Reversed－Phase High－Performance Liquid Chromatographic Determination of Drugs of Abuse

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Application of High Performance Liquid Chromatography to Separation of Novel Chiral Tetrahedral Heterometal Clusters

A series of novel chiral tetrahedral heterometal clusters have firstly been separated on cellulose tris-(3,5-dimethylphenylcarbamate) stationary phase by high performance liquid chrom-atography, using hexane as the mobile phase with various alcohols as modifiers.     

High‐Performance Liquid Chromatographic Determination of Parecoxib in Human Plasma and Pharmaceutical Formulations

Abstract

A simple and sensitive RP‐HPLC method for the determination of parecoxib (PXB) in human plasma and pharmaceutical formulations has been developed and validated. The separation of PXB and the internal standard, ibuprofen (IBF) was achieved on a CLC C₁₈ (5 μ, 25 cm×4.6 mm i.d.) column using UV detector at 200 nm. The mobile phase consisted of acetonitrile‐water (92:8 v/v). The linear range of detection was found to be 0.9–18.4 µg/ml (r=0.9985). Intra‐ and inter‐day assay relative standard deviations were observed to be less than 0.3%. The method has been applied successfully for the determination of PXB in spiked human plasma and pharmaceutical preparations. Analytical parameters were calculated and complete statistical evaluation is incorporated.     

Integrated Micro Bio Systems and High Performance Liquid Chromatographic System on Chip

1　Microchemicalsystemonchip　　Microintegratedchemicalsystemsareexpect edaspromisingultrahighthroughputchemicalandbioprocessorswithextremelysmallvolume .Ourresearchgroupshaveproposedanddevelopedtheo riginalmethodologiesformicrointegrationofgen eralchemic…     

Integrated Micro Bio Systems and High Performance Liquid Chromatographic System on Chip

1 Micro chemical system on chip Micro integrated chemical systems are expected as promising ultra high throughput chemical and bio processors with extremely small volume. Our research groups have proposed and developed the original methodologies for micro integration of general chemical systems as well the electropho-     

Development and Validation of High‐Performance Liquid Chromatographic Method for Estimation of Lercanidipine in Rabbit Serum

Abstract

A new, simple, and sensitive reverse‐phase liquid chromatographic method was developed and validated for the estimation of Lercanidipine hydrochloride in rabbit serum using UV detector under isocratic conditions. After subjecting serum to simple and efficient one‐step extraction procedure, 100 µl of sample was injected onto high‐performance liquid chromatography system. The detector response was linear in the concentration range of 25–1000 ng/ml. The developed method was validated as per standard guidelines. Validation demonstrated accuracy, precision, and selectivity of the proposed method. The drug was found to be stable under various processing and storage conditions.     

Liquid Chromatographic Separation of Olefin Oligomers and its Relation to Separation of Polyolefins – an Overview

Summary: Linear and branched alkanes are oligomers of polyethylene. Alkanes with higher molar masses are called waxes. These substances are widely used as fuels, oils, lubricants, etc. and for these reasons many groups have tried to analyse, separate and characterise alkanes by various methods, including liquid chromatography. Alkanes may be separated according to their size in solution by SEC. In addition to chromatographic systems separating in the SEC mode, various sorbent-solvent systems have been published, where alkanes have been separated one from another by adsorption and/or precipitation mechanism. The mobile phase is either a non-polar solvent or a polar solvent or a mixture of a solvent and a non-solvent for alkanes. Even near critical conditions, which have several advantages for applications of HPLC in polymer analysis, have been identified for alkanes. Moreover, selective separations of branched alkanes according to their structure have been published. In the majority of these published studies, solvents with low boiling points have been used as the mobile phases, which do not allow dissolution of crystalline polyolefins at atmospheric pressure. However, taking into account experiences with the separation of alkanes, new HPLC systems for the separation of polyolefins may be developed. This is a major challenge and first results are presented in this contribution.     

Characterization of High‐Pressure Liquid Chromatography Columns using Chromatographic Methods

Abstract

A great variety of columns for liquid chromatography (LC) are available in dimensions ranging from industrial scale to micro‐bore, nano‐bore, and capillary size, and on‐chip columns. The columns may be used in various liquid chromatography modes or in capillary electrochromatography, depending on the support materials and stationary phase chemistry. Every year many new column types are introduced on the market, with improved selectivity and efficiency, long lifetime, and mobile phase compatibility, intended for general use, for liquid chromatography/mass spectrometry (LC/MS) applications, proteomic research, or for the analysis of other specific sample types. Considerable improvement in pH, high‐temperature, and high‐pressure stability of new column types, together with advances in the instrumentation, enabled introduction of capillary, high‐temperature, and ultra‐high‐pressure HPLC into routine practice. Even though reversed‐phase mode is still by the most widely used in contemporary LC, applications of other separation modes (such as ion, normal‐phase, or high‐interaction liquid chromatography (HILC)) have become more frequent recently, because of unique separation selectivity for certain sample types.

