly (RJ). Of the above compound number, 169 compounds were positively identified by means of gas chromatography–mass spectrometry. The volatile fraction of RJ consists of 25 different compounds where approximately 47% of the total ion current (TIC) of volatile compound chromatograms were composed of substances characterized by bactericidal (phenols) and repelling (octanoic acid and 2-heptanone) activities. Preliminary investigations have shown that RJ stored for 10 months at -18 °C and 4 °C keeps its composition of volatile compounds unchanged, however, at the same time at room temperature RJ phenol contents is decreased twice, whereas the fraction of aliphatic acids is increased 2.8 times due to the presence of both acetic and butyric acids. The chromatogram of RJ ether extracts showed 85 different compounds, however about 88% of TIC consisted exclusively of 8 compounds, i.e. 10-hydroxy-2-decenoic, 10-hydroxydecanoic, 3,10-dihydroxydecanoic, 8-hydroxyoctanoic, 2-decene-1,10-dioc and (Z)-9-hydroxy-2-decenoic acids. Nine aliphatic acids, which were detected for the first time, are the homologues of hydroxy- and oxo-acids identified earlier in RJ. In the RJ methanol extracts 82 compounds were identified, mainly carbohydrates and their derivatives. Approximately 87% of TIC consisted of fructose, glucose and sucrose. Special attention was paid to discrepancies between obtained and literature data concerning the presence of free amino acids in RJ. It was suggested that these inconsistencies can be explained by the differences in the methods of RJ collection and/or sample preparation.
Highlights
► Volatile compounds of fresh royal jelly ► bactericidal and repelling activities ► markers of inappropriate storage ► extractable compounds of royal jelly ► possible source of free amino acids.Determination of atomoxetine metabolites in human plasma by liquid chromatography/tandem mass spectrometry and its application to a pharmacokinetic study
31 December 2011, 21:55:15
Publication year: 2011
Source: Journal of Chromatography B, Available online 30 December 2011
Chang-Ik Choi, Jung-Woo Bae, Hye-In Lee, Choon-Gon Jang, Uy Dong Sohn, ...
4-Hydroxyatomoxetine (4-HAT) andN-desmethylatomoxetine (N-DAT) are major metabolites of atomoxetine, a potent and selective inhibitor of the presynaptic norepinephrine transporter that is used for the treatment of attention deficit/hyperactivity disorder. The pharmacological activity of 4-HAT is similar to that of atomoxetine. We have developed and validated a simple, rapid and sensitive liquid chromatography analytical method with tandem mass spectrometry (LC-MS/MS) for the determination of 4-HAT and N-DAT in human plasma. After liquid-liquid extraction with methylt-butyl ether, chromatographic separation of analytes was performed using a reversed-phase Luna C18column (2.0 mm × 100 mm, 3 μm particles) with a mobile phase of 10 mM ammonium formate buffer (pH 3.5)-methanol (10:90, v/v) and quantified by MS/MS detection in ESI positive ion mode. The flow rate of the mobile phase was 250 μL/min and the retention times of 4-HAT, N-DAT and internal standard (IS, metoprolol) were 0.9, 1.0 and 1.0 min, respectively. The calibration curves were linear over the range of 0.05-20 ng/mL for 4-HAT and 0.1-20 ng/mL for N-DAT. The lower limits of quantification, using 200 μL human plasma, were 0.05 and 0.1 ng/mL for 4-HAT and N-DAT, respectively. The mean accuracy and precision for intra- and inter-day validation of 4-HAT and N-DAT were both within the acceptable limits. This LC-MS/MS method showed improved sensitivity for quantification of the two main metabolites of atomoxetine in human plasma compared with previously described analytical methods. The validated method was successfully applied to a pharmacokinetic study in humans.
Source: Journal of Chromatography B, Available online 30 December 2011
Chang-Ik Choi, Jung-Woo Bae, Hye-In Lee, Choon-Gon Jang, Uy Dong Sohn, ...
