Clause 7.2 – Selection, Verification, and Validation of Methods, Clause 7.2.1.1 and 7.2.1.2

Clause 7.2 of ISO/IEC 17025:2017 outlines critical requirements for how laboratories select, verify, and validate the methods they use in testing or calibration activities. A method, in this context, is the systematic procedure used to perform a test, which includes the instructions, equipment, reagents, and calculations required to produce valid results.

This clause is crucial because using the wrong or poorly validated method can lead to inaccurate results, potentially affecting consumer safety, regulatory compliance, and the credibility of the lab.

7.2.1 – Selection and Verification of Methods

📌 7.2.1.1: Use of Appropriate Methods

“The laboratory shall use appropriate methods and procedures for all laboratory activities and, where appropriate, for evaluation of the measurement uncertainty as well as statistical techniques for analysis of data.”

This subclause requires laboratories to choose methods that are fit for purpose—meaning they must be suitable for the intended testing or calibration task. The methods should yield reliable, accurate, and traceable results.

It also mandates the use of proper procedures for evaluating measurement uncertainty (i.e., how much doubt exists in the result) and applying statistical techniques for analyzing data.

Example –

A customer submits a sample of wheat flour for testing the iron content. The food testing laboratory has two possible methods:

• A spectrophotometric method that is quick and cost-effective.

• An atomic absorption spectrometry (AAS) method that offers higher accuracy.

Depending on the regulatory requirement or the detection limit requested by the customer (e.g., per FSSAI standards), the lab must select the appropriate method. If regulatory compliance requires results with higher precision and lower detection limits, the AAS method would be appropriate.

Additionally, when reporting results, the lab must include measurement uncertainty, especially when results are close to the maximum permissible limit. The uncertainty calculation may include variables such as calibration, sample preparation error, instrument drift, and analyst variability.

Also, statistical techniques like standard deviation, control charts, or ANOVA may be used to assess and monitor data quality over time.

📌 7.2.1.2: Documentation and Accessibility

“All methods, procedures and supporting documentation, such as instructions, standards, manuals and reference data relevant to the laboratory activities, shall be kept up to date and shall be made readily available to personnel.”

This subclause ensures that the laboratory maintains updated documentation for all its testing methods. These documents must include not just the method itself but also:

• Operating instructions

• Reference standards (such as USFDA-BAM,IS, ISO,AOAC, FSSAI methods)

• SOPs (Standard Operating Procedures)

• User manuals for equipment

• Reference data (e.g., permissible limits, conversion tables)

These documents must be readily available to laboratory personnel performing the work. This can be in the form of a document management system, printed SOP folders, or a secured intranet portal.

Example – 

In a lab testing milk powder for melamine, analysts must follow a validated LC-MS/MS method. The lab must ensure:

• The latest version of the method is available and used.

• Relevant manuals for LC-MS operation and maintenance are accessible.

• FSSAI and Codex limits for melamine are documented for reference.

Suppose a newer version of the method is published (e.g., from AOAC or BIS), the Quality Manager or Technical Manager must update the lab’s method and ensure all analysts are trained in the new procedure.

What Is “Appropriate Method”?

The phrase “appropriate method” refers to a method that is:

• Validated or verified

• Suitable for the matrix (e.g., milk, spice, oil)

• Sensitive and selective enough for the required detection limit

• Compliant with customer and regulatory requirements

• Performed using properly calibrated equipment

If the method is from a recognized source like AOAC, ISO, IS standards, USP, FSSAI manuals, or manufacturer’s validated protocols, then it is often accepted as suitable. However, if a lab uses its own-developed or modified method, it must be validated (see Clause 7.2.2).

Method Selection Process in Practice

A well-functioning food testing lab typically uses a flowchart or checklist for method selection and verification that includes:

1. Reviewing customer request and matrix type.

2. Checking scope and regulatory requirements.

3. Selecting a standard or validated method.

4. Verifying the method for intended use (if not validated in-house).

5. Documenting the method and training staff.

Verification vs. Validation

• Verification is confirming that a standard method (e.g., AOAC 991.31) works well in the lab’s environment and gives accurate results for the tested matrix.

• Validation is required when a method is developed in-house or significantly modified from a standard method.

Clause 7.2.1 mostly concerns selection and verification, while Clause 7.2.2 goes deeper into validation.

Maintaining Method Records

The laboratory should ensure:

• SOPs have unique ID numbers and version control.

• Obsolete versions are archived but not accessible to daily users.

• Staff are trained in the current versions (training records must be retained).

A digital system can help ensure version control, reduce human error, and make documents easily searchable.