Journal of Chromatography B (v.837, #1-2)
Editorial Board (iii).
Quantification of uric acid, xanthine and hypoxanthine in human serum by HPLC for pharmacodynamic studies by Nancy Cooper; Reza Khosravan; Carol Erdmann; John Fiene; Jean W. Lee (1-10).
A simple HPLC method was developed and validated for the determination of uric acid (UA), xanthine (X) and hypoxanthine (HX) concentrations in human serum to support pharmacodynamic (PD) studies of a novel xanthine oxidase inhibitor during its clinical development. Serum proteins were removed by ultrafiltration. The hydrophilic analytes and the I.S. were eluted by 100% aqueous phosphate buffer mobile phase. The hydrophobic matrix components (late peaks) were eluted with a step gradient of a higher organic mobile phase. Validation on linearity, sensitivity, precision, accuracy, stability, and robustness of the method for PD biomarkers (UA, X, and HX) was carried out in a similar manner to that for pharmacokinetic (PK) data where applicable. Issues of selectivity for endogenous biomarker analytes and individual concentration variations were addressed during method validation. Standards were prepared in analyte-free phosphate buffer. Quality control samples were prepared in control serum from individuals not dosed with the xanthine oxidase inhibitor. The method was simple and robust with good accuracy and precision for the measurement of serum UA, X, and HX concentrations.
Keywords: Uric acid; Xanthine oxidase inhibitor; HPLC; Pharmacodynamic biomarkers; Human serum;
Determination of three bile acids in artificial Calculus Bovis and its medicinal preparations by micellar electrokinetic capillary electrophoresis by Zhen Hu; Lang-Chong He; Jian Zhang; Guo-An Luo (11-17).
A micellar electrokinetic capillary electrophoresis (MEKCE) method for the determination of cholic acid (CA), hyodeoxycholic acid (HDCA) and chenodeoxycholic acid (CDCA) in artificial Calculus Bovis and its four medicinal preparations is described. The buffer solution consisted of 40 mM disodic phosphate and 40 mM sodium dodecylsulfate (SDS) adjusted to pH 9.0. UV detection was set to 200 nm. Under optimum conditions, the analytes were baseline separated within 11 min. The linear calibration range was 12.1–970 μg ml−1 for CA and 18.8–950 μg ml−1 for HDCA and CDCA, respectively. It was found that overall recoveries were within the range of 98–102%, and R.S.D.s were less than 5% for the analytes. This method, due to its convenience, high accuracy and good reproducibility can be employed in quality control of artificial Calculus Bovis and its medicinal preparations.
Keywords: Artificial Calculus Bovis; Capillary electrophoresis; Bile acids;
Features of the milk whey protein partitioning in polyethyleneglycol-sodium citrate aqueous two-phase systems with the goal of isolating human alpha-1 antitrypsin expressed in bovine milk by Andrea Boaglio; Georgina Bassani; Guillermo Picó; Bibiana Nerli (18-23).
Partitioning behaviour of the bovine whey proteins (bovine serum albumin, α-lactoalbumin and β-lactoglobulin) and human alpha-1 antitrypsin in aqueous two-phase systems prepared with polyethyleneglycol (molecular masses: 1000, 1450 and 3350)-sodium citrate was analysed at pH 5.2, 6.2 and 8.2. Alpha lactoalbumin concentrated in the polyethyleneglycol rich-phase, while β-lactoglobulin, bovine serum albumin and alpha-1 antitrypsin showed affinity for the citrate rich-phase. In aqueous two-phase systems of high medium pH and high polyethyleneglycol molecular mass the protein partitioning equilibrium is displaced to the citrate rich-phase. The polyethyleneglycol 1450-pH 5.2 system with a top/bottom phase-volume ratio of 3 showed to have the best capability of recovering the alpha-1 antitrypsin from a mixture prepared with natural milk whey and human alpha-1 antitrypsin. The recovery of this protein in the bottom phase was of 90% and the purity of the obtained product was of 98%. The method appears to be suitable as a starting point to isolate other human proteins expressed in transgenic bovine milk.
Keywords: Alpha-1 antitrypsin; Milk whey proteins; Protein isolation; Transgenic milk;
Sensitive microanalysis of gabapentin by high-performance liquid chromatography in human serum using pre-column derivatization with 4-chloro-7-nitrobenzofurazan: Application to a bioequivalence study by Gholamreza Bahrami; Bahareh Mohammadi (24-28).
