Posted by: tvasailor | May 1, 2011

Dead-time Correction Limitations on Time-of-flight Mass Spectrometers

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We don’t have extensive information on the long-term precision and accuracy of our TOF instruments.  However, we have performed some basic studies to understand the limitations of the LCT and GCT.  Our Waters’ instruments are based on TDC (time-to-digital converters), which affects the accuracy and the precision of the instruments.

deadtime_graph

The TDC approach has two significant limitations:

1)  When two or more ions hit the detector in one flight cycle the TDC counts them as one event.

2)  When two ions hit the detector within a certain time interval, the TDC does not count the second ion (dead time loss)

The LCT and GCT correct for this problem via software.  Our ASMS poster session addresses these limitations and Excel ”program” models the effect.

Deadtime_poster

deadtime_model (Excel)

Here is a good literature reference that discusses the topic:

Chernuschevich, I. V.; Loboda, A. V.; Thomson, B. A. Special Feature Tutorial: An Introduction to Quadrupole-Time-of-Flight Mass Spectrometry. J. Mass Spectrom. 2001, 36, 849-865.

Link to Paper

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