qhum
第1楼2008/02/23
Hi,
因为每次重新操作仪器得时候,仪器各部分得电压都需要一个稳定得过程,并且都会有一定的偏差。 假设你用的是Time of flight mass spectrometry. The acceleration voltage will affect the flight time of the ions. THere is a formula relating the Total of flight time 'T' with the mass of the ions 'm' :
T= A*m^(1/2)+B
where A and B are two parameters which are related to the instrument conditions, mostly to the voltages applied on the instrument.
So everytime when you start the instrument, the parameters of A and B are different. We can use two known masses to calibrate the instruments, basically that is to determine these two parameters of A and B. All these are actually done by the software. As long as you follow the procedure of the software, the instrument will be calibrated automatically.
There are normally some standard samples (known masses) to calibrate the instument. It depends on what kind of instrument you are using. But the fundamental principle from the point view of physics is just what I have briefly said.