For students and curious beginners: The very same LC-MS run can produce three very different-looking chromatograms. Learn what TIC, BPC and XIC show—and what each hides.
See the big picture
| 🔵 1. Collect scans
At each time point the MS records ion intensities. |
🟣 2. TIC sums
Add up signal from all included ions. |
🟡 3. BPC selects
Find the strongest ion in each scan. |
🟢 4. XIC extracts
Track one selected m/z across time. |
Imagine a concert with thousands of listeners
You could ask three questions: how loud is the entire audience, who is the loudest person, or how loud is your friend? The three answers differ even though the crowd is the same. LC-MS data behave similarly: each scan contains many measured ion signals, and we can summarize them in different ways.
What does TIC mean?
Total ion chromatogram (TIC) usually plots the sum of all recorded ion intensities within the acquired or chosen mass range, one value per scan, against retention time. It can give a broad view of the run. But a strong background or highly abundant ion may dominate the signal, and a trace substance can be invisible.
What does BPC mean?
Base peak chromatogram (BPC) plots the intensity of the most intense ion in each scan. A surprising detail: the identity of that ion may change from scan to scan. Therefore, the BPC is not necessarily the chromatogram of one compound.
What does XIC or EIC mean?
Extracted ion chromatogram (XIC/EIC) plots only the signal within a selected mass or m/z interval. It acts like a color filter on a photograph, isolating one feature. Selecting m/z 301.1234 within a suitable tolerance may reveal a peak hidden in the TIC.
Mini experiment with one imaginary scan
| Recorded ion | Intensity |
|---|---|
| m/z 100 | 20 |
| m/z 200 | 70 |
| m/z 300 | 10 |
At that scan, the TIC intensity is 20 + 70 + 10 = 100. The BPC intensity is 70, contributed by m/z 200. An XIC for m/z 300 has intensity 10. Repeat this calculation at every scan time to obtain three chromatograms.
Which should you use?
| Your question | Useful first view |
|---|---|
| Was the run broadly consistent? | TIC |
| When did the dominant ions elute? | BPC |
| Does a specific ion co-elute at 5.2 min? | XIC/EIC |
Important limitation: an XIC at one m/z does not prove the signal comes from one compound. Different compounds and isotopes can share nearly the same m/z, and fragments or adducts can create additional traces. Confirm identification with other evidence.
Related: How to Read an HPLC Chromatogram.
Test yourself (answers below)
- Which chromatogram adds intensities of all included ions?
- Does one BPC trace always correspond to one compound?
- Which view helps track an ion at a selected m/z?
Reveal the answers
- TIC.
- No. The most intense ion can change at each scan.
- XIC or EIC.
Learn more: reliable references
Educational note: The images and numerical examples are schematic. Real LC-MS methods depend on analyte, instrument and laboratory conditions.