Detecting Cell

For values of, (Xm(n)), where n l, however, they developed a separate mathematical argument, 

Some examples of the type of curves predicted by the theory of Atwood and Golay are given in figure 6. 

Elution Profiles as a Function of Tube Length for Low Aspect 

It is seen that from a short tube, of relatively large diameter, a broad asymmetrical peak is obtained and as the diameter of the tube is reduced (resulting in an increase in the efficiency of the tube in theoretical plates, (n)) the peaks become sharper in the front but with an extended tail. It should also be noted that the tube diameter must be decreased to a point where the efficiency, in theoretical plates, approaches the value of 30 

LC Detector Cell Designed to Introduce Secondary Flow and Reduce Dispersion 

---

As the (n)th plate of the column acts as the detecting cell, there can be no heat exchanger between the (n-l)th plate and the (n)th plate of the column. As a consequence, there will be a further convective term in the differential equation that must account for the heat brought into the (n)th plate from the (n-l)th plate by the flow of mobile phase (dv). Thus, heat convected from the (n-l)th plate to plate (n) by mobile phase volume (dv) will be... 

The alternative method is continuous-flow , in which the reactants flow through the detection coil during data acquisition. Continuous-flow NMR techniques have been used for the direct observation of short-lived species in chemical reactions [4—6]. The main difference between stopped- and continuous-flow NMR is that in the latter the sample remains inside the detection coil only for a short time period, termed the residence time, x [7], which is determined by the volume of the detection cell and the flow rate. The residence time alters the effective relaxation times according to the relationship in Eq. (2.5.1) ... 

Figure 5.3.8 displays a photograph of the actual combustion zone. The methane-xenon gas was mixed with air before entering the NMR detection cell in the probe head. The gas mixture was blown through an area with molecular sieve pellets (i.e.,... 

The detection of the migrating sample boundary in CE can be accomplished by UV, fluorescent, electrochemical, radiochemical, conductivity, and mass spectrometry (MS) means. The use of high-sensitivity detection systems is always a key issue in CE applications. The sensitivity of HPCE detectors may be at least 2 to 3 orders of magnitude better than that of HPLC detectors. Since the detection cell volume is very small, the concentration sensitivity... 

Numerous articles have demonstrated the availability of RNA extracted from a few cells or even a single cell taken by laser captured microdissection (LCM) system from archival FFPE tissue sections that had been previously stained by IFIC. Using a combination of pre-immunostained FFPE tissue section with LCM, a sensitive real-time quantitative RT-PCR can be achieved based on a few immuno-detected cells, creating a way to study pathophysiological gene regulation in a cell-specific manner in archival tissues housed in... 

Consideration should be given to the flow rate of the sample through the detection cell. Shultz and co-workers have demonstrated the wide variability in reaction kinetics between ECL reactions, and hence the influence of flow rate on ECL intensity [60], For example, the rate constants (k) of the Ru(bpy)32+ ECL reactions of oxalate, tripropylamine, and proline were calculated to be 1.482, 0.071, and 0.011/s, respectively. Maximum ECL emission was obtained at low linear velocities for slow reactions ranging up to high linear velocities for fast reactions. That is, the flow rate and flow cell volume should be optimized such that the light-emitting species produced is still resident within the flow cell, in view of the light detector, when emission occurs. 

Figure 9 Schematic diagram for capillary electrophoresis with postcapillary ECL detection. (A) Overview of the apparatus. (B) Enlarged view of the etched joint and ECL detection cell. The PMT (not shown) is positioned directly over the Pt working electrode, and the entire apparatus placed inside a light-tight housing. (From Ref. 64.)...

The flow rate can be altered either by changing the diameter of tubes or by changing the rotation speed of the roller, provided that all other parameters are kept constant. Modern pumps can be controlled by microcomputer and different flow rates can be established during one analytical measurement. The pump is usually located before the injection port but sometimes it can be placed after the detection cell to reduce the effect of pulsation. 

Luminol Microperoxidase-catalyzed ILITC- H202 Phosphate buffer (pH 10.8) Compact detection cell using optical fiber 14 amol (for luminol) 110... 

Figure 4 Schematic diagram of the postcolumn reactor developed by Wu and Huie. One arm of the tee contains the electrophoretic capillary, which is inserted in the reaction capillary (10 cm X 200 pm id X 400 pm od) situated at the opposite arm of the tee. The tee is connected to the detection cell via an adaptator and both the electrophoretic and reaction capillaries are inserted into the detection cell through the inner core of a PTFE tubing (400 pm id X 1.5 mm od). Two reagent capillaries (15 cm X 75 pm id X 144 pm od) inserted into the central arm of the tee are used to deliver the TCPO and H202 reagents into the mixing area through the small gaps that exist between the outer surface of the electrophoretic capillary and the inner surface of the reaction capillary. (From Ref. 78, with permission.)...

Figure 14 Schematic representation of the Ru(bpy)33+ CL in situ detection cell. (From Ref. 98, with permission.)...

The time resolution of stopped flow experiments is typically 1-2 ms,21 and is determined by the time required to mix the solutions, flow the mixed solution to the detection chamber, and stop the flow. Smaller detection cells can be used to decrease the time resolution at the expense of the signal-to-noise ratio of the detected signals. Various kinetic traces have to be averaged to achieve good kinetic profiles and sample volumes of milliliters with concentrations of micromolar to millimolar are required. 

---