Shiqiang_Huang Hi Shiqiang,
Yes, you can avoid spikes in iolite. In fact, iolite performs an outlier rejection automatically when reporting the mean and uncertainty for each selection. You can set the level of outlier rejection in Preferences -> Stats (2SD outlier, 3SD outlier, or none). By default, any data points greater than 3SD from the mean will be treated as outliers and not included in the reported mean for that selection.
Even better is that iolite does this on a channel by channel basis, so that if a point is an outlier in one channel, it is not automatically then assumed to be an outlier in other channels. An example of when this is advantageous is if you have a signal spike which when one channel is ratioed to another is not an outlier (that is, the count rates might vary by more than 3SD, but the ratio between two channels for that datapoint is not an outlier, and iolite will not treat it as such).
Regarding selecting two intervals for one sample (due to an inclusion or similar): yes, this is possible. It's called selection linking. You may have seen the little link icon that appears when you're editing one selection and then hover the mouse over another selection. If you click the link icon, the two selections will then create a linked selection. In the case of an inclusion, you could select the data before the inclusion, and then create a second selection for the data after the inclusion, and while you're still in Edit Mode, click the Link Icon on the first selection to link the two. iolite will report the stats for the combined datapoints as the Linked Selection. You can tell a that a selection is a linked selection because it is colored orange in the Time Series View.
If you have any questions about these topics, please just let me know.