4-Hydroxyatomoxetine (4-HAT) andN-desmethylatomoxetine (N-DAT) are major metabolites of atomoxetine, a potent and selective inhibitor of the presynaptic norepinephrine transporter that is used for the treatment of attention deficit/hyperactivity disorder. The pharmacological activity of 4-HAT is similar to that of atomoxetine. We have developed and validated a simple, rapid and sensitive liquid chromatography analytical method with tandem mass spectrometry (LC-MS/MS) for the determination of 4-HAT and N-DAT in human plasma. After liquid-liquid extraction with methylt-butyl ether, chromatographic separation of analytes was performed using a reversed-phase Luna C18column (2.0 mm × 100 mm, 3 μm particles) with a mobile phase of 10 mM ammonium formate buffer (pH 3.5)-methanol (10:90, v/v) and quantified by MS/MS detection in ESI positive ion mode. The flow rate of the mobile phase was 250 μL/min and the retention times of 4-HAT, N-DAT and internal standard (IS, metoprolol) were 0.9, 1.0 and 1.0 min, respectively. The calibration curves were linear over the range of 0.05-20 ng/mL for 4-HAT and 0.1-20 ng/mL for N-DAT. The lower limits of quantification, using 200 μL human plasma, were 0.05 and 0.1 ng/mL for 4-HAT and N-DAT, respectively. The mean accuracy and precision for intra- and inter-day validation of 4-HAT and N-DAT were both within the acceptable limits. This LC-MS/MS method showed improved sensitivity for quantification of the two main metabolites of atomoxetine in human plasma compared with previously described analytical methods. The validated method was successfully applied to a pharmacokinetic study in humans.
Highlights
► A sensitive LC-MS/MS assay method for two metabolites of atomoxetine was developed. ► LLOQ was 0.05 ng/mL for 4-hydroxyatomoxetine and 0.1 ng/mL forN-desmethylatomoxetine. ► The validated method was successfully applied to a pharmacokinetic study in humans.Determination of landiolol, an ultra-short-acting β1-receptor antagonist, in human plasma by liquid chromatography-tandem mass spectrometry
31 December 2011, 21:55:15
Publication year: 2011
Source: Journal of Chromatography B, Available online 30 December 2011
Qun He, Meiyun Shi, Xidong Liu, Yantong Sun, Lianghai Hu, ...
A method for the determination of landiolol, an ultra-short-acting β1-adrenoreceptor antagonist, in human plasma has been developed and validated. With the addition of pyridostigmine bromide to stabilize landiolol in the blood/plasma samples, and bisoprolol as internal standard, plasma samples were subjected to liquid-liquid extraction with diethyl ether:dicholoromethane (60:40, v/v) prior to assay by liquid chromatography-tandem mass spectrometry. Separation was performed on a TC-C18column (150 × 4.6 mm, 5 μm) using a mobile phase of methanol:10 mM ammonium acetate containing 1% formic acid (65:35, v/v) in a run time of 3.5 min. Detection involved electrospray ionization in the positive ion mode followed by multiple reaction monitoring of the precursor-to-product ion transitions of landiolol atm/z510.1→157.2 and bisoprolol atm/z326.3→116.1. The method was linear over the concentration range 0.5-500 ng/ml with a lower limit of quantitation of 0.5 ng/ml. Intra- and inter-day precisions (as relative standard deviation, RSD) were < 4.4% and < 10.0%, respectively, with accuracy (as relative error, RE) < 10.0%. The method was successfully applied to a clinical pharmacokinetic study involving a continuous infusion of landiolol hydrochloride to healthy Chinese volunteers.
Source: Journal of Chromatography B, Available online 30 December 2011
Qun He, Meiyun Shi, Xidong Liu, Yantong Sun, Lianghai Hu, ...
