Effect of the Wavelength of the Laser Beam on the Response of an Evaporative Light Scattering Detector

Evaporative light scattering detection: trends in its analytical uses

Evaporative light scattering detection (ELSD) is widely recognized as a universal tool for liquid and supercritical chromatographies. In addition, this detection technique is fully compatible with continuous-flow systems. In fact, the combination of continuous non-chromatographic techniques and ELSD affords the design of simple, reliable systems for extracting qualitative information. This paper reviews instrumental innovations regarding the miniaturization of evaporative light scattering detectors and their uses in micro and capillary liquid chromatography; also, it discusses their increasingly important role in the development of vanguard configurations for sample screening and the determination of total indices without the need for chromatographic separation. Moreover, it compares them with other types of chromatographic detectors in terms of performance. Finally, the potential of ELSD for solving real-life analytical problems arising from the need to meet (bio)chemical information needs is illustrated with various selected applications.

Application of a xenon arc lamp as a light source for evaporative light scattering detection

The standard tungsten-halogen light source used in a commercial evaporative light scattering detector (ELSD) was replaced with a 180 W xenon arc lamp. The xenon arc lamp possesses a broader spectrum in the UV region than the halogen source. The influence of the UV transmittance of five selected solvents was studied with a size-exclusion chromatography column. This solvent parameter was not observed to influence the ELSD response between the two light source settings. With the solvents studied, better sensitivity was obtained with the xenon arc lamp than the halogen lamp. This high-energy source was applied to ceramide III analysis with an octadecyl-grafted silica column and methanol:tetrahydrofuran 97:3 as the mobile phase, and the sensitivity of the quantification of ceramide III increased 16-fold for injected amounts of 14 approximately 140 ng. The molecular species in a sample of naturally occurring ceramides was analyzed using two C18 columns at 40 degrees C and gradient elution from 100% acetonitrile to 100% isopropanol in 30 min. The increased ELSD sensitivity achieved when using the xenon arc lamp allowed both the minor and major ceramide species to be observed, in contrast to the results achieved when the halogen lamp was used, where the increased photomultiplier voltage needed to observed the signals from the minor species caused the signals from the major ceramide species to occur above the detector response window.

High-performance liquid chromatography of lipids for the identification of human metabolic disease

We describe a system for quantitative lipid analysis employing ternary gradient high-performance liquid chromatography with evaporative light scattering detection. This technique was applied to extracts of cultured fibroblasts, cultured lymphocytes, and leukocytes and to liver and spleen biopsy specimens. Separation of nonpolar lipids, glycolipids, phospholipids, and sphingolipids was achieved in a single run. Detection did not depend on the presence of any specific chemical reactions, uv absorption, or fluorescence. The sensitivity of the technique is well below 200 ng for individual lipids, and many individual lipid classes were detected in samples as small as 1 mg of total protein, the yield of a single flask of cultured skin fibroblasts. The characteristic stored lipids cholesterol ester and sphingomyelin were seen in excess in human fibroblast cultures from patients with Wolman's disease and Niemann-Pick disease, respectively. A biopsy spleen sample from a patient with Gaucher's disease showed a large glucosylceramide peak. This system provides a tool for detecting lipids that accumulate in tissues of patients with currently unidentified metabolic storage disorders.