Schematic diagram showing the implementation of the DSMC method for the in vitro system from Leo et al. (2013), with the control volume (CV) and the actual tube labeled as 1 and 2, respectively along with an image (inset) of the actual Eppendorf tube used for the in vitro measurements. Nanoparticles, dissolved oxygen (DO), hydrogen, and citrate ions are represented in the system. Total length, L, and diameter, D, are 4 cm and 1.4 cm, respectively based on the actual Eppendorf tube used for measurements. L1, the length of the cylindrical portion of the tube, is 47 % of the total length of the tube. (Diagram not drawn to scale and is for illustration purposes only)