A method for the determination of landiolol, an ultra-short-acting β1-adrenoreceptor antagonist, in human plasma has been developed and validated. With the addition of pyridostigmine bromide to stabilize landiolol in the blood/plasma samples, and bisoprolol as internal standard, plasma samples were subjected to liquid-liquid extraction with diethyl ether:dicholoromethane (60:40, v/v) prior to assay by liquid chromatography-tandem mass spectrometry. Separation was performed on a TC-C18column (150 × 4.6 mm, 5 μm) using a mobile phase of methanol:10 mM ammonium acetate containing 1% formic acid (65:35, v/v) in a run time of 3.5 min. Detection involved electrospray ionization in the positive ion mode followed by multiple reaction monitoring of the precursor-to-product ion transitions of landiolol atm/z510.1→157.2 and bisoprolol atm/z326.3→116.1. The method was linear over the concentration range 0.5-500 ng/ml with a lower limit of quantitation of 0.5 ng/ml. Intra- and inter-day precisions (as relative standard deviation, RSD) were < 4.4% and < 10.0%, respectively, with accuracy (as relative error, RE) < 10.0%. The method was successfully applied to a clinical pharmacokinetic study involving a continuous infusion of landiolol hydrochloride to healthy Chinese volunteers.
Highlights
► A novel method for determination of landiolol in plasma by LC-MS/MS was developed. ► Landiolol in blood/plasma samples is stabilized by pyridostigmine bromide. ► The plasma samples were prepared by liquid-liquid extraction. ► The LLOQ of the method is 0.5 ng/ml which is the lowest reported so far. ► The method was successfully applied to a clinical pharmacokinetic study of landiolol.DEVELOPMENT AND OPTIMIZATION OF SIMPLIFIED LC-MS/MS QUANTIFICATION OF 25-HYDROXYVITAMIN D USING PROTEIN PRECIPITATION COMBINED WITH ON-LINE SOLID PHASE EXTRACTION (SPE)
27 December 2011, 23:59:53
Publication year: 2011
Source: Journal of Chromatography B, Available online 27 December 2011
Denis Thibeault, Nicolas Caron, Rose Djiana, Richard Kremer, David Blank
25-hydroxyvitamin D, the most useful marker of the vitamin D status of an individual, has seen an exponential growth of its routine measurement in recent years. Several methods are currently offered but the most specific is LC-MS/MS. However, the routine use of this technique in the clinical laboratory makes it essential to improve key steps of this method for high throughput delivery. Importantly, the preanalytical steps of this assay and the efficacy of the separation system need to be optimized prior to MS detection. In this report we replaced the standard and time consuming liquid-liquid extraction method of vitamin D metabolites with hexane (LLE) combined with centrifugation (LLE/centrifugation) by a simpler protein precipitation with extraction (PPE) in acetonitrile combined with a fast separation process using a 96-well plate filtration system (PPE/filtration). This rapid extraction was then followed by an on-line solid phase extraction (SPE) using a selective chromatographic separation. We also optimized the operational and consumable costs, by using an inexpensive guard column as a trapping column to significantly enhance the lifespan of the analytical column 2-3 times as compared to conventional chromatography. The LC-MS/MS technique permits the measurement of both 25-hydroxyvitaminD2(25-OH D2)and the 25-hydroxyvitaminD3(25-OH D3) metabolites in electrospray ionization (ESI) mode. The chromatographic system consisted of a 2.1 × 50 mm C18 3.5 μM column with a 2.1 × 20 mm C18 3.5 μM guard column connected with two 6 ports switching valves. Quantifications were done using the isotopic dilution technique with hexadeutered 25-OH D3and 25-OH D2.The ion suppression problem with phospholipids was also evaluated and optimized to minimize this effect through the chromatography process and the on-line SPE trapping. Calibration curves were prepared by diluting a commercial high calibrator Chromsystems (München, Germany) with either pure triple stripped blank serum or diluted in 6% phosphate buffer saline at pH 7.2. Linearity was tested up to 160 nmol/L for 25-OH D3and 75 nmol/L for 25-OH D2. Low limit of quantification (LLOQ) were established at 3 nmol/L for 25-OH D2and 4 nmol/L for 25-OH D3. Inter-assay and intra-assay precision (CV%) was determined using 3 levels of commercial controls (Utak, CA 91355, USA) for 25-OH D2and 25-OH D3. Results obtained for intra-assay and inter-assay precision (CV%) were 1.1 to 3.4% and 5 to 8.9% respectively for the PPE/centrifugation technique and 2.0 to 3.1% and 4.6 to 6.6% for the PPE/filtration technique. Accuracy was estimated with the same commercial controls: % bias was -11.2 to 4.9% with PPE/centrifugation and -3.2-6.1% with PPE/filtration. 25-OH D2and 25-OH D3concentrations in human serum with LLE were compared to the new extraction methods using either PPE/centrifugation or PPE/filtration. Correlations comparing the two methods revealed a slope approximately 1.0 ± 0.3 with R ≥ 0.98 with a bias < 1 nmol/L. In summary, the new LC-MS/MS method described in this report using an on-line SPE technique with a simple off-line pre-treatment is faster, cost-effective, more reliable and more robust than current and widely used LLE/centrifugation methods coupled with LC-MS/MS.
