New Principle of Magnetophoretic Velocity Mass Analysis

Abstract

Mass spectrometry is now a most important analytical technique. It has been widely used throughout various scientific disciplines for the identification and detection of trace amounts of various compounds. 1 In general, a mass spectrometer is composed of three parts: that is, the ionization part of a sample, the separation part of the ion and the detection part of the ion. Over almost one century, tremendous efforts have been devoted to the improvement of the ionization efficiency to measure the larger molecules in their trace amounts. MALDI 2 and ESI 3 are now the most effective ionization methods for biological macromolecules. Ion mobility mass analysis has also been developed by employing low vacuum conditions. These methods have made it possible to detect macromolecules of larger than 100 kDa by the multi-charge mode. 4 However, the ionization efficiency has still room to be improved to measure much larger proteins and DNA.The present study proposes an innovative mass analysis method by using magnetophoretic force 5 as a migrating force on a sample particle in a gas phase or low vacuo. All compounds have their own magnetic susceptibilities. Therefore, each compound can be caused to migrate by the characteristic magnetophoretic force under the high magnetic field gradient without any ionization process, only depending on its magnetic susceptibility and mass. Figure 1 illustrates the experimental setup used in the present study to demonstrate the new mass analysis method. A droplet generator was purchased from MicroFab (MJ-AB, MicroFab, TX). It could produce fluid micro-drops ranging from 50 to 200 picoliters in volume. The frequency of droplet generation was controlled between 120 and 600 Hz. The strobe illumination was synchronized with the droplet generation. The migration behavior of micro-droplets was observed by a microscope with a 1 × objective (LD-647-S2, Chuo Precision Industrial, Tokyo, Japan) and a CCD camera (ME421R, ELMO, Nagoya, Japan). The CCD images were captured into PC, and analyzed with an image processing program written in Java. A high magnetic field was generated by a cryogen free superconducting magnet (JMTD-10T100HH1, JMT, Tokyo, Japan). A high magnetic field gradient was generated by a pair of iron chips (pole pieces), which had a gap of 300 µm as shown in Fig. 1(B). The magnetic field near the edge of pole pieces along the vertical direction was simulated by Super Moment 2.0, which is available for free on the web. Water and 0.3 M aqueous solution of manganese(II) chloride (GR grade, Nacalai Tesque, Kyoto, Japan) were used as test samples. Water was purified by a Milli-Q system (Millipore, Billerica, MA, USA). The magnetic susceptibilities of the MnCl2 solutions were measured with a magnetic susceptibility balance (MSB-AUTO, Sherwood Scientific Ltd., Cambridge, UK). Experimental Results and DiscussionAt first, the principle of magnetophoretic velocity mass analysis is described below. We define the direction of gravity as the xdirection, and the edge of pole pieces as x = 0 as illustr...

Magnetophoretic Velocity Modulation Mass Analysis of a Single Microparticle in an Atmosphere

“…The nonsteady-state migration has also been observed in the case of the magnetophoretic effect on the falling velocity of droplets in an atmosphere. 19 The reason is that the relaxation time for the translational motion in air of a 15-µm-diameter particle is as long as 7.3 × 10 -4 s, which is much longer than the response time of the measurement electronics, including the PMT, whose response time is shorter than 100 ns.…”

Application of magnetic particle tracking velocimetry to quadrupole magnetic sorting of porcine pancreatic islets

“…Both features are essential for high accuracy and precision of the MPTV analysis (Moore et al, 2004; Sridhar Reddy et al, 1996; Zborowski et al, 2003). Those features are at the basis of the competitive advantage of the MPTV over other magnetic motion analyzers that are based on single‐particle analysis in high‐gradient magnetic fields which is difficult to measure (Suwa and Watarai, 2004; Watanabe et al, 2004; Watarai and Namba, 2001).…”

Magnetic susceptibility measurement of single iron/cobalt carbonyl microcrystal by atmospheric magnetophoresis

“…More recently, a novel type of magnetophoretic technique has been developed, which is analogous to the concept of ion mobility mass analysis [46,47]. The magnetophoretic velocity in gaseous phase can include inertia, which contains mass information.…”