Detection methods in superheated water chromatography

Because water at elevated temperatures can be used as a mobile phase for reversed-phase HPLC or as an extraction solvent, it has attracted considerable recent interest as a green mobile phase, avoiding the use of organic solvents in analytical chemistry. Because of the low vapour pressure of water, even at 200 °C, the instrumentation required is simple and standard HPLC systems can be readily adapted by the addition of a high temperature oven and the creation of a pressure restrictor. This can be as simple as a 2-3 m length of narrow bore PEEK tubing or a mechanical SFC type restrictor

On-line coupled extraction and separation using superheated water for the analysis of the triazine herbicides

Superheated water extraction (SWE) has been coupled on-line with superheated water chromatography (SWC) via a solid phase trap. The extraction, trapping, release from the trap and chromatography are all controlled by altering the temperature and no organic solvents are required at any stage of the process. Cold and warm wash aqueous steps were included to remove humic acids and other interfering components of the compost samples

Applications of a novel flame ionisation detector for liquid chromatography

Over the last twenty years liquid chromatography has come to dominate analytical chemistry because of its ability to analyse a wide range of products from pharmaceuticals to environmental and forensic samples but some groups of analytes still cause practical difficulties in detection. The most common detector for HPLC is the UV-Visible spectroscopic detector, which is both sensitive and linear. However, detection is limited to analytes containing chromophores. For other analytes the analyst has to either rely on derivatisation or employ a “universal detector”, such as the less sensitive refractive index detector or the evaporative light scattering detector, which cannot easily detect small, volatile compounds. The universal flame ionisation detector when interfaced to LC has had problems in the past because of the signal from the organic component of the mobile phase, however, the use of superheated water as the eluent overcomes this problem and enables reversed-phase separations with the ability to detect analytes with and without chromophores. A revised design of interface (patent pending) enables a wide range of columns to be employed with differing flow rates

Hydrophobicity of highly ordered nanorod polycrystalline nickel and silver surfaces

Highly ordered nickel and silver nanorods arrays prepared by alumina template assisted electrodeposition were investigated to determine the effect of the array geometry on metal surface hydrophobicity and adhesion forces. The nanorod geometry, clustering and pinning were used to characterize surface hydrophobicity and its modulation. A contribution of metal crystallographic orientation to the surface energy was calculated. To characterize nanorod array surface properties and elucidate the source of the particle adhesion effects has been calculated. The dispersive components of surface tension D S γ and surface polarizability kS, as surface features that markedly characterize hydrophobicity and adhesion, were calculated. The highest hydrophobicity was found for Ag nanorods with aspect ratio of 10 then Ni nanorods with aspect ratio 10. The same geometry of nanorods particles resulted in different surface hydrophobicity and it was ascribed to the orientation of Ag and Ni crystals formed on the top of nanorods. Due to high hydrophobicity nanorod array surfaces could be used as an antifouling surface in medicine to select areas on implant surface not to be colonized by cells and tissues

HPLC Reference column CRM-722

The BCR-CRM is intended to be used:   to provide a separation column with known characteristics for certification exercises, e.g. in EC projects where RP-HPLC is conducted, or in any other round robin studies; to check the performance of an HPLC equipment (provide a chromatographic check on operating conditions, which could influence selectivity, relative retention and separation efficiency); to improve the accuracy, repeatability, reproducibility and transferability in HPLC analysis; as an independent secondary standard; to provide a help for accreditation, qualification/validation; as a benchmark column for column manufacturers

Solid phase microextraction of Eucalyptus ixophleba leaves

The volatile essential oils of the numerous Eucalyptus species have been widely studied for their chemical and commercial value, and also because a study of the oils can be used in supporting botanical relationships. In most cases the oils are obtained by traditional steam distillation methods, but also solvent extraction and headspace techniques have been employed