Two kinds of ISO/IEC 17025 calibration.

The auditor picks one reported result and asks where it came from. You pull the ICAL, the prep log, the balance and pipette certificates, and the certificate for the stock. Each record has to point to the next one.

ISO/IEC 17025:2017 sets the rules for that walk. It is the international standard for the competence of testing and calibration labs. It is also the basis for most lab accreditation programs, including the TNI standard used by environmental labs [1]. It covers every kind of lab, so it never mentions a calibration curve.

In a chromatography lab, its calibration rules apply in two places. The first is the equipment behind every standard: balances, pipettes, volumetric glassware and thermometers. An outside provider calibrates them.

The second is the ICAL, which turns a peak area into a concentration. The standard treats both as measuring equipment. Expect the auditor to ask about both.

The ISO/IEC 17025 clauses that matter.

The table paraphrases the ISO/IEC 17025:2017 clauses as accreditation bodies present them in training material [2][3][4]. The right column shows the evidence that usually answers each clause for an ICAL.

Clause summaries are paraphrases. The standard itself is the authority and is available from ISO and national standards bodies.

Tracing an ICAL back to the SI.

Clause 6.5 asks for an unbroken chain of calibrations that links a result to a reference. Each link adds to the measurement uncertainty, and a gap in any link breaks the chain. For a chemical result, the usual route to the SI runs through a certified reference material. It comes from a competent producer and states its traceability to the SI [3].

ILAC P10 is the policy accreditation bodies apply to traceability. It recognizes calibrations from national metrology institutes covered by the CIPM Mutual Recognition Arrangement. It also recognizes calibrations from accredited calibration labs, and reference values from competent reference material producers [5].

In practice, the auditor follows the chain one link at a time. First comes the certificate of analysis for the stock, then the balance and pipettes used to dilute it. Next is the prep record for each ICAL level, and last the ICAL that used them.

Two links are often the weakest. The first is the prep record, where the dilution is written down and the equipment is not. The second is the last link. The chain only covers results inside the calibrated range, so a result above the top standard is diluted and never extrapolated.

Showing results stay valid.

Clause 7.7 asks for a procedure to monitor the validity of results. It lists checks that equipment works, and intermediate checks on measuring equipment. They also include check or working standards, with control charts where they apply [4]. So do proficiency testing and comparisons between labs.

In chromatography, these map straight onto routine work. The second-source ICV checks the standards behind the curve. The CCV is the intermediate check.

Control charts of CCV recovery and ICAL response show drift before it becomes a failure. Insights 09 covers how to judge each one. A chart only counts if someone reviews it and acts on what it shows.

The calculation is part of the record.

Clause 7.11 covers control of data and information management. A LIMS must be checked to work before use. It must be kept safe from unauthorized access, tampering and loss. Calculations and data transfers must be checked in a suitable and systematic way [6].

That last rule reaches further than many labs assume. The model you fit is a calculation. So are its weighting, the back-calculated errors, and any spreadsheet you use to judge RSE or relative error.

If your lab relies on a calculation to accept a curve, you need evidence that the calculation is correct.

The same goes for the CDS regression itself, which most labs accept without a separate check. Check both, and keep a record that you did.

An ISO/IEC 17025 readiness checklist.

1. Trace one result end to end. Go from the reported value to the ICAL, the prep record, the equipment certificates and the reference material certificate.
2. Confirm equipment status at the time of use. The balances and pipettes used for the standards were in calibration on the prep date.
3. Write down the calibration programme. Record ICAL frequency, recalibration triggers and the CCV procedure, and follow them.
4. Keep the ICAL decision record. Keep the model, weighting, excluded points and acceptance results, along with the final curve.
5. Show results stay valid. Review the ICV, CCV and control charts, and act on what they show.
6. Check the math. Check the CDS and spreadsheet calculations used to accept a calibration, and record the check.

Where WLTR fits.

Most of the evidence an auditor asks for already exists in the lab. What is usually missing is the ICAL decision record and a check of the math behind it, both kept so they can be produced on request.

WLTR is calibration data integrity infrastructure for regulated analytical laboratories. For each analyte, it derives nine calibration regression models: average response factor, plus linear and quadratic fits across four weightings each. It scores every model against fifteen ICAL parameters, including RSE. All of it is computed orthogonally to the CDS, under U.S. Patent 12,038,448 B2 [P].