Used for the identification of relative atomic masses. This is useful for identifying substances, such as illegal drugs. Mass spectrometers work by forming ions then separating them according to the mass and/or charge (mass-to-charge ratio).
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The mass spectrometer: The process
Step 1: Ionisation The sample to be investigated is dissolved in a volatile solvent before being injected through a fine hollow needle that is connected to the positive terminal of a high voltage supply. This forms single positively charged ions.
Step 2: Acceleration
The positive ions accelerate towards a negatively charged plate. Lighter ions and ions with higher charges accelerate at a faster rate.
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The mass spectrometer: The process
Step 3: Ion drift
The ions pass through a hole in the negatively charged plate, forming a beam that travels along the flight tube towards a detector.
Step 4: DetectionThe flight times are recorded and the ions gain an electron which causes a current to flow.
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The mass spectrometer: The process
Step 5: Data analysisThe signal from the detector is passed to a computer that produces a mass spectrometer.
Additional Information:
Lighter ions and ions with a higher charged arrive first at the detector
The whole apparatus is kept under a vacuum to prevent the ions from colliding with air molecules
