Gated sampling

Sources featuring good frequency and intensity stability are necessary to recover a reliable decay curve. The time resolution of the equipment is affected by time duration of the pulse and by time resolution of the oscilloscope. At present, a time resolution of about 20 ns can be achieved. 

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Xu, H., Roddy, T.P., Lapos, J.A., Ewing, A.G., Parallel analysis with optically gated sample introduction on a multichannel microchip. Anal. Chem. 2002,74(21), 5517-5522. 

Due to these uncertainties, several recent studies have avoided factors altogether (Table 7.2, Tables 7.4-7.6) and reported the difference between fumigated and non-fumi-gated samples corrected for sorption. Some studies simply report the measured difference between fumigated and non-fumigated samples (Selles et al., 1995 Grierson et al., 1998 Myers et al., 1999 Daroub et al., 2000). Many studies, however, have applied a correction for phosphate sorption in addition to the factor of 0.4 proposed by Brookes et al. 

Xu, H. et al. Parallel separations of oligonucleotides with optically gated sample introduction on multichannel microchips. J. Sep. Scl 27, 7, 2004. 

Boxcar averagers are normally used in one of two modes, namely in static-gate sampling or in waveform recovery mode these operating modes are shown schematically in Figure 14.8. 

Fig. 7.6 Operating principle of a gated sampling acquisition. The decay curve bottom curve) is recovered by plotting the emission intensity as a function of the delay time with respect to excitation pulse...

Hz repetition rate of the lasers and is usually sampled with a gated integrator, whose output is reeorded with a laboratory eomputer. Analogue, rather than digital, eleetronies is usually employed beeause of pile-up of the deteeted photon eounts in an experiment with reasonable produet intensities. 

The gates referred to above can be created in various ways. For example, suppose that the probe beam goes tlirough the sample, but only half of its physical width (in the sample) is crossed with the pump beam. Now, if we have two photodiodes, one can measure the intensify of the perturbed part of the probe beam, whilst the second measures the unperturbed part as a result of creating spatial gates, the two recorded output signals can be used to measure the... 

In 1995, Moore and Jorgenson used the optically gated CZE system to obtain extremely rapid separations with HPLC coupled to CZE. The rapid CZE analysis made possible more frequent sampling of the HPLC column, thus increasing the comprehensive resolving power. Complete two-dimensional analyses were performed in less than 10 min, with the CZE analyses requiring only 2.5s. A peak... 

C. A. Monnig and J. W. Jorgenson, On-column sample gating for high-speed capillary zoneelectiophoresis . Awn/. Chem. 63 802-807 (1991). 

The polymers studied and the experimental procedure were described in the last section. The samples were made of the same PC-TLCP composite and the pure TLCP Vectra A950, respectively. To study the influence of sample forms and geometries on mechanical constants, plate samples (80 x 80 x 2 mm-) were also injection molded with a film gate. Tensile samples were then cut from the plate in the longitudinal (//) and transverse... 

NOTE All intermittent BD arrangements require a properly adjusted throttling gate valve on the BD line (and sample coolers) for good results. It may be appropriate to lock the valve or remove the wheel to ensure that the valve position is not inadvertently further opened or closed. 

Many boilers are fitted with a heat exchanger-type water sampling coil that permits the collection of a representative and cooled BW sample. The design generally provides for a coil of copper or stainless steel (SS) fitted inside a small SS shell. The unit is fitted with gate valves to control the flow of cooling water and BW. 

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