Tool free gas cone retaining device for mass spectrometer ion block assembly

A mass spectrometer is disclosed comprising an atmospheric pressure interface comprising an ion block or sub-assembly 3 with an inner sampling cone 13, capillary or other gas limiting orifice. The mass spectrometer further comprises a clamp 2 formed from a thermally insulating material such as plastic, and a removable outer gas cone 1 which is slidably inserted into or onto the clamp 2 so that the outer gas cone 1 is retained by the clamp 2 in use. The clamp 2 is arranged and adapted to be pushed by a user into engagement with the ion block or sub-assembly 3 so as to secure the outer gas cone 1 to the ion block or sub-assembly 3 in a position adjacent the inner sampling cone 13 and to form a gas tight seal with the ion block or sub-assembly 3 without use of mechanical fasteners such as screws or allen bolts.