INJECTION TIME

When only a few solutes are separated, they may occupy only a small portion of the total column volume at any given instant. In such cases, the productivity is improved by cyclic feed injections, timed so that the most strongly retained component from an injection elutes just before the least strongly retained component from the following injection (see Fig. 16-57). For a mixture of two components with k > 1, when the same resolution is maintained between bands of the same injections and bands of successive injections, the cycle time tc and the plate number requirement are ... 

A decrease of injection time (an increase of injection time—up to a limit— would allow more material to be packed into the mould). 

Example 5.4 Eight polypropylene mouldings, each weighing 10 g are to be moulded using the runner layout shown in Fig. 5.19. If the injection time is 2 seconds and the melt temperature is 210°C, calculate the pressure at each cavity if the injection pressure at the sprue is 80 MN/m. The density of the pwlypropylene is 909 kg/m3 and the volume of the sprue is 5000 mm. Assume that the flow is isothermal and ignore the pressure losses at comers. 

FIGURE 4.47 Dependence of HETP on sample volume. Column Toyopearl HW-55F, 22 mm X 30 cm. Sample 0.1% myoglobin. Elution 14 mM Tris-HCI, pH 7.9, in 0.3 M NaCI. Flow rate 52 cm/ hr. Detection UV at 220 nm. Legend to. sample injection time Z, column length u. linear velocity. 

Desktop tools address design and manufacturing concerns such as gate placement, injection time/rate, injection pressure, melt and mold temperatures, packing time and pressure, cooling time requirements, and machine size requirements. 

Dec, J. and Kelly-Zion, P, The Effect if Injection Timing and Diluent Addition on Late-Combustion Soot Burnout in a Dl Diesel Engine Based on Simultaneous 2-D Imaging of OH and Soot, SAE, 2000-01-0238,2000. 

The PBL reactor considered in the present study is a typical batch process and the open-loop test is inadequate to identify the process. We employed a closed-loop subspace identification method. This method identifies the linear state-space model using high order ARX model. To apply the linear system identification method to the PBL reactor, we first divide a single batch into several sections according to the injection time of initiators, changes of the reactant temperature and changes of the setpoint profile, etc. Each section is assumed to be linear. The initial state values for each section should be computed in advance. The linear state models obtained for each section were evaluated through numerical simulations. 

It should be noted that, in two of these studies, " the perfusion parameter used to define the mismatch was not CBF or MTT, but instead the time it took for contrast concentration to reach peak concentration in each image voxel after contrast injection ( time to peak or TTP). TTP measurements are often used as rough approximations of MTT measurements because calculation of CBF and MTT are somewhat complex, requiring a mathematical process called deconvolution. The details of deconvolution are beyond the scope of this chapter, and the reader is referred to other sources for further explanation. In many clinical settings, maps of parameters like TTP that do not require deconvolution may be available much more quickly than those that do require deconvolution. TTP is less specific than MTT in detecting underperfused tissue because it does not distinguish between delayed contrast arrival time (such as that related to perfusion via collateral vessels) and truly prolonged intravascular transit time. 

Hot needle or solvent flush method. Rapid injection. Reproduce injection time as close as possible. 

FIGURE 16.2 Representative base peak electropherograms from CZE runs of RPLC fractions, (a) Fraction 15 (5 peptide identifications) and (b) fraction 20 (19 peptide identifications). Column, bare fused silica capillary, 60 cm x 180 pm ODx30pm i.d. separation voltage, 15 kV observed CZE current, 1.91 p.A running electrolyte, 200 mm acetic acid + 10% isopropanol temperature, 22°C injection time, 10 s at 2 psi ( 4 nL total injection volume) supplementary pressure, 2 psi flow rate, 25nL/min spray voltage, 1.5 kV (reprinted with permission from Electrophoresis). 

Fig. 3.146. Electropherograms of commercially available jelly and milk products determined by LVSS. (a) Grape-flavoured jelly, (b) peach-flavoured jelly, and (c) apple-flavoured milk. LVSS conditions were sample injection time 25 s (2 psi) sample stacking time 2.9 min (—5 kV), after which the current reached 95 per cent of its maximum value. Samples were heated with a polyamide column SPE and then separated by LVSS-CE. Reprinted with permission from H.-Y. Huang el cd. [189].

Since the HPLC-MS cycle time (the chromatographic run time plus the autosampler injection time) is usually governed by the chromatographic system, focus has been given to sample preparation and chromatographic techniques. 

Burke and his students (11) have published a proposal for solving the non-linearity problem associated with CC and the consequent correlation noise. They used a constant frequency multiple injection signal while this occurred, this frequency was modulated. Before each injection, a random number was generated to determine the magnitude and sign of the deviation from the carrier frequency for the next injection time. Thus, the next... 

Injection mode-. Hydrodynamic injection is generally more reproducible than electrokinetic injection. The electrokinetically injected amount has a non-linear relationship with the injection time. °... 

Injection time-. Most modern instruments have a control function of the injection pressure that automatically corrects for hydrodynamic injection variability through the injected time. An injection time of at least 3 s is needed for this to function properly. Too short injection times decrease precision and too long injection times induce band broadening. Rather increase pressure if possible. 

Sample concentration Sample Injection time Voltage Amount of filtering... 

Examined factors were organic solvent concentration, buffer or electrolyte concentration, - - buffer or electrolyte pH,7 7 - T83,85,86 voltage,chiral selector concentration " and supplier, active pharmaceutical ingredient (API) concentration, internal standard concentration, injection time - and pressure, ... 

Each type of instrument uses different pressure settings, so injection times cannot be directly transferred. Therefore, it is preferable to specify an injection volume or the product of pressure difference and injection time in the method which can be considered instrument independent. 

For validation the following robustness factors should be considered different lots of the capillary, temperature ( 2°C), applied voltage/current ( 2% relative), buffer electrolyte concentration ( + 10% relative), pH ( 0.1), concentration of additives, e.g., organic modifiers or chiral additives ( 10% relative), injection time ( 0.5s), detection wavelength ( + 2nm), batch-to-batch variation of chiral selectors ( 2—3 different lots), CE instruments (two instruments of two different manufacturers preferentially). 

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