A series of experiments were performed to optimize analytical conditions with 1.0 × 10−6 mol L−1 uric
acid.
The flow rate was an important factor which influences the
analytical sensitivity. The effect of the flow rate of two pumps
on CL intensity was examined in the range of 0.5–3.5 mL min−1.
The results showed that the CL signal increased with flow rate
increased, because the CL reaction is rapid. So the flow rate of
3.5 mL min−1, the maximal flow rate under present conditions, was
selected as optimum.
The CL reaction was performed in alkaline condition and the
alkalinity of reaction medium was adjusted by varying the concentration of KOH in DPA solution. The effect of KOH concentration
on the CL reaction was examined in the range of 0.01–0.5 mol L−1.
As can be seen from Fig. 4a, the suitable concentration of KOH was
0.2 mol L−1 because a maximal CL intensity could be obtained under
this alkalinity.
DPA was the oxidant in the CL reaction which effect on CL intensity was investigated. The range of the concentration of DPA was
5.0 × 10−4–1.0 × 10−3 mol L−1. The experiments showed the maximal CL signal could be obtained when the concentration of DPA
was 4.0 × 10−4 mol L−1 (Fig. 4b).