Development of a real-time, in-situ particle sizing technique: Real-time light transmission spectroscopy (RTLTS)

We developed an improved particlemeasurement spectroscopic technique, real-time laser transmission spectroscopy (RTLTS), to detect the number-weighted distribution of particles in real time. The measurement system used a deuterium-tungsten lamp for the light source and a spectrometer as the detector. The operating wavelength range was 300-810 nm. To obtain a physically reasonable number concentration from the experimental results, a sequential regularization method was used during the calculations. To verify the feasibility and reliability of RTLTS, the number-weighted distribution of polystyrene particle suspensions was determined over diameters ranging from 0.005 to 2.000 μm in 0.005-μm increments. The measured concentration error was 0.67-32.67%. A mean diameter of the smallest particle we had detected was 0.09 μm, with a 16% oversizing. The measurable concentration range was ~10⁸ #/cc to ~10¹¹ #/cc for 0.895-μmdiameter particles. The measurable concentration range could be adjusted simply by changing the system configuration. This technique is available for both waterborne and airborne particles.