Naphthenic acid has been recovered from products of petroleum refining for well over 100 years. The metal soaps, specifically copper and zinc naphthenate, have been evaluated and used as commercial wood preservatives for in excess of 60 years. Most of the early data supporting the continued use of copper naphthenate as a wood preservative was based on materials manufactured from naturally occurring naphthenic acid derived from petroleum. Recent work investigating pesticide label claims for materials asserting to be naphthenic acid salts of copper has in fact shown the presence of many synthetic carboxylic acids as substitutes for naphthenic acid. Additionally, some earlier efficacy studies indicated that non-naphthenate salts of copper actually seemed to promote decay in laboratory tests. This work investigates several sources of copper naphthenate in commercial markets and investigates a novel analytical technique and a modification of this technique to characterize the copper naphthenates found in commercial use worldwide. The basic analytical technique was recently published as an appendix to the American Wood Preservers' Association P-5 (Methods for Chemical Analysis) Sub-Committee annual report to assure compliance with the AWPA P8 Standard.

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