Post-acquisition processing

Line broadening. Syn. Apodization (not strictly correct). Any process that increases the measured width of peaks in a spectrum. This can either be a natural process we observe with our instrument, or the post-acquisition processing technique of selectively weighting different portions of a digitized FID to Improve the slgnal-to-nolse ratio of the spectrum obtained following conversion of the time domain to the frequency domain with the Fourier transformation. 

Because the application of the apodization function can be done after an NMR data set has been collected, we are free to experiment rvith different functions to evaluate the effect various functions have on the quality of the processed NMR data. We always disclose exacdy what post-acquisition processing has taken place to generate our final spectrum, and many researchers, research advisors, supervisors, reviewers, and regulators do not hold excessive and/or fancy NMR data processing manipulations in high regard. It is best to keep our NMR processing... 

Today, the use of sophisticated and large capacity computers with faster and more wide ranging ADCs and DACs allows con tlete conttol of all the mass spectrometers functions, acquisition of data in several forms, and powerful post acquisition processing to automatically search the enormous data files for relevant information. A high degree of automation is possible including conttol of any hyphenated separation technique. The mass spectrometer operator can load the samples and then process the information at a comfortable work station away from the noisy laboratory as the instrument carries out the analyses. The scope of the computer s abilities will be exenplified by the exanples given as apphcations. 

With triple quadrupole MS, automatically obtaining sensitive full scan CID spectra can serve as a powerful tool in metabolite identification due to flexibility in performing post-acquisition data processing. 

As it is with all TS techniques, rate data acquisition using a TS-PFR can be very fast and a vast amount of data can be obtained from a single experiment. Unfortunately, in the TS-PFR rates cannot be calculated in real time, as was the case with the TS-BR and will be the case with the TS-CSTR. Instead, rate data is obtained after all the readings from the several runs of a TS-PFR experiment are available. This post-experiment processing of the raw data will, however, produce the same X-r-T triplets as we discussed above. The triplets will be available over the whole range of X-T conditions covered by the experiment, just as they were for the TS-BR. 

Post-acquisition data processing need not be on a separate computer, particularly for data on small molecules. Large sets of biopolymer and metabolomic data, often on the gigabyte scale, are processed separately. 

Because the ion trap MS is not capable to conduct CNL or PI acquisition, detection of metabolites will rely on post-data-processing of CNL or product ion scans. However, MS" function of ion trap MS provides its advantage on structural assignment. The application of quadrupole—linear ion trap (QqLIT) on metabolite identification is described in more details in Chapter 15. 

QqQ in MRM mode and enables use of shorter chromatography columns and shorter run times (and thus increased throughput), while the additional selectivity provided by MRM detection can permit simplification of sample preparation procedures (Chapter 3). In practice, usually for each target analyte just one reaction channel (sometimes referred to as an MRM transition) is used to provide the quantitative data while one or two others are sometimes monitored simultaneously in order to provide confirmation of analyte identity via the relative responses (essentially a check on the selectivity of the analytical method. Section 9.4.3b). In contrast with the QqQ, the 3D ion trap has a poor duty cycle in MRM mode and the full scan product ion scan method is the method of choice if this analyzer is used for quantitation, since it is often possible to acquire 10 such scans across a chromatographic peak with adequate S/B values. Additional post-acquisition data processing is required to obtain quantitation data from such full scan MS/MS experiments. 

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