Browsing by Author "Masujima T."

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A combination of isocratic and gradient elution modes in HPLC with the aid of time-overlapping process for rapid determination of methyldopa in human urine
(Taylor and Francis Inc., 2015) Emara S.; Masujima T.; Zarad W.; Kamal M.; Fouad M.; El-Bagary R.; Department of Pharmaceutical Chemistry; Faculty of Pharmacy; Misr International University; Km 28 Ismailia Road; Ismailia; Cairo; 41522; Egypt; P.I. Lab. Single Cell MS; RIKEN Quantitative Biology Center; Suita; Osaka; Japan; Department of Pharmaceutical Analytical Chemistry; Faculty of Pharmacy; Modern Sciences and Arts University; Cairo; Egypt; Department of Pharmaceutical Chemistry; Faculty of Pharmacy; Cairo University; Cairo; Egypt
A new rapid time-overlapping high-performance liquid chromatography method using coupled-column double-injection technique with fluorescence detection has been developed and validated to determine methyldopa (MTD) in human urine. The method was based on injecting a new sample onto the second column before finalizing the cleanup and the re-equilibration of the first column for the former sample. A combination of isocratic and gradient elution was employed according to a pre-set program. At the beginning, isocratic step of acetate buffer solution (0.1 M, pH 2.4) was set until 7 min. Subsequently, a gradient elution step using acetate buffer (0.1 M, pH 2.4) as mobile phase A and acetonitrile as mobile phase B was employed. After the end of each gradient step, the column was re-equilibrated with 4 mL of the starting isocratic elution system before the next analysis. The overall cycle time was 7 min per each sample. The calibration curve was linear over the concentration range of 0.1-40 ?g/mL MTD. The overall mean recoveries were in the range of 98.29-101.39%. The applicability of the method was successfully evaluated by monitoring the incremental urinary excretion of MTD in human urine over 12 hr after a single oral administration of 250 mg. � 2015 Taylor & Francis Group, LLC.
An eco-friendly direct injection HPLC method for methyldopa determination in serum by mixed-mode chromatography using a single protein-coated column
(Oxford University Press, 2015) Emara S.; Masujima T.; Zarad W.; Kamal M.; Fouad M.; El-Bagary R.; Pharmaceutical Chemistry Department; Faculty of Pharmacy; Misr International University; Km 28 Ismailia Road; Cairo; Egypt; P.I. Lab. Single Cell MS; RIKEN Quantitative Biology Center; 6-2-3; Furuedai; Suita; Osaka 565-0874; Japan; Pharmaceutical Analytical Chemistry Department; Faculty of Pharmacy; Modern Sciences and Arts University; 26 July Mehwar Road Intersection With Wahat Road; 6 October City; Egypt; Pharmaceutical Chemistry Department; Faculty of Pharmacy; Cairo University; Kasr El Aini St.; Cairo; 11562; Egypt
A simple, rapid and environment-friendly direct injection HPLC method for the determination of methyldopa (MTD) in human serum has been developed and validated. The method was based on cleanup and separation of MTD from serum by mixed-mode liquid chromatography using a single protein-coated TSK gel ODS-80 TM analytical column (50 x 4.0 mm i.d., 5 ?m). The protein-coated column exhibited excellent resolution, selectivity and functioned in two chromatographic modes: size-exclusion chromatography [i.e., solid-phase extraction (SPE) for serum proteins] and reversed-phase chromatography for the final separation of MTD. SPE and HPLC separation were carried out simultaneously with a green mobile phase consisting of acetate buffer (0.1 M, pH 2.4) at a flow rate of 1 mL/min and at room temperature (23 � 1�C). The eluent was monitored at emission and excitation wavelengths of 320 and 270 nm, respectively. A calibration curve was linear over the range of 0.1-30 ?g/mL with a detection limit of 0.027 ?g/mL. This online SPE method was successfully applied to real samples obtained from patients receiving MTD therapy. � The Author 2015. Published by Oxford University Press. All rights reserved.
