A secondary goal of the study was to explore the aging characteristics of currency inks in order to establish the useful lifetime of currently used training aids. Solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) was used to ascertain the volatile components found in the headspace of samples of United States currency and its inks and in Canadian currency. Several compounds were identified that can be attributed to the ink-curing process: straight-chain aldehydes, alkenals, acids, alcohols, and ketones, as well as a series of lactones and 2-alkyl furans. Solvent compounds were identified as naphthenic and parraffinic hydrocarbons, alkyl cyclohexanes, ethylene glycol alkyl ethers, and chlorinated solvents. A number of environmental contaminates found on circulating currency but not in currency ink were also identified. In all, more than 100 compounds were identified in the headspace of currency-related samples. The authors concluded that currency inks, currency-scented cotton balls, and shredded currency are useful supplementary training aids for currency detecting canines. However, it should be noted that there was a lack of consistent correlation between the odor levels of the training aids and the authentic currency. As such, authentic currency remains the best training aid. References