High throughput, outstanding certainty in peptide/protein identification, exceptional resolution, and quantitative information are essential pillars in proteome research. Capillary electrophoresis (CE) coupled to mass spectrometry (MS) has proven to meet these requirements. Soft ionization techniques, such as matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI), have paved the way for the story of success of CE-MS in the analysis of biomolecules and both approaches are subject of discussion in this article. Meanwhile, CE-MS is far away from representing a homogeneous field. Therefore the review will cover a vast area including the coupling of different modes of CE (capillary zone electrophoresis, capillary isoelectric foscusing, capillary electrochromatography, micellar electrokinetic chromatography, nonaqueous capillary electrophoresis) to MS as well as on-line preconcentration techniques (transient capillary isotachophoresis, solid-phase extraction, membrane preconcentration) applied to compensate for restricted detection sensitivity. Special attention is given to improvements in interfacing, namely addressing nanospray and coaxial sheath liquid design. Peptide mapping, collision-induced dissociation with subsequent tandem MS, and amendments in mass accuracy of instruments improve information validity gained from MS data. With 2-D on-line coupling of liquid chromatography (LC) and CE a further topic will be discussed. A special section is dedicated to recent attempts in establishing CE-ESI-MS in proteomics, in the clinical and diagnostic field, and in the food sector.

This review addresses the fundamentals governing the adsorption of individual protein molecules onto the surface of fused-silica capillaries, the protein aggregation to adsorbate clusters and their final accretion to monolayers with subsequent stratification to protein multilayers. The attention in CE protein separation has primarily been focused on (i) tuning the BGE including the buffer type, ionic strength, pH and additives, (ii) tailored post-rinse procedures to detach adhered protein residues and (iii) the optimization of capillary wall shielding in order to reduce protein attachment. Improvements in protein separation as well as related adverse effects are mainly discussed on the basis of parameters known to become deteriorated in case of protein adhesion, e.g. repeatability of the EOF and of migration times, peak width, theoretical plate numbers, resolution and asymmetry factor. However, knowledge of the molecular principles controlling protein adsorption onto silica surfaces is indispensable for separation optimization. Furthermore, it facilitates troubleshooting and the interpretation of undesired concomitant phenomena. This review comprehensively discusses protein adsorption models derived from surface chemistry primarily in terms of their relevance for CE, clearly showing that the adsorption process in its complexity is only partially revealed by models, which address single or binary protein solutions. In a further section theoretical concepts and surface models are related to surface phenomena encountered in CE. The final part of the review surveys recent concepts for prevention of protein adhesion, thereby addressing capillary treatment, favorable buffer types, dynamic and adhesive semi-permanent coating strategies covering the literature from 2000-2008.

A capillary zone electrophoresis (CZE) method with preceding cationic transient capillary isotachophoresis (tCITP-CZE) was developed for uncoated fused-silica capillaries to analyze metal-binding proteins (MBPs) of clinical relevance. UV detection was followed by mass spectrometry (MS). Optimization was done with model proteins of properties similar to relevant human MBPs. Using 1.0 mol x L(-1) formic acid (pH 1.78) as electrolyte resulted in up to 165000 plates m(-1) in CZE and 230000 plates m(-1) in combination with tCITP and analysis time was less than 5 min in uncoupled mode. Cationic tCITP with 125 mmol x L(-1) ammonium formate, buffered to pH 4.00, as leading electrolyte improved sample loadability considerably in comparison with sample stacking without impairing resolution. Following systematic optimization of the electrospray ionization process (ESI) the coupled system ((tCITP)-CZE-UV-ESI-MS) was tested with protein model mixtures and human MBPs. Repeatability of migration times was < 0.64% in pure CZE mode and in tCITP-CZE mode and < 0.83% in CZE-ESI-MS coupled mode. Mass accuracy was < 0.015%. Limits of detection were found to be in the range 50-160 fmol.

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Ground beef (GB) samples were maintained in atmospheres of 2 or 18% oxygen. Similar putrid spoilage occurred at both concentrations, although the microflora differed. Two of 10 isolates from fresh and spoiled GB, nonfluorescent pseudomonads, produced putrid aromas but only 4 volatile compounds in common when inoculated into sterile GB. AMorarelIa isolate produced a pronounced estery, decayed vegetable odor while others produced a decayed straw, ammoniacal or sour aroma. Differences in spoilage aromas apparently were not characterized by individual compounds but rather by the concentration of sulfur compounds and their ratio to other compound classes. Acetone, methyl ethyl ketone, dimethyl sulfide and dimethyl disulfide were indexes of microbial spoilage.