Most Cited Articles:

Abstracts


[Back to top]
Comparative Study of the Derivative and Partial Least Squares Methods Applied to the Spectrophotometric Simultaneous Determination of Atorvastatin and Amlodipine from their Combined Drug Products
Siavash Riahi, Mohammad R. Ganjali, Eslam Pourbasheer and Parviz Norouzi

The simultaneous spectrophotometric determination of Atorvastatin calcium (ATV) and Amlodipine besylate (AML) in tablets in the presence of the overlapping spectra was accomplished with the derivative spectrophotometry (DS) and the partial least squares (PLS) approaches without using any chemical pre-treatment. In this study, the concentration model was based on the absorption spectra in the range of 220-400 nm for 25 different mixtures of ATV and AML. The calibration curve was linear over the concentration range of 10-160 and 3-33 μg mL^-1 for ATV and AML, respectively. These two methods were tested by analyzing the synthetic mixtures of the above drugs and they were applied to the real samples, containing two commercial pharmaceutical preparations of the subjected drugs. A comparative study was carried out using the experimental results obtained from the two analytical methodologies. The root mean squares differences (RMSD) with PLS and DS were 0.6618 and 1.2555 for ATV and 0.1589 and 0.3490 for AML, respectively. It should also be mentioned that the accuracy of the PLS method was better than that of DS.


[Back to top]
Application of a New Tramadol Potentiometric Membrane Sensor as a Useful Device for Tramadol Hydrochloride Analysis in Pharmaceutical Formulation and Urine
Mohammad R. Ganjali, Taherehsadat Razavi, Farnoush Faridbod, Siavash Riahi and Parviz Norouzi

Tramadol, a 4-phenyl-piperidine analogue of codeine, is usually marketed as the hydrochloride salt and is a centrally acting analgesic, used for treating moderate to severe pain. In this study, a potentiometric liquid membrane sensors for simple and fast determination of tramadol hydrochloride in pharmaceutical formulation and urine was constructed. For the membrane preparation, tramadol-tetraphenyl borate complexes were employed as electroactive material in the membrane. The wide linear range (10^-5-10^-1 M), low detection limit (3 μg/ml), and fast response time (10s) are the characterizations of the proposed sensors. Validation of the method shows suitability of the sensors for applies in the quality control analysis of tramadol hydrochloride in pharmaceutical formulation and urine. The proposed method is found to be simple, accurate and precise which can be used as a detector for HPLC.


[Back to top]
An Orthogonal Approach to Chiral Method Development Screening
Anne Akin, Frederick J. Antosz, Jenny L. Ausec, Kimberly F. Greve, Rebecca L. Johnson, Lars-Erik Magnusson, Tore Ramstad, Stephen L. Secreast, Donna S. Seibert and Gregory K. Webster

Many of the new chemical entities under development in the pharmaceutical industry are chiral. The specific stereochemistry of these substances affects both the biological activity and commercial viability of the potential new drug. Thus, enantioselective separation techniques play a vital role in the development of these entities into commercial products.

In an attempt to improve upon the efficiency of chiral method development, column manufacturers and industry scientists have developed screening procedures to efficiently evaluate various chiral separation conditions in an unattended mode. While these systems have been shown to be successful in their initial and literature studies, it is important to evaluate these systems for the molecules of interest to each particular business concern. After optimizing the analysis conditions of several literature chiral screening procedures, the individual screens were challenged by novel chemical entities developed for commercial use. The entities were randomly selected based on availability and how well they represent molecules of interest to common pharmaceutical portfolios.

Our chiral screening program is currently focusing on four separation technologies: a) Liquid Chromatography (LC), b) Supercritical Fluid Chromatography (SFC), c) Capillary Electrophoresis (CE), and Gas Chromatography (GC). An overview of the results from each of these screens, future directions and a final unified strategy for chiral method development screening are presented.


[Back to top]
Mass Spectrometric Analysis of F₂-Isoprostanes: Markers and Mediators in Human Disease
Edzard Schwedhelm, Ralf A. Benndorf, Rainer H. Böger and Dimitrios Tsikas