Most of the published methods for analysis of gabapentin, an antiepileptic agent, in human serum require automated o-phthalaldehyde derivatization of the drug and immediate injection of the unstable derivatives formed. A new, very sensitive and simple high-performance liquid chromatographic method for quantitation of the drug in human serum using 4-chloro-7-nitrobenzofurazan (NBD-Cl) as a fluorescent labeling agent is presented. In this method the sensitivity was significantly improved and the limit of quantification of 0.002 μg/ml was obtained using 100 μl serum sample and 10 μl injection. However, the LOQ can be improved by increasing the sampling volume. The procedure involved protein precipitation of serum by acetonitrile followed by derivatization with NBD-Cl. Amlodipine was used as internal standard and chromatographic separation was performed on a Shimpack CLC-C18 (150 mm × 4.6 mm) column. The fluorescence derivative of the drug was monitored at excitation and emission wavelengths of 470 and 537 nm, respectively. A mobile phase consisting of methanol and sodium phosphate buffer (0.05 M; pH 2.5) containing 1 ml/l triethylamine (65:35, v/v) was used. The calibration curve was linear over the concentration range of 0.002–15 μg/ml. No interferences were found from commonly co-administrated antiepileptic drugs. The method was applied in a randomized cross-over bioequivalence study of two different gabapentin preparations in 24 healthy volunteers.
Keywords: HPLC; Gabapentin; Serum; 4-Chloro-7-nitrobenzofurazan; NBD-Cl;
Specific determination of intact cisplatin and monohydrated cisplatin in human plasma and culture medium ultrafiltrates using HPLC on-line with inductively coupled plasma mass spectrometry by Deanna N. Bell; Johnson J. Liu; Malcolm D. Tingle; Mark J. McKeage (29-34).
We have developed a specific assay for cisplatin in human plasma ultrafiltrate (PUF) and cell culture medium ultrafiltrate (MUF) using HPLC on-line with inductively coupled plasma mass spectrometry (ICP-MS). Separation of cisplatin (6 min) and monohydrated cisplatin (12 min) was achieved using a μBondapak C18 column (Waters) and a mobile phase (0.075 mM sodium dodecyl sulfate and 3% methanol, adjusted to pH 2.5 with triflic acid) pumped at a flow rate of 0.5 mL/min. The analytes were detected with little background interference by ICP-MS monitoring of platinum masses (m/z 194/195). Calibration curves were linear over three orders of magnitude (0.05–8 μM) and the limit of quantitation was 0.1 μM. Intra- and inter-assay accuracy (range 91.6–113%) and precision (range 1.00–12.3%) were acceptable for PUF and MUF. The method was applied to determining cisplatin during ex vivo incubation of the drug in whole human blood at 37 °C. In conclusion, a specific, sensitive and reliable HPLC–ICP-MS assay has been established for determining intact cisplatin in PUF and MUF.
Keywords: Cisplatin; Inductively coupled plasma mass spectrometry; Monohydrated cisplatin;
Characterization of the stability of a fully human monoclonal IgG after prolonged incubation at elevated temperature by Hongcheng Liu; Georgeen Gaza-Bulseco; Joanne Sun (35-43).
The susceptible degradation sites of therapeutic proteins are routinely assessed under accelerated conditions such as exposure to chemicals or incubation at elevated temperature or a combination of both. A fully human monoclonal IgG1 antibody was characterized after incubation at 40 °C for 6 months by employing mass spectrometry and chromatography analyses. It was found that deamidation, fragmentation and N-terminal glutamate cyclization to form pyroglutamate are the major degradation pathways. Three major deamidation sites were identified and one site in a small tryptic peptide accounted for more than 80% of the total. Peptide cleavage was observed at several positions between different pairs of amino acids. Most of the cleavage sites were located in the hinge or other flexible regions of the IgG molecule.
Keywords: Recombinant monoclonal antibody; Peptide mapping; Deamidation; Pyroglutamate;
Liquid chromatography method for quantifying d-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (d-threo-PPMP) in mouse plasma and liver by Xiaqin Wu; Youngleem Kim; Bee-Chun Sun; Jeff D. Moore; Walter A. Shaw; Barry J. Maurer (44-48).