Source: Journal of Chromatography B, Available online 27 December 2011
Denis Thibeault, Nicolas Caron, Rose Djiana, Richard Kremer, David Blank
25-hydroxyvitamin D, the most useful marker of the vitamin D status of an individual, has seen an exponential growth of its routine measurement in recent years. Several methods are currently offered but the most specific is LC-MS/MS. However, the routine use of this technique in the clinical laboratory makes it essential to improve key steps of this method for high throughput delivery. Importantly, the preanalytical steps of this assay and the efficacy of the separation system need to be optimized prior to MS detection. In this report we replaced the standard and time consuming liquid-liquid extraction method of vitamin D metabolites with hexane (LLE) combined with centrifugation (LLE/centrifugation) by a simpler protein precipitation with extraction (PPE) in acetonitrile combined with a fast separation process using a 96-well plate filtration system (PPE/filtration). This rapid extraction was then followed by an on-line solid phase extraction (SPE) using a selective chromatographic separation. We also optimized the operational and consumable costs, by using an inexpensive guard column as a trapping column to significantly enhance the lifespan of the analytical column 2-3 times as compared to conventional chromatography. The LC-MS/MS technique permits the measurement of both 25-hydroxyvitaminD2(25-OH D2)and the 25-hydroxyvitaminD3(25-OH D3) metabolites in electrospray ionization (ESI) mode. The chromatographic system consisted of a 2.1 × 50 mm C18 3.5 μM column with a 2.1 × 20 mm C18 3.5 μM guard column connected with two 6 ports switching valves. Quantifications were done using the isotopic dilution technique with hexadeutered 25-OH D3and 25-OH D2.The ion suppression problem with phospholipids was also evaluated and optimized to minimize this effect through the chromatography process and the on-line SPE trapping. Calibration curves were prepared by diluting a commercial high calibrator Chromsystems (München, Germany) with either pure triple stripped blank serum or diluted in 6% phosphate buffer saline at pH 7.2. Linearity was tested up to 160 nmol/L for 25-OH D3and 75 nmol/L for 25-OH D2. Low limit of quantification (LLOQ) were established at 3 nmol/L for 25-OH D2and 4 nmol/L for 25-OH D3. Inter-assay and intra-assay precision (CV%) was determined using 3 levels of commercial controls (Utak, CA 91355, USA) for 25-OH D2and 25-OH D3. Results obtained for intra-assay and inter-assay precision (CV%) were 1.1 to 3.4% and 5 to 8.9% respectively for the PPE/centrifugation technique and 2.0 to 3.1% and 4.6 to 6.6% for the PPE/filtration technique. Accuracy was estimated with the same commercial controls: % bias was -11.2 to 4.9% with PPE/centrifugation and -3.2-6.1% with PPE/filtration. 25-OH D2and 25-OH D3concentrations in human serum with LLE were compared to the new extraction methods using either PPE/centrifugation or PPE/filtration. Correlations comparing the two methods revealed a slope approximately 1.0 ± 0.3 with R ≥ 0.98 with a bias < 1 nmol/L. In summary, the new LC-MS/MS method described in this report using an on-line SPE technique with a simple off-line pre-treatment is faster, cost-effective, more reliable and more robust than current and widely used LLE/centrifugation methods coupled with LC-MS/MS.
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