An adapter for securing a probe (P) 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 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 (P) is passed through the adapter by passing the probe (P) through the axial bores in the cover plate , elongate body portion , first anvil , collet , second anvil and probe gripping portion ; characterized in that the conical face 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 (P) 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 (V) 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 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 (P) is passed through the adapter by passing the probe (P) through the axial bores in the cover plate , elongate body portion , first anvil , collet , second anvil and probe gripping portion ; characterized in that the conical face 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 (P) 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 (V) when the adapter is in use. <EOS>