As discussed in Question #11, aluminum foil serves three purposes to minimize biases associated with Methods 0010 and 0030. First, the hexane-rinsed aluminum foil prevents ultraviolet light from effecting the resin bed and analytes attached to the resin bed. Second, the aluminum foil helps to minimize the influence of heat from either the sun or the stack. In addition, the application of the aluminum foil helps to minimize influence of outside contamination on the walls of the cartridge.
Sometimes in stack testing, it is the small things that can add up to create large biases in the test data. The aluminum foil helps us to maintain some small biases within our accepted control limits.