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Analyses for Co, Zn, and Pb on mixed bed and SA-2 cation exchange resin-loaded paper disks in amounts approaching the theoretical limits of detection were attempted. Based on the results, the definition of limit of detection which requires a line intensity above background equal to three times the square root of the background, using a 10-min count, was modified to the line intensity above background equal to three times the standard deviation of the background counted for 10 min on a series of blank disks. Chemical precleaning of the disks and corrections for paper density were shown to be advantageous for work close to the limit of detection by lowering the background count and reducing the weight-corrected standard deviation.