Instrumentation fluidics

The concept of an integrated micro-fluidic-based system has now been developed (Zhang et al. 2006), with an example shown in Fig. 7. This particular system is based on conventional chromatographic instrumentation and employs a multi-valving system, located between two syringe pumps, shown in the foreground, to enable the introduction of multiple reagents from an auto-sampler to be loaded onto the micro-reactor. Because of the low diffussional distances obtained in this sys-... 

S12. Swerdlow, H., Jones, B. J., etal., Fully automated DNA reaction and analysis in a fluidic capillary instrument. Anal. Chem. 69(5), 848-855 (1997). 

Sample injection in NCE is very important for reproducible results with low limits of detection. In spite of some development in NCE very little effort has been made to develop sample injection devices in this technique. Of course sample injection in NCE is a challenging job due to small volume requirement [87], The controlled injection of small amounts of sample is a prerequisite for successful analysis in NCE. Electrokinetic injection (based on electroosmotic flow) is the preferred method and Jacobson et al. [88] optimized sample injection using this approach. Pinched injection allowing injection in minute quantities [89,90] and double-T shaped fluidic channels [91] have also been used for this purpose. Furthermore, Jacobson et al. [92] used a single high voltage source to simplify instrumentation. Similarly Zhang and Manz [93] developed a narrow sample channel injector to improve... 

Fig. 1 Multiple-capillary instrument employing the sheath-flow technique. Key 14, capillary 18, capillary outlet 20, capillary inlet 22, buffer well 24, microtiter plate 26, quartz chamber 36, laser 38, laser beam 40, lens 58, fluidic stream. The electrodes are not shown nor is the device for delivering the sheath fluid. (Reprinted in part from U.S. Patent No. 5,741,412, Figure 1.)...

Biotrace International (Bridgend, UK) and was mounted so that the light measurements could be made directly from the reaction chamber. As a developmental iteration the National Instruments control hardware was substituted for electronic control components integrated into a light tight box together with the fluidic block. A compact controlling computer was built in order to make the device portable. 

Installation qualification (IQ) verifies that the instrument is received in good order as designed and specified by the manufacturer and is properly installed in the user s location. Table 9.2 lists the IQ steps recommended before and during installation. IQ should also include the analysis of a test sample to verify the correct installation of all modules including electrical, fluidics, and data connections. 

Although monitoring of a flowing sample is inherent to techniques such as mass spectrometry, flame atomic absorption spectrometry and chromatography, even when the instrument is operated manually these techniques are not considered to belong to the field of flow analysis by the analytical community. Therefore, a deeper discussion of these techniques, as well as capillary electrophoresis and micro-fluidic systems, is not undertaken. 

Recently, we described the first example of the coupling of a microfluidics device to a MALDI-TOF mass spectrometer, by integrating an on-chip microreaction unit with a MALDI-TOF standard sample plate.27 This allows (bio)chemical reactions to take place in the MALDI-TOF instrument. Since it is based on a pressure-driven fluidics handling method, using the vacuum in the ionization chamber of the MALDI-TOF-MS system, this approach avoids wires and tubes for feed and flow control. 

Figure 11.4 Passive pressure-driven mechanism of fluidics handling, (a) The liquid is kept in the inlet reservoirs by air (p=patm) present in the channel, (b) Inside the MS instrument the decrease in pressure at the outlet causes the liquid to flow to the outlet through the microchannel.

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