A system for measuring a sample comprising: an integrating sphere light collectorfor collecting light and containing the sample; a light source for introducing light in the integrating sphere light collector, wherein the light source is operable to output light with a known modulation, preferably by using a signal generator; a detector for detecting scattered light in the integrating sphere lightcollector and generating a signal indicative of the scattered light, and a lock-in amplifier operable use the known light modulation and the signal generated by the detector to provide an output for analysis.