Field-amplified sample stacking cyclodextrin modified capillary electrophoresis for quantitative determination of diastereomeric saponins
(Springer Netherlands, 2014) Emara S.; Masujima T.; Zarad W.; Mohamed K.; Kamal M.; Fouad M.; EL-Bagary R.; Faculty of Pharmacy; Pharmaceutical Chemistry Department; Misr International University; Km 28 Ismailia Road; Cairo; Egypt; P.I. Laboratory Single Cell MS; RIKEN Quantitative Biology Center; 6-2-3; Furuedai; Suita; Osaka; 565-0874; Japan; Faculty of Pharmacy; Pharmacognosy Department; Assiut University; Assiut; 71526; Egypt; Faculty of Pharmacy; Pharmaceutical Analytical Chemistry Department; Modern Sciences and Arts University; 26 July Mehwar Road Intersection with Wahat Road; 6 October City; Egypt; Faculty of Pharmacy; Pharmaceutical Chemistry Department; Cairo University; Kasr El Aini St.; Cairo; 11562; Egypt
Successful simultaneous diastereomeric separation and sensitive determination of two pairs of triterpenoidal saponins have been achieved by capillary electrophoresis (CE) using ?-cyclodextrin (?-CD) as a stereoselective agent to cooperate with borate complexation. A usual technique for isolation and group separation of saponins was developed as an appropriate purification step prior to the determination of individual saponins by CE. Soyasaponin I (S1), azukisaponin V (S2), bersimoside I (S3) and bersimoside II (S4) could be well separated within 14 min in a fused-silica capillary (60 cm long to the detector with an additional 10 cm to the cathode; 75 ?m i.d.). The background electrolyte was borate buffer (80 mM, pH 10), containing 24 mM ?-CD. The separation voltage was 14 kV with a detection wavelength of 195 nm. The sample was electrokinetically injected using a voltage of 16 kV for 12 s. Methanol (70%) was used as the diluent for field-amplified sample stacking after hydrodynamic injection of short water plug (5 cm, 4 s). The method was partially validated for linearity, repeatability, reproducibility, limits of detection and limits of quantification. The correlation coefficients of the calibration curves were all >0.998, and the recoveries were from 98.23 to 96.21%. The Author [2013]. Published by Oxford University Press. All rights reserved.
On-line coupling of derivatization with pre-concentration to determine trace levels of methotrexate
(Xi'an Jiaotong University, 2013) Emara S.; Masujima T.; Zarad W.; Kamal M.; El-Bagary R.; Pharmaceutical Chemistry Department; Faculty of Pharmacy; Misr International University; Km 28 Ismailia Road; Cairo; Egypt; Analytical Molecular Medicine and Devices Laboratory; Hiroshima University; Graduate School of Biomedical Sciences; 1-2-3; Kasumi; Minami-ku; Hiroshima 734-8551; Japan; Pharmaceutical Analytical Chemistry Department; Faculty of Pharmacy; Modern Sciences and Arts University; 26 July Mehwar Road intersection with Wahat Road; 6 October City; Egypt; Pharmaceutical Chemistry Department; Faculty of Pharmacy; Cairo University; Kasr El Aini St.; Cairo 11562; Egypt
A new simple, sensitive and precise green analytical procedure using an automated packed-reactor derivatization technique coupled with on-line solid-phase enrichment (SPEn) has been developed and evaluated to determine trace levels of methotrexate (MTX). The method was based on injection of MTX into a flowing stream of phosphate buffer (0.04 M, pH 3.4), carried through the packed oxidant reactor of Cerium (IV) trihydroxyhydroperoxide for oxidative cleavage of the drug into highly fluorescent product, 2,4-diaminopteridine-6- carboxylic acid, followed by SPEn on a head of short ODS column (10 mm�4.6 mm i.d., 5 ?m particle size). The flow rate was 0.25 mL/min and packed reactor temperature was 40 �C. The trapped product was back-flush eluted from the ODS column to the detector by column-switching with an environmentally friendly mobile phase consisting of ethanol and phosphate buffer (0.04 M, pH 3.4) in the ratio of 5:95 (v/v). The eluent was monitored at emission and excitation wavelengths of 460 and 360 nm, respectively. The calibration curve was linear over the concentration range of 1.25-50 ng/mL with a detection limit of 0.08 ng/mL. The method was successfully applied to determine MTX in pharmaceutical formulations with mean percentage recovery ranging from 99.48 to 99.60. � 2013 Xi'an Jiaotong University.
