Which of the following is not a problem inherent in turbidimetry?

• A. Variation in particle size of samples
• B. Variation in particle size of standards
• C. Rate of aggregation or settling of particles
• D. Need to maintain a constant and specific temperature

Answer: (D)

Turbidimetry measures how much light is scattered by suspended particles, so the signal depends on particle characteristics and how stable those characteristics are over time. If sample particle size varies, the amount of scattering changes, leading to inconsistent results. Calibration also hinges on using standards whose particle size behavior matches the samples; otherwise the standard curve doesn’t reflect the same light-scattering relationships. Particles that aggregate or settle alter the number and size distribution in suspension, causing turbidity to drift during measurement. Maintaining a constant and specific temperature, however, is a procedural control to keep conditions uniform rather than a fundamental problem of the measurement itself. Temperature mainly affects factors like solvent properties and refractive index, but with proper temperature control it doesn’t define a basic limitation of turbidimetry.