Which of the following is a laboratory method used to measure magnesium?

• A. Atomic Absorption Spectrometry
• B. Polymerase Chain Reaction
• C. Liquid Chromatography
• D. Enzyme-Linked Immunosorbent Assay

Answer: (A)

Magnesium is a metal ion, so measuring it in the lab is best done with atomic absorption spectrometry. This technique quantifies elements by passing light of a specific wavelength through free atoms that have been produced from the sample. The atoms absorb light at a characteristic wavelength for magnesium, and the amount of light absorbed is proportional to the magnesium concentration. The sample is atomized in a flame or graphite furnace to generate these free atoms, and a magnesium-specific wavelength is monitored to provide the measurement.

The other methods serve different purposes. Polymerase chain reaction amplifies DNA and isn’t used for elemental measurement. Liquid chromatography separates and quantifies compounds but doesn’t directly measure elemental ions like magnesium without a specialized detector, and enzymatic immunoassays (ELISA) detect proteins or other molecules using antibodies, not metals.