By Sarah L. Harrer – Updated Mar 24, 2022
Copper, often referred to as the world’s oldest metal, remains a cornerstone of construction, electronics, and even U.S. currency. As the most recycled metal in the world, maintaining its purity—typically over 99.99%—is essential for both industrial applications and financial integrity. The gold standard for measuring copper purity is spectrometry, a method that assesses how much visible light a sample absorbs without contaminating the metal.
Power on the device and allow it to warm up to its optimal operating temperature. Set the wavelength to copper’s characteristic absorption band, ensuring the instrument is tuned to detect copper’s unique spectral fingerprints.
Adjust the front knob to the “0 percent T” setting to establish a baseline. This calibration guarantees accurate absorbance readings for the sample.
Use a water‑scented wipe to remove any residue or fingerprints from the copper tube. This “waste‑water” cleaning—known as an “e‐waste” process—ensures the sample’s integrity without introducing contaminants.
Place the cleaned copper tube into the sample compartment, close the lid, and set the knob to “100 percent T.” This prepares the instrument to measure the sample’s absorbance accurately.
Observe the absorbance value on the spectrometer’s display. A high purity copper sample will show a distinct, sharp peak at its characteristic wavelength.
Pure copper exhibits a faint blue‑green hue. Any deviation—such as discoloration—indicates the presence of impurities. The spectrometer should also reveal copper’s “faint, bright” emission bands, confirming its authenticity.
For more on copper’s role in national currency, visit the U.S. Mint.
