Injection voltage

Fig. 1 The view of the polar display with monitors arcs and control panel for SFT6000N board parameters. Recorded signal is from the eddy current probe moved along in a brass tube of inner diameter 20 mm with 2 mm holes as artificial flaws. SFT6000N card operates with 40 kHz injection voltage firequency.

As mentioned earlier, the injection conditions can be optimized by varying injection time and injection voltage. Figure 6A shows the linearity study plot of peak area versus injection... 

Sample concentration linearity was also evaluated at a fixed injection voltage of —5 kV and injection time of 25 s. Figure 9 shows the e-grams obtained from the linearity study. 

Different parameters such as electrode alignment, detection potential and separation/injection voltage can affect the good performance of the amperometric detection in microchips. 

On the other hand, although injection voltage does not directly influence the amperometric detection, it affects the analytical signals recorded. Thus, the influence of the injection voltage on the analytical signals has been studied in a PMMA microchip with an end-channel... 

Pt-wire detector (Fig. 34.8B) [19]. When an injection time is fixed, the peak current increases with the injection voltage. This could be due to the fact that a higher flow is obtained for higher voltages and a better-defined sample plug (with smaller dispersion) is obtained. When an injection voltage is fixed, the peak current also increases with the injection time. However, peaks are widened. Since an unpinched injection is performed, this peak current and width increase could be due to a small increase in the injected volume via dispersion at the intersection. 

Injection voltage is varied between +500 and + 2000 V and maintained for 5, 10, and 20 s. Separation is carried out by applying a voltage of +2000 V using a detection potential of +0.7 V and 50 mM Tris-based buffer pH 9.0. Choose optimal injection time/voltage taking into account of peak current (7P) and half-peak width (1U1/2). 

Detection potential (V) Injection voltage (V) Injection time (s) Separation voltage (V) tm (s)... 

Fig. 49.2. Microchip electrophoregram of 20 ppm 1,3,5-TNB, 2,4,6-TNT, 2,4-DNT, and 2,6-DNT. Detection electrode graphite-epoxy composite electrode separation buffer 15 mM borate buffer (pH 9.2, containing 20 mM SDS) separation voltage 1500 V injection voltage 1500 V injection time 5 s detection potential —0.5 V.

In one report, even though pinched injection was used, the actual injected amount did depend on loading time if the ionic strengths of the sample and run buffers did not match [552]. It was also found that unless the sample is strongly pinched, pinched injection will inject different volumes depending on the injecting voltage [71]. 

Sample is introduced into the capillary by hydrostatic injection (gravity, pressure, or vacuum) or by electromigration injection (voltage). 

Figure 147 The relative cascade-like pattern of the increase of triplet exciton monomolecular decay rate constant (/ = t 1) as a function of charge-injecting voltage in anthracene crystal. Consecutive trap-filled limits are indicated by C/TFL (1), /TFL(2) and C/TFL (3). Dotted line indicates the averaged (linear) dependence of A/ // 0 as resulted from the standard interpretation assuming a continuous increase in the charge density proportional to the injecting voltage [334]. Adapted from Ref. 240.

Figure 7 Impact of added acid on peptides using field-amplified electrokinetic injection. Conditions capillary, 40 cm (effective length) x 50 pm BF3 buffer, 50 mM phosphate, pH 2.5 buffer equilibration, 3-min rinse between runs, dip inlet in water prior to injection voltage, 30 kV injection, 10 kV for 15 s temperature, 30°C detection, UV, 200 nm sample, peptide GGR, 0.54 pg/mL GGYR, 0.92 qg/mL.

FIGURE 6.15. The temperature dependence of current injection voltage. Shown are the I-V curves of the same device taken under different temperature. 

ED (BGE optimization). Plackett-Burman design, CCD. Eactors BGE concentration, pH, injection voltage, injection time, separation voltage. Response resolution, migration time. 

In previous work of the same group (72), the electrokinetic injection of DNA fragments was optimized as well by means of a simplex method. CGE-LIF was also used. In this case, BGE concentration, sample injection voltage, and time were the factors to be optimized. The optimum conditions were reached after only nine experiments. Figure 6.5 shows the spatial evolution of the simplex method used in this work (the initial tetrahedron (vertices 1-4) and the subsequent movements of reflection and contraction). Vertex 9 was considered as the optimum for injection of the Ikbp DNA ladder (l.OmM TTE buffer, 20s injection, 55V/cm electric field injection). 

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