Passage
In mass spectrometry, a sample's molecules are ionized in a vacuum and then exposed to a uniform electric field created by a high-voltage plate in the acceleration chamber. The electric field accelerates the ions until they arrive at the next section of the device, designated as the separation chamber. In this section, the drifting ions are sorted by their mass-to-charge ratio (m/q) .The separation chamber in a time-of-flight mass spectrometer (TOF-MS) is linear and has no electric or magnetic fields. The ions travel at a constant velocity through the chamber until they reach the detector. The time it takes for an ion to reach the detector depends on its m/q ratio.
Figure 1 Time-of-flight mass spectrometerA magnetic sector mass spectrometer (MS-MS) has a curved separation chamber where a magnetic field is generated. The magnetic field exerts a centripetal force on drifting ions, bending their trajectories into curved paths. The radius of the curvature depends on the ion's m/q.
Figure 2 Magnetic sector mass spectrometerThe centripetal force (F) acting on a particle can be determined from its mass (m) and velocity (v) and the radius (r) of the curved path:F = mv²/rEquation 1
-In the MS-MS separation chamber, the direction of the magnetic force on a moving ion is:

Question

Passage
In mass spectrometry, a sample's molecules are ionized in a vacuum and then exposed to a uniform electric field created by a high-voltage plate in the acceleration chamber. The electric field accelerates the ions until they arrive at the next section of the device, designated as the separation chamber. In this section, the drifting ions are sorted by their mass-to-charge ratio (m/q) .The separation chamber in a time-of-flight mass spectrometer (TOF-MS) is linear and has no electric or magnetic fields. The ions travel at a constant velocity through the chamber until they reach the detector. The time it takes for an ion to reach the detector depends on its m/q ratio.

Figure 1 Time-of-flight mass spectrometerA magnetic sector mass spectrometer (MS-MS) has a curved separation chamber where a magnetic field is generated. The magnetic field exerts a centripetal force on drifting ions, bending their trajectories into curved paths. The radius of the curvature depends on the ion's m/q.

Figure 2 Magnetic sector mass spectrometerThe centripetal force (F) acting on a particle can be determined from its mass (m) and velocity (v) and the radius (r) of the curved path:F = mv²/rEquation 1
-In the MS-MS separation chamber, the direction of the magnetic force on a moving ion is:

Quizplus · Accepted Answer

11ecba2d_12e3_3f69_a3bf_3134c5b38538_MD0008_00 The Lorentz force is the force exerted on a moving charge in the presence of an electric field E and a magnetic field _EMEM_. Electric and magnetic fields are known as vector fields; both quantities include magnitude and direction. The Lorentz force for a particle with a charge of q and a velocity of v in an electric field (E) and magnetic field (_EMEM_) is: 11ecba2d_12e3_3f6a_a3bf_1f6549848bcd_MD0008_00 The quantities F, E, v, and _EMEM_ are denoted as vector quantities. Because there is no electric field in the MS-MS separation chamber, the Lorentz force is simplified (E = 0) for the presence of a magnetic field only: 11ecba2d_12e3_667b_a3bf_c9e30f1a939c_MD0008_00 The quantity (v × _EMEM_) is the cross product of the vectors v and _EMEM_. The cross product of two vectors is a vector perpendicular to both vectors. Therefore, the direction of the magnetic force is perpendicular to both the ion's velocity v and the direction of the magnetic field _EMEM_. The specific direction of a cross-product vector can be determined through the right-hand rule. (Choice B) The force due to an electric field is parallel to the direction to the electric field, but the force due to a magnetic field is perpendicular to its field. (Choices C and D) If the magnetic force were parallel to the ion's velocity, the ion would accelerate linearly and not be forced into a curved trajectory. Educational objective: The Lorentz force equation is used to determine the force exerted on a charge in the presence of an electric and magnetic field. The force exerted on a moving charge due to a magnetic field is perpendicular to both the ion's velocity and the direction of the magnetic field.

Passage in Mass Spectrometry, a Sample's Molecules Are Ionized in a a Vacuum