Copper(I) chloride is a white, tetrahedral crystalline powder that readily oxidizes to a grayish-green color when exposed to light and slowly oxidizes to form copper(II) salts when exposed to moist air. It is a strong reducing agent and is commonly used as a catalyst for diazotization reactions in organic synthesis and as an aid in acetylene polymerization. It is also used in electroplating, as a decolorizing agent, for impurity removal in metallurgy, and as an intermediate in pesticide production.

Electrolytically produced copper(I) chloride on the copper wire

A new solid-phase microextraction (SPME) fiber has been developed and applied for the determination of some amines (n-pentylamine, tripropylamine, dibutylamine, diisobutylamine and tributylamine). In this study two copper wires were immersed in sodium chloride solution and electrolysis was performed at a constant potential. Anode was oxidized to copper(I) to produce copper(I) chloride as a sorbent for the studied amines on the copper wire. Several parameters affecting the fiber preparation and SPME procedure such as electrolysis time, selection of the SPME coating, extraction time and temperature were optimized. The copper(I) chloride fiber was the most appropriate one for the determination of amines by SPME–GC–FID. The optimized method was linear over the range studied (1–100 μg L?1) and showed good precision, with R.S.D values less than 3% for all analytes. Fiber production was reproducible and R.S.D for fiber-to-fiber was less than 8%. The proposed SPME–GC method showed some advantages such as lower detection limits, a shorter analysis time and the avoidance of expensive commercial fibers. A method for the preparation of fiber to sampling amines from gas phase has been optimized. Three different fibers were tested and the copper(I) chloride fiber showed good efficiency in the adsorption of the studied amines compounds. Different effective parameters on the extraction have been optimized and 15 min extraction time, 10 °C extraction temperature, 300 °C desorption temperature, 5 min desorption time and 100 mL vessel were selected.[1]

Copper(I) chloride antiperspirant action

Copper compounds have been used for more than 4000 years for human cosmetic and topical “medical-dermatological” purposes. Despite copper's ancient and premodern history of topical skin usage, the modern scientific utilization of topically applied copper compounds is limited. Regarding modern scientific antiperspirant preparations, these were originally based on, and remain based on, aluminum compounds, not copper compounds. Since the commercialization of modern antiperspirants, many studies have been published on the efficacy of aluminum-based antiperspirant formulations, but there are no published papers of copper(I) chloride in terms of antiperspirant efficacy. The evaluation of the effect of copper(I) chloride on axillary sweating was conducted as a controlled, clinical trial. The study conformed to the Declaration of Helsinki guidelines, and had IRB approval.[2]

In terms of possible negative effects of topical copper application, we note that copper(I) chloride can cause bleaching of clothing fabric colors due to the acidity of the formulation, and that copper compounds can cause irritation. (Both these examples are also true with aluminum chloride). However, importantly, there are no reported long-term, negative health effects due to the application of copper(I) chloride formulations on the skin. The present study utilized a direct quantitative measure of the real-life/patient-concerning aspect of axillary hyperhidrosis. Exercise-induced sweating, of course, is only one type of sweating, and future studies may wish to address the effect of copper(I) chloride on psychologically induced sweating. Further, it would be interesting to use other available research techniques, such as the gravimetric or the silicone imprint method, to measure the antiperspirant efficacy of copper(I) chloride. Also, larger population studies using patient-to-patient design protocols (instead of the side-to-side axillae comparisons used here) would be interesting. Hopefully, these, and other scientific questions related to this ancient medicinal metal will be addressed in future studies.

References

[1]Mir Ali Farajzadeh,  Nafiseh A. R. (2005). Electrolytically produced copper(I) chloride on the copper wire as an excellent sorbent for some amines. Talanta, 65 3, Pages 700-704. https://doi.org/10.1016/j.talanta.2004.07.039

[2]Ernest Bloom,  Jerrold S. P.,  Howard I. Maibach. (2012). Copper chloride antiperspirant action. Indian Dermatology Online Journal, 3 2, 150–151. https://doi.org/10.4103/2229-5178.96724