Time resolved acquisition

Owen et al. [32] used RPLC to speciate Zn compounds in an in vitro gastrointestinal digest of chicken meat. C8 and CJ8 columns were connected in series to achieve the separation. It was found that time resolved acquisition software needed improvement for peak areas to be determined. 

B.2.1. Ethene, Propene, and Butene Oligomerization in Zeolites with Three-Dimensional or Two-Dimensional Sets of Interconnected Channels. Spoto et al. (6) employed the FTIR technique to investigate the interaction of ethene with HZSM-5. The sequence of spectra shown in Fig. 16 was obtained when dosing a fixed pressure of ethene at room temperature and recording a spectrum every 6.8 s. It is evident that in these short-time intervals there was a dramatic change of the spectral features that would be completely lost by operating under the conventional (non-time-resolved) acquisition conditions (note that spectrum 19 in Fig. 16 corresponds to a total contact time of only about 130 s). 

Waddell E, Wang Y, Stryjewski W, McWhorter S, Henry AC, Evans D, McCarley RL, Soper SA (2000) High-resolution near-infrared imaging of DNA microarrays with time-resolved acquisition of fluorescence lifetimes. Anal Chem 72(24) 5907-5917... 

There are also two methods of defining how to acquire data. In continuous acquisition the number of sweeps of the defined regions is specified, and in TRA (time resolved acquisition) the number of sweeps of the defined regions is specified in terms of the number of time slices to store, each time slice being one sweep. The main difference in acquisition terms between continuous and TRA is how the acquired data are stored. In continuous acquisition the data are accumulated over the number of sweeps and then the accumulated data are stored. In TRA the data acquired for each sweep are stored separately. 

An interesting feature of polarized IR spectroscopy is that rapid measurements can be performed while preserving molecular information (in contrast with birefringence) and without the need for a synchrotron source (X-ray diffraction). Time-resolved IRLD studies are almost exclusively realized in transmission because of its compatibility with various types of tensile testing devices. In the simplest implementation, p- and s-polarized spectra are sequentially acquired while the sample is deformed and/or relaxing. The time resolution is generally limited to several seconds per spectrum by the acquisition time of two spectra and by the speed at which the polarizer can be rotated. Siesler et al. have used such a rheo-optical technique to study the dynamics of multiple polymers and copolymers [40]. 

Conventional TCSPC equipment has been successfully employed in LSM for fluorescence spectroscopy on discrete microscopic volumes [18, 19] and for fluorescence lifetime imaging at a low acquisition speed [1], The use of conventional TCSPC equipment for imaging results in very long acquisition times, several to many minutes per (time-resolved) image. Importantly, operating the TCSPC detection system at too high detection rates, above 5% of the excitation frequency, results in distortion of the recorded decay curve [20],... 

The degree of activation of the sample is measured by post-irradiation spectroscopy, usually performed with high-purity semiconductors. The time-resolved intensity measurements of one of the several spectral lines enables to get the half-life of the radioactive element and the total number of nuclear reactions occurred. In fact, the intensity of a given spectral line associated with the decay of the radioactive elements decreases with time as Aft) = Aoexp[—t/r], where Aq indicates the initial number of nuclei (at t = 0) and r is the decay time constant related to the element half-life (r = In2/ /2), which can be measured. Integrating this relation from t = 0 to the total acquisition time, and weighting it with the detector efficiency and natural abundance lines, the total number of reactions N can be derived. Then, if one compares this number with the value obtained from the convolution of... 

E. Gratton, B. Feddersen, M. vandeVen, Parallel acquisition of fluorescence decay using array detectors, in Time-Resolved Laser Spectroscopy in Biochemistry II (J. R. Lakowicz, ed.), Proc. SPIE 1204, 21-25(1990). 

A Zenith Z-158 PC computer (8 MHz 20 MB, 640 kB RAM 8087 coprocessor) is interfaced to the experiment and controls the interferometer sampling, data acquisition, and subsequent sorting/Fourier transformation of the data to produce time-resolved spectra. Two digitizers were employed to record the temporal evolution of the IR emission and were fully dedicated... 

Figure 11. The interleaved sampling scheme used to increase the efficiency of data acquisition in time-resolved CS spectrometer experiments (see text for details). Reproduced with permission from Ref. 86.

Time Resolution. Time-resolved studies of surface species are of considerable interest in the field of catalysis since they offer a means for investigating the kinetics of adsorption and surface reaction and for distinguishing between species active and inactive in catalysis (32, 33, 34). Dispersive spectrometers can be used for this purpose (33, 35) but are restricted to the observation of either a single frequency or a narrow range of frequencies, unless the dynamics of the observed phenomenon are very slow compared to the time required for the acquisition of a spectrum. FT spectroscopy allows these limitations to be surmounted and opens up the possibility of recording complete spectra very rapidly. 

Metal complexes like lanthanide chelates (mainly europium or terbium), ruthenium phenanthrolines or bipyridyls, and platinum porphyrins can be used as fluorescent labels for biomolecules. Their long decay times are perfectly suited for a detection by time-resolved imaging, and the labeled target molecules can be used for the determination of intracellular recognition processes or for the screening of DNA and protein arrays. Ratiometric lifetime-based imaging methods in combination with sophisticated data acquisition and evaluation tools can substantially contribute to the development... 

Hydrocarbons (99 % purity) were from Aldrich and Sigma Corps. The nonionic surfactants used in this work were single component alkyl poly(ethyleneoxides) (for example C12E05), obtained from Nikko Chemicals Co. (Japan), dissolved in HPLC grade water at a concentration of 0.03 wgt. %. The use of static surfactant solutions at this low concentration has been found (5) to slow the removal process enough to allow the acquisition of several time - resolved spectra within the first 3 minutes of exposure. 

The ultimate goal in time-resolved proximal probe methods, however, is not always faster image acquisition. Rather, the most useful methods provide a large dynamic range, allowing processes that occur on time scales ranging from seconds to picoseconds and even femtoseconds to be studied. Such issues are best defined in relation to the exact form of probe microscopy employed, as described below. 

P 26] Time-resolved FTIR spectroscopy was performed by operation of an infrared spectrometer in the rapid scan acquisition mode (see Figure 1.59) [110]. The effective time span between subsequent spectra was 65 ms. Further gains in time resolution can be achieved when setting the spectral resolution lower (here 8 cm4) or by using the step-scan instead of rapid-scan mode. 

M 35] [protocol see [119]] A protein conformation kinetic study of the small protein ubiquitin was performed both in the continuous and in a stopped-flow mode at low reactant consumption [119], The bifurcation mixer was used prior to an IR flow cell for data monitoring. The change of conformation from native to the A-state was followed when adding methanol under low pH conditions to the protein solution. In the continuous mode, long data acquisition could be made and the reaction time was determined by the flow rate and the volume interconnecting zone between the mixer and IR flow cell, which was small, but not negligible. In the stopped-flow mode, the reaction time resolved was dependent on the time resolution of the FTIR instrument. 

Time resolved analysis is essential for monitoring of chromatographic separations. Rapid data acquisition may now be performed, using ICP-MS instruments equipped with software capable of monitoring signal versus time at several different mlz values. 

Sweedler et al.224 have exploited the mass sensitivity of pCoil NMR probes in the development of micromixer-based time-resolved NMR, demonstrating the application of the method to the conformation of the protein ubiquitin. To probe changes in protein conformation based on the elapsed time after a change in solvent composition, two capillary flows are mixed rapidly followed by the acquisition of... 

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