Free radical-induced peroxidation of arachidonic acid and other polyunsaturated fatty acids esterified to lipids and subsequent hydrolysis generates prostaglandin-like compounds including the isoprostanes and neuroprostanes. These compounds are endogenously formed, characteristic in structure, stable, and accessible to quantitative determination in tissue, plasma and urine. Isoprostanes have emerged as reliable markers of lipid peroxidation in vivo in humans. Among them 8-iso-prostaglandin (PG) F_2α (8-iso-PGF_2α, 8-epi-PGF_2α, 15-F_2t-IsoP, iPF_2α-III) and its major urinary metabolites, i.e. 2,3-dinor-4,5-dihydro-8-iso-PGF_2α and 2,3-dinor-8-iso-PGF_2α, are subject of extensive investigation. Different analytical approaches are currently used to isolate, identify and quantify various members of the isoprostane and neuroprostane families. They include chromatographic approaches such as thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), and gas chromatography (GC), and in particular mass spectrometry (MS)-based techniques. Gas chromatography-mass spectrometry (i.e. GC-MS and GC-tandem MS), previously proved as the most reliable quantitative technique in the field of prostanoid research, was the first method which was applied to measure isoprostanes. In recent years, liquid chromatography-tandem mass spectrometry (i.e. LC-tandem MS) has also been introduced and established in the analysis of isoprostanes and related compounds. The present paper gives an overview of analytical methods currently applied to analyze isoprostanes in various biological matrices. Special emphasis is given to the quantitative determination in human urine which is a non-invasive method. In this context, the impact of solid-phase extraction (SPE), immunoaffinity column chromatography (IAC), HPLC, and TLC in sample preparation/purification is discussed. Differences in sample preparation depending on the biological matrix, i.e. tissue, blood plasma, and urine, are outlined. Furthermore, to meet increasing interest in isoprostanes as valid and stable markers of oxidative stress in human disease, results from various clinical trials in the cardiovascular field are discussed and relevant experimental findings as well as potential direct effects of isoprostanes in these pathophysiological settings are reviewed. Moreover, relevant clinical data from other disease entities is summarized in a schematic fashion.


[Back to top]
Chromatographic Performance of Silica-Based Stationary Phases in High Temperature Liquid Chromatography: Pharmaceutical Applications
Davy Guillarme, Rossana Russo, Serge Rudaz, Carlo Bicchi and Jean-Luc Veuthey

High temperature liquid chromatography is currently well established in separation sciences. The decrease of mobile phase viscosity with temperature provides fast separations with high efficiency, limiting excessive backpressure. Furthermore, the water polarity decreases with temperature allowing a reduction of the organic modifier content in the mobile phase. These advantages are already observed for temperature below 100°C.

Recently, the commercialization of dedicated instrumentation for preheating and cooling the mobile phase, and of new stationary phases stable at high temperature containing carbon, zirconia, titania or polymeric material, allows a routine use of high temperature liquid chromatography (HTLC). The latter stationary phases could however exhibit high retentions and different selectivity in comparison with the traditional silica-based columns. Therefore, embedded, hybrid or new silica-based stationary phases, possessing similar chromatographic behaviour and good thermal resistance at temperatures as high as 100°C, are often selected.

Kinetic, stability and chromatographic performance of a silica-based stationary phase (Zorbax Stable Bond) were evaluated up to a temperature of 120°C. This chromatographic support was successfully used for separating numerous drugs at ambient and high temperatures. Improvements of performance due to temperature increase were reported, such as the decrease in analysis time (separations in only few seconds) and the peak shape improvements (higher efficiency and lower asymmetry). Furthermore, several modifications of selectivity and the possibility to use a lower content of organic modifier into the mobile phase were demonstrated.


[Back to top]
Recent Advances in Chromatographic Methods to Detect Drugs of Abuse in Alternative Biological Matrices
Carolina D.R. de Oliveira, Marli Roehsig, Rafael M. de Almeida, Willian L. Rocha and Mauricio Yonamine

In recent years, many studies have been developed with the aim of improving drug detection in both conventional specimens and alternative biological matrices. A large number of drug abuse studies, forensic toxicology analyses, drugs in the workplace and even in doping control in sports activities related to drug detection in biological samples have been reported in the literature. The interest in the development and optimization of analytical techniques to detect drugs of abuse in different specimens is explained by the several possibilities and information that they can provide. Conventional samples such as urine and blood and more recently, saliva and sweat, are of fundamental importance whenever recent exposure to drugs is under investigation. Human keratinized tissues such as hair and nails are especially important for obtaining data of chronic long-term exposure with the great advantage of being collected in a non-invasive way. Meconium can be a useful biological sample to evaluate fetal drug exposure following maternal drug use. This paper reviews chromatographic procedures for determination of amphetamines, cannabinoids, opiates, nicotine, cocaine and alcohol in alternative biological matrices. Gas chromatographic and liquid chromatographic procedures with different detectors (including mass spectrometry) and sample preparation techniques such as liquid-liquid extraction (LLE), solid phase extraction (SPE) and solid phase microextraction (SPME) were considered.


