Particle detection in liquid reagents for various manufacturing processes is important, especially for the semiconductor industry, to maintain the yield and quality of the end products. As semiconductor devices become smaller, the critical diameters of particle contaminants also become smaller. A measurement system should be correctly calibrated to provide reliable measurements with suitable traceability. Owing to the lack of suitable standard solutions for particle concentration in terms of number, an automatic sampling module compliant with SEMI C-77 has been developed to generate standard solutions with particle concentration as low as 102–103 particles/cm3 depending on the quality of the ultrapure water (UPW) used. With the precise control of flow rates at low and high flux ranges, a dilution factor as high as 4.8 × 109 can be achieved with high accuracy. A concentration standard of polystyrene latex (PSL) nanoparticles with a size of >30 nm was used as stock solution to verify the particle numbers counted by light scattering. The homogeneity of the dilution process was evaluated on the basis of the variation in particle counts during 10 min after sample injection. This automatic system can be applied to the real-time monitoring of the nanoparticles in liquid reagents used in device fabrication.