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The amine derivatization reagent p-nitrophenol-2,5-dihydroxyphenylacetate bis-tetrahydropyranyl ether (NDTE) was used in conjunction with capillary electrophoresis (CE) and electrochemical detection (EC) for the pre-separation derivatization of primary amine analytes present in aqueous solution. Glycine, several dipeptides and angiotensin II were used as model analytes. A miniaturized EC detection cell was designed and fabricated, which featured a fractured-joint field decoupler with a fixed end-column carbon fiber electrode. When a series of glycine and angiotensin II calibration solutions were derivatized with NDTE followed by CE–EC determination, linear calibration plots resulted with pre-derivatization concentration limits of detection of 500 nM (106 attomoles on-column) and 6 μM (1.275 femtomoles on-column), respectively. [Copyright &y& Elsevier]

Many separation methods have been developed for biomedical analysis, including chromatographic ( e.g. high performance liquid chromatography (HPLC) and gas chromatography (GC)) and electrophoretic methods ( e.g. gel electrophoresis and capillary electrophoresis (CE)). Among these techniques, CE provides advantages in terms of high separation efficiency, simplicity, low sample and solvent volume consumption, short analysis time and applicability to a wide range of biomedically important substances. Microchip electrophoresis (ME) is a miniaturized platform of CE and is now considered as a simpler and more convenient alternative, which has demonstrated potential in analytical chemistry. High-throughput, cost-effective and portable analysis systems can be developed using ME. The current review describes different separation modes and detectors that have been employed in ME to analyze various classes of biomedical analytes ( e.g. pharmaceuticals and related substances, nucleic acids, amino acids, peptides, proteins, antibodies and antigens, carbohydrates, cells, cell components and lysates). Recent applications (during 2010–2014) in these areas are presented in tables and some significant findings are highlighted. [ABSTRACT FROM AUTHOR]

Abstract: Substance P (SP) has been associated with pain and depression as well as neurodegenerative diseases. Many of these diverse actions of SP can potentially be attributed to SP metabolites generated at the blood–brain barrier (BBB). In this study, the metabolism of SP was investigated using an in vitro model of the BBB and LC–MS/MS. Substance P metabolism was found to be non-saturable in the concentration range of 100nM to 10μM, with approximately 70% of the peptide remaining intact after 5h. The major metabolites of SP were identified by MS as 3-11 and 5-11. Two previously unreported metabolites, 5-11 and 6-11, were also found in our studies. Several additional minor SP metabolites, including 1-9 and 2-11, were also identified. A profile of the SP metabolites generated by the BBB over time was obtained. The results from the present study provide a better understanding of the role of the blood–brain barrier in the pharmacology of SP. [Copyright &y& Elsevier]

Abstract: The integration of rapid on-chip sample derivatization employing naphthalene 2,3-dicarboxaldehyde and 2-mercaptoethanol (NDA/2ME) with an easily assembled microdialysis/microchip electrophoresis device was carried out. The microchip device consisted of a glass layer with etched microfluidic channels that was sealed with a layer of poly(dimethylsiloxane) (PDMS) via plasma oxidation. This simple sealing procedure alleviated the need for glass thermal bonding and allowed the device to be re-sealed in the event of blockages within the channels. The device was used for analysis of a mixture of amino acids and peptides derivatized on-chip with NDA/2ME for laser-induced fluorescence (LIF) detection. A 0.6mM NDA/1.2mM 2ME mixture was simply added into the buffer reservoir for dynamic on-column derivatization of sample mixtures introduced at a flow rate of 1.0μl/min. Using this scheme, sample injection plugs were derivatized and separated simultaneously. Injections of ca. 12fmol of 5mM amino acid and peptide samples were conducted using the system. Finally, a three-component mixture of Arg, Gly–Pro, and Asp was sampled from a vial using microdialysis, derivatized, separated and detected with the system. The ultimate goal of this effort is the creation of a micro-total analysis system for high-temporal resolution monitoring of primary amines in biological systems. [Copyright &y& Elsevier]