Which method measures antigen-antibody complexes by light scattering?

• A. Turbidimetry
• B. Nephelometry
• C. Electrophoresis
• D. Chromatography

Answer: (B)

Nephelometry measures antigen-antibody complexes by light scattering. In this approach, light is directed at the sample and the intensity of light scattered at an angle (commonly around 90 degrees) is detected. As antigen–antibody complexes form, they create particles that scatter more light, so the amount of scattered light increases with the amount of complexes, providing a quantitative readout of the reaction.

Turbidimetry also involves scattering, but it tracks the drop in light that passes straight through the sample (transmitted light), which is generally less sensitive for small complexes. Electrophoresis separates molecules in an electric field, not by light scattering, and chromatography separates components on a column based on interactions with the stationary phase, not by measuring scattered light.