An adapter for securing a probe to a reaction vessel, comprising: a cover plate having an elongate body portion extending from one side thereof, an axial bore passing through the cover plate and elongate body portion; a probe gripping portion secured to a distal end of the elongate body portion, the probe gripping portion having an axial bore passing therethrough; a collet residing in the axial bore in the probe gripping portion, the collet having a split conical face (65, 70) at each end and an axial bore passing therethrough; a first anvil located in the axial bore in the elongate body portion proximally of the collet, the first anvil having a distal end adapted to engage the conical face at a corresponding end of the collet, and an axial bore passing therethrough; a second anvil located in the axial bore in the probe gripping portion distally of the collet, the second anvil having a proximal end adapted to engage the conical face at a corresponding end of the collet and an axial bore passing therethrough; and wherein, a probe is passed through the adapter by passing the probe through the axial bores (20, 45) in the cover plate, elongate body portion, first anvil, collet, second anvil and probe gripping portion; characterized in that the conical face (65, 70) at each end of the collet is split into a plurality of flexible spring fingers; and the collet exerts a gripping force on the probe passing through the adapter via an inward compression of the flexible spring fingers, when the collet is subjected to an axial force applied to its conical face by the first anvil, the axial force applied by the first anvil resulting from an axial pressing force that will be exerted against the first anvil as a result of pressure from within a reaction vessel when the adapter is in use. a cover plate having an elongate body portion extending from one side thereof, an axial bore passing through the cover plate and elongate body portion; a probe gripping portion secured to a distal end of the elongate body portion, the probe gripping portion having an axial bore passing therethrough; a collet residing in the axial bore in the probe gripping portion, the collet having a split conical face (65, 70) at each end and an axial bore passing therethrough; a first anvil located in the axial bore in the elongate body portion proximally of the collet, the first anvil having a distal end adapted to engage the conical face at a corresponding end of the collet, and an axial bore passing therethrough; a second anvil located in the axial bore in the probe gripping portion distally of the collet, the second anvil having a proximal end adapted to engage the conical face at a corresponding end of the collet and an axial bore passing therethrough; and wherein, a probe is passed through the adapter by passing the probe through the axial bores (20, 45) in the cover plate, elongate body portion, first anvil, collet, second anvil and probe gripping portion; characterized in that the conical face (65, 70) at each end of the collet is split into a plurality of flexible spring fingers; and the collet exerts a gripping force on the probe passing through the adapter via an inward compression of the flexible spring fingers, when the collet is subjected to an axial force applied to its conical face by the first anvil, the axial force applied by the first anvil resulting from an axial pressing force that will be exerted against the first anvil as a result of pressure from within a reaction vessel when the adapter is in use.