Showing papers by "King Faisal Specialist Hospital & Research Centre published in 2003"

Enantioseparation of some clinically used drugs by HPLC using cellulose Tris (3,5-dichlorophenylcarbamate) chiral stationary phase.

Abstract: The chiral resolution of some clinically used drugs namely metoprolol, teratolol, tolamolol, nebivolol (β-adrenergic blockers), econazole, miconazole (anti-fungal agents), cromakalim (anti-hypertensive agent) and etodolac (anti-inflammatory agent) was achieved on cellulose tris (3,5-dichlorophenylcarbamate) chiral stationary phase. The mobile phase used was 2-propanol at 0.5 mL/min with detection at 220 nm. The separation factors (α) of these drugs ranged from 1.24 to 3.90 while the resolution factors were from 1.05 to 5.0. The chiral recognition mechanisms between the racemates and the chiral selector are discussed. Copyright ­© 2003 John Wiley & Sons, Ltd.

Rapid Determination of Sildenafil Citrate in Pharmaceutical Preparations Using Monolithic Silica HPLC Column

Abstract: A simple, rapid, and sensitive high performance liquid chromatography (HPLC) method has been developed and validated for the determination of sildenafil citrate in pharmaceutical preparations. The ...

Chiral resolution of some environmental pollutants by capillary electrophoresis

Abstract: The chiral resolution of the environmental pollutants by capillary electrophoresis is reviewed. Various aspects of the chiral resolution such as chiral selectors, optimization of capillary electrophoresis conditions including composition of the background electrolyte (BGE), pH of the BGE, ionic strength of the BGE, structures and types of the chiral selectors, applied voltage, temperature, structures of the chiral pollutants, use of organic modifiers and other parameters are presented. Furthermore, detection, sample treatment, validation of the methods, and the chiral recognition mechanisms, have been discussed.

Effect of psoralens on Fenton-like reaction generating reactive oxygen species.

Abstract: Psoralens (psoralen, 5-methoxypsoralen, 8-methoxypsoralen, khellin, and visnagin) in 1 mM doses were shown to enhance the generation of reactive oxygen species, such as the hydroxyl radical (HO·), the superoxide anion radical ( ), and singlet oxygen (1O2), from the system generating chemiluminescence (CL), as well as free radicals in the absence of light. The system that generated CL was made up of CoCl2 and H2O2. Incubation of psoralens in 0.2 mM doses with the generating system showed that only 8-methoxypsoralen and khellin have antioxidative effects. Antioxidative effects were also observed in the case of visnagin but in low concentration (0.05 mM). High doses of psoralens (1 mM) showed prooxidative effects. Measurements were done using a deoxyribose assay, the CL method, and spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide and 2,2,6,6-tetramethylpiperidine combined with electron spin resonance spectroscopy and spectrophotometry methods. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 59–68, 2003

A validated method development for ketoprofen by a flow-injection analysis with UV-detection and its application to pharmaceutical formulations.

Abstract: A simple, sensitive and fast flow-injection analysis method with UV-detection method was developed for the determination of ketoprofen in pharmaceuticals. The standard and sample solutions were dissolved in a 10% ethanol which was suitable for this study. A flow-rate of 0.6 ml min −1 was used and the analyte was monitored at 260 nm. Variables such as concentrations, flow rate of reagents and other flow injection parameters were optimized to produce the most sensitive and reproducible results. Linear calibration curves were obtained in the range of 1.6×10 −6 and 1.7×10 −4 M. Limit of detection and limit of quantification were 1.7×10 −6 M ( S / N =3.3) and 5.3×10 −6 M ( S / N =10), respectively. The method was applied successfully to the analysis of ketoprofen pharmaceutical tablets. The recoveries were 102.75% for peak area and 98.42% for peak height. The proposed method is fast, precise, sensitive and easy to use for the determination of ketoprofen in pharmaceuticals.

High throughput analysis of lamivudine in pharmaceutical preparations using monolithic silica HPLC column

Abstract: A new, rapid and sensitive high performance liquid chromatography (HPLC) assay was developed and validated, which utilized a monolithic column (100 × 4.6 mm I.D.) for the determination of lamivudine in pharmaceutical preparations. The method used a mobile phase consisting of acetonitrile/water (65:35, v/v) and flow rate of 2.0 mL/min. The elution of the analyte was monitored at 285 nm and conducted at ambient temperature. The method was validated with respect to linearity range, limit of detection and quantitation, precision, accuracy, selectivity, and robustness. The method exhibited low limit of detection (LOD) of 12.5 ng/mL, wide linearity range of 25–800 ng/mL and correlation coefficient (R 2) greater than 0.999. Parameters of validation prove the precision of the method and its applicability for the determination of lamivudine in pharmaceutical tablet formulations. The method is fast (less than one minute) and is suitable for high throughput analysis of the drug.

