FAIMS, a new technology that promises mass spectrometrists better detection of peptides in complex mixtures, is gaining fame. The acronym stands for high-Field Asymmetric waveform Ion Mobility Spectrometry — quite a mouthful. What it does, however, is simple: It allows only certain ions to enter the mass spectrometer, thereby reducing the background and lowering the detection limit.
FAIMS is slated to be commercialized this fall by a company called Ionalytics, based in Ottawa, Canada, which has been developing it into an ion filtering device, called Selectra. The instrument, which will cost $75,000 in the US, sits at atmospheric pressure between the ion source and the inlet to the vacuum of the mass spectrometer. It separates ions in the gas phase based on differences in their mobility when a high voltage asymmetric waveform is applied. By choosing a selecting or compensation voltage, users can choose to transmit only a subset of the ions into the mass spectrometer. In a typical proteomics experiment, scientists mainly look for multiply charged peptide ions, according to Barbara Ells, Ionalytics’ marketing and product manager. These ions can be selected using a fairly narrow range of compensation voltages: “We find that three different voltages give us quite good coverage across the multiply charged species,” she said. At the same time, researchers lose most of the singly charged ions, many of which represent background resulting, for example, from solvent species or column bleed. As a result, the multiply charged ions of interest become the dominant peaks in the spectrum, “so it’s easier for the mass spectrometer to go and pick out which ions it wants to perform MS/MS on,” Ells said. This improves their detection limit, bringing it down to high-attomole levels in some cases. Typically, the signal-to-noise ratio improves 6-12-fold, she said.
Besides removing noise, FAIMS can sometimes even enhance the signal, depending on the ion: The inlet of the instrument, since it operates at atmospheric pressure, is bigger than the inlet to the mass spectrometer, “so we can sample more of the electrospray plume,” and transmit the ions efficiently, said Ells.
So will proteomics researchers seek out FAIMS? “At this point, I am guardedly optimistic about FAIMS and its various potential applications in proteomics,” commented Richard Smith from PNNL in an e-mail message. Its main attraction, he said, is that separation in the gas phase is much faster than in liquids or gels. “This potentially provides a significant increase in throughput for those of us interested in comprehensive proteomics studies.” In addition, FAIMS might also be able to speed up, or make more sensitive, targeted analyses of subproteomes such as phosphorylated proteins, he added.
Caprion Pharmaceuticals has been an alpha-tester for Ionalytics, using the instrument in nano-LC/MS experiments. “What’s possible is to identify things that are below the [usual] threshold of detection, and be able to identify them unambiguously,” said Pierre Thibault, Caprion’s director of protein analysis. The technology is compatible with the time constraints of LC/MS, he said: “Because the peaks are typically 30-40 seconds wide, you can integrate three compensating voltages of three seconds each and still have 10-15 datapoints.”
At the moment, Ionalytics has only developed FAIMS for electrospray mass spectrometry, but MALDI “is down the road for sure,” Ells said. Last week, Ionalytics announced an OEM agreement with Waters, under which Waters will be selling, distributing, and supporting Selectra starting this fall, initially for its Q-Tof micro, Q-Tof Ultima, and Q-Tof API-US instruments. “We are speaking with the other vendors” about similar agreements, said Ells.
Ionalytics will also be providing Selectra for Applied Biosystem’s API 3,000 mass spectrometer and, later this fall, for Thermo Electron’s ion trap. The instrument has so far also been tested by MDS Pharma Services, several mass spec vendors, as well as a number of government and academic labs both in Canada and the US. Ionalytics was founded in the fall of 2001 as a spinoff from the National Research Council of Canada, where Roger Guevremont, the company’s CSO, developed FAIMS — originally invented 20 years ago in Russia — for mass spectrometry applications. The 15-person company raised CA$2 million ($US 1.5 million) in a first round and CA$4.5 million ($3.4 million) in a second round of venture capital funding, led by Genesys Capital.
— JK