The influence on the environment of trace heavy elements such as Cd, Pb, As, Cr, Se, etc. in water is considered a serious social problem. In order to control this problem, it is essential to monitor water quality. Considering the large number of test samples required for assessment of water quality, the test method should be simple, rapid, and reproducible. X-ray fluorescence (XRF) analysis has many positive features, such as simple sample preparation, short analysis time, and high repeatability with low human error, compared to other elemental analysis methods, such as ICP-OES or AA. XRF is the best method for the above test. Concentrations of some trace heavy elements are too low for XRF analysis in direct liquid analysis, where water solution is poured into a liquid cell with analysis thin film. In this application note, the micro-droplet method was used. An improved filter paper “Ultra Carry®” for the micro-droplet method achieved an LLD lower than 0.1 ppm. This application note demonstrates the analysis results and performance of the micro-droplet method with Ultra Carry.