Microchip separations

Liu, S., and Dolnik, V. (2006). Analytical applications on microchips. Separation Methods in Microanalytical Systems. Conference Proceeding. 

Data from A. W. Moore, Jr., S. C. Jacobson, and J. M. Ramsey, Microchip Separations of Neutral Species via Micellar Electrokinetic Capillary Chromotography, Anal. Chem. 1995,67, 4184. 

K. Uchiyama, H. Nakajima and T. Hobo, Detection methods for microchip separations, Anal. Bioanal. Chem., 379 (2004) 375-382. 

J. Wang, G. Chen and M. Pumera, Microchip separation and electrochemical detection of amino acids and peptides following precolumn de-rivatization with naphthalene-2,3-dicarboxyaldehyde, Electroanalysis, 15 (2003) 862-865. 

Pushing detection limits of nitroaromatic explosives into the parts per trillion (ppt) level requires sample preconcentration. Collins and coworkers used solid-phase extraction (SPE) of explosives from sea water which was followed by rapid on-chip separation and detection [18]. Explosives were eluted from SPE column by acetonitrile and were injected in the microchip separation channel. Lab-on-a-chip analysis was carried out in nonaqueous medium. The mixed acetonitrile/methanol separation buffer was used to produce the ionized red-colored products of TNT, TNB and tetryl [27,28]. The chemical reaction of the bases (hydroxide and methoxide anions) with trinitroaromatic explosives resulted in negatively charged products, which were readily separated by microchip... 

FIGURE 4.19 Microchip separation of an FITC-labeled synthetic peptide mixture following (a) electrokinetic injection (0.25 s) and (b) diffusion-based injection (0.5 s). Mobile phase 1 mM carbonate buffer (pH = 9.0 separation electric field 300 V/cm 1, FITC-Gly-Phe-Glu-Lys-OH 2, FITC-Gly-Phe-Glu-Lys(FITC)-OH 3, FITC 4, FITC-Gly-Tyr-OH. Analyte concentrations 1 + 2 = 4 = 50 iM [566]. Reprinted with permission from the American Chemical Society. 

FIGURE 6.16 Effect of surfactant type on the microchip separation of 2 mg/L TNT, 1 mg/L TNB, and 2 mg/L tetryl. The separation buffer contained MeCN/MeOH (87.5/12.5 ([v/v])), 2.5 mM NaOH, and with (a) no surfactant, (b) 0.5 mM CTAB, (c) 1.0 mM SDS. Applied separation field strength, 506 V/cm, using a 1-s floating injection. Colorimetric detection was achieved using a green LED source (505 nm) [622]. Reprinted with permission from Elsevier Science. 

Moore, A.W., Jr., Jacobson, S.C., Ramsey, J.M., Microchip separation of neutral species via micellar electrokinetic capillary charomatography. Anal. Chem. 1995, 67, 4184—4189. 

Reichmuth, D.S., Shepodd, T.J., Kirby, B.J., RP-HPLC microchip separations with subnanoliter on-chip pressure injections. Micro Total Analysis Systems 2003, Proceedings 7th ftTAS Symposium, Squaw Valley, CA, Oct. 5-9, 2003, 1021-1024. 

Wang, J., Pumera, M., Nonaqueous electrophoresis microchip separations Conductivity detection in UV-absorbing solvents. Anal. Chem. 2003 75, 341-345. 

Mass spectrometric detection has also been directly interfaced with microchip separations for drug detection. These studies, detecting imipramine and desipramine in fortified human plasma, show analysis of spiked analytes in clinical sample matrices for drug detection [3]. These widely used tricyclic antidepressants inhibit the reuptake of the neurotransmitters serotonin and norepinephrine in the central nervous system. Unfortunately, the 5-mg/mL detection limit found for these antidepressants with this method is not low enough to detect typical clinical levels of the drugs. Combinatorial library characterization and preclinical drug delivery studies should benefit, however, since the concentra-... 

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