Characterization of column quality is not a simple task, because a number of factors should be taken into account, that affect the selectivity, efficiency and resolution of sample separation and the reproducibility of chromatographic data. These include the type of the support, the arrangement and density of the stationary phase on the adsorbent surface, the homogeneity of the chromatographic bed, etc. Various physicochemical techniques are used for characterization of the properties of column packings however, most of them are suitable for bulk materials only and cannot be directly applied for commercial columns without damaging them. Not to destroy the columns, often precious and expensive, practicing chromatographers can apply chromatographic methods to characterize columns and evaluate their analytical suitability under real‐life conditions, where the intermolecular interactions between the analytes, the stationary phase, and the mobile phases affect the retention. The present review reports various chromatographic tests and strategies available for column evaluation.     

High Performance Liquid Chromatographic Separation of Estradiol-17 α and -17/β in Biological Fluids; Application to Plasma,Milk and Urine of Cows

Abstract

A rapid HPLC technique was developed to separate estradiol epimers. In order to improve the sensitivity of the detection, a radioitmmunoassay was used.

Estrone, estradiol-17α and estradiol-17β were separated within 20 min using 10 ml of chloroform: acetone (90:10), as the mobile phase. The efficiency of the technique was assessed with ₃ steroids and the assay of collected fractions with antlsera specific to each estrogen. Using a non-specific radioimmunoassay, profiles of endogenous estrogens in different biological fluids (blood plasma, milk, urine) were obtained.

The efficiency of HPLC as a separation method and the high sensitivity of radioimmunoassay as a detector allows us to obtain profiles of estrogens from biological samples where steroid concentration is below lOOpg/ml.     

A Simple and Rapid Reversed Phase High Performance Liquid Chromatographic Method for Quantification of Alprazolam and α-Hydroxyalprazolam in Plasma

Abstract

A simple and rapid reversed-phase liquid chromatographic method for the determination of alprazolam and a-hydroxyalprazolam in plasma is described. Flunictrazepam was used as internal standard. Plasma samples were buffered with sodium borate and extracted with dichloromethane /n-pentane 4:6 v/v for 60 sec on a vortex apparatus. Extraction solvent was evaporated to dryness and extraction residues were reconstituted in the mobile phase. Samples were chromatographed on a 5μ Lichrospher RP-18 column (25cm × 4mm i. d) using acetonitrile/water 40:60 v/v as the mobile phase. The column effluent was monitored at 230nm. The lower limit of detection was 1ng/ml for alprazolam and a-hydroxyalprazolam while the lower limit of quantification was 2ng/ml for both compounds. Peak height and plasma     

Isolation of Thymosin α1 from Thymosin Fraction 5 by High Performance Liquid Chromatography

Abstract

An HPLC system for quickly isolating individual peptides from thymus extract is described. A series of reversed phase separations followed by ion-exchange HPLC produces pure peptides with minimal chromatographic time. A 2.4 gram column load of crude extract was carried through to the isolation of 4 mg of pure thymosin α₁ within 6–8 hours of chromatography.     

Performance and Attributes of Liquid Chromatography–Mass Spectrometry with Targeted Charge Separation in Quantitative Analysis of Therapeutic Peptides

Herein we describe a new method, targeted enhanced multiply charged scans (tEMC), for the quantification of therapeutic peptides in tandem mass spectrometry on the linear ion trap mass spectrometer. Therapeutic peptides with chain lengths between eight and 39 amino acid residues and charge states from 2+ to 6+ were used to evaluate and illustrate the method which relies on the ability to separate ions trapped in a linear ion trap according to their charges. In particular, interference from singly charged ions on multiply charged ions can be effectively minimized. The method requires optimization of relatively few parameters, the most important of which being the exit lens barrier (EXB) voltage, thereby offering substantial time saving in a high-throughput quantification environment that currently relies on selected reaction monitoring.     

Separation of the α-Tocopherol Model Compound 2,2,5,7,8-Pentamethyl-6-Chromanol from its Oxidation Products by High Performance Liquid Chromatography

Abstract

A rapid method is described for the separation of the α-tocopherol model compound, 2,2,5,7,8-pentamethyl-6-chromanol (6), from 9 of its oxidation products in a single 35 minute run. Separated derivatives of 6, in order of elution, included the 5-cholesteroxymethyl (1), spirotrimer (2), spirodimer (3), 5-formyl (4), 5-ethoxymethyl (5), dihydroxydimer (7), chroman dione (8), quinone (9) and pyrano xanthene (10). A normal phase system, using gradient elution is employed, the eluent being monitored at 290 nm. The minimum detection limit for compounds 1–8 was 0.1 μg per injection and for compounds 9 and 10 it was 0.3 μg per injection.     

