What is the magnitude of the magnetic field that the spectrometer uses? In the operating room, anesthesiologists use mass spectrometers to monitor the respiratory gases of patients undergoing surgery. One gas that is often monitored is the anesthetic isoflurane (molecular mass = 3.06 × 10-25 kg). In a spectrometer, a single ionized molecule of isoflurane (charge = + e) moves at a speed of 6.16 × 103 m/s on a circular path that has a radius of 0.240 m.