What Method Validation Actually Requires Under TNI Standards

For environmental laboratories, producing a test result is only part of the job. The laboratory must also demonstrate that its analytical methods are suitable for their intended purpose, perform as expected, and produce data that can be supported by documented evidence.

That is where method validation comes in.

Under The NELAC Institute (TNI) laboratory accreditation standards, method validation is an important part of demonstrating technical competence and ensuring the quality of environmental data. Yet the process is often misunderstood. Some laboratories treat validation as a one-time experiment. Others confuse method validation with method verification or assume that following a published EPA method is sufficient on its own.

In practice, laboratories need a documented, systematic process that connects the analytical method, its intended use, performance evidence, quality control requirements, and ongoing records.

For laboratories managing increasing volumes of samples and compliance documentation, a Laboratory Information Management System (LIMS) such as LEAF LIMS can help bring these activities together in a more organized, traceable workflow.

What Does TNI Require for Method Validation?

The TNI Laboratory Accreditation Standards establish requirements for laboratories performing environmental analyses. Under the 2016 standard, method validation requirements are addressed in Volume 1, with technical requirements varying according to the type of testing performed. For chemical testing, relevant provisions appear in Volume 1, Module 4, including Section 1.5.

The general principle is straightforward: before a laboratory accepts and implements a method for reporting results, it must establish that the method is suitable for its intended use and meets the applicable requirements.

The exact work required depends on the method, the technology, the laboratory’s application, and whether the method is standard, modified, non-standard, or developed internally.

A laboratory should therefore begin by identifying the applicable TNI requirements, the regulatory or client requirements, and the method-specific criteria that govern its work. The laboratory’s accreditation body and applicable program requirements should also be considered.

Method Validation vs. Method Verification: What’s the Difference?

These terms are related, but they are not interchangeable.

For example, a laboratory adopting a published analytical method may need to demonstrate that its personnel, equipment, procedures, and laboratory conditions can produce acceptable results. If the laboratory substantially modifies that method or applies it beyond its intended scope, a more extensive validation may be necessary.

The distinction matters because applying the wrong process can lead to unnecessary testing, incomplete documentation, or gaps during an accreditation assessment.

The laboratory should document which approach applies, why it applies, and what evidence supports the decision.

The Key Elements of a Defensible Method Validation

01Define the Intended Use

Validation begins before laboratory testing. The laboratory needs to understand what the method is expected to measure, which sample types it will handle, the concentration range of interest, and the quality of data required.

Relevant considerations may include:

• The analyte or characteristic being measured.
• The sample matrix, such as drinking water, wastewater, soil, or another environmental material.
• The expected concentration range.
• Applicable regulatory limits and reporting requirements.
• Required detection or quantitation capabilities.
• Method-specific quality control and acceptance criteria.

These factors help determine the extent of validation needed and the performance characteristics that must be evaluated.

A method that performs adequately for one matrix or concentration range may not be suitable for another. Defining the intended use helps prevent laboratories from relying on performance evidence that does not reflect actual testing conditions.

02Evaluate the Relevant Performance Characteristics

Method validation is not simply a matter of running a few samples and confirming that results look reasonable. The laboratory must evaluate the characteristics relevant to the method and its intended application.

Depending on the analytical method, these may include:

Accuracy or bias

How closely the results agree with an accepted reference value or expected concentration.

Precision

How closely repeated measurements agree under specified conditions.

Selectivity

Whether the method can distinguish the target analyte from other substances or potential interferences.

Detection capability

Whether the method can reliably detect the analyte at the levels required for the intended use.

Limit of quantitation (LOQ)

The concentration at which the laboratory can quantify the analyte with acceptable performance, according to applicable criteria.

Working range and linearity

Whether the method produces suitable results across the intended concentration range.

Robustness and matrix effects

Where relevant, whether variations in operating conditions or differences in sample matrices affect performance.

Not every characteristic applies in the same way to every method. The laboratory must follow the applicable standard, approved method, regulatory requirements, and established acceptance criteria rather than assume that a single checklist covers every situation.

03Establish and Apply Acceptance Criteria

Validation results must be evaluated against defined criteria. Without established acceptance criteria, the laboratory may collect data without having a defensible basis for deciding whether the method performs adequately.

Criteria may come from the approved analytical method, applicable regulatory requirements, accreditation requirements, client data quality objectives, or scientifically justified laboratory procedures where permitted.

The laboratory should establish criteria before evaluating the study whenever practicable, document the source of those criteria, and explain any applicable deviations.

For example, a laboratory assessing precision may compare replicate results against an established limit. An accuracy study may compare measured concentrations with known spike concentrations or reference values.

If results fail to meet the applicable criteria, the laboratory should investigate the cause, document the findings, and determine whether corrective action or additional study work is necessary.

The goal is not simply to complete the validation. It is to demonstrate, with evidence, that the method is appropriate for the work the laboratory intends to perform.

04Document the Study and Its Conclusions

A successful validation requires more than acceptable analytical results. It also requires records that allow the laboratory to explain what was done, how the data were evaluated, and why the method was accepted.

