Characterization of a sampling tube used in a chemical filterpack sampler

A 100 cm long teflon sampling tube that is used in the National Oceanographic and Atmospheric Administration's chemical filterpack samplers was evaluated as to its effectiveness as a gravity settler. The evaluation found the tube to have a large variation of collection efficiency with time which is not anticipated in gravitational theory. The tube initially had large collection efficiencies before declining to theoretically predicted values. The tube was evaluated under numerous conditions and the following conclusions were determined. The high initial efficiencies are due to electrostatic forces and the tube's ultimate approximate efficiency for particles 2 to 7 microns in diameter is 3 to 6%, respectively. The tube's efficiency can be increased to over 50% by coiling it into a cyclonic configuration and applying a coating of silicone grease.