Double-T injector

Figure 4.2 A schematic diagram of an integrated polymer monolith NCE with ESI-MS detection, (a) 1, separation channel 2, double-T injector 3, ESI source 4, eluent reservoir 5, sample inlet reservoir 6, sample waste reservoir 7, eluent waste reservoir that houses a porous glass gate 8, side channel for flushing the monolithic channel and 9, ESI emitter, (b) Cross-sectional view of reservoir 7, showing the position of the semipermeable glass gate, (c) Image of on-chip junction between the separation channel and the ESI emitter [25].

For EK injection, a cross-injector and a double-T injector have been constructed. The injection and separation modes for a cross-injector versus double-T injectors (with the 100- im and 250- im sampling loop ) were visualized as shown in Figure 4.1 [620]. 

It was found that a 250-pm double-T injector increased in the peak signal as compared to a straight cross-injector [548,620], Although a five-fold increase was expected based on the intersection volume calculation of a 250-pm injector versus a cross-injector, the discrepancy was likely to be caused by the back flow of... 

Various experimental conditions have been optimized for DNA sequencing on a glass chip. These conditions include separation matrix (denaturing 3-4% LPA), separation temperature (35—40°C), channel length (7.0 cm), channel depth (50 pm), injector parameters (100-pm or 250-p.m double-T injector, 60-s loading time). These optimal conditions facilitated the one-color detection of separation of 500 bases of M13mpl8 ssDNA in 9.2 min, and four-color detection of 500-base separation in 20 min [548]. 

FIGURE 9.22 Mask pattern for the 96-channel radial CAE microplate (10 cm in diameter). Separation channels with 200-pm double-T injectors were masked to 10-pm width and then etched to form 110-pm-wide by - 50-pm-deep channels. The diameter of the reservoir holes is 1.2 mm. The distance from the injector to the detection point is 33 mm [977]. Reprinted with permission from the American Chemical Society. 

EOF has been applied as a pumping or mixing mechanism in microreactors (Fletcher et al., 2002). Mixing concepts include the introduction of two (or more, see Kohlheyer et al., 2005) parallel streams from a T- of Y-junction, where mixing at the low Reynolds numbers achieved occurs principally by interdiffusion of the two streams. This is a relatively slow process which may take tens of seconds to complete. Faster mixing can be achieved by injection of a sample of a specific composition via, for example, a double T-injector into a stream of liquid with a different composition. 

Figure 7.1 Schematic of a microfluidic LC system. (A) Sample loading (B) sample analysis. 1A and IB, pumping channels 2A and 2B, eluent inlet reservoirs 3, eluent outlet reservoir 4, double-T injector that contains the sample plug 5, separation channel 6, sample reservoir 7, sample waste reservoir 8, sample inlet channels 9, sample outlet channels 10, ESI capillary emitter 11, LC waste reservoir. Note arrows indicate the main flow pattern through the system. (Reprinted with permission from ref. 33).

Figure 7.4 Microfluidic LC injector designs. (A) Double-T injector (B) on-column (head) preconcentrator (C) stand-alone preconcentrator (D) microfluidic arrangement for sample loading onto a particle packed on-column preconcentrator (E) enlarged view of a packed on-column preconcentrator with sample loading area highlighted (F) Rhodamine fluorescent dye loading at the front of the preconcentrator. (Adapted with permission from Ref. 33).

Fig. 5.3 A wireless ECL detection for chip-based CE. 1 sample reservoir 2 buffer reservoir 3 sample waste 4 buffer waste 5 double-T injector 6 separation channel 7 floating platinum electrode (leg width 50 pm, distance between legs 50 pm) 8 sample filled into the double-T injector 9 vacuum 10 direction of plug during separation. Adapted from Ref. [17]. Copyright 2001 American Chemical Society... 

Figure 3 shows data obtained in another device, Jet-1, with the layout indicated in the figure. The resistances of each of the channels of this device were determined as described above. The separation of fluorescein isothiocyanate (FITC) labelled arginine (arg) and tyrosine (tyr) is shown. For these experiments sample solution was present in reservoir 2, which was held at ground. As shown in the diagram at the top, samples were injected across a "double T" injector towards reservoir 1, which was at -3 kV. This injector creates a sample plug in the separation channel about 150 pm in length. 

A method for the determination of GSH was developed by using a microfluidic chip coupled with electrochemical detection [85]. In this method, the cell injection, loading, and cytolysis, as well as the transportation and detection of intracellular GSH, were integrated in a microfluidic chip with a double-T injector and an end-channel amperometric detector. A single cell was loaded in the double-T-injector on the microfluidic chip. The GSH from the single cell was electrochemically detected at an Au/Hg electrode. 

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