The last peak shape problem we will cover today, is negative peaks.
This is when the peak goes down below the baseline background absorbance.
This means that the adsorbance of this peak is less than the mobile phase absorbance.
This occurs sometimes at the void as an equilibrium disturbance when the sample solvent passes through the column. By dissolving the sample in the mobile phase, this can be reduced.
Negative peaks are normal and measured in RI detection because the refractive index can be positive or negative with respect to the mobile phase RI.
Negative peaks can be useful if the sample does not absorb in the UV detector. An additive which doe absorb can be put into the mobile phase and the sample negative peaks can then be measured. This is called indirect UV detection.
宽 峰
* 在进样口到柱或柱到检测器之间，使用细的短的连接管
* 保证所有的管路接头都使用正确
* 用小体积检测池
* 减少进样量
