Investigations into the use of copper and other metals as indicators for the authenticity of Scotch whiskies

Trace element analyses were conducted on 35 Scotch Whiskies to investigate if the trace element fingerprint is characteristic for different kinds of Scotch Whiskies. The element concentrations of the eight elements investigated varied considerably; for zinc and iron three orders of magnitude (0.02 to 20 mg Zn L-1 and 0.02 to 28 mg Fe L-1), while nickel and magnesium varied within two orders of magnitude (0.002 to 0.6 mg Ni L-1 and 0.02 to 4 mg Mg L-1). Small variations were detected for calcium, sodium and copper (0.5 to 4 mg Ca L-1, 2 to 24 mg Na L-1, 0.1 to 1.7 mg Cu L-1), while lead, with one exception was usually below 0.005 mg L-1. Using Cluster analysis no characteristic metal fingerprints were identified for the different geographical regions. However, when a second set of samples (42 malt and 8 blend whiskies) were analysed for copper, the copper concentration could be used as a criterion to distinguish Blended or Grain Scotch from Malt Whisky. The Malt Whiskies had a copper concentration between 385 and 480 ng mL(-1) (95% confidence limit) while the copper concentration of the blended whiskies was between 143 and 242 ng L-1. Since the difference was highly significant (p < 0.0001), it is suggested that a simple copper analysis could be used as one test to distinguish between a Blended and Malt Scotch Whisky.