Compact mass spectrometer

A 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;
• and
• a first RF ion guide located within said first 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;
• and
• wherein 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 is in the range 10-100 mbar-cm.

A 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;
• and
• 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;
• and
• wherein the product of the pressure P2 in the vicinity of said second RF ion guide and said length L2 of said second RF ion guide is in the range 0.05-0.3 mbar-cm.

A method of mass spectrometry comprising:

• providing a 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, and an ion detector, 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;
• and
• providing a first RF ion guide located within said first vacuum chamber, 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, and passing analyte ions through said first RF ion guide;
• and/or
• providing a second RF ion guide located within said second vacuum chamber, 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.