Capillary electrophoresis portable

EC detection is a promising alternative for capillary electrophoresis microchips due to its inherent characteristics, allowing a proper miniaturisation of the devices and compatibility with the fabrication processes, in case of an integrated detection. Moreover, the low cost associated permit the employment of disposable elements. As the EC event occurs on the surface of electrodes and the decrease in size usually results in new advantages (see Chapter 32), the possibilities of incorporating EC detectors are broad. The simplicity of the required instrumentation, portable in many cases, suit well with the scaling-down trend. Moreover, as the sample volume in conventional micro-channel devices is less than 1 nL, a very highly sensitive detector should be constructed to analyse even modest concentrations of sample solutions. Since sensitivity is one of the accepted characteristics of EC detection EC-CE microchips approach to the ideal analytical devices. 

There can be found good reviews on conventional and microchip capillary electrophoresis in forensic/security analysis [4 7] in the literature. The aim of this chapter is to overview the progress which has been made towards the development of portable microfluidic device for on-site and fast detection of nitrated explosives and to describe the major developments in this field (summarized details on analytical methods for microchip determination of nitroaromatic explosives can be found in Table 35.2). The corresponding practical protocol for measurements of explosives on microfluidic device with amperometric detector is described in Procedure 49 (see CD accompanying this book). 

Jackson, D.J., Naber, J.F., Roussel, T.J., Jr., Crain, M.M., Walsh, K.M., Keynton, R.S., Baldwin, R.P., Portable high-voltage power supply and electrochemical detection circuits for microchip capillary electrophoresis. Anal. Chem. 2003, 75, 3643-3649. 

Because CE is a modular system that is easily put together with off-the-shelf components, it can be made small if required. The limiting component in terms of size is usually the power supply and the ruggedness of the system can be an issue. Also, there has not been the same level of demand for portable CE for field or point-of-care applications as there has for other techniques such as HPLC. Yuan et al. have described the use of a portable capillary electrophoresis system for analysis of neomycin compounds within four minutes. The instrument was suitcase-sized and the LOD of neomycin B obtained was 7 ppm. 

Yuan, L.L., Wei, H.P., Feng, H.T. and Li, S.F.Y. (2006) Rapid analysis of native neomycin components on a portable capillary electrophoresis system with potential gradient detection. Anal Bioanal Ghent, 385 (8), 1575-1579. 

The transposition of capillary electrophoresis (CE) methods from conventional capillaries to channels on planar chip substrates is an emergent separation science that has attracted widespread attention from analysts in many fields. Owing to the miniaturization of the separation format, CE-like separations on a chip typically offer shorter analysis times and lower reagent consumption augmented by the potential for portability of analytical instrumentation. Microchip (p-chip) electrophoresis substrates boast optically flat surfaces, short diffusion distances, low Reynolds numbers, and high surface (or interface)-to-volume ratios. By exploiting these physical advantages of the chip over conventional capillaries, efficient p-chip electrophoresis systems can accomplish multiple complicated tasks that may not be realized by a conventional CE system alone. 

The high separation efficiency of capillary electrophoresis is valuable for the analysis of proteins (27) however the concentration detection limits for UV absorbance detection is limited to the micromolar range. Capillary zone electrophoresis with laser induced fluorescent detection (CE-LIF) is an attractive technology because of its ultra-low sensitivity detection limits. (28) Further sensitivity can be gained by using a state-of-the art sheath-flow cuvette flow chamber. (29) A field portable, sheath flow cuvette based CE-LIF instrument has been constructed (Figure 3) for analysis of proteins in field and portable laboratories. 

In the future, capillary electrophoresis with electrochemical detection will continue to be important for the analysis of small volume samples. The direct coupling of microdialysis with CEEC yields a separation-based sensor that is capable of near real-time monitoring of drugs and neurotransmitters. New on-line systems for the detection of catecholamines and peptides are currently under development. Electrochemical detection is very amenable to miniaturization and, therefore, is uniquely compatible with the microchip format. In the future, the integration of microchip CEEC with microdialysis sampling will lead to truly portable separation-based sensors. 

Kappes, T. and Hauser, P.C. (1998) Portable capillary electrophoresis instrument with potentiometric detection. Ann/. Commun., 35 (10), 325-329. 

D.J. Jackson, et al.. Portable high-voltage power supply and electrochemical detection circuits for microchip capillary electrophoresis. Analytical Chemistry 75 (14) (2003) 3643-3649. 

Mai, T.D., Le, M.D., Saiz, J., Duong, H.A., Koenka, I.J., Pham, H.V., Hauser, P.C., 2016. Triple-channel portable capillary electrophoresis instrument with individual background electrolytes for the concurrent separations of anionic and cationic species. Anal. Chim. Acta 911,121-128. http //dx.doi.Org/10.1016/j.aca.2016.01.029. 

Mai TD, Pham TTT, Pham HV, Saiz J, Ruiz CG, Hauser PC (2013) Portable capillary electrophoresis instrument with automated injection and contactless conductivity detection. Anal Chem 85 2333-2339... 

Capillary electrophoresis (CE) is a separation technique for ionic or ionizable compounds. CE is particularly attractive because the instrumentation is inexpensive and separations are quick and efficient. As with GC and LC, CE can be coupled to and flame photometric detection (FED) to detect alkylphosphonic acids [30-32]. Indirect UV absorbance detection with CE has also been used for the analysis of nerve agents and their degradation products [33]. In an attempt to meet the demands of portable and efficient field instruments, miniaturized analytical systems with CE microchips have also been made for the separation and detection of alkylphosphonic nerve agents [34]. The aforementioned CE procedures all provide rapid identification without extensive sample preparation. CE is most likely to be used as a guide in order to select the appropriate methods for further analysis by more definitive techniques such as GC-MS, as most of the products detected and analysed are degradation products [35]. A review depicting various CE separation techniques, lab-on-a-chip technology and detection limits has been compiled by Pumera and is shown in Table 3.1. 

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