Digital Techniques for Spectroscopy

Big data is the digital technology of pattern recongnition for effective information retrieval. Large data sets, however, cause a dramatic data deluge, which is difficult to handle with. In imaging and transient spectroscopy large data are common. Thus, it is desirable to have smart collection methods to deal with fast undersampled processes, whose information is preserved and digitally retrieved.

 

Compressed Data Collection
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It is familiar the practice to compress digital files in formats such as ZIP, or JPG for images, or MP3 for audio. The process is done in a way that the original information is still accessible, though at reduced level of detail. While  in non-compressed files that level of details contributes to the overall quality of the visual or auditive experience, it is redundant to recongnize the specific picture or sound. The signal is largerly oversampled with respect to the information retrieval. Compression methods thus "reduce it to the essential".

In scientific applications, such as analytical spectroscopy it is not really the beauty of the signal that is in first-place important, rather the information within. We deploy digital strategies to "efficient-ize" data collection as well as their processing in chemical analysis. Be it for chemical imaging of 3D hyperspectral mappings, or transient signals of a large number of states or compounds, the ability to focus on the least sufficient data set is extremely valuable in terms of information coverage as well as space/time resolution. The traditional Nyquist limit is beaten adopting newest methods of compressed sensing.

Digital Processing of Time-Domain Data
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The range of commercial techniques for high-resolution gas-chromatography–mass spectrometry (GC–MS) has been recently extended with the introduction of GC Orbitrap Fourier transform mass spectrometry (FTMS). We report on progress with quantitation performance in the analysis of persistent organic pollutants (POP), by averaging of time-domain signals (transients), from a number of GC–FTMS experiment replicates. Compared to a standard GC–FTMS measurement (a single GC–FTMS experiment replicate, mass spectra representation in reduced profile mode), for the 10 GC–FTMS technical replicates of ultratrace POP analysis, sensitivity improvement of up to 1 order of magnitude is demonstrated. The accumulation method was implemented with an external high-performance data acquisition system and dedicated data processing software to acquire the time-domain data for each GC–FTMS replicate and to average the acquired GC–FTMS data sets. Concomitantly, the increased flexibility in ion signal detection allowed the attainment of ultrahigh-mass resolution (UHR), approaching R = 700 000 at m/z = 200.
PD Dr. habil. Davide Bleiner

PD Dr. habil. Davide Bleiner
Head Advanced Analytical Technologies

Phone: +41 58 765 4934

References

Nagornov, K. O.; Zennegg, M.; Kozhinov, A. N.; Tsybin, Y. O.; Bleiner, D. Trace-level persistent organic pollutant analysis with gas-chromatography orbitrap mass spectrometry - enhanced performance by complementary acquisition and processing of time-domain data. J. Am. Soc. Mass Spectrom. 2020, 31 (2), 257-266. https://doi.org/10.1021/jasms.9b00032
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