Inductively coupled plasma mass spectrometry device

An inductively coupled plasma mass spectrometric device, for identification and measurement of impurity elements in a sample solution using an inductively coupled plasma, comprising:

• a plasma torch for generating the inductively coupled plasma;
• a high-frequency coil surrounding said torch for generating a high frequency electromagnetic field to maintain the inductive coupling plasma;
• a gas control unit connected for supplying plasma-producing gas to said plasma torch;
• a high-frequency power source coupled to said coil for applying high-frequency electric power to said coil;
• a matching circuit for electrically matching said high-frequency power source to the inductively coupled plasma;
• an analysis tube disposed for detecting an impurity element ionized by the inductively coupled plasma after mass separation has been performed by introduction of the ionized impurity element into a vacuum;
• a connection point at circuit ground potential;
• a shield plate made of metal interposed between said plasma torch and said high-frequency coil, a variable capacitor having first and second terminals, said first terminal being conductively connected to said shield plate;
• means for connecting said second terminal of said variable capacitor to said connection point;
• and means for maintaining said shield plate out of contact with said coil to enable control of the plasma potential of the inductively coupled plasma.