Design and Characterization of a Multisource Hand-Held Tandem Mass Spectrometer

Abstract

A wireless-controlled miniature rectilinear ion trap mass spectrometer system, total weight with batteries 5.0 kg, consuming less than 35 W of power, and having dimensions of 22 cm in length by 12 cm in width by 18 cm in height, is characterized. The design and construction of the mass spectrometer including mass analyzer, vacuum system, electronics system, and data acquisition and processing systems, is detailed. The mass spectrometer is compatible with various types of ionization sources including a glow discharge electron impact ionization source used in the internal ionization mode, and various atmospheric pressure ionization sources, including electrospray ionization, atmospheric pressure chemical ionization, and desorption electrospray ionization, which are employed for external, atmospheric pressure ionization. These external sources are coupled to the miniature mass spectrometer via a capillary interface that is operated in a discontinuous fashion (discontinuous atmospheric pressure interface) to maximize ion transport. The performance of the mass spectrometer for large and small molecules is characterized. Limits of detection in the parts-per-billion range were obtained for selected compounds examined using both the internal ionization and external ionization modes. Tandem mass spectrometry and fast in situ analysis capabilities are also demonstrated using a variety of compounds and ionization sources. Protein molecules are analyzed as the multiply protonated molecules with mass/charge ratios up to 1500 Da/charge.Miniature mass spectrometers are useful because they combine the usual advantages of mass spectrometrysbroad applicability, high sensitivity, high specificityswith the convenience of fast in situ analysis. These features are important to many applications in the area of public safety, environmental protection, and industrial process monitoring, among others.1 After a decade of increased attention, progress in the development of hand-portable mass spectrometers is becoming increasingly rapid. Ion traps of a variety of types have been the mass analyzer of choice in most recent miniature mass spectrometers, a choice made mainly because of their inherent tandem MS capability, relaxed requirement for high vacuum, and flexible modes of operation.2-8 Batterypowered ion trap miniature mass spectrometers with weights below 10 kg have been developed and a few have began to appear as commercial products. [9][10][11][12]

Non-contact halogen lamp heating assisted LTP ionization miniature rectilinear ion trap: a platform for rapid, on-site explosives analysis

“…The distance between the z pair of electrodes (z 0 ) was 43.2 mm. Different from the Mini 11 ion trap mass spectrometer, 23 an einzel lens comprised of three cylinder electrodes was added between the second capillary and the RIT to focus the ions. And the ions were detected by a conversion dynode electron multiplier (CDEM) detector (Model 397, Detector Technology, Inc., Palmer, MA), which was capable of detecting the positive and negative ions.…”

Ion trap mass analysis at high pressure: A theoretical view

“…Helium gas is typically used in commercial ion trap mass spectrometers as a buffer gas while recently heavier gases such as N 2 and air have also been used for linear ion traps [16,32,65]. It is highly preferable to use air as the buffer gas for portable instruments since no special gas supply is needed for field operations [66].…”

“…For each of these steps, dedicated experimental conditions are used to reach a balance between providing adequate collision energies and minimally interfering with intentionally stable ion trajectories. Helium is most commonly used as the buffer gas [22], with a pressure of several mTorr, although nitrogen and air have been used as buffer gases for linear ion traps [16,32,33]. An experimental exploration of ion trap operation at pressures higher than a few mTorr has been done and was recently reported in a separate manuscript [34].…”

Optimization and simulation of MEMS rectilinear ion trap

“…Among them, the most famous one is the MINI series portable mass spectrometer reported by Cooks and Ouyang at Purdue University. [8][9][10] The MEMS mass spectrometer with an ion trap as a mass analyser is still under study. At present, most researches in this field focus on the independent study of the MEMS ion trap.…”