Abstract: A microbalance and method for measuring the total mass of small quantities of material (mass ranging from about 10 nanograms to about 0.1 gram) using Compton and Rayleigh scattered radiation provides excellent mass measurements for these samples. The apparatus includes a standard radiation generation and detection assembly, including a substantially evacuated chamber through which incident radiation travels, and commercially available radiation generators, power sources, and detectors, having enough spectral resolution to identify the scattered radiation of interest.