Compact Mass Spectrometer

A method of mass spectrometry comprising:

• providing a miniature mass spectrometer comprising an atmospheric pressure ionisation source, a first vacuum chamber having an atmospheric pressure sampling orifice or capillary, a second vacuum chamber located downstream of said first vacuum chamber, a third vacuum chamber located downstream of said second vacuum chamber, an ion detector located in said third vacuum chamber, a first RF ion guide located within said first vacuum chamber, a second RF ion guide located within said second vacuum chamber, wherein the ion path length from said atmospheric pressure sampling orifice or capillary to an ion detecting surface of said ion detector is ≦400 mm;
• maintaining the product of the pressure P1 in the vicinity of said first RF ion guide and said length L1 of said first RF ion guide in the range 10-100 mbar-cm;
• maintaining the product of the pressure P2 in the vicinity of the second RF ion guide and the length L2 of the second RF ion guide in the range 0.05-0.3 mbar-cm;
• and
• passing analyte ions through said second RF ion guide.

A miniature mass spectrometer comprising:

• an atmospheric pressure ionisation source;
• a first vacuum chamber having an atmospheric pressure sampling orifice or capillary, a second vacuum chamber located downstream of said first vacuum chamber and a third vacuum chamber located downstream of said second vacuum chamber;
• an ion detector located in said third vacuum chamber;
• an RF ion guide located within said second vacuum chamber;
• wherein the ion path length from said atmospheric pressure sampling orifice or capillary to an ion detecting surface of said ion detector is ≦400 mm;
• wherein:
• the product of the pressure P1 in the said first vacuum chamber and the length L1 of said first vacuum chamber is in the range 10-100 mbar-cm;
• and
• the product of the pressure P2 in the vicinity of said RF ion guide and said length L2 of said RF ion guide is in the range 0.05-0.3 mbar-cm.

A method of mass spectrometry comprising:

• providing a miniature mass spectrometer comprising an atmospheric pressure ionisation source, a first vacuum chamber having an atmospheric pressure sampling orifice or capillary, a second vacuum chamber located downstream of said first vacuum chamber, a third vacuum chamber located downstream of said second vacuum chamber, an ion detector located in said third vacuum chamber, an RF ion guide located within said second vacuum chamber, wherein the ion path length from said atmospheric pressure sampling orifice or capillary to an ion detecting surface of said ion detector is ≦400 mm;
• maintaining the product of the pressure P1 in said first vacuum chamber and the length L1 of said first vacuum chamber in the range 10-100 mbar-cm;
• maintaining the product of the pressure P2 in the vicinity of said RF ion guide and the length L2 of said RF ion guide in the range 0.05-0.3 mbar-cm;
• and
• passing analyte ions through said RF ion guide.