TOFMS is extending its reach into areas traditionally dominated by other MS instruments.

摘要

TOF instruments (TOFs) have become real contenders in the MS market. Although the instruments' share of the life sciences market is currently small, experts say that scientists are beginning to realize that TOFMS has many advantages, including exact mass determinations. "I think people are just waking up to the power of exact mass and the extra dimension that it brings to problem solving and structure elucidation and confirmation," says Steve Smith at Waters Corp. (U.K.). "Only TOFs can deliver that." Exact mass measurements are particularly important when one is trying to identify an unknown molecule. Knowing an ion's m/z to four decimal places, for example, allows researchers to narrow down the list of possible identities, say experts. On the basis of this information, some computer programs can even pinpoint the exact combination of elements that must be present in the molecule or the chemical formula. TOFs are also less expensive and easier to use than some other MS instruments, such as sector and FT devices. According to Smith, TOFs "are now perceived as not being frightening." He says, "We're seeing people buy TOF technology now who, five years ago, wouldn't have touched it at all." And unlike scanning quadrupole or sector mass spectrometers, TOFs record all the ions in a batch of sample at once. "You get the entire spectrum every time you fly a batch of ions, and you can do this literally thousands of times per second," says Chris Enke at the University of New Mexico. "The rate of spectral production by a TOF mass spectrometer is completely unmatched by any other technique." Researchers also do not have to decide in advance which m/z range to analyze with a TOF instrument. The advantages of TOFs are so numerous, says Enke, that these instruments have replaced sector mass spectrometers for many applications. Experts say that researchers are starting to turn to TOFs for biological applications, such as biomarker discovery and metabolomics, which were traditionally studied with FTMS and triple-quadrupole instruments. Tables 1, 2, and 3, which are meant to be representative rather than comprehensive, list several commercially available TOF and TOF-TOF tandem MS instruments.