ABSTRACT
The benefits of simultaneous multichannel detection over single-channel scanning detection are well established in analytical chemistry. Multichannel detection increases duty cycle, which leads to enhanced sensitivity, detection limits, and reduced analysis time. Also, multichannel detection used with either isotope-ratio or internal-standard techniques provides a mechanism to reduce the effect of multiplicative or flicker noise prevalent in plasma sources. An additional benefit of simultaneous detection is superior analysis of short-lived transient signals. Presented here is a theoretical comparison between simultaneous/continuous multichannel acquisition and single-channel scanning acquisition. To conduct this comparison, reported sensitivity, single-channel precision, and background values for commercial inductively coupled plasma sector-field mass spectrometers (ICP-SFMS) are used to generate theoretical figures of merit for both acquisition methods. Among the figures of merit that will be considered are detection limits, precision, and analysis time, particularly for multi-element or multi-isotope analysis.
ABSTRACT
Throughout the history of mass spectrometry, array detectors have been used to conduct simultaneous and continuous mass-spectrographic studies. The benefits of acquiring multichannel data through the use of an array detector are well known and include greater duty cycle, improved precision through ratioing and internal-standardization techniques, and better quantitative analysis of fast signal transients. Because of these benefits, numerous types of array-detector-based instrumentation have been developed, including optical and mass spectrometers. Presented here is the improved performance of a plasma-source Mattauch-Herzog mass spectrograph fitted with a multichannel electro-optic ion detector. A glow-discharge source is used for all measurements. Previously reported array-detector-based data for this mass spectrograph were severely limited in quality and featured extremely poor peak shapes and resolution. Several figures of merit relevant to array detectors will be presented, including sensitivity, resolution, peak shape, and abundance sensitivity, all of which have been significantly improved. Remaining negative aspects of the array-detector performance include susceptibility to a magnetic field and the absence of uniform sensitivity across the array surface.
