Cross-injection analysis

Chips have also been applied to cross-injection analysis (CIA) [29] (see Figure 1.26). 

D. Nacapricha, P. Sastranurak, T. Mantim, N. Amomthammarong, K. Uraisin, C. Boonpanaid, C. Chu3fprasartwattana, P. Wilairat, Cross injection analysis concept and operation for simultaneous injection of sample and reagents in flow analysis, Talanta 110 (2013) 89—95. 

Some methacrylate chips built by combined use of VCarve and MACHS, (a) Chip on valve mounted atop the selection valve, (b) Chip designed for cross-injection analysis, (c) Chip especially used in kinetic methods. (For color version of this figure, the reader is referred to the online version of this book.)... 

FIGURE 1.12 (a) Schematic manifold of the stepwise injection analysis. (Adapted from Bulatov, A. V. et al. 2012. Talanta 96 62-67.) (b) Cross injection analysis manifold. P—peristaltic pump, MC—mixing column, V—switching vale, C—carrier solution, S— sample, R—reagents. (Adapted from Nacapricha, D. et al. 2013. Talanta 110 89-95.)... 

Proposed by Nacapricha et al. (2013), cross injection analysis (CIA) has passed the proof-of-concept phase. It is based on an analytical platform drilled in an acrylic rectangular block where a single channel (designated as analytical flow path) is placed in the X-axis... 

Isosbestic (crossing) points are observed when a solution contains variable proportions of two components with a constant total concentration. A Scatchard plot is used to measure an equilibrium constant, and the method of continuous variation allows us to determine the stoichiometry of a complex. In flow injection analysis,... 

LIF detection (X,cx = 351.1 nm, Xm = 440 nm) of two amino acids (0.58 mM glycine, 0.48 mM arginine) was achieved by pre-column derivatization with 5.1 mM o-phthaldialdehyde (OPA) [106]. A reaction chamber was constructed before the cross-injection (see Figure 6.33). The chamber is wider than the separation channel to allow for a lower electric field and hence longer residence time for the derivatization reaction [106]. This method may be more advantageous than post-column derivatization [317], when the analysis time is faster than the product reaction time (tm for OPA 4 s [106]). 

At about fhe same time, lin and coworkers [84] at fhe National Cheng Kung University in Tainan, Taiwan published fheir version of a chip, which is similar to that of Harrison s group in Alberta. This group had extensive experience in flow injection analysis and on-line analysis wifh conventional electrophoresis. In their design, a 3 mm wide X 40 pm deep sample inlet channel (SIC) was etched for sample flow-through, which in turn was connected to fhe electrophoretic manifold of 80 X 40 pm cross section, in a configuration similar to the Alberta chip (see... 

Y. Yang and R. E. Hairrell, Single Laser Crossed Beam Thermal Lens Detection for Short Path Length Samples and Flow Injection Analysis. Anal. Chem., 56 (1984) 3002. 

A flow injection analysis system (FIAS) for direct analysis of raw nrine was mentioned earlier (Lorber et al. 1997). No sample preparation was carried ont so the probability of cross contamination was negligible. The response profile of the ICPMS detector is typical of the FIAS sample introduction method, as shown for a calibration solution containing 100 ng L" uranium (top frame of Figure 4.11) and an actual raw urine sample containing 3.8 ng L (bottom frame). 

Hapten monolayer electrode sensor assembly was used to detect triazine in a flow injection analysis mode. The interaction of the electrode with different antibody concentrations resulted in the formation of an antibody-antigen (Ab-Ag) complex which insulated the electrode towards the [Fe(CN)6] /Fe(CN)6] " redox probe and diis in turn resulted in no charge transfer. The extent of insulation depends on the antibody concentration and the time of exposure to the antibody solution. The decrease in amperometric response of the antigenic monolayer to corresponding antibody solution for a fixed time produces a quantitative measurement of the antibody concentration. Typical responses obtained for cyanazine-hapten monolayer electrode to different antibody concentrations is shown in Figure 4. The lowest detection limit achieved for cyanazine sensor was 4.0 pg/ml at a response time of few minutes and a less-than 2% cross-reactivity to atrazine, simazine and other metabolites. 

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