Speaker: Maria C. Prieto, Department of Pharmacology, Johns Hopkins University, Baltimore, MD 21205

Topic: Miniaturized Linear Time-of-Flight Mass Spectrometer with Pulsed Extraction - or - Honey, I Shrunk the Mass Spectrometer

Place: Building 426, Conference Room, NCI-Frederick, Frederick, MD

Time: Tuesday, September 26, 2001, at 2:00 PM

Abstract: We have designed and built a miniaturized (3-inch) linear time-of-flight mass analyzer with pulsed extraction for high mass resolution. Applications of interest for this instrument include rapid mass spectral reading of oligonucleotides that differ by one base (single nucleotide polymorphisms, or SNPs), distinction of biomarker signatures from different species of bacterial spores (biological weapons detection), and, likely in the near future, multiplex use of several miniature instruments for studies in the field of proteomics. Distributions due to initial conditions of the ions affect flight times, and consequently the mass accuracy and peak resolution (resolution defined as m/delta m or t/2delta t, where t is the time of flight and linewidths are measured at half maximum). Ion distributions become critical in small instruments and can be classified as temporal, spatial or kinetic energy distributions. Common methods for correction of energy distributions in a time-of-flight mass spectrometer (TOF MS) are to reduce the laser power, use high accelerating voltages, and use of reflectrons (ion mirror devices). Methods used to reduce the spread in initial positions of the ions in the ion source include using thin sample deposition methods and implementing a dual stage extraction to provide a space-focus of the ions at the detector.