Timed Injection

With timed injection, an electrical or pneumatic actuator is used to keep the inject position long enou for transferring the bulk of the sample to the column, but removing the tailing portion of the sample plug. The remainder in the loop must then be washed to waste before next injection. An internal standard is required for this technique. 

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At the time injection began, a shallow monitoring well was placed 23 m (75 ft) south of the injection well in the upper part of the Floridan aquifer above the confining layer. A downgradient, deep monitoring well was placed in the injection zone 300 m (1000 ft) southeast of the injection well. Another shallow well, located 3.2 km (2 miles) southeast of the injection site at the University of Florida s Everglades Experiment Station, has also been monitored for near-surface effects. 

One drawback of this approach is the relatively low sample throughput of traditional HPLC systems. The primary reason for this low throughput is that each standard and sample must be assayed under a minimum of three different isocratic conditions. Assuming a run time (injection to injection) of 10 min, it would take 50 hr to analyze 4 standards and 96 unknowns. /./PLC is ideally suited for determination of log P since it facilitates parallel analysis of a large number of compounds under identical chromatographic conditions (Table 6.4). 

Sample picking Inaccurate temperature Unstable temperature Inaccurate pressure Unstable pressure Inaccurate vacuum Unstable vacuum Inaccurate time Inaccurate voltage Unstable voltage Inaccurate time Injection volume not linear... 

Experimental (simplex and window diagram). The chromatographic system consisted of a Model 501 supercritical fluid chromatograph (Lee Scientific, Salt Lake City, Utah) with the flame ionization detector (FID) set at 375°C. The instrument was controlled with a Zenith AT computer. A pneumatically driven injector with a 200 nL or a 500 nL loop was used in conjunction with a splitter. Split ratios used were between 5 1 and 50 1, depending on sample concentration and the chosen linear velocity, while the timed injection duration ranged from 50 ms to 1 s. We found that the variation of both the split ratio and injection time allowed greater control over the... 

Harrison and Royle s experiments109,110 with 211At-labelled anti-Thy 1.1 IgG,OX7 monoclonal antibody appeared more promising. When used for treating Thy 1.1T cell lymphoma in mice, the astatinated antibody was stable in vivo and considerably increased the median survival time. Injection of 80-90 kBq (ca 2.2-2 A fiCi) [211At]astato-OX7 resulted in a complete cure—i.e.survival over 200 days—in 78% of the treated mice. 

The error terms might be correlated with each other or with an external parameter (i.e., time, injection sequence). It is always a good idea to plot the residuals vs. time and injection sequence to evaluate possible correlation effects. Detector drift, carry-over or other elfects can be easily detected with these plots. For a correct evaluation of the independence of the error, however, the calibration solutions should be injected in a randomized manner and correction for heteroskedasticity and/or curvilinearity should be applied on the calibration model. 

Total Time Injection — Injection Cycle Time for Run( A/d... 

Figure 5 Schematic of traditional sequential mode injection to injection cycle time (injection overhead) operation of an LC system.

SES Pre-load Step (allows for precisely timed injection into the THz RDC)... 

The use of CS techniques reduces the column equilibration time and flushes the matrix components to waste (decreases source contamination), while narrow-bore LC columns help not only with flow rates that were amenable to most atmospheric- pressure ionization (API)- interfaces but also provide increased sensitivity [28]. A change from a serial to a parallel format further increases throughput for bioanalysis, with timed injections at intervals from multiple LC systems and staggered MS detection [29-31]. 

A single cylinder of a super-long stroke crosshead engine can have an area of up to 7 m. Cylinder lubrication is achieved by timed injection through approximately eight lubricating points spaced equidistantly around and near the top of the liner. The injection points are connected by moustached grooves to assist the oil to spread. Approximately 1 g of oil is injected every revolution or second. 

The fast HPLC development in our work has closely followed the availability and improvements in chromatographic stationary phase and column technology. The initial methodology, based on Luna material, was centered on a 5- m particle size. These analyses with columns of 75 mm length and conventional 4.6 mm internal diameter gave analysis times of the order of 3.5 min (Fig. 3) with an overall cycle time, injection to injection, of almost 6 min. For such a cycle time the analysis of a 96-well microtiter plate (MTP) would be completed in 8 h, permitting the analysis of three MTPs per day. 

Increase in or effect Melt temperature Holding pressure Holding time Injection speed Mold temperature... 

The principal valve injection techniques are complete fill or partial fill with respect to the loop volume, timed injection and on-column focusing. The volume injected for the complete till technique is determined by the size of the loop, which has been overfilled to completely displace the mobile phase. As a sample is introduced into the loop, it displaces the mobile phase ahead of it out of the loop. As this process proceeds, the... 

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