A defensible validation record will generally identify:

• The method and version evaluated.
• The intended application and sample matrices.
• The study procedure and relevant conditions.
• Equipment, standards, reagents, and materials used, as applicable.
• Raw data and calculated results.
• The performance characteristics evaluated.
• Acceptance criteria and their sources.
• Any deviations, failures, investigations, or corrective actions.
• The conclusion about fitness for the intended use.
• The review and authorization required by the laboratory’s quality system.

The specific records depend on the applicable requirements and method. The important principle is that the conclusion must be supported by evidence that can be retrieved and reviewed later.

Scattered spreadsheets, paper worksheets, disconnected instrument files, and undocumented decisions can make this process difficult. Even when the analytical work is sound, weak recordkeeping can complicate an assessment.

05Control the Method After Approval

Method validation is not an isolated administrative exercise. Once a method is approved for use, the laboratory must continue to operate it under controlled conditions.

This includes maintaining current procedures, using qualified personnel, following calibration and quality control requirements, monitoring performance, and documenting changes.

Changes to an analytical method, equipment, software, sample matrix, or operating conditions should be assessed to determine whether they affect the method’s validated performance. Depending on the change, the laboratory may need additional verification, partial validation, or a more extensive reassessment.

Routine quality control results can also reveal emerging problems. Unexpected changes in precision, accuracy, blank results, or other indicators may signal that a method needs investigation.

A controlled process for method approval, revision, and ongoing monitoring helps ensure that the laboratory continues to have a defensible basis for reporting results.

Where Laboratories Commonly Encounter Problems

Several recurring issues can undermine an otherwise well-designed validation program.

These problems are not necessarily caused by poor analytical science. Often, they arise because the laboratory lacks a consistent way to manage the information surrounding the analytical work.

How LEAF LIMS Can Support Method Validation

A well-configured Laboratory Information Management System can help laboratories manage method-related information and maintain traceability throughout their quality processes.

LEAF LIMS supports the broader goal of organizing laboratory workflows, sample data, and records so laboratories can work more consistently and retrieve information more efficiently.

For a laboratory implementing or strengthening its method validation program, relevant LIMS capabilities may include the following, depending on the system’s configured features:

The important distinction is that a LIMS supports the laboratory’s quality system; it does not replace the technical work required to validate a method. The laboratory remains responsible for performing appropriate studies, establishing justified acceptance criteria, reviewing the evidence, and approving the method.

LEAF LIMS should be configured and evaluated against the laboratory’s actual workflows, applicable TNI requirements, and any additional regulatory or client requirements. Laboratories should confirm the availability and suitability of specific features before relying on them for a compliance purpose.

A Practical Method Validation Workflow

Laboratories can make the process more manageable by establishing a repeatable workflow:

1. 01Identify the requirement. Determine the applicable method, accreditation requirements, and intended application.
2. 02Classify the method. Establish whether validation, verification, or another defined evaluation is appropriate.
3. 03Plan the study. Specify the performance characteristics, acceptance criteria, materials, and procedures.
4. 04Perform the work. Collect the required data under documented conditions.
5. 05Evaluate the evidence. Compare results against established criteria and investigate exceptions.
6. 06Document the decision. Record the conclusion, supporting evidence, and required approvals.
7. 07Control implementation. Make the approved method and associated procedures available to authorized personnel.
8. 08Monitor ongoing performance. Review quality control results and assess changes that may affect suitability.

A LIMS can help organize several of these steps, particularly record linkage, workflow consistency, approvals, and retrieval. The laboratory’s quality management system must define responsibilities and determine how each requirement is satisfied.

Build a Stronger Foundation for Laboratory Data Quality

Method validation is about demonstrating that an analytical method is appropriate for its intended purpose—and preserving the evidence that supports that conclusion.

Under TNI standards, laboratories need more than a completed study. They need a documented approach to method selection, performance evaluation, acceptance criteria, review, approval, and ongoing control that reflects the applicable requirements for their testing activities.

With a structured quality process and the right digital tools, laboratories can reduce administrative friction, improve traceability, and make supporting records easier to retrieve when questions arise.

LEAF LIMS helps environmental laboratories organize laboratory information and workflows in support of more consistent, traceable operations. By bringing relevant sample, analytical, and quality records into a structured system, laboratories can build a stronger foundation for managing the documentation associated with method validation and routine testing.

Disclaimer: This article is intended for general educational purposes and is not a substitute for the applicable TNI standard, approved analytical methods, regulatory requirements, or guidance from your laboratory’s accreditation body. Requirements vary by testing discipline and method. Laboratories should consult the current applicable standards and verify their obligations before implementing a validation or verification program.

References

1. The NELAC Institute (TNI), Laboratory Accreditation Standards, including the applicable Volume 1 modules. nelac-institute.org/content/CSDP/standards.php
2. The NELAC Institute (TNI), Assistance to Laboratories and quality-system resources. nelac-institute.org/content/NELAP/howto.php