Simultaneous monitoring

Another approach to multielemental analysis is to use a multichannel instrument that allows for the simultaneous monitoring of many analytes. A simple design for a multichannel spectrometer consists of a standard diffraction grating and 48-60 separate exit slits and detectors positioned in a semicircular array around the diffraction grating at positions corresponding to the desired wavelengths (Figure 10.50). 

Sohd-state multi-element detector arrays in the focal planes of simple grating monochromators can simultaneously monitor several absorption features. These devices were first used for uv—vis spectroscopy. Infrared coverage is limited (see Table 3), but research continues to extend the response to longer wavelengths. Less expensive nir array detectors have been appHed to on-line process instmmentation (125) (see Photodetectors). 

Chromatograms Demonstrating the Simultaneous Monitoring of a Mixture by All Three Detector Functions... 

Fig. 11. Photograph of the four-electrode, vacuum flange and dual, quartz crystal, microbalance assembly, (A) side view, and (B) front view, used for mixed Cr atom. Mo atom matrix depositions with simultaneous monitoring of the individual metal flows. (The resolution of the microbalance is 10 g) (113).

All S FG spectra were obtained by averaging 50 400 pulses per data point and were normalized against the intensity of the visible and infrared inputs, which were simultaneously monitored by a power meter (Oriel instruments. Model 70833 and 70811) and Si photodiode, respectively. 

JW Cropp, LL Augsburger, K Marshall. Simultaneous monitoring of tamping force and piston displacement... 

In-situ emulsion formation, as proposed by Kamath et al(19), with DAS surfactants may cause higher pressure drops across the core. This is because of the blocking tendency of the emulsion which has lower mobility. This could explain the earlier plugging of the core compared to other runs. Effluent pH and viscosity showed behavior similar to the previous runs. It is worthwhile noting here that such pressure drops were not manifested by face plugging of the core near the entrance. This was confirmed by simultaneously monitoring the pressure at the inlet end of the core as well as the differential pressure across the two pressure taps located about 1 cm. from each end of the core. The inlet end pressure transducer showed reasonably low pressures throughout the run for each experiment. 

O Neill R. D., Fillenz M. (1985). Simultaneous monitoring of dopamine release in rat frontal cortex, nucleus accumbens and striatum effect of drugs, circadian changes and correlations with motor activity. Neuroscience 16(1), 49-55. 

Figure 7. Simultaneously monitoring vapor signatures of 1000 sensors for 2,4-DNT, 1,3-DNB, and TNT vapor strips at 8% saturated vapor levels. The (noisy) responses for 250 individual sensors are compared to the averaged response profile for 1000 individual sensors. Reprinted with permission from ref. 12a. Copyright 2000 American Chemical Society.

Simonsen s group has performed some elegant work over the years on NO release characteristics from rat superior mesenteric artery. Initially, Simonsen s group simultaneously monitored artery relaxation and NO concentration in the artery using a NO microsensor in response to various drugs [120], NO concentration was monitored via an ISONOP30 electrode, purchased from WPI and inserted into the artery lumen using... 

Automated online SPE systems have been applied to various phases of drug discovery. McLoughlin et al. (1997) utilized the Prospekt system in pharmacokinetic animal studies for rapid drug candidate screening. Up to 10 compounds were simultaneously monitored. The lower limits of detection were... 

Further proof for the fact that these induction periods are caused by slow hydrogenation of the diene ligand was obtained by NMR-spectroscopic measurements under hydrogenation conditions [10f, 15]. The registration of 31P- and 1H-spectra allows the simultaneous monitoring of changes in the bisphosphine complexes and substrate conversion. The results of the hydrogenation of methyl-... 

K.L. Vikse, Z. Ahmadi, C.C. Manning, D.M. Harrington, J.S. Mclndoe, Powerful insight into catalytic mechanisms through simultaneous monitoring of... 

By simultaneous monitoring of tidal volume and respiratory rate, or minute volume, and the concentration of an inhaled vapor in the bloodstream and the vapor in the exposure atmosphere, pharmacokinetic studies on the C t relationship have shown that the effective dose was nearly proportional to the exposure concentration for vapors such as 1,1,1-trichloroethane (Dallas et al., 1986), which has a saturable metabolism, found that the steady-state plasma concentrations were disproportion-ally greater at higher exposure concentrations. 

It is more difficult to perform ultrafast spectroscopy on neat H20 (than it is on H0D/D20 or HOD/H20) since the neat fluid is so absorptive in the OH stretch region. One innovative and very informative technique, developed by Dlott, involves IR pumping and Raman probing. This technique has a number of advantages over traditional IR pump-probe experiments The scattered light is Stokes-shifted, which is less attenuated by the sample, and one can simultaneously monitor the populations of all Raman-active vibrations of the system at the same time. These experimental have been brought to bear on the spectral diffusion problem in neat water [18, 19, 75 77],... 

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