Search results for "COLUMN"

Determination of alinidine in human plasma by high-performance liquid chromatography.

1981

Non-porous microparticulate supports in high-performance liquid chromatography (HPLC) of biopolymers — concepts, realization and prospects

1986

On the measurement of consistent long-term retention factor values in micellar liquid chromatography

2007

Abstract In the field of the quantitative structure–retention and retention–activity relationships (QRAR and QSRR) is crucial to obtain consistent retention factors (k). For this purpose, two unbiased approaches to estimate k are used: (i) the IUPAC approach (based on the extra-column time correction) and (ii) the ‘2-references’ approach (based on the k estimation respect to two prefixed reference k values). Three reference chemicals were selected attending to their retention time, chemical stability and non-ionic character. Consistent retention factor values for these references were estimated for C18 chromatographic columns and Brij35 solutions as mobile phases after statistical analysis.…

Gel permeation Chromatography in coiled columns

1973

Whereas in gas chromatography the use of coiled columns is the usual procedure, in liquid chromatography the use of straight columns is favoured. Bent columns give an additional contribution to peak spreading which is of greater importance in liquid chromatography than in gas chromatography owing to smaller diffusion coefficients. The low linear velocities of the mobile phase used in gel permeation chromatography enable conditions to be found where the additional contribution of bending to peak spreading is small. In the separation of oligomers, columns of 2-mm tube diameter and 20-cm coil diameter were used. With total lengths of 10 and 20 m, theoretical plate counts of ca. 70,000 and 150,…

Analysis of pharmaceutical preparations containing local anesthetics by micellar liquid chromatography and spectrophotometric detection

1999

An HPLC procedure for the determination of six local anesthetics, bupivacaine, lidocaine, mepivacaine, procaine, propanocaine and tetracaine, in pharmaceutical silane ODS-2 C18 analytical column and spectrophotometric detection at 230 nm were used. The chromatographic tographic behaviour of local anesthetics with different micellar eluents of sodium dodecyl sulphate (SDS) is described. Selection of the adequate composition of the micellar mobile phase (SDS and 1-propanol concentrations) for the analysis of pharmaceuticals was studied. Adequate retention was achieved with an eluent containing 0.15 M SDS +10% 1-propanol at pH 3. Application of the proposed method to the analysis of eight phar…

Packing technology, column bed structure and chromatographic performance of 1-2-μm non-porous silicas in high-performance liquid chromatography

1989

This work is aimed at further elucidating the aggregation behaviour of micron- and submicron-size non-porous silicas and the column performance of 1–2-μm C18 silicas in reversed-phase high-performance liquid chromatography of low-molecular weight compounds. It is demonstrated that highly ordered, dense, porous aggregates of such silica beads were obtained by gravity settling and centrifugation. The slurry techniques applied at constant flow-rate and a pressure up to 50 MPa provided less-ordered aggregates, but generated an acceptable performance of columns when 1–2-μm C18 silica beads were employed. To operate columns of 53 mm × 4.6 mm I.D., the maximum flow-rate needs to be ca. 2.5 ml/min …

Isolation of chlorinated dibenzothiophenes by high-performance thin-layer chromatography

1991

Abstract Chlorinated dibenzothiophenes can cause environmental problems analogous to chlorinated dibenzodioxins and dibenzofurans. In the analysis of chlorinated dibenzodioxins by gas chromatography—mass spectrometry some unknown chlorinated compounds have been found. The chlorinated dibenzothiophenes have the same m/z values as the corresponding dioxins in low-resolution mass spectrometry and they are found in same planar aromatic compound fraction in alumina and carbon column chromatography. Some chlorinated dibenzothiophenes were synthesized to serve as model compounds in analytical work. High-performance thin-layer chromatography (TLC) with different plates and several eluents was tried…

Gas-liquid chromatographic analyses

1984

A mixture of all nine chlorinated 4-hydroxybenzaldehydes and the parent homologue was separated on a non-polar SE-30 capillary column using various isothermal and temperature-programmed operating conditions. The relative retention data for the compounds are given and the retention indices together with the retention index increments for each position of chlorine substitution are examined. The retention order 3-Cl<parent<2,5-di-Cl<2,3-di-Cl<3,5-di-Cl<2-Cl<2,3,5-tri-Cl<2,3,6-tri-Cl<2,6-di-Cl<tetra-Cl isomer obtained indicates that the effect of the position of substitution on the retention behaviour is greater than that of the number of chlorine atoms. The retention is maximal with 2-Cl and 2…

Multidimensional Column Liquid Chromatography (LC) in Proteomics – Where Are We Now?

2006

SilicaROD™ — A new challenge in fast high-performance liquid chromatography separations

1998

Abstract High performance liquid chromatography (HPLC) has become one of the most used methods for the analysis of compound mixtures in industry, especially for the quality control of products. Nowadays productivity is the major and dominant upcoming issue, i.e. the goal is to drastically reduce the analysis time and cost per analysis. The solution of the task is higher throughput and faster HPLC methods. Here we describe a new monolithic type of HPLC column, the SilicaROD™ column, which permits the fast HPLC separation of compound mixtures within a few minutes.