Mix Two Parts Quadrupole, One Part Ion Trap, and Stir

Photo: Courtesy of Applied Biosystems/MDS Sciex THE Q TRAP SYSTEM Last October, long-time mass spectroscopist Gerard Hopfgartner got a new toy. Applied Biosystems (AB) and its partner, MDS Sciex, sent Hopfgartner, professor of pharmaceutical analytical chemistry at the University of Geneva, a prototype instrument that combines the attributes of triple- quadrupole and ion trap mass spectrometers in a novel, hybrid configuration. Hopfgartner uses the instrument for both small-molecule and proteomics applications, and says he has been "personally quite impressed" with its performance so far. Now the rest of the mass spec community can take a gander as well: The two companies--from Foster City, Calif., and Concord, Ontario, respectively--officially launched the system, called Q TRAP™ LC/MS/MS, at the 50th Annual American Society of Mass Spectrometry conference in May. Like standard triple-quad mass spectrometers (MS), the tandem Q TRAP system features three instruments.1 The first provides ion filtration, allowing users to select individual ions for further study. The second instrument is a collision cell, fragmenting the selected ion by collision with nitrogen gas. These fragments are then analyzed in the third instrument, a linear ion trap, which operates like a standard three-dimensional ion trap instrument, but employs fundamentally different ion optics. Unlike a traditional ion trap, in which ions circle an enclosed spherical chamber before being ejected and analyzed, the Q TRAP's linear system holds ions in a two-dimensional, quadrupole configuration, explains Joe Anacleto, AB/MDS Sciex's director, LC/MS product line. The system can accommodate 45 times more ions than a standard three- dimensional machine, with a trapping path length 20 times longer. According to Anacleto, triple-quads and ion traps serve fundamentally different purposes. A triple-quad MS excels at quantitative measurement--determining how much of a given analyte is present in a sample. But ion traps traditionally are "very poor" at this type of analysis, he says, and instead excel at qualitative assessments--determining what analytes a given sample contains. With a hybrid instrument, however, researchers can perform both analyses with one machine. "You have very sensitive quantitative analysis, and very high sensitivity qualitative analysis, all in one package," explains Anacleto. AB/MDS Sciex offers the Q TRAP system in two configurations that take advantage of the instrument's dual strengths. The two systems differ in the analysis software and ionization sources bundled with the instrument, but both cost $260,000 (US). The small molecule analysis system includes AB/MDS Sciex's Analyst™ and MetaboliteID™ (the company's metabolite identification) software, and the Turbo Ionspray and heated nebulizer atmospheric pressure chemical ionization (APCI) sources. The proteomics package includes BioAnalyst™ and ProID™ (protein identification) software, the Turbo Ionspray, and a nanoflow ionization source. As both configurations come with liquid-phase ionization sources, scientists can place the Q TRAP system downstream of liquid chromatography or capillary electrophoresis modules. AB/MDS Sciex positions the Q TRAP platform as a competitor to standard, 3D ion traps, says Anacleto, but the Q TRAP system offers some functions lacking in typical ion traps, such as ion scanning and filtering functions usually only available on triple-quad instruments. And because of the Q TRAP's novel ion optics, it does not suffer from some of the limitations of standard ion trap instruments, such as loss of low molecular weight ions and low-mass accuracy. Hopfgartner cites two additional benefits of the Q TRAP platform. First, it saves precious biological samples by allowing researchers to perform more experiments on a single machine in one run. In addition, he notes, the Q TRAP system's filtering functions help with data reduction. "What's important in science," he says, "is not to generate data, but to generate relevant data." Traditionally proteomics researchers produce reams of data and rely on bioinformatics software to filter it, but the hybrid instrument provides data reduction on the front end. "It's like ... radar," he says. "I want to see only things which are relevant for my work, and not have all the trash being accumulated and using software to reduce it." --Jeffrey M. Perkel 1. J.M. Perkel, "Mass spectrometry applications for proteomics," The Scientist, 15[16]:31, Aug. 20, 2001.

Mix Two Parts Quadrupole, One Part Ion Trap, and Stir

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Photo: Courtesy of Applied Biosystems/MDS Sciex
THE Q TRAP SYSTEM