Liquid Chromatographic Determination of NSAIDs in Urine After Dispersive Liquid–Liquid Microextraction Based on Solidification of Floating Organic Droplets

An environmentally benign method of sample preparation based on dispersive liquid–liquid microextraction and solidification of floating organic droplets (DLLME-SFO) coupled with high-performance liquid chromatography with ultraviolet detection has been developed for analysis of non-steroidal anti-inflammatory drugs (NSAIDs) in biological fluids. A low-toxicity solvent was used to replace the chlorinated solvents commonly used in conventional DLLME. Seven conditions were investigated and optimized: type and volume of extraction solvent and dispersive solvent, extraction time, effect of addition of salt, and sample pH. Under the optimum conditions, good linearity was obtained in the range 0.01–10 µg mL⁻¹, with coefficients of determination (r ²) >0.9949. Detection limits were in the range 0.0034–0.0052 µg mL⁻¹ with good reproducibility (RSD) and satisfactory inter-day and intra-day recovery (95.7–115.6 %). The method was successfully used for analysis of diclofenac, mefenamic acid, and ketoprofen in human urine. Analysis of urine samples from a patient 2 and 4 h after administration of diclofenac revealed concentrations of 1.20 and 0.34 µg mL⁻¹, respectively.

     

Quantification of Levosulpiride in Human Plasma by High‐Performance Liquid Chromatography

Abstract

An analytical procedure was developed and validated for the quantification of levosulpiride in human plasma. After subjecting a plasma sample to a two‐step extraction procedure, an aliquot of the aqueous phase was injected onto an high‐performance liquid chromatography system equipped with a fluorescence detector. The detector response was linear for levosulpiride concentrations in the range of 2.5 to 500 ng/ml. The intra‐ and inter‐day precision was below 15.4 and 10.1%, and the accuracy was in a range from 89.7 to 109.4%. The method is applicable for use in the pharmacokinetic characterization of levosulpiride after a 75‐mg oral dose in humans.     

Reversed‐Phase High‐Performance Liquid Chromatography with Electrochemical Detection of Anthocyanins

Abstract

Anthocyanins, flavonoid compounds present in grapes and wines, were determined by reverse‐phase high‐performance liquid chromatography (RP‐HPLC) with electrochemical detection (RP‐HPLC‐ED). The method developed consists of RP‐HPLC gradient elution with voltammetric detection using a glassy carbon electrode after separation in an Inertsil ODS‐3V analytical column. Good peak resolution was obtained following direct injection of a 50 µL sample of anthocyanins in a mobile phase of pH 2.20. The results show that six different anthocyanins: cyanidin‐3‐O‐glucoside chloride (kuromanin chloride), cyanidin‐3,5‐di‐O‐glucoside chloride (cyanin chloride), malvidin‐3‐O‐glucoside chloride (oenin chloride), malvidin‐3,5‐di‐O‐glucoside chloride (malvin chloride), delphinidin‐3‐O‐glucoside chloride (myrtillin chloride), and peonidine‐3‐O‐glucoside chloride, all with antioxidant properties, can be separated in a single run by direct injection of solution. The limit of detection (LOD) for these compounds was lower than 0.3 µM. The method can also be applied to the analysis of these compounds in red wines and in skins and pulp extracts of red grapes, since all these antioxidants are electroactive.     

Evaluation of Drug Interaction in Binding to Protein by High Performance Liquid Chromatography

Drugs in the body are bound to metabolizing enzymes, targets/receptors and transport proteins in certain extent. The binding of drugs to targets or receptors is mainly specific and responsible for its pharmacological and therapeutic effects. The metabolizing of drugs by enzyme involves both     

β-Blocking Agents: Determination of Biological Levels Using High Performance Liquid Chromatography

Abstract

Nine β-blocking agents have been tested and dosed by high performance liquid chromatography. Six of them, acebutolol an acebutolol metabolite, atenolol, metoprolol, propranolol and sotalol are detected with a fluorometric detector. Oxprenolol, pindolol and timolol can be quantified by their UV absorption at variable wavelength. A method is developped to find the best conditions of extraction and detection for each blocking agent. Experimental trials have led to a simple procedure for all compounds. Only pindolol and timolol plasma levels are non suitable for high performance liquid chromatography and need mass fragmentography or gas chromatography with electron capture detection.

However, pharmacokinetic parameters can be reached, for timolol and pindolol, through urinary excretion since sensitivity of the procedure is within the range of urinary levels.

The method has been applied, as well, to pharmacokinetic studies on sotalol, acebutolol, acebutolol metabolite, atenolol, propranolol, pindolol and timolol.     

Classification of Chili Powders by High Performance Liquid Chromatography‐Diode Array Detection

Abstract

The color pigments of six chili powders of different origins (China, Bali, Pakistan, Malaysia, India, and Thailand) were separated and quantified by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) using a narrow‐bore octadecylsilica column (Purospher, 125×3 mm I.D., Merck, Darmstadt, Germany), gradient elution, and diode array detector (DAD). The similarities and dissimilarities among the pigment composition of chili powders have been elucidated by principal component analysis (PCA). The RP‐HPLC separated 71–111 pigment fractions depending on the detection wavelength and on the origin of chili powder. The pigment composition of chili powders from Malayia and China showed marked similarities while the composition of pigments of other chili powders was different. It was concluded that RP‐HPLC–DAD can be successfully employed for the separation and quantitative determination of pigments of chili powders of various origins and may help the classification of chili powders and facilitate the authenticity test of such food products.