Enantioselective determination of arotinolol in human plasma by HPLC using teicoplanin chiral stationary phase.

Abstract: A sensitive enantioselective high-performance liquid chromatography (HPLC) method was developed and validated to determine S-(+)- and R-(-)-arotinolol in human plasma. Baseline resolution was achieved by using teicoplanin macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic T with a polar organic mobile phase consisting of methanol:glacial acetic acid:triethylamine, 100:0.1:0.1, (v/v/v) at a fl ow rate of 0.8 mL/min and UV detection set at 317 nm. Human plasma was spiked with stock solution of arotinolol enantiomers and labetalol as the internal standard. The assay involved the use of liquid-liquid extraction procedure with ethyl ether under alkaline condition for human plasma sample prior to HPLC analysis. Recoveries for S-(+)- and R-(-)-arotinolol enantiomers were in the range 93-103% at 200-1400 ng/mL level. Intra-day and inter-day precision calculated as %RSD was in the ranges 1.3-3.4 and 1.9-4.5% for both enantiomers, respectively. Intra-day and inter-day accuracies calculated as percentage error were in the ranges 1.2-3.5 and 1.5-6.2% for both enantiomers, respectively. Linear calibration curves in the concentration range 100-1500 ng/mL for each enantiomer showed a correlation coefficient (r) of 0.9998. The limit of quantitation (LOQ) and limit of detection (LOD) for each enantiomer in human plasma were 100 and 50 ng/mL (S/N = 3), respectively.

Optimization of the chiral resolution of baclofen by capillary electrophoresis using β‐cyclodextrin as the chiral selector

Abstract: The chiral resolution of baclofen was achieved by capillary electrophoresis using a fused-silica capillary (60 cm x 75 microm ID) The background electrolyte (BGE) was phosphate buffer (pH 70, 50 mM)-acetonitrile (95:5 v/v) containing 10 mM beta-cyclodextrin The applied voltage was 15 kV The values of alpha and R(s) were 106 and 100, respectively The electrophoretic conditions were optimized varying the pH and the ionic strength of the BGE, concentrations of beta-cyclodextrin and acetonitrile and the applied voltage

Investigation of the Reaction Kinetics of o‐Phenylenediamine in the Presence of Cu(II)

Abstract: The reactions involving o‐phenylenediamine (OPDA) in the presence of Cu(II) was studied and the reaction rate was found to be v = k[Cu2+]/[o‐phen]. Using a perpetual change curve, the ratio of [Cu2+]/[o‐phen] was found to be 1:1. The rate equations perpetual change curve demonstrates that one molecule of OPDA reacts with one Cu2+ ion and a monoimine is formed as the transfer of one electron occurs in the oxidation reaction.

Effects of the vasoactive intestinal peptide on stress-induced mucosal ulcers and modulation of methylation of histamine in gastric tissue of the rats.

Abstract: Vasoactive intestinal peptide (VIP) prevents stress-induced gastric ulcers, inhibits mast cell degranulation and protects gastric tissue from lipid peroxidation. Histamine has an important role in the development of gastric ulcers and mast cell derived histamine might be essential in this process.

Rapid Determination of Naproxen Sodium in Pharmaceutical Formulations by Flow Injection Analysis (FIA) Using UV‐Detection

Abstract: A flow injection analysis (FIA) of Naproxen sodium (NAPS) using UV detection is described in this study The best solvent system used as a carrier solution was found to be an aqueous solution of EtOH (10% v/v) A flow‐rate of 12 mL min−1 was used and Naproxen was detected at 230 nm Repeatability was examined using 8 × 10−6 M NAPS solution and relative standard deviation (RSD) values were found to be about 22 for intra‐day and inter‐day studies The calibration equation was the linear range of 4 × 10−6 to 118 × 10−5 M Limit of detection (LOD) and limit of quantification (LOQ) were calculated as 58 × 10−7 (S/N = 33) and 17 × 10−6 M (S/N = 10), respectively The proposed method was applied for the determination of NAPS in pharmaceutical tablet formulation, containing 275 mg active material The proposed method is reliable, precise, accurate, and rather cost effective, and can be applied for uniformity tests in NAPS tablets