On-line solid-phase enrichment coupled to packed reactor flow injection analysis in a green analytical procedure to determine low levels of folic acid using fluorescence detection
(2012) Emara S.; Masujima T.; Zarad W.; Kamal M.; EL-Bagary R.; Pharmaceutical Chemistry Department; Faculty of Pharmacy; Misr International University; Km 28 Ismailia Road; Cairo; Egypt; Analytical Molecular Medicine and Devices Laboratory; Hiroshima Univ.; Graduate School of Biomedical Sciences; 1-2-3; Kasumi; Minami-ku; Hiroshima; 734-8551; Japan; Pharmaceutical Analytical Chemistry Department; Faculty of Pharmacy; Modern Sciences and Arts University; 26 July Mehwar Road intersection with Wahat Road; 6 October City; Egypt; Pharmaceutical Chemistry Department; Faculty of Pharmacy; Cairo University; Kasr El Aini St; Cairo; 11562; Egypt
Background: Analysis of folic acid (FA) is not an easy task because of its presence in lower concentrations, its lower stability under acidic conditions, and its sensitiveness against light and high temperature. The present study is concerned with the development and validation of an automated environmentally friendly pre-column derivatization combined by solid-phase enrichment (SPEn) to determine low levels of FA.Results: Cerium (IV) trihydroxyhydroperoxide (CTH) as a packed oxidant reactor has been used for oxidative cleavage of FA into highly fluorescent product, 2-amino-4-hydroxypteridine-6-carboxylic acid. FA was injected into a carrier stream of 0.04 M phosphate buffer, pH 3.4 at a flow-rate of 0.25 mL/min. The sample zone containing the analyte was passed through the CTH reactor thermostated at 40�C, and the fluorescent product was trapped and enriched on a head of small ODS column (10 mm x 4.6 mm i.d., 5 ?m particle size). The enriched product was then back-flush eluted by column-switching from the small ODS column to the detector with a greener mobile phase consisting of ethanol and phosphate buffer (0.04M, pH 3.4) in the ratio of 5:95 (v/v). The eluent was monitored fluorimetrically at emission and excitation wavelengths of 463 and 367 nm, respectively. The calibration graph was linear over concentrations of FA in the range of 1.25-50 ng/mL, with a detection limit of 0.49 ng/mL.Conclusion: A new simple and sensitive green analytical procedure including on-line pre-column derivatization combined by SPEn has been developed for the routine quality control and dosage form assay of FA at very low concentration level. The method was a powerful analytical technique that had excellent sensitivity, sufficient accuracy and required relatively simple and inexpensive instrumentation. � 2012 Emara et al.; licensee Chemistry Central Ltd.
Online pre-column derivatization with chromatographic separation to determine folic acid
(2013) Emara S.; Masujima T.; Zarad W.; Kamal M.; Ei-Bagary R.; Pharmaceutical Chemistry Department; Faculty of Pharmacy; Misr International University; Km 28 Ismailia Road; Cairo; Egypt; Analytical Molecular Medicine and Devices Laboratory; Hiroshima University; Graduate School of Biomedical Sciences; 1-2-3; Kasumi; Minami-ku; Hiroshima; 734-8551; Japan; Pharmaceutical Analytical Chemistry Department; Faculty of Pharmacy; Modern Sciences and Arts University; 26 July Mehwar Road intersection with Wahat Road; 6 October City; Egypt; Pharmaceutical Chemistry Department; Faculty of Pharmacy; Cairo University; Kasr El Aini St.; Cairo 11562; Egypt
A simple, sensitive, and selective online pre-column derivatization high-performance liquid chromatographic method was developed and validated for the first time to determine trace levels of folic acid (FA). An oxidant cerium (IV) trihydroxyhydroperoxide packed reactor was used for pre-column oxidation and was combined by column switching with a C18 analytical column for sample enrichment and separation. The method was based on oxidative cleavage of FA into highly fluorescence products, 2-amino-4-hydroxypteridine-6-carboxaldehyde and the corresponding 2-amino-4-hydroxypteridine-6-carboxylic acid, during the flow of 0.04 M phosphate buffer (pH 3.5) containing the analyte through packed reactor at a flow rate of 0.2 mL/min and 40�C. The fluorescent products were enriched on the head of the analytical column for the final separation. The separation was performed at room temperature using a mobile phase consisting of phosphate buffer (0.04 M, pH 3.5) and acetonitrile (90:10, v/v). The eluents were monitored at emission and excitation wavelengths of 463 and 367 nm, respectively. The method showed excellent recovery, precision and accuracy with detection limits of 0.067 ng/mL from 500 L of sample FA. The developed method was successfully applied to the determination of FA in pharmaceutical formulations and showed a recovery of 99.31% and a relative standard deviation of 1.72%. 2012 � The Author [2012].