Lipoic acid formulations for the removal of arsenic and mercury from museum artifact materials

Abstract

Museums currently face a tremendous task of identification, mitigation, and remediation of pesticides from artifacts in order to protect museum workers and the general public. Additionally artifacts are being repatriated by Native American tribes for use in cultural ceremonies which may subject the practitioner to health risks. Arsenic and mercury salts are among the most persistent poisons used and so a critical challenge is removing these hazardous metals without damaging the material composition or decorations of the objects. At this time, there are no feasible procedures that can meet both of these objectives. Reported here is the development of a procedure involving concentrated aqueous reduced lipoic acid solutions for the removal of arsenic and mercury pesticides from substrate materials commonly encountered in museums. Sample materials comprised of cotton, wool, paper and feathers (models of real artifact materials) were artificially contaminated with sodium arsenite and mercuric chloride and evaluated for removal treatment with aqueous reduced lipoic acid solutions. A Niton Xli handheld X-ray Fluorescence Spectrometer (XRF) was used to monitor metal contamination levels before and after treatment. The methods developed were capable of removing over 1000 μg/cm 2 arsenic (of sodium arsenite) from simulated artifacts to levels near the lower detection limit of the XRF (1 μg/cm 2). Similar results were achieved in removing mercury (of mercuric chloride) from cotton and paper; however, the solutions and processes developed were not capable of removing mercury from sulfur-bearing materials such as wool and feathers.