Thin layer chromatographic resolution of some 2‐arylpropionic acid enantiomers using L‐(−)‐serine, L‐(−)‐threonine and a mixture of L‐(−)‐serine and L‐(−)‐threonine‐impregnated silica gel as stationary phases

Abstract: Impregnated silica TLC plates with L-(−)-serine and L-(−)-threonine and a mixture of L-(−)-serine and L-(−)-threonine (1:1) as chiral selectors were prepared to use as chiral stationary phases (CSPs) in thin layer chromatography. The resolution of the enantiomers of 2-arylpropionic drugs, including ibuprofen, ibuproxam, ketoprofen, pranoprofen, benoxaprofen, flurbiprofen and tiaprofenic acid was investigated on these CSPs. A mobile phase system of acetonitrile–methanol–water (16:4:0.5, v/v/v) was used. The spots were detected with iodine vapours and the detection limits were found to range between 0.25 and 0.5 µg/mL for all racemic compounds investigated. The effect of temperature, pH and concentration of the impregnating chiral selectors on resolution has been studied. Copyright © 2003 John Wiley & Sons, Ltd.

Biotin dissolution from pharmaceutical dosage forms using an automated HPLC system

Abstract: A novel, rapid, accurate, and sensitive automated high‐performance liquid chromatographic assay was developed to determine biotin (BI) in pharmaceutical dosage forms and to follow its dissolution pattern. An efficient separation of BI was performed using a stainless steel Supelcosil LC‐18 column (25 cm × 4.6 mm; 5 µm particle size) preceded by a Sentry guard column. The mobile phase consisted of an 80% aqueous solution (pH 2.5 adjusted with phosphoric acid) containing 20% acetonitrile delivered at a flow rate of 1.5 mL/min. The compound of interest was detected using a photodiode array detector at 190 nm. Under these conditions, the assay run time was 6 min since the retention time of BI was 3.8 ± 0.2 min. The detector response was linear for BI in alkaline solution (r > 0.999) in the range of 0.01–2.00 µg/mL. The detection and the quantification limits for BI were 0.005 and 0.01 µg/mL, respectively. The dissolution data showed RSD% of 3.6–12.7% for all BI determined concentrations. No interferen...

Enantioseparation of Organophosphonate Derivatives on Amylose Tris(3,5‐Dimethylphenylcarbamate) Chiral Stationary Phase by HPLC

Abstract: The enantiomers of fourteen O,O‐dialkyl‐2‐benzyl‐oxycarbonyl‐aminoaryl‐ methyl‐phosphonates are directly separated on tris(3,5‐dimethyl‐phenylcarbamate) amylose chiral stationary phases, known as Chiralcel AD. All of the selected compounds are baseline separated. The influence of the position and properties of substituents in benzene rings, the length and steric hindrance of alkoxyl groups of the phosphonate ester on the chiral separation are discussed. When the substituents are in the para‐position of the benzene ring, the separation factor is in the following order α p‐NO2 ≫ α p‐Cl > α p‐CH3 > α p‐H > α p‐OCH3 . When the same substituent is in a different position of the benzene ring, the order of the separation factor is α p‐Cl > α m‐Cl and α p‐NO2 ≫ α m‐NO2 . The values of the separation factor α of the enantiomers where R 1 substituent is a hydrogen (R 1 = H) are always smaller than those of the enantiomers with p‐Cl substituent, whether R 2 was Me, Et, Pr or i‐Pr. Compounds with differen...

Influence of the Alcoholic Modifier on the Enantioseparation of Organophosphonate Derivatives on Cellulose tris(3,5-Dimethylphenylcarbamate) Chiral Stationary Phase Under Normal Phase Mode

Abstract: The enantiomers of fifteen O,O-dialkyl-2-benzyloxycarbonyl- aminoarylmethyl-phosphonates are directly separated on cellulose tris(3,5-dimethyl-phenylcarbamate) chiral stationary phase using different alcohols as organic mobile phase modifier. The influence of the position and properties of substituents in benzene ring, the length and steric hindrance of alkoxyl groups of the phosphonate ester on the chiral separation were discussed using different alcohol modifiers namely, ethanol, n-propyl alcohol, isopropyl alcohol, and n-butyl alcohol. The study indicates that with the use of different alcohol modifiers in mobile phase, the capacity factor (k) was in the order of k EtOH

Simple HPLC Method for the Determination of Enalaprilat in Human Plasma

Abstract: A simple and reliable isocratic reversed phase high performance liquid chromatography (HPLC) method for the determination of enalaprilat in human plasma is described. After plasma extraction, enalaprilat is analyzed using a µ Bondapak C18 column kept at 50°C. The mobile phase consists of 60% A (0.01 M KH2PO4, pH 4.0) and 40% B (80% of 50:50 CH3CN:CH3OH + 20% A) v/v. Enalaprilat is monitored by UV detection at 205 nm. The method is quite simple and sufficiently sensitive, with a limit of quantitation of 5 ng/mL and limit of detection of 1 ng/mL; within day and between‐days assays showed a relative standard deviation (RSD) below 15%.

