Two liquid crystal compounds, cholesterol-10-undeceneoate and 4-cyano-4‘-pentoxybiphenyl, are attached to the inner wall of a fused-silica capillary that has been etched by ammonium hydrogen fluoride. The bonding process involves formation of a hydride layer on the etched surface via a silanization reaction with triethoxysilane followed by attachment of the liquid crystal using a hydrosilation reaction. The etched surface is characterized by photoelectron spectroscopy (ESCA) and the inner wall after being chemically modified with the liquid crystal is analyzed by diffuse reflectance infrared Fourier transform spectroscopy. The surface properties of these materials are further probed by measuring electroosmotic flow as a function of pH. The performance of the etched chemically modified capillaries as a separation medium is evaluated by electrochromatographic experiments using mixtures of proteins, pyrimidine/purine bases and a nucleoside, benzodiazepines, the synthetic and metabolic compounds of serotonin, and other small basic molecules. In all cases, peak symmetry is good and efficiency is generally considerably higher than in packed capillary CEC. In some instances, there are significant differences in selectivity between the two capillaries indicating that the type of liquid crystal (cholesteric or nematic) is an important factor in the separation mechanism. Finally, during the evaluation period for the capillaries used in this study there was no significant loss in chromatographic performance, indicating that the long-term stability of these materials is good.

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Geflügelte Elefanten: eine unglaubliche Vorstellung? Mindestens genauso unvorstellbar erschien es vor einigen Jahren, dass der massenspektrometrische Nachweis von Proteinen oder Polymeren gelingen könnte. Die Technik der Wahl – die Elektrospray‐Ionisation – gehört heute zur Standardausrüstung von Massenspektrometern.

In this paper, we report on investigations related to the performance characteristics of two different types of etched chemically (n-octadecyl- and cholesterol-) modified capillaries in the open tubular format of capillary electrochromatography (CEC) for the analysis of synthetic peptides. The results confirm that the nature of the surface chemistry used to modify the capillary wall and type of chemically bonded group employed can affect the selectivity as well as the resolution of peptide samples. The results are consistent with the participation of selective peptide interactions with the bonded phase, although other factors, such as the morphology of the capillary wall surfaces, appear to be also involved. Moreover, several surprising observations related to peptide-specific multi-zoning effects have been observed. Additional experimental variables that can also be utilized to affect the retention of peptides in this approach to OTCEC include the type and percentage of organic solvent modifier employed in the eluent and the pH of the buffer system. To evaluate the reproducibility of different batches of the n-octadecyl- and cholesterol-modified capillaries and the stability of the chemically modified surface, the OTCEC selectivity and peak shape behavior of two small basic molecules (serotonin and tryptamine) and two proteins (turkey and chicken lysozyme) were also investigated. Finally, the use of the "bubble" cell technology for creating the detector window has been shown to provide significantly higher detection sensitivity with peptides, as compared with the conventional capillary format.

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Aqueous normal-phase chromatography was used for the analysis of metabolites in human saliva and urine samples. The column was packed with a silica hydride type separation material. Several gradients were tested with different mobile phase additives in order to produce retention for amino acids, small organic acids, and carbohydrates. Detection was done by TOF MS. In some cases the relative concentration levels of various metabolites in human saliva were compared for normal patients and patients with pancreatic cancer or pancreatitis. The reproducibility of retention of individual metabolites in these complex matrices was tested for several compounds.