Isocratic Liquid Chromatography Research Articles

Liquid chromatography of erythromycin A and related substances on poly(styrene-divinylbenzene)

An isocratic liquid chromatography method for assay and purity control of erythromycin is presented. Erythromycin A is separated from all its potential impurities, except erythromycin D. The selectivity depends on the pore size of the poly(styrene-divinylbenzene) stationary phase. Wide pore PLRP-S 8 μm 1000 A shows the best selectivity. The column is heated at 70°C. The mobile phase is acetonitrile-2-methyl-2-propanol-0.2 M potassium phosphate buffer pH 9.0-water (3:16.5:5:75.5). The flow rate is 2 ml/min. UV detection is performed at 215 nm. The total analysis time is about 30 min. The method was used to compare official standards.

High performance liquid chromatographic analysis of a multicomponent product using a silica stationary phase and an aqueous—organic mobile phase

Elution behaviour of a drug substance in liquid chromatography (LC) depends on the interaction between the substance, the mobile phase and the stationary phase. Because of these interactions, isocratic LC assays of multicomponent drug products often require a compromise among the optimal chromatographic conditions for each drug. The analgesic combination in this report contains acetaminophen, butalbital and caffeine (Fig. l), three drugs of widely different physicochemical properties. Butalbital is a weak acid of pK, 7.6 [ 1, 21. In contrast, acetaminophen is neutral and caffeine is slightly basic. Also, butalbital is only slightly soluble in water (1: >lOO), compared with acetaminophen (1:70) and caffeine (1:50) [2]. Because of these differences, simul-

Analysis of Triglyceride Methanolysis Mixtures Using Isocratic HPLC With Density Detection

Abstract A simple and reliable method is described, which allows the determination of the overall content of tri-, di-, and monoglycerides in fatty acid methyl esters (FAME) by isocratic liquid chromatography using a density detector. The separation is achieved by coupling a cyano-modified silica column with two GPC-columns; chloroform with an ethanol content of 0.6% is used as an eluent. The response factors were determined experimentally for the pure triglycerides and methyl esters of various fatty acids as well as for the di- and monoglyceride of palmitic acid and calculated for the mixed products obtained in the methanolysis of vegetable oils. The performance of the method is demonstrated in the analysis of methanolysis mixtures of varying conversion.

Retention prediction and computer-assisted optimization for the separation of PTH-amino acids in isocratic reversed-phase liquid chromatography

Retention prediction of phenythiohydantoin amino acid derivatives in isocratic reversed-phase liquid chromatography was investigated. The predicted retention data of all derivatives were evaluated by comparing them with actually measured retention data. Excellent agreements between these data were found. The optimized conditions to separate overlapping components can also be predicted using the developed computer-assisted optimization system with the concept of retention prediction.

Reverse-Phase Liquid Chromatographic Determination of Lysine in Complete Feeds and Premixes, Using Manual Precolumn Derivatization

A sample portion is hydrolyzed with 6N HCl for 23 h and cooled, the pH is adjusted to 7.7 with NaOH, and the solution is diluted with pH 7.7 borate buffer. An aliquot of the sample extract is derivatized with 9-fluorenylmethyl chloroformate (9-FMC). Lysine is separated from other amino acids by isocratic reverse-phase liquid chromatography (LC) using fluorescence detection: 260 nm excitation and 313 nm emission. The mobile phase is acetonitrile-0.1M acetic acid (pH 4.2) buffer (53 + 47). Linearity is satisfactory over a range of 0.4-24 micrograms/mL. Results from 9 feed samples (1.1-2.7% lysine) analyzed by both the LC method and an amino acid analyzer were not significantly different statistically. Recovery of standard lysine, spiked just before derivatization on these same 9 samples (in duplicate), was 100.9% with a coefficient of variation (CV) of 2.4%. A study of within-day and between-day method precision resulted in CVs of 1.1 and 1.8%, respectively. The variation of results was negligible when the method was tested for ruggedness on 7 factors.

