The effect of porphyrin concentration (in 0.05 M borate buffer) was investigated. The results showed that the absorption signal for 1.2 μg of manganese increased when the concentration of TCPP was increasing up to 10−5 M, since the equilibrium was shifted toward complex formation. The variation in the absorbance signal along with a further increase in the ligand concentration was negligible.
The changes in a flow rate during preconcentration step between 0.6 and 3 ml min−1 (15 ml of a Mn standard of 100 μg l−1) resulted in very small variations in measured signal (Fig. 3). At higher flow rates, the analytical signal decreased owing to short resistance time of the sample, which resulted in an incomplete retention of manganese. In further study for sample and TCPP solutions flow rates of 3 ml min−1 were applied.
Effect of flow rates during preconcentration (!) and elution (○) on the ...