Capillary Centrifugation

Abstract

When using micro methods, it is frequently necessary to centrifuge very small volumes. The arrangement shown in Fig. 1 is suitable for the centrifugation of small volumes of liquid; it also has the advantage of being independent of special adaptors (Neuhoff, 1968b). A Pyrex glass tube of suitable dimensions is sealed carefully by rounding it off at one end and is then annealed. It is filled with the solution by means of a capillary pipette, and is sealed with Parafilm. Some fine quartz sand is placed in a suitable centrifuge bucket and cotton wool is packed well down on top of it to form a layer 2–4 mm thick. Next, a layer of quartz sand is poured on top of the cotton wool; the capillary is inserted into this layer so that it stands centrally on the cotton wool. Then quartz sand is added from a pipette with a wide nozzle, until the glass tube projects about 3 mm out of the layer of sand. The parafilm prevents the solution from contamination during the addition of the sand. The layer of cotton wool ensures that the glass tube does not touch the bottom of the centrifuge bucket even during high speed centrifugation. The layer of cotton wool can be adjusted according to the length of the glass tube. Using this simple set-up, even very small volumes can be centrifuged at up to 15000–20000 rpm in an angle-head rotor for any length of time. The only precautions to be observed are that the centrifuge bucket is filled up almost to the sealed tip of the tube, and that the opposite bucket is tared with quartz sand.