FAQ

Quantitation

1. What does relative quantitation mean?

Relative quantitation provides information about the amounts of a compound in a sample relative to another sample. Example. We can say that compound X is 2-times more concentrated in sample a than b.

2. What does the absolute quantitation mean?

Absolute quantitation (also known as targeted metabolomics analysis) refers to the analysis that results in metabolites concentration or amount of a compound tissues or other biological material. It can be expressed in mg/g or ml. The analysis is performed using standard curves with a pure compound of known concentration that are measured in the same batch as the biological samples of interest. The signal of a compound in biological samples is than compared to the signal of a reference compound in standard curve sample. This is followed by the calculation of concentration. The whole workflow includes measurements of samples and standard curves by GC-MS or LC-MS. This kind of analysis has limitations. The efficiency of an extraction of a compound can differ between matrices and a pure solution, therefore the extraction efficiency can lead to over or underestimation of concentration. Nevertheless, extraction efficiency should be considered during analysis, or the standard curves should be measured using extracted compounds. It is required that the pure standard of know concentration is available or can be purchased.

3. How is the relative quantitation performed?

For relative quantitation, samples are measured in an untargeted manner by GC- or LC-MS. Ionized metabolites reach mass spectrometer detectors to create the signal proportional to their ionization efficiency and abundance. The signal of a compound can be compared across the samples. The intensities of a detected metabolite can be expressed as the ratio of a metabolite in sample A vs B. The same metabolite can be compared across samples, but different metabolites cannot be compared within the same sample.
If the intensity signal of a metabolite X is 20 in control and 80 in a sample subjected to a treatment, we can calculate that the relative amount of this metabolite increased 4-fold.

4. How is the absolute quantitation performed?

We perform absolute quantitation by measuring reference compound in different concentrations (standard curves) in one batch with biological samples using LC-MS or GC-MS. To perform absolute quantitation, a reference compound of known concentration must be available. This service is offered only on request as this requires of optimization of many parameters: finding linear range of the mass spectrometer response for this compound

5. What is the usual timeline for untargeted metabolomics?

The turnaround time of the analysis depends on the scope and complexity of the experiment. For large-scale studies with multiple analytical platforms, the full workflow—including measurement, data processing, and quality control—may take up to three months from the time of sample receipt.
For smaller-scale experiments or projects utilizing a single platform, results are typically delivered within four weeks after the samples arrive at MetaSysX.
We always aim to provide high-quality data within the shortest possible timeframe, and our team will inform you of the expected turnaround time during project planning.
The turnaround times may vary depending on overall workload and demand, which can fluctuate during periods of the year. We recommend discussing timelines with our team during project planning.