A high-performance liquid chromatography (HPLC) method was developed to measure levels of d-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (d-threo-PPMP) in mouse plasma and liver. d-threo-PPMP was measured by HPLC with a Luna Pheny-Hexyl column (5 μm, 250 mm × 4.6 mm) employing UV detection at 210 nm using a mobile phase of potassium phosphate buffer (20 mM, pH 3.0)–acetonitrile in a 45:55 (v/v) ratio. d-threo-1-phenyl-2-pentadecanoylamino-3-morpholino-1-propanol (PC15MP) was employed as an internal standard (IS). The lower limit of quantitation (LLOQ) was 0.3 μg/ml. The assay was linear over a concentration range of 0.3–10 μg/ml, with acceptable precision and accuracy. Assayed in plasma, the intra- and inter-day validation for all coefficients of variation (R.S.D.%) were found less than 15%. The method was applied to samples from athymic (nu/nu) mice treated with d-threo-PPMP by intraperitoneal injection. d-threo-PPMP levels of ∼10–20 μg/ml (∼20–40 μM) in plasma and ∼45 μg/g in liver were obtained. The present method can be used to quantify d-threo-PPMP in mice for bioavailability and dose-response studies.
Keywords: D-threo-PPMP; HPLC;
Development and validation of a quantitative assay for the measurement of two HIV-fusion inhibitors, enfuvirtide and tifuvirtide, and one metabolite of enfuvirtide (M-20) in human plasma by liquid chromatography–tandem mass spectrometry by I. van den Broek; R.W. Sparidans; A.D.R. Huitema; J.H.M. Schellens; J.H. Beijnen (49-58).
A method for the quantification of two peptide HIV-1 fusion inhibitors (enfuvirtide, T-20 and tifuvirtide, T-1249) and one metabolite of enfuvirtide (M-20) in human plasma has been developed and validated, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC–MS/MS). The analytes were extracted from plasma by solid-phase extraction (SPE) on vinyl-copolymer cartridges. Chromatographic separation of the peptides was performed on a Symmetry 300 C18 column (50 mm × 2.1 mm I.D., particle size 3.5 μm), using a water–acetonitrile gradient containing 0.25% (v/v) formic acid. The triple quadrupole mass spectrometer was operated in the positive ion-mode and multiple reaction monitoring (MRM) was used for peak detection. Deuterated (d60) enfuvirtide and (d50) tifuvirtide were used as internal standards. The assay was linear over a concentration range of 20–10,000 ng/ml for enfuvirtide and tifuvirtide and of 20–2000 ng/ml for M-20. Intra- and inter-assay precisions and deviations from the nominal concentrations were ≤13%. Stability of the analytes was tested under all relevant conditions for sample handling. The method was capable to measure concentrations of enfuvirtide and its metabolite in plasma samples of human immunodeficiency virus type-1 (HIV-1) infected patients treated with the drug.
Keywords: HIV-fusion inhibitor; Enfuvirtide; Tifuvirtide; Peptide; LC–MS/MS;
Screening anion-exchange chromatographic matrices for isolation of onco-retroviral vectors by Teresa Rodrigues; Andreia Carvalho; António Roldão; Manuel J.T. Carrondo; Paula M. Alves; Pedro E. Cruz (59-68).
The adsorption kinetics of retroviral vectors to several chromatographic media, DEAE FF, Streamline™ Q XL and CHT™ Ceramic Hydroxyapatite, in batch mode was investigated. The effects of buffer type, pH and operational temperature were studied. A mathematical model describing viral adsorption kinetics that considers viral degradation in solution was developed. The best results, either in terms of speed and extent of adsorbed infectious particles, were obtained with DEAE FF and Streamline™ Q XL. Fixed-bed chromatography was further investigated using DEAE FF, Q XL and Q FF, for validation of the batch adsorption process. Fixed-bed DEAE FF and Q XL proved to be good candidates for purification of MoMLV derived vectors due to resulting high yields, 53 ± 13% and 51 ± 7%, respectively, while removing more than 99% of protein and 90% of the DNA contaminants.
Keywords: Retroviral vectors; Purification; Anion-exchange chromatography; Adsorption kinetics; Gene therapy;
A new simple HPLC method for measuring mitotane and its two principal metabolites by Sivia De Francia; Elisa Pirro; Franco Zappia; Francesca De Martino; Andrea Elio Sprio; Fulvia Daffara; Massimo Terzolo; Alfredo Berruti; Francesco Di Carlo; Franco Ghezzo (69-75).
