CPN−1 coupled to gauge fields: Mean field theory and monte carlo results

We define a two parameter lattice field theory which interpolates between the O (2N) Heisenberg model, pure U(1) gauge theory, and a lattice version of the CP^N?1 model. The phase diagram in space-time dimension d=4 is obtained by Monte Carlo simulation on a 4⁴ lattice, and the nature of the phases is discussed in mean field approximation.     

Quantitative measurements on wetted thin layer chromatography plates using a charge coupled device camera

This paper presents the first study of imaging of spots on thin-layer chromatographic plates whilst still wet with solvent. Imaging and quantification of Sudan II after development with dichloromethane was carried out in both reflectance and transmission modes, using a charge coupled device (CCD) camera. The relationship between peak area and sample loading was established at low sample loading, and found to be linear over an order of magnitude for both wet and dry modes with r2-values > 0.99. All data processing was carried out using the Beer-Lambert equation. Curvature at high loadings in the plots of integrated absorbance as a function of sample loading was accounted for using an empirical expression designed for use with the Kubelka-Munk treatment and apparent absorbance of the stationary phase due to scattering. Results are consistent with an effective pathlength significantly longer than the thickness of the sorbent layer. The limit of detection on a dry plate (0.5 ng) was found to be lower than on a wetted plate (2 ng). Precision was found to be 1-4% RSD intra-plate and 8-14% RSD inter-plate. Results are compared with quantification of the same analyte on dried plates.     

Quantitative ultraviolet measurements on wetted thin-layer chromatography plates using a charge-coupled device camera

This paper presents the first study of the UV imaging of spots on thin-layer chromatographic plates whilst still wet with solvent. Imaging of spots of benzophenone during and after development was carried out using a charge-coupled device camera. Limits of detection were found to be 5ng on a wetted plate and 3ng for a dry plate and the relationship between peak area and sample loading was found to be linear in the low nanogram range over an order of magnitude for both wet and dry modes with r(2) values>0.99. It was found that UV measurements on wet glass-backed plates suffer from low sensitivity; however, the use of aluminium-backed plates gave increased sensitivity. The apparent absorption coefficient epsilon(app) of 10AUm(2)g(-1) at 254nm is consistent with reflection of the light from the aluminium surface with a double pass through the sorbent layer, and suggests that use of aluminium-backed plates should enable monitoring of separations by UV absorbance during TLC development.     

TLC Image Capture and Analysis by use of a Prototype Device for Visualizing Fluorescence

JPC – Journal of Planar Chromatography – Modern TLC - This paper reports the evaluation of a novel, low-cost imaging device for use in TLC — a commercial flat-bed scanner modified...     

Development and assessment of a miniaturised centrifugal chromatograph for reversed-phase separations in micro-channels

This paper describes the micro-fabrication and preliminary assessment of a miniature polydimethylsiloxane (PDMS) device for performing rapid, parallel liquid phase chromatographic separations driven by centrifugal force in microchannels. Device components include a main separating channel, into which a high performance liquid chromatography (HPLC) particulate stationary phase was packed under pressure by application of centrifugal force, in addition to solvent and sample reservoirs. Also described are methods for sealing such devices based upon partial polymerisation of PDMS. The mobile phase flow rate through a typical device was measured and several important chromatographic parameters determined from a test separation. An expression describing mobile phase flow through packed channels was also developed, based upon work on liquid flow in open micro-channels. Good agreement between predicted and measured flow rates were observed. Some predictions for potential uses of such devices and possibilities for further miniaturisation are discussed.     

Use of p-Benzoquinone as a TLC Derivatization Reagent for 2-(Methylamino)ethanol and for the Analysis of Other Primary and Secondary Amines

JPC – Journal of Planar Chromatography – Modern TLC - TLC is an ideal technique for quantitative analysis of an ethanol-amine compound, 2-(methylamino)ethanol. A semi-quantitative TLC...