[Back to top]
Development and Validation of a Rapid Chemometrics-Assisted Spectrophotometry and Liquid Chromatography Methods for the Simultaneous Determination of the Phenylalanine, Tryptophan and Tyrosine in the Pharmaceutical Products
Siavash Riahi, Mohammad R. Ganjali, Eslam Pourbasheer, Faten Divsar, Parviz Norouzi and Marzieh Chaloosi

The simultaneous multicomponent analysis is usually carried out using multivariate calibration models, such as the partial least squares (PLS). The genetic algorithm (GA) is a suitable method for the wavelength selection for the PLS calibration of the mixtures with almost identical spectra and without loss of the predictive ability, using the spectrophotometric method. In this work, a simple and precise method for rapid and accurate simultaneous determination of phenylalanine, tryptophan and tyrosine is proposed with the employment of the PLS regression together with GA for the variable selection. The method was successfully applied to the quantitation of these amino acids in aminoplasmal serum, providing results in agreement with those obtained by high performance liquid chromatography (HPLC).


[Back to top]
Proteases from South American Snake Venoms Affecting Fibrinolysis
Eladio F. Sanchez and Steve Swenson

Venoms of the viperidae (vipers and pit vipers) snakes are rich sources of proteinases which render fibrinogen incoagulable and solubilize fibrin. Many of these compounds have profound effects (stimulating or inhibiting) on the hemostatic mechanism, including, blood coagulation cascade, fibrinolysis, hypotension, vascular integrity and platelet function. The lethality of a venom often appears to be due to the combined action of several of these components, but severe consequences are frequently connected with hemostatic disorders. Viperid snake bite accidents in human and other large animals are characterized by localized or generalized bleeding and or thrombotic sequelae. This review is focused on the structural properties and features of a number of South American snake venom enzymes possessing clearly defined (pro)fibrinolytic activity. Under physiological conditions the venom proteins active on the plasminogen/fibrinolytic system can be grouped into two main categories: 1) direct-acting fibrinolytic endoproteinases which are related in amino acid sequence to the major family of metalloproteinases known as the metzincins. The members of this group are zinc-containing metalloproteinases (SVMPs) varying in size from 20 to 100 kDa and often more than one example is present in the same venom. 2) serine proteinases which specifically activate plasminogen into plasmin, and contain at least one catalytic domain structurally similar to trypsin. A number of these proteinases have been isolated and their mechanism of action established. Both direct and indirect endoproteinases on their own are practically nontoxic; however, they may act synergistically with other factors aggravating their toxic effects. Moreover, these proteinases are characterized by a relatively high degree of substrate specificity and resistance to physiological inhibitors. Indeed, some of these venom components are thought to hold promise as agents for medical applications in the field of thrombosis and diagnosis, or to hold the key for the design of pharmaceuticals.


[Back to top]
Immunochemical Analysis of Endogenous and Exogenous Estrogens
Meiping Zhao, Shuang Zhou, Jin Yan and Lin Li

Endogenous estrogens, namely estradiol, estriol and estrone are essential substances for the sexual determination, growth and reproduction of human beings. Their levels in the human sera are important index in monitoring pregnancy, evaluating menstrual dysfunctions and diagnosing many other diseases. On the other hand, many exoestrogens, including the phytoestrogen such as isoflavones, the synthetic estrogens such as diethylstilbestrol and chemicals of industry origin with suspected estrogenic activity such as bisphenol A and 4-nonylphenol, are drawing increasing attention in recent years. This paper reviews the main immunochemical analytical methods for these important estrogenic substances. The immunizing hapten design and its influence on the specificity of produced antibody were discussed. The typical available immunoassays including enzyme immunoassay (EIA), fluoroimmunoassay (FIA) and chemiluminescence immunoassay (CLIA) for the detection of estrogens were compared with respect to their features (especially dynamic range and limit of detection). The performance of different types of immunosensors with respect to their advantages and disadvantages were evaluated. The future developing trend in this field was also briefly discussed.


[Back to top]
Immobilized Polysaccharide CSPs: An Advancement in Enantiomeric Separations
Imran Ali and Hassan Y. Aboul-Enein

With the advancement of science and technology chiral chromatography has achieved an important place in analytical science. Coated polysaccharide chiral stationary phases (CSPs) are most popular due to their high chiral recognition power. But during last few years, immobilization of polysaccharide derivatives with silica gel has opened new realms in this area as these CSPs can be used with normal and prohibited solvents (tetrahydrofuran, chloroform, dichloromethane, acetone, 1,4-dioxane, ethylacetate, and certain other ethers). The present article describes status and method protocol of immobilized polysaccharides CSPs for the chiral resolution of different racemates using liquid chromatography. The contents of this article include methods of immobilization, their applications under optimized conditions, enantioselectivities, efficiencies and a comparison of the chiral recognition capabilities of coated vs immobilized CSPs.