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Matrix effects caused by thermally ionized elements in laser-enhanced ionziation (LEI) were reduced by using a water-cooled, coil electrode. The behavior of four different coils was studied. The performance of each coil was compared to that of a reference electrode fitting the description of the water-cooled, rodlike cathode designed at the National Institute of Standards and Technology. Both the linear dynamic range and limit of detection for this coil were generally comparable to those of the water-cooled reference electrode

The analysis of citrus oils is aided by the use of selective fluorescence detection with high-pressure liquid chromatography. The differing fluorescence properties of the nonvolatile components present in the oil make detection at one excitation and emission wavelength unsuitable. Therefore, replicate chromatograms are obtained at particulare wavelength combinations for the classification of those components based on peak intensity variations. From results with lime oil, this technique is successfully appied to lemon, grapefruit and bergamot oils.

Protein-dodecyl sulfate complexes, labeled at room temperature for 15 min under slightly basic conditions with 4-(3′-phenyl-2′-pyrazolin-1′-yl)benzenesulfonyl chloride, exhibit a fluorescence emission band centered at 420 nm. Their fluorescence intensity is independent of pH in the range 2–8. In polyacrylamide gel electrophoresis, their relative mobilities are not different from their unlabeled counterparts. The limit of detection for protein in solution is 2 μg/ml. Following electrophoresis of 10-μl sample volumes in 5-mm-diameter gel cylinders, and without extrusion from the glass tubes, the typical detection limit of the labeled protein-dodecyl sulfate complexes is 250 ng. The rate of increase of the fluorescence signal with increasing amount of labeled protein-dodecyl sulfate complex in the sample volume varies from one protein to another. The linear range for these growth curves is also different. These differences are related to the lysine content of each protein.

The development of direct fluorimetric scanning for thin-layer chromatogram analysis has introduced a versatile tool which has diversified applications in the analysis of citrus oils and potential for analysis of a wide variety of other natural products. The characterization of citrus oils from fluorescence and fluorescence quenching profiles which result from the presence of crystalline components in the oils can be accomplished. Quantitative determination of two coumarin derivatives, 5-geranoxy-7-methoxycoumarin and 5,7-dimethoxycoumarin, by in situ fluorimetry of lemon, lime, and bergamot oil thin-layer chromatograms provides an accurate and rapid procedure for quality control based on coumarin derivative content.

This report describes the relationship between the amount of sodium dodecyl sulfate present in a sample solution and the electrophoretic mobility of the protein-dodecyl sulfate complexes. In order to determine the extent of any conformational changes in the proteins and to establish a correlation between any of these structural changes and the electrophoretic behavior, visible absorption spectra and circular dichroism spectra were obtained for heme proteins in the presence of the same amounts of surfactants as used in electrophoresis. From the results obtained, it is apparent that the amount of sodium dodecyl sulfate present in the sample solution must be taken into consideration when performing a separation. Optimum experimental conditions are chosen for attaining enhanced separation and a maximized linear range of molecular weights of proteins that can be accurately determined.