A simple device for washing out radioimmunoassay tubes.

The use of disposable polystyrene tubes for radioimmunoassay is now widespread. Washing out such tubes before disposal is tedious and time-consuming, especially if they contain dense charcoal or doubleantibody pellets. In this laboratory the simple device described below has much reduced the time and tedium involved in this task. It was constructed in a frew minutes for a cost of a few pence. *A hypodermic needle (19 g x 2 inches) is fixed to a length of plastic or rubber tubing (about 5 mm outside diameter, 4 mm bore) either by tying or simply by threading as shown in the figure. The plastic tube is connected to a pump which preferably discharges directly into a sink outlet or overflow. The needle is connected to a tap. Part of a disposable 1 ml-syringe makes a convenient adaptor. The apparatus is fixed in a clamp at a comfortable working height above a sink. For use water is passed through the needle (about 100-120 ml/min) and the pump turned on. Tubes to be washed are uncapped, held as shown over the apparatus for a few seconds, and discarded, conveniently into a plastic disposal bag fixed to the edge of the sink or bench. Obstinate