A new C18 reversed-phase column and UV HPLC method for the detection of mitotane, its principal metabolites, dichlorodiphenylacetate and dichlrodiphenylethene, and its precursor DDT is described. In this article mitotane, dichlorodiphenylacetate, and dichlrodiphenylethene concentrations in organs of rats fed on a mitotane diet, and the effects of erythromycin and grapefruit juice as cytochrome P450 common inhibitors are presented. Tissue accumulation of mitotane and dichlrodiphenylethene, the acquired ability to eliminate dichlorodiphenylacetate, and inhibition of β-hydroxylation by both inhibitors are illustrated here. Blood samples from mitotane-treated patients revealed two correlations: plasma mitotane/dichlrodiphenylethene and plasma mitotane/red cell mitotane.
Keywords: Mitotane; DDA; DDE; DDT; HPLC; Adrenocortical carcinoma;
Size-exclusion chromatography of heparin oligosaccharides at high and low pressure by André Ziegler; Joseph Zaia (76-86).
Recent findings on specific and non-specific interactions of glycosaminoglycans (GAGs) accentuate their pivotal role in biology and the call for improved sequencing tools. The present study evaluates size-exclusion chromatography (SEC) of heparin oligosaccharides at high and low pressure, requiring amounts as low as 0.2 microgram, using conventional UV detection after depolymerization with heparin lyases. Because of their high charge at physiological pH, SEC elution volumes of heparin oligosaccharides depend on both molecular size and charge repulsion from the matrix. As a consequence, SEC elution volumes of GAGs are smaller than those of globular proteins of similar molecular weight, and this might be exploited. Accordingly, larger heparin oligosaccharides are best separated according to their size at high ionic strength of the mobile phase (>30 mM); in contrast, disaccharides are best separated according to their charge at low ionic strength, compatible with on-line coupling to mass spectrometry. Optimized SEC affords separation of characteristic heparin trisaccharides that contain uronic acid at the reducing end and suggest cellular storage of heparin as a free glycan.
Keywords: Bio-Gel; Heparan sulfate proteoglycans; Heparin-binding proteins; Heparinase; Heparin oligosaccharides; Mass spectrometry; Size-exclusion chromatography; Superdex; van Deemter plot;
Determination of 5-chloro-7-iodo-8-quinolinol (clioquinol) in plasma and tissues of hamsters by high-performance liquid chromatography and electrochemical detection by G.P. Bondiolotti; C. Pollera; R. Pirola; S.R. Bareggi (87-91).
This paper describes a method of determining clioquinol levels in hamster plasma and tissue by means of HPLC and electrochemical detection. Clioquinol was separated on a Nucleosil C18 300 mm × 3.9 mm i.d. 7 μm column at 1 ml/min using a phosphate/citrate buffer 0.1 M (400 ml) with 600 ml of a methanol:acetonitrile (1:1, v/v) mobile phase. The retention times of clioquinol and the IS were, respectively, 11.6 and 8.1 min; the quantitation limit (CV > 8%) was 5 ng/ml in plasma and 10 ng/ml in tissues. The intra- and inter-assay accuracies of the method were more than 95%, with coefficients of variation between 3.0 and 7.7%, and plasma and tissue recovery rates of 72–77%. There was a linear response to clioquinol 5–2000 ng/ml in plasma, and 10–1000 ng/g in tissues. The method is highly sensitive and selective, makes it possible to study the pharmacokinetics of plasma clioquinol after oral administration and the distribution of clioquinol in tissues, and could be used to monitor plasma clioquinol levels in humans.
Keywords: Clioquinol; Hamsters; HPLC; Electrochemical detection;
First LC–MS/MS electrospray ionization validated method for the quantification of perindopril and its metabolite perindoprilat in human plasma and its application to bioequivalence study by Deepak S. Jain; Gunta Subbaiah; Mallika Sanyal; Umesh C. Pande; Pranav Shrivastav (92-100).
