DETECTOR BIAS GATING FOR IMPROVED DETECTOR RESPONSE AND CALIBRATION IN MATRIX-ASSISTED LASER DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY/

Simple circuitry was developed for detector bias grating as an effecti ve and convenient scheme for conserving the charge in detectors used i n mass-analysed laser desorption/ionization time-of-flight mass spectr ometry. An enhanced detector response by a factor of 3-10 was observed by detector gating compared with the commonly used low-mass deflectio n. Further, detector gating allowed the acquisition of the low-mass re gion of the time-of-flight spectrum at reduced sensitivity. Thus the a nalyte signal and matrix signals could be obtained in the same spectru m with an excellent signal-to-noise ratio and without exceeding the dy namic range of the digitizer. This feature, along with the recently de scribed sample preparation procedure by fast evaporation, yields matri x ion signals that are very well defined and can be used for highly ac curate spectrum calibration. Together, these developments open the way to routine mass determinations with errors in the sub-50 ppm range wi thout adding internal standards.