Which instrument is typically used with colorimetric copper reduction methods such as Folin-Wu?

• A. Colorimetric-Spectrophotometer
• B. Polarimeter
• C. Mass spectrometer
• D. pH meter

Answer: (A)

These colorimetric copper reduction assays rely on forming a colored product whose intensity is proportional to the amount of analyte. To quantify that color, you need an instrument that measures how much light the sample absorbs at a specific wavelength. A colorimetric spectrophotometer does exactly that: it passes light through the sample and records absorbance, giving a numeric value that correlates with concentration. In the Folin-Wu copper reduction approach, the resulting blue color is read spectrophotometrically, typically at a wavelength around 750 nm, enabling accurate quantification. A polarimeter measures how light’s polarization changes, which isn’t what these assays rely on. Mass spectrometry determines molecular masses, not color, and a pH meter gauges hydrogen ion activity, not absorbance. So the colorimetric spectrophotometer is the appropriate instrument.