DESIGN, CONSTRUCTION, AND EVALUATION OF AN INTEGRATING TRANSIENT RECORDER FOR DATA ACQUISITION IN CAPILLARY GAS-CHROMATOGRAPHY TIME-OF-FLIGHT MASS-SPECTROMETRY

An integrating transient recorder (ITR) has been designed, constructed, and evaluated to accomplish time-array detection in gas chromatography time-of-flight mass spectrometry (GC-TOFMS) applications. The ITR consists of a 200-MHz flash analog-to-digital converter, 16 high-speed 100K emitter-couple logic (ECL) summing boards, three parallel processors for real-time data reduction, instrument control and routing functions, and a 300-Mbyte mass storage device. The ITR is capable of recording 80 mu-s bursts of transient information with a time resolution of 5 ns. For each transient, up to 16 384 sequential time-resolved channels may be recorded. An operator-selectable number of sequential transients may be summed in a locked time registry creating a summed scan file while maintaining the integrity of the transient time resolution. The information from each transient is read, summed, and stored in one of two summing registers (16 x 1024 x 24 bits). While incoming information is being stored in one summing register, the information in the other summing register is processed and read out to disk, thus permitting high-speed data collection continuously for long periods of time. The information from successive transients is summed in order to improve signal-to-noise, dynamic range, and sensitivity, and produces scan files at a rate sufficient to maintain all of the chromatographic information. GC-MS data collected at 1, 20, and 50 spectra per second are presented for a nine-component aliphatic/aromatic mixture. Although the ITR was specifically designed for GC-TOFMS studies, the overall design concepts of the ITR are universal and apply to any situation where information from two or more phenomena occur at the output of a single detector and occur over vastly different time domains.