A high throughput bioanalytical method based on solid phase extraction and liquid chromatography–tandem mass spectrometry (LC–MS/MS), has been developed for the estimation of perindopril and its metabolite perindoprilat, an angiotensin-converting enzyme inhibitor in human plasma. Ramipril was used as internal standard (IS). The extraction of perindopril, perindoprilat and ramipril from the plasma involved treatment with phosphoric acid followed by solid phase extraction (SPE) using hydrophilic lipophilic balance HLB cartridge. The SPE eluate without drying were analyzed by LC–MS/MS, equipped with turbo ion spray (TIS) source, operating in the negative ion and selective reaction monitoring (SRM) acquisition mode to quantify perindopril and perindoprilat in human plasma. The total chromatographic run time was 1.5 min with retention time for perindopril, perindoprilat and ramipril at 0.33, 0.35 and 0.30 min. The developed method was validated in human plasma matrix, with a sensitivity of 0.5 ng/ml (CV, 7.67%) for perindopril and 0.3 ng/ml (CV, 4.94%) for perindoprilat. This method was extensively validated for its accuracy, precision, recovery, stability studies and matrix effect especially because the pattern of elution of all the analytes appears as flow injection elution. Sample preparation by this method yielded extremely clean extracts with very good and consistent mean recoveries; 78.29% for perindopril, 76.32% for perindoprilat and 77.72% for IS. The response of the LC–MS/MS method for perindopril and perindoprilat was linear over the range 0.5–350.0 ng/ml for perindopril and 0.3–40 ng/ml for perindoprilat with correlation coefficient, r ≥ 0.9998 and 0.9996, respectively. The method was successfully applied for bioequivalence studies in human subjects samples with 4 mg immediate release (IR) formulations.
Keywords: LC–MS/MS; SRM; Perindopril; Perindoprilat; Human plasma;
Isolation of lipids from photosystem I complex and its characterization with high performance liquid chromatography/electrospray ionization mass spectrometry by Hongjun Yao; Yujie Shi; Rongfu Gao; Guifeng Zhang; Rumin Zhang; Caixia Zheng; Bingjiu Xu (101-107).
A method for simultaneous analysis of lipids extracted from photosystem I complex was developed with high performance liquid chromatography/electrospray ionization mass spectrometry. The photosystem I complex was firstly solubilized and separated using deoxycholate polyacrylamide gel electrophoresis method after ultrasonic treatment of the sample (leaves of pea, Pisum sativum L.). The Photosystem I complexes were electrophoretically eluted from the deoxycholate polyacrylamide gel electrophoresis bands containing them, and the electron transport activity of the eluent measured as confirmation. Lipids, which were isolated from the complex having photosystem I activity, were separated and characterized with high performance liquid chromatography/electrospray ionization mass spectrometry. Five lipids, monogalactosyldiacylglycerol, digalactosyldiacylglycerol, phosphatidylglycerol, sulphoquinovosyldiacylglycerol and phosphaditylcholine were found combining with photosystem I complex. Different species of these lipids were found in the ESI mass spectra and the compositions of the acyl groups in them were determined.
Keywords: Photosystem I; Lipids; Reversed-phase high performance liquid chromatography; Electrospray ionization mass spectrometry;
Determination of 1-furan-2-yl-3-pyridin-2-yl-propenone, an anti-inflammatory propenone compound, by high performance liquid chromatography with ultraviolet spectrometry by Sang Kyu Lee; Tae Won Jeon; Arjun Basnet; Eung Seok Lee; Tae Cheon Jeong (108-111).
1-Furan-2-yl-3-pyridin-2-yl-propenone (FPP-3) has recently been synthesized and characterized to have an anti-inflammatory activity. In the present study, pharmacokinetic parameters for FPP-3 and its metabolites were determined at the same time by using high-performance liquid chromatography-ultraviolet spectrometry. Two metabolites were detected in sera when FPP-3 was administered intravenously to male SD rats. The linearity of FPP-3, M1 (1-furan-2-yl-3-pyridin-2-yl-propan-1-one) and M2 (1-furan-2-yl-3-pyridin-2-yl-propan-1-ol) was confirmed in the concentration ranges of 0.5–20, 0.101–4.04 and 1.04–20.4 μg/ml, respectively. The lower limits of quantitation of FPP-3, M1 and M2 were 0.5, 0.1 and 1.0 μg/ml, respectively. The intra- and inter-day precision and accuracy over the concentration range of target compounds were within 13.5 and 14.2%, respectively. The half-lives of FPP-3, M1 and M2 were 16.3, 27.7 and 22.1 min, respectively.
