3.2.6. Effect of injection time
Injection time had a great influence on signal amplification. In our study, different injection times varying from 150 to 330 s were evaluated. The result showed in Fig. 3F. Both the peak heights and areas of the analytes obviously increased without a deterioration of peak shapes with increasing injection time from 150 to 300 s.These could be explained by the fact that the online preconcentration technique decreases the width of the injected sample band, so that there is neither breakdown in resolution nor efficiency despite the larger-than-usual injection volumes. However, with a longer
injection time, remarkable broadening peaks were observed, which led to the decrease of separation efficiency and a failure to achieve baseline separation. A 300 s injection time was suitable for the standard. However, it wasn't nice to apply to the real samples. The optimization of injection time for real samples was given in Sections 3.3 and 3.4.