The results showed that a flow rate of 1.5 and 2 mL/min gave the highest absorbance for nFIA and rFIA, respectively, (Fig. 3(D)) and they were used in all subsequent experiments. The volume of the sample was varied between 50 and 250 mL using different lengths of sample loop and showed that a sample of 150 mL gave the best absorbance for both methods (Fig. 3(E)).