ACD/IntelliXtract

Technical Information

What is componentization?

A component represents a single chemical entity eluting in chromatographic space. A component can be used to describe a single ion peak (in a mass chromatogram), or the collection of single ion peaks associated with a single chemical entity. Chromatographic information, such as peak shape, and the mass spectrum may be used to confirm the presence of a chemical species eluting at a particular retention time. Componentization is the ability to separate the individual ion signals as a function of retention time, and to classify the individual ion peaks that are associated with a single chemical species. In other words, the process of componentization finds all of the possible chromatographic peaks in the dataset, and interprets the corresponding mass spectrum (assigning where possible the (de)protonated molecule, adducts, multimers, isotopes, and fragments).

Componentization is a function of sensitive peak extraction, the discrimination of peaks from noise, accurate determination of the retention times of individual ion peaks, the determination of ion mass clusters, including isotopic ions, and the analysis of adduct ions and multimers. Many other software packages offer peak extraction algorithms, but only IntelliXtract performs componentization.

The image on the left shows two overlapping component peaks. The image on the right shows a single component comprised of multiple single ion chromatogram peaks.

How does it work?

ACD/IntelliXtract uses the following logic to determine the molecular ions of the components present in an LC/MS dataset. This logic is very similar to the approach that expert mass spectrometrists would use to interpret the data.

1. Generate a list of single ion peaks (mass chromatogram peaks) present in the dataset using the CODA algorithm
2. Filter the real peaks from noise
3. Group the single ion chromatogram peaks based on accurate retention times
4. Sort the extracted ion peaks for each retention time into primary ion clusters
5. Search for missing isotope peaks which may have been filtered out in Step 2 (see the section on Self-Optimization below)
6. Determine the first ion (X) in a cluster
7. Assign multimers, adduct ions, possible fragment ions, and [M+H]⁺ or [M-H]^- within each component.

Self-Optimization

ACD/IntelliXtract was designed to be reliable and easy-to-use, and features a unique self-optimizing algorithm. A number of tests are applied (e.g. the expected ¹²C/¹³C isotope ratio, a search for expected adducts based on the presence of adduct ions) to evaluate the quality of the data, and to confirm the presence of a component. Because there is a processing step which filters peaks from noise (step 2 above), there is a chance that important peaks may be filtered out. If there are expected isotopes missing that are necessary to confirm the presence of a component, ACD/IntelliXtract will go back and search for the missing isotope peak. This makes the algorithm very robust with respect to the selection of input parameters, which means that the user doesn't have to spend too much time fiddling around with software input parameters in order to achieve a quality result.

Still want additional technical information? Read a poster describing the technology behind ACD/IntelliXtract...