2 TRENDS OF SAMPLE DISPERSION VARIATION WITH CARRIER FLOW-RATE IN A SINGLE FLOW-INJECTION MANIFOLD

Two trends of sample dispersion variation with carrier flow rate in a single flow-injection manifold are completely revealed for the first t ime and an inflection point in the dispersion coefficient (D) vs. flow rate (q) curve is discovered. With the increase of the flow rate, the value of D increases before the inflection point but decreases after the inflection point. The value of the earlier flow rate at the inflec tion point (q(m)) is independent of the sample injection volume, the t ube length, the tube coil radius and the tube inner diameter. It is on ly affected by the substance diffusion coefficient (D-m) of the analys is. The value of q(m) decreases as D-m increases. Therefore, the value of D-m for a sample can be estimated according to the D-m vs. q(m) cu rve.