The use of correlation techniques in chromatography has been critically examined both in the laboratory and by computer simulation. The origin of a number of previously reported difficulties is established and some basic guide-

Summary: Environmental scanning electron microscopy (ESEM) is a technique capable of imaging volatile and/or insulating samples in their natural state, without prior specimen preparation. It is thus a powerful potential tool for the study of the structure and dynamics of emulsions and other complex liquid systems, at a resolution greater than that obtainable by conventional optical microscopy. We present images of a variety of liquid systems containing micronscale and smaller features. The morphology of these systems may be clearly discerned. The contrast observed between the liquid phases was consistent with the model proposed by Stokes et al. (1998). The limits of resolution were determined by sample motion and by beam damage effects; under optimum conditions, resolution of a few tens of nanometers was obtained. This compares favourably with conventional and confocal optical microscopy. In some samples, thin films (solid or liquid) could be observed at the liquid/gas interface. Some of these films were so thin that they did not completely obscure the underlying structure of the bulk sample.

the combustion products of the vapor may already be so high as to bring about alterations in the properties of the flame and, consequently, in the magnitude of the net response. This may also constitute a factor contributing to the decrease of the net response. If the decrease were due to some variations in the working parameters (detector temperature, flow rate of the gases), it should be the same with both types of stationary phase.The above account indicates that the enhancement of the decrease in the net response due to the background one is likely a case applying especially to the flame ionization detector. Since this effect cannot be suppressed by any method of compensating for the background response, it is advisable that the use of stationary phases producing a high background signal be avoided in accurate quantitative analysis by gas chromatography.

No abstract

No abstract