System suitability testing
Establishing that the instrument, column and method were performing when the sample was run.
Purpose
Establishing that the instrument, column and method were performing when the sample was run.
This page exists so that a discussion about a number can start from a shared understanding of what produced it. It is written for a reader who is technically literate but not a practising analyst.
How it works
System suitability is a set of injections run before, and often interspersed with, the sample injections. Its purpose is to demonstrate that the analytical system was capable of producing valid data at the time of the run. It is not a formality.
If the suitability criteria were not met, the sample results from that run are not conservative or approximate — they are uninterpretable, and a competent laboratory will not report them. A report that makes no mention of suitability is not necessarily invalid, but you cannot tell.
What determines the result
The criteria typically cover replicate precision, peak shape, resolution against a specified nearby peak, and column efficiency. Which criteria apply and at what limits is a property of the validated method rather than a universal standard.
Typical criteria
| Parameter | Typical value or criterion |
|---|---|
| Replicate area precision | ≤ 2.0% RSD, n = 5 or 6 |
| Tailing factor | Within the method window |
| Resolution | ≥ 1.5 against the specified peak |
| Blank injection | No interfering peak at the analyte retention time |
These are typical values, not universal standards. The criteria that apply to a specific result are the ones in the validated method that produced it, which is why a report without a method identifier is harder to interpret than one with.
What it cannot tell you
Every analytical method answers one question. The most common error in this community's discussions is treating an answer to one question as an answer to another: a mass match read as a purity result, a purity figure read as a content determination, a sterility test read as a guarantee of safety.
When you read a report, write down which question was asked. The rest follows.
Related pages
Other method notes in this commons cover the neighbouring techniques, and the certificate interpretation page covers how these results get reported. The method validation subcategory is where the discussion happens.
Revision history
| 2026-04-24 | r.aldana_pharmd | Plain-language pass on the opening section after feedback from a newcomer. |
| 2026-01-31 | a.reyes | Added cross-references to the two topics that most often ask this question. |
| 2025-12-21 | batchlog | Reverted an unsourced change and asked the editor to re-apply it with a citation. |
| 2025-08-03 | np_gilmore | Added the worked example that the review thread asked for. |
| 2025-04-27 | d.szymanski | Initial promotion from the source topic. Structure taken from the marked solution. |
Every edit to a maintained document records its author and a note explaining the change. An edit without a note may be reverted by any wiki editor under R9, and the revert is logged. Disagreements about content belong on the source topic rather than in the revision history (R10).
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