Figure 1
(a)–(b) A small piece of heat-shrink tubing of size 2.4/1.2 mm (inside diameter before/after heating) is manually stretched to ±4 times its initial length, (c) cut into ±5 cm segments and slid over the capillary. (d) In the next step, a ±2 cm piece of standard Swagelok tubing (which has been deburred on the outside and the inside) with an outer diameter of 1/8 inch (= 3.175 mm) is slid over the covered capillary. (d)–(e) The heat-shrink tube is then slowly heated from the bottom up (towards the open end of the capillary) with a heat gun (first at 100 and then 350°C). For the setup to work properly, it is crucial to use heat-shrink tubing shrinking lengthwise along the capillary towards the inside of the Swagelok tube after the initial stretch. The best results were obtained with 2.4/1.2 mm heat-shrink tubing (product code LSTT-R-2.4-0) manufactured by TE Connectivity (part of the Raychem group, USA). The shrinking procedure is exemplified in a video available in the supporting information (Video S1). (e) Any residual heat-shrink tubing sticking out of the Swagelok tube after shrinkage is removed with a razor blade. The open end of the capillary is then carefully cut at the Swagelok tube, preferably with a ceramic blade to prevent the formation of micro-fractures along the capillary wall. (f) A set of 1/8-inch Swagelok nuts and ferrules connects the capillary to the Swagelok parts and (g) allows pressures up to 65 bar in the case of 1 mm quartz capillaries. A second video showcasing pressurization of the newly developed capillary setup with 60 bar of N2 is also provided in the supporting information (Video S2). |