Estimation of tetrahydrobiopterin and other pterins in plasma by isocratic liquid chromatography with electrochemical and fluorimetric detection

Estimation of tetrahydrobiopterin and other pterins in plasma by isocratic liquid chromatography with electrochemical and fluorimetric detection

Improved Liquid-Chromatographic Determination of Quinidine in Plasma

Abstract Arrhythmic patients treated with quinidine have been found to ingest caffeine from various sources. Caffeine interferes with the quantitation of quinidine in plasma samples. This method for determination of quinidine in plasma is based on high performance isocratic liquid chromatography with the use of a C-18 bonded reverse phase column at room temperature. Unlike some liquid chromatographic procedures for quinidine, caffeine does not interfere. Quinidine is extracted from alkalinized plasma into benzene. The benzene layer is removed and evaporated to dryness under nitrogen at 50 C. The residue is reconstituted with methanol and injected into the column. The mobile phase is 30/70 (v/v) mixture of methanol/0.4% glacial acetic acid. Analysis can be completed within 10 minutes. The procedure is sensitive (0.5mg/L) and is well reproducible (CV= 3.5% for a 2 mg/L concentration in plasma).

Determination of ten anti-inflammatory drugs in serum by isocratic liquid chromatography

A high performance liquid chromatographic system has been developed for the resolution of ten anti-inflammatory drugs. Isocratic separation was achieved using a Spherisorb 5μm ODS column with an eluent consisting of water-orthophosphoric acid to pH 3.2: acetonitrile: methanol (52∶35∶13). A comparison was made between chloroform/acetonitrile (3∶2) and hexane/ether (1∶1) as solvents for the extraction of these drugs from serum.

Retinol, alpha-tocopherol, lycopene, and alpha- and beta-carotene simultaneously determined in plasma by isocratic liquid chromatography.

Retinol, alpha-tocopherol, lycopene, and alpha- and beta-carotene can be simultaneously determined in human plasma by reversed-phase liquid chromatography. Plasma--0.5 mL plus added internal standard, retinyl acetate--is deproteinized with 0.5 mL of ethanol, then extracted with 1.0 mL of petroleum ether. The organic layer is removed and evaporated, the residue is redissolved in 0.25 mL of ethanol, and 8-microL samples are injected into a 60 X 4.6 mm column of Hypersil ODS 3-microns particles at 35 degrees C. An isocratic methanol mobile phase, flow rate 0.9 mL/min, is used for the 9-min run. Retinol and retinyl acetate are monitored at 305 nm, the tocopherols at 292 nm, and the carotenoids at 460 nm. Between-run CVs were 3.1, 6.9, 6.1, and 6.5% for retinol, alpha-tocopherol, lycopene, and beta-carotene, respectively. Small sample requirement, simplicity of extraction, short run time, and good reproducibility make this procedure ideal for clinical or research use.

Optimization of mobile phase composition in liquid chromatography

A simple method is suggested for the optimization of the mobile phase composition in isocratic reversed-phase liquid chromatography. The function f = Σ(Rs,i -Rso)2, where Rs,i is the attained resolution for two successive peaks and Rso is the desired resolution for the chosen time of analysis (hence, a chosen capacity ratio of the last component eluted), was used as the chromatographic response function. The minimum of this function, corresponding to the optimum state, can be found rapidly by the statistical simplex method. This approach was applied to the separation of Cu, Co, Ni, Pb, and Hg diethyldithiocarbamates in a reversed-phase system with silica gel-C18.

Retention prediction of phenylthiohydantoin amino acid derivatives in reversed-phase liquid chromatography

The concept of retention prediction for the separation of phenylthiohydatoin-amino acid derivatives in isocratic reversed-phase liquid chromatography is described. A novel retention-solubility parameter, R, is defined, for the retention prediction strategy and the performance of this R value is evaluated by comparing measured and predicted retention data. Excellent agreement between these values were observed. It is concluded that the R value has a very high potential in describing the retention of phenylthiohydantopinamino acid derivatives withdifferent types of separation systems consisting of C-18, C-8 and phenethyl bonded stationary phases and various mobile phases.

Liquid Chromatographic Determination of Carbadox Residues in Animal Feed

A liquid chromatographic (LC) method for determining residues of carbadox in the 0.01-10 ppm range in swine feed is described. Carbadox is extracted from ground feed with 25% acidified methanol-CHCl3, removed from emulsion-forming coextractables via an alumina column, separated from highly colored pigments by acid-base liquid-liquid partitioning, and finally isolated from interferences on a second alumina column. Isocratic reverse phase LC at 305 nm is used for quantitation. The average overall recovery at the 0.1, 0.5, and 1.0 ppm spike levels was 83.0% with a standard deviation of 2.04% and a coefficient of variation of 2.46%.

