Analysis cycle time

Analysis cycle time (irradiation, y-spectrometry, data evaluation 8h to 14 days)... 

Editor You estimated 3 minutes per analysis on board the MRV. You also state an analysis cycle time of 18 seconds. How do these two times relate to each other ... 

Figure 6.24 The SIM profiles of 12 lead candidates incubated with human liver microsomes, using a high throughput LC/MS system equipped with column switching to desalt and analyze the incubates. The reproducibility of the system over 960 injections is demonstrated. Analysis cycle time is approximately 0.5min. (Ackermann et al., 1998.)...

The detection limits of a pulsed flame photometric detector (PFPD) are much better than those of any conventional FPD, and in addition the detector does not suffer the quenching of co-eluting hydrocarbon chemicals (45). The ability to also detect arsenic or nitrogen containing chemicals makes the PFPD very useful for the screening of CWC-chemicals. Frishman and Amiraw (46) used fast GC equipped with a short capillary column (1.5 m) and PFPD for the analysis of air samples. A complete analysis cycle time of 30 s was demonstrated. Killelea and Aldstadt (47) used PFPD in the arsenic selective mode for the analysis of organoarsenic chemicals. 

Several series of tests were carried out to optimize the amounts of sample and reagent, and the reaction time and temperature. Completeness of reaction was confirmed by GPC analyses. To shorten the analysis cycle time and increase the useful life of the FID, back-flushing of high-boilers was implemented. The fluorosilanes can be substantially separated by gas chromatography using two wide-bore Rtx-200 capillary columns df= 1 mm, / = 60 m, di = 0.53 mm) connected in series at 45°C isothermal. 

Once the chemical vapor comes into contact with the SAW sensors, a response is developed within seconds. A complete analysis cycle for a SAW-based detector includes sampling time, desorption time from the preconcentrator, analysis time by the sensors, and recovery time to clear the sorbed chemicals from the polymer. Additional elution time is added when a GC column is incorporated. Analysis time is only a very small portion of the entire cycle. Detection speed depends on sampling time, especially when a preconcentrator or GC column is used for low-concentration samples. While it is possible to bypass the preconcentrator to reduce the analysis cycle time, the probability of false responses by the sensors significantly increases. Recovery time depends on the quantity of chemicals sorbed, strength of the bond between the sorbed molecules and sorption polymer, and the temperature necessary for releasing sorbed chemicals. Recovery time ranges from a few seconds to several minutes. 

For these concentration-type detectors, control of the carrier-gas flow is critical to maintain repeatable peak areas and retention times (136). Pressure regulation is typically used as it responds quickly to valve switching as well as compensating for leaks. Electronic controllers offer the additional option of pressure to reduce analysis cycle time. 

In order to minimize the problem of window fouling, it was found to be necessary to decrease the laser power to a level where the analyzer would not be able to meet the analysis cycle time. Therefore, Gervasio and Pelletier [21] investigated the use of a more modem analyzer based on a dispersive CCD spectrometer. The results of their work are summarized in Table 2. 

The scan rate of the MS run in full scan mode has been set to a very fast scan speed of only 75 ms/scan. This allows a very high chromatographic resolution especially of unresolved chromatographic peaks in the applied complex mixture of amines. Short analysis cycle times can be achieved for an increased sample throughput. 

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