Which instrument is used for determination of particle size?

Particle size determination requires direct imaging capabilities provided by electron microscopy techniques. SEM offers surface visualization for measuring particle dimensions through high-resolution topography, while TEM achieves higher resolution for nanoscale internal structure analysis and particle measurement.

Spectroscopic methods prove unsuitable for direct size determination: FTIR identifies functional groups and chemical composition, and UV-visible spectroscopy quantifies concentrations and electronic transitions, though it may provide indirect size information through plasmon resonance effects in specific cases.

The instruments directly capable of particle size determination are $\boxed{\text{A, B}}$.