When a magnetic sector mass spectrometer was operated with an initial accelerati

Question

When a magnetic sector mass spectrometer was operated with an initial accelerating voltage (V1) of 3.00 x 103 V, a magnetic field (B1) of 0.126 T was required to focus the CH4 + ion on the detector.
a. (2 marks) What magnetic field strength would be required to scan the mass range between 16 and 250 for singly charged ions if the accelerating voltage is held constant?
b. (2 marks) What accelerating voltage would be required to scan the mass range between 16 and 250 for singly charged ions if the magnetic field strength is held constant?

Explanation / Answer

a) (a) For , m/z = 16 and

16 = Br^2 r^2 e / 2 V = k x (0.126 T) ^2

m/z = 250

250 = kB^2

Dividing the second equation by the first yields

250/16 = B^2 / (0.126 T) ^2

B = 0.498 T

Thus, to scan the range of m/z from 16 to 250, the field strength would be scanned from 0.126 to 0.498 T. ----ANSWER

=======================================================

16 = Br^2 r^2 e / 2 V = k’ /V = k’ / 3.00 X10^3

At m/z = 250

250 = k/V

Dividing the first equation by the second gives

16 /25 =      k/ 3.00 X10^8 / (k/   V) = V / 3.00X 10^3

V = 16 × 3.00 × 10^3 /250 = 192 V T

Thus, scan from 3000 to 192 V. ----ANSWER

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.