Measuring multimodal size distributions of aquatic colloids at trace concentrations

Many applications in research as well as industry require a highly sensitive detection of particulate matter in water or process liquids. We present a technique to measure the distribution of colloid sizes between 20 and 100nm in situ at ultratrace concentrations. The method is based on laser-induced breakdown detection, which has been applied for trace detection of colloids and determination of the weighted mean size. Using a refined method of data evaluation, we are now able to measure the number density of inorganic colloids in six size classes between 20 and 100nm simultaneously below ppb concentration.