Improved liquid-chromatographic determination of haloperidol in plasma.

This method for determination of haloperidol in plasma is based on "high-performance" isocratic liquid chromatography with the use of a C8 bonded reversed-phase column at room temperature. Haloperidol and the internal standard (chloro-substituted analog) are extracted from alkalinized plasma into isoamyl alcohol/heptane (1.5/98.5 by vol) and back-extracted into dilute H2SO4. The aqueous phase is directly injected onto the column. The mobile phase is a 30/45/25 (by vol) mixture of phosphate buffer (16.5 mmol/L, pH 7.0), acetonitrile, and methanol. Unlike other liquid-chromatographic procedures for haloperidol, commonly used psychotropic drugs do not interfere. Analysis can be completed within an hour. The procedure is extremely sensitive (1.0 microgram/L) and is well reproducible (CV 5.6% for a 2.5 micrograms/L concentration in plasma).

Preparation of chlorophylls and pheophytins by isocratic liquid chromatography

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPreparation of chlorophylls and pheophytins by isocratic liquid chromatographyTadashi. Watanabe, Akinori. Hongu, Kenichi. Honda, Masataka. Nakazato, Mitsuo. Konno, and Sadao. SaitohCite this: Anal. Chem. 1984, 56, 2, 251–256Publication Date (Print):February 1, 1984Publication History Published online1 May 2002Published inissue 1 February 1984https://doi.org/10.1021/ac00266a030RIGHTS & PERMISSIONSArticle Views576Altmetric-Citations150LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (758 KB) Get e-Alerts Get e-Alerts

Isocratic liquid chromatography method for the simultaneous determination of aspartame and other additives in soft drinks

Isocratic liquid chromatography method for the simultaneous determination of aspartame and other additives in soft drinks

Simultaneous determination of haloperidol and its reduced metabolite in serum and plasma by isocratic liquid chromatography with electrochemical detection.

We describe a liquid-chromatographic method for simultaneous quantification of haloperidol and its reduced metabolite in plasma and serum. Haloperidol and reduced haloperidol are concentrated from blood samples by liquid/liquid extraction into a hexane/isoamyl alcohol mixture, with chlorohaloperidol as the internal standard. For chromatographic separation we used a reversed-phase cyano-bonded column and a mobile phase of pH 6.8 phosphate buffer/acetonitrile (55/45 by vol). Haloperidol and its reduced metabolite are detected electrochemically at +0.90 V potential between the working and reference electrodes. As little as 0.5 ng per injection is detectable. Within- and between-day CVs for determinations of haloperidol and reduced haloperidol ranged from 4 to 7% each at a concentration of 10 micrograms/L. Haloperidol concentrations measured by this method correlated well with those by gas-chromatography with nitrogen-sensitive detector and by radioimmunoassay. The present method can be used to study the effects of haloperidol on the central nervous system. It is simple enough for use in clinical laboratories that are monitoring haloperidol concentrations in the blood of psychiatric patients.

Quantitative high pressure liquid chromatography of 6-thioguanine in biological fluids.

The determination of 6-thioguanine in human plasma and urine is described. By using isocratic reversed-phase high pressure liquid chromatography (HPLC) the purine analogues, 6-thioguanine, guanine, 8-azaguanine, allopurinol, oxipurinol, and uric acid, are completely separated within 8 min. the sensitivity of the assay for 6-thioguanine is 0.2 microgram/ml (1.2 x 10(-6) M) with a precision of 3.7%. The applicability for clinical monitoring in a patient's plasma and urine is demonstrated.

The Analysis of Putrescine in Plant Samples by Automated Hplc

Abstract The quantitative analysis of putrescine from plant tissue can be achieved using isocratic reversed-phase high performance liquid chromatography (HPLC). After preliminary extraction and clean up involving an ion exchange purification step, the isolated diamines are derivatised with benzoyl chloride for determination by HPLC. Automation of the HPLC step has led to a considerable saving in time for the total analysis. Potential problems associated with the analytical procedure are described.