Keywords: 1-Furan-2-yl-3-pyridin-2-yl-propenone (FPP-3); Rat; Metabolites; Kinetics;
Determination of omeprazole in rat plasma by high-performance liquid chromatography without solvent extraction by Huijuan Jia; Wei Li; Kang Zhao (112-115).
A HPLC method without solvent extraction and using ultraviolet detection at 302 nm for the determination of omeprazole in rat plasma has been validated. Plasma samples after pretreatment with acetonitrile to effect deproteinization were dried under N2 at 40 °C and reconstituted with mobile phase. The standard calibration curve for omeprazole was linear (r 2 = 0.9999) over the concentration range of 0.02–3 μg ml−1. The intra- and inter-day assay variability range was 4.8–9.2% and 5.2–10.3% individually. This method has been successfully applied to a pharmacokinetic study of omeprazole in rats.
Keywords: Omeprazole; Rat plasma; High-performance liquid chromatography;
Determination of a prostaglandin D2 antagonist and its acyl glucuronide metabolite in human plasma by high performance liquid chromatography with tandem mass spectrometric detection—A lack of MS/MS selectivity between a glucuronide conjugate and a phase I metabolite by Michael S. Schwartz; Rajesh B. Desai; Sheng Bi; Alisha R. Miller; Bogdan K. Matuszewski (116-124).
A method for the determination of a prostaglandin D2 receptor antagonist (I, a compound being evaluated for the prevention of niacin induced flushing) and its acyl glucuronide metabolite (II) in human plasma is presented. The method utilized high performance liquid chromatography (HPLC) with tandem mass spectrometric (MS/MS) detection using an atmospheric pressure chemical ionization (APCI) interface operated in the positive ionization mode. The product ion was a radical cation generated via a homolytic bond cleavage. A chemical analog of the drug was used as internal standard (III). The acyl glucuronide metabolite (II) was detected using the same precursor-to-product ion transition used for the parent compound after chromatographic separation of I and II. Drug and metabolite were extracted using semi-automated, 96-well format solid phase extraction (SPE), and chromatography was performed using a reverse phase analytical column with an isocratic mobile phase. The chromatographic retention factor (k′) of II was found to be highly sensitive to mobile phase formic acid concentration. An adjustment in mobile phase formic acid concentration improved the chromatographic separation between II and a mono-hydroxylated metabolite after an unexpected lack of MS/MS selectivity between the two molecules was observed. The dependence of retention factor on formic acid concentration (k′ increased as formic acid concentration decreased) was thought to indicate polar interactions between II and the stationary phase. The stability of II in spiked human plasma was determined. The rate of hydrolysis back to parent compound was relatively low (approximately 0.1 and 0.5% per hour at room temperature and 4 °C, respectively) indicating that significant changes in analyte concentrations did not occur during sample processing. The concentration range of the assay was 10–2500 ng/mL for both drug and glucuronide metabolite.
Keywords: Prostaglandin D2 antagonist; LC–MS/MS;
A GC–MS/MS method for the quantitative analysis of low levels of the tyrosine metabolites maleylacetone, succinylacetone, and the tyrosine metabolism inhibitor dichloroacetate in biological fluids and tissues by Melissa D. Zolodz; Minghong Jia; Huiping Liu; George N. Henderson; Peter W. Stacpoole (125-132).
We developed a sensitive method to quantitate the tyrosine metabolites maleylacetone (MA) and succinylacetone (SA) and the tyrosine metabolism inhibitor dichloroacetate (DCA) in biological specimens. Accumulation of these metabolites may be responsible for the toxicity observed when exposed to DCA. Detection limits of previous methods are 200 ng/mL (1.2 pmol/μL) (MA) and 2.6 μg/mL (16.5 pmol/μL) (SA) but the metabolites are likely present in lower levels in biological specimens. To increase sensitivity, analytes were extracted from liver, urine, plasma and cultured nerve cells before and after dosing with DCA, derivatized to their pentafluorobenzyl esters, and analyzed via GC–MS/MS.
Keywords: DCA; MA; SA; GC–ECNCI-MS; PFB-Br; Tyrosine metabolites;
HPLC resolution of thioridazine enantiomers from pharmaceutical dosage form using cyclodextrin-based chiral stationary phase by R. Bhushan; Deepak Gupta (133-137).