Determination of S‐Adenosyl‐L‐methionine in Dietary Supplement Preparations by Capillary Electrophoresis

Abstract: A method for the quantitative determination of S‐adenosyl‐L‐methionine (SAM) in dietary supplement preparations using capillary zone electrophoresis (CZE) is described. Linearity was observed in a concentration range of 10–200 µg mL−1 with r = 0.9997. The limit of detection was 0.5 µg and the limit of quantification 2 µg. The intra‐day and the inter‐day precision was in the range of 0.52–0.89 and 1.15–1.60% RSD, respectively. The mean recovery determined by spiking with known amounts of SAM was 97.9%. Furthermore, stability investigations of SAM were carried out using this method.

Determination of formoterol by capillary electrophoresis and its application to inhaler capsules

Abstract: A capillary electrophoretic (CE) method for the determination of formoterol (FOR) in a pharmaceutical preparation is described. Analysis was made in a background electrolyte consisting of 20 % acetonitrile and 50 mM phosphoric acid at pH 2.5, using fused silica capillary (86 cm x 75 microm ID), 27 kV potential, and detecting at 200 nm. Under these electrophoretic conditions 3, 4-dihydroxybenzylamine used as an internal standard (IS) and FOR showed symmetrical peaks at 6.1 and 8.3 min., respectively. The inter-day and intra-day precision was examined in the concentration range of 2.98 x 10(-6) M to 8.94 x 10(-6) M. Good correlation and accuracy were obtained. Limit of detection, (LOD) and limit of quantitation (LOQ) values were 3.71 x 10(-7) M and 1.11 x 10(-6) M, respectively. The method was applied for the analysis of FOR in pharmaceutical inhaler capsules. The proposed method is reliable, precise, accurate, fast, and cost effective.

Estimation of uncertainties for the application of electrochemical sensors in clinical analysis

Abstract: The influence of the selection of type of electrochemical sensor, its design and calibration, data processing and sample history on the uncertainty of measurements in clinical analysis is discussed. Special requirements for in vivo analysis that may minimize the value of uncertainty of measurements are given.

Enantiomeric resolution of some human aldosterone synthase [CYP 11 B2] inhibitors on derivatized polysaccharide chiral stationary phases

Abstract: Aldosterone synthase (CYP 11 B2) is a mitochrondrial cytochrome P450 enzyme catalyzing the last steps of aldosterone production in the adrenal cortex. A new pharmacological approach for the treatment of the aldosterone-induced effects in congestive heart failure and all forms of hyperaldosteronism could be achieved through the use of (CYP 11 B2) inhibitors. The chiral resolution of some of active compounds, namely 1-(4-pyridyl(methyl)tetralin (I)), 7-chloro-1-(1-imidazolyl)tetralin (II), and 5-hydroxy-2-(4-pyridylmethyl)indane (III), on various polysaccharide derivative chiral stationary phases, namely Chiralcel OD, OJ, OC, and Chiralpak AD and AS, in normal phase mode was achieved. The mobile phase used was hexane/2-propanol/triethylamine (9 : 1 : 0.1 v/v/v). The flow rate of the mobile phase was 0.8 mL/min and the wavelengths of detection of compounds I, II, and III were set at 288, 271, and 254 nm, respectively. The chromatographic parameters: retention factor (k), selectivity (α), and resolution factor (Rs) were calculated. The chiral recognition mechanisms between these analytes and chiral selectors are discussed.

Chemical modification of milk xanthine oxidase with different modifiers.

Abstract: Xanthine oxidase (XO), purified from buttermilk was subjected to modification with N-phenylmaleimide, p-toluene-sulfonyl chloride, and 2-mercaptobenzimidazole. Spectrophotometric monitoring of the enzyme before and after treatment with these modifiers are presented. The results show that the interaction of XO with the modifiers was accompained by a change in UV absorption, as compared with untreated enzyme. The data indicate that these modifiers caused conformational changes in the polypeptide chain of milk XO due to interaction of these modifiers with sulfahydryl and/or hydroxyl groups. Moreover, the modifiers induce uptake inhibition of milk XO and appeared to be dependant upon either the concentration or incubation time.