Search results for "Capillary action"

High-resolution pyrolysis–gas chromatography with a movable reaction zone

1997

Abstract A new device was constructed for pyrolysis–gas chromatography and it was laboratory tested. The device enables the thermal degradation of polymers inside a capillary pre-column and transfer of the reaction zone into a column oven. The pyrolysis procedure described protects the thermally sensitive compounds prior to pyrolysis, prevents the process of irreversible condensation of high-boiling pyrolysis products during the chromatographic process and eliminates extracolumn effects on the peak broadening.

Gas—liquid chromatographic analyses

1984

Abstract The gas choromatographic retention behaviour of veratrole and all nine chlorinated veratroles was studied on SE-30 and OV-351 capillary columns. Temperature programming from 100°C at 6°C min−1 and isothermal operation at 140, 160, 180 and 200°C were used. The complete separation of a mixture was obtained on SE-30, the isomers being eluted in order of their degree of chlorination. On OV-351, however, the 3,4,5-trichloro and tetrachloro isomers overlap with temperature programming, being separated at 140, 160 and 200°C. Retention indices and increments of retention indices for each position of substitution are examined and the effect of increasing temperature on retention is discusse…

Application of a new glass capillary chromatographic technique in the analysis of phenoxyacetic acid herbicides.

1976

The application of porous silica layers in open tubular columns for liquid chromatography

1987

Two methods to realize a porous retentive silica layer on the inner wall of 10–25 µm fused silica capillaries for OTLC, etching and precipitation of silica from solution, have been investigated. Etching of the fused silica capillaries with 1M KOH, creates an activated surface, but the capacity of the silica layer is too small to serve as retentive layer in OTLC. Better prospects are offered by the precipitation of silica from a solution of polyethoxysiloxane, dynamically coated on the inner wall of the fused silica capillary. It appears to be possible to deposite a porous silica layer up to 0.8 µm thick (in a 25 µm capillary) by this method, which seems to be suitable for liquid-solid an dy…

Fast enantiomeric separation of propranolol by affinity capillary electrophoresis using human serum albumin as chiral selector: application to qualit…

2004

Abstract In the last years, capillary electrophoresis (CE) has gained considerable interest in pharmaceutical laboratories for controlling the chiral purity of drugs. This paper describes a simple and fast method for resolution of propranolol enantiomers by affinity capillary electrophoresis (ACE) using human serum albumin (HSA) as chiral selector. The effect of several experimental variables such as HSA concentration, temperature, chiral selector plug length and addition of organic modifiers, on the separation is evaluated. Complete enantioresolution of R- and S-propranolol was achieved in less than 5 min when the capillary was completely filled with 100 μM HSA solution and the electrophor…

Study on the efficiency of assembled packed microbore columns in HPLC

1984

Stainless steel columns (internally mirror-finished, 125 or 250nm in length, of bore 1.0 or 1.6mm) were slurry-packed with 5µm and 4µm reversed phase silicas (Hypersil ODS, LiChrosorb RP-8 and RP-18 and Superspher RP-8. The HPLC equipment consisted of a pump LC5A (Shimadzu) or a pump 2150 (LKB Instruments), a rheodyne valve 7413 with loops of 0.5, 1.0 and 5.0mm3 and a Jasco-Uvidec 100-II UV detector, variously with one of three specially constructed cells of 0.2, 0.4 and 1.3mm3 volume. Columns were assembled using two types of coupling device employing a stainless steel capillary of 0.12mm bore. The effect of sample volume, design of coupling device in assembled column, detector cell volume…

Assessment of haemoglobin measurement by several methods - blood gas analyser, capillary and venous HemoCue® , non-invasive spectrophotometry and lab…

2018

A laboratory haematology analyser is the gold standard for measuring haemoglobin concentration but has disadvantages, especially in neonates. This study compared alternative blood-sparing and non-invasive methods of haemoglobin concentration measurement with the gold standard. Haemoglobin concentrations were measured using a laboratory haematology analyser (reference method), blood gas analyser, HemoCue® using venous and capillary blood samples and a newly developed non-invasive sensor for neonates < 3 kg. A total of 63 measurements were performed. Body weight (2190 (1820-2520 [967-4450]) g) and haemoglobin concentration (12.3 (10.6-15.2 [8.2-20.5]) g.dl-1 ) varied widely. Bias/limits of ag…

Gas—liquid chromatographic analyses

1985

Abstract The gas chromatographic retention behaviour of methylethyl, 1-methylpropyl, 2-methylpropyl, 1,2-dimethylpropyl, 1-methylbutyl and 3-methylbutyl esters of benzoic and o-, m- and p-chlorobenzoic acids on low-polarity (SE-30) and polar (OV-351) capillary columns under several temperature-programmed and isothermal conditions is reported. The retention data and the Kovats retention indices for all 24 components are given and the separation of a complex mixture is discussed. The retention index increments have been used to examine the effects of chain branching and chlorine substitution. The results are compared with those for n-alkyl benzoates and monochlorobenzoates.

Theoretical and Experimental Studies of Capillary Hysteresis in MCM-41

1996

Mesoporous materials of MCM-41 type are considered to be reference model adsorbents due to their regular pore structure. Nitrogen adsorption isotherms on MCM-41 are modeled using the Non-Local Density Functional Theory (NLDFT). The thermal dependence of the thermodynamic hysteresis predicted by the NLDFT is confirmed by experimental measurements. The nitrogen hysteresis on MCM-41 at temperatures below 77.4 K or in pores greater than 4 nm is associated with the metastability of the adsorption branch of the isotherm. In the hysteresis regime, the desorption branch is likely to be thermodynamically stable and is recommended for calculating pore size distributions.

Direct measurement of forces between particles and bubbles

1999

One of the elementary stages of the flotation process is the formation of an aggregate between the particle and a bubble. This aggregate formation is governed by hydrodynamic, capillary and interparticle forces. During the last four years, techniques have been developed to measure directly the force between a colloidal particle and a bubble. These techniques are closely related to the development of atomic force microscopy. Advantages and possibilities, as well as limits and drawbacks are described.