Resolution of racemic thioridazine obtained from Thioril® tablets (Cipla Ltd., Goa, India) into its enantiomers has been achieved by HPLC using a β-cyclodextrin (CD)-bonded stationary phase. Thioridazine was isolated from commercial formulations and was purified using preparative TLC. The purity was ascertained by RP-HPLC. For the resolution of rac-thioridazine using cyclodextrin based CSP and mobile phase of 0.05 M phosphate buffer (pH 6.5)–acetonitrile (50:50) was found to be successful. The optimum conditions of resolution were established by systematically studying the effect of organic modifier, concentration of buffer, pH and flow rate of mobile phase. The detection limit was found to be 10 μg (5 μg of each enantiomer). The enantiomeric purity of each of the resolved isomers was verified by optical rotation.
Keywords: Thioridiazine; Cyclodextrin-based CSPs; RP-HPLC; Enantiomeric separation;
Chromatographic analysis of carbamazepine binding to human serum albumin by Hee Seung Kim; Rangan Mallik; David S. Hage (138-146).
Recent studies with carbamazepine on human serum albumin (HSA) columns have noted an appreciable degree of non-specific binding on supports prepared by the Schiff base immobilization method. This work examines an alternative immobilization method for HSA based on N-hydroxysuccinimide (NHS)-activated silica. This support was prepared by reacting HPLC-grade silica directly with disuccinimidyl carbonate. The resulting material was compared to an HSA support prepared by the Schiff base method in terms of its activity for carbamazepine and non-specific interactions with this drug. When examined by frontal analysis, both supports gave comparable association equilibrium constants for carbamazepine interactions with HSA ((0.53–0.55) × 104 M−1 at 37 °C). However, columns prepared by the Schiff base method gave greater non-specific binding. These columns, as well as control columns prepared using the carbonyldiimidazole (CDI) immobilization method, were also evaluated for their non-specific binding to a variety of other solutes known to interact with HSA. From these results it was concluded that the NHS method was an attractive alternative to the Schiff base technique in the preparation of immobilized HSA for HPLC-based binding studies for carbamazepine. However, it was also noted that non-specific binding varies from one drug to the next in these immobilization methods, indicating that such properties should be evaluated on a case-by-case basis in the use and development of HSA columns for binding studies.
Keywords: Carbamazepine; Human serum albumin; High-performance affinity chromatography; Binding studies; Schiff base method; N-Hydroxysuccinimide method;
Identification of conjugated linoleic acid elongation and β-oxidation products by coupled silver-ion HPLC APPI-MS by André Müller; Markus Mickel; Roland Geyer; Robert Ringseis; Klaus Eder; Hans Steinhart (147-152).
Atmospheric pressure photoionisation (APPI) was used in combination with silver-ion (Ag+)-HPLC for detection of (conjugated) fatty acid methyl esters (FAME) by tandem-mass spectrometry. APPI-MS of methyl esters of conjugated linoleic acid showed an increase in signal-to-noise ratio by a factor of 40 compared to atmospheric pressure chemical ionization in the positive mode. It was possible to identify double bond position, configuration and chain length of FAME based on chromatographic separation and mass detection. The developed LC–MS method is useful for the analysis of CLA elongation and β-oxidation products, especially with trans,trans-configuration, which are difficult to analyze by conventional GC–MS techniques.
Keywords: Conjugated linoleic acids; Silver-ion HPLC; Mass spectrometry; Bioactive lipids; Fatty acid metabolism; Atmospheric pressure photoionization;
Erratum to “Measurement of drug–protein binding by immobilized human serum albumin-HPLC and comparison with ultrafiltration” [J. Chromatogr. B 834 (2006) 108–116]☆ by Sonu Sundd Singh; Jitendra Mehta (153).
Erratum to “Analysis of agaritine in mushrooms and in agaritine-administered mice using liquid chromatography–tandem mass spectrometry” [J. Chromatogr. B 834 (2006) 55–61]☆ by Kazunari Kondo; Asako Watanabe; Yuko Iwanaga; Ikuro Abe; Hideya Tanaka; Megumi Hamano Nagaoka; Hiroshi Akiyama; Tamio Maitani (154).
Author Index Vol. 837 (155-156).
Keyword Index Vol. 837 (157-160).