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Standards and Guidelines - Forensic Science Communications - January 2005 11

Standards and Guidelines - Forensic Science Communications - January 2005

January 2005 - Volume 7 - Number 1

Standards and Guidelines 

Validation of Analytical Methods

Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG)

October 2003

Introduction | General Validation Plan | Quality Control |References

1. Introduction


Validation is the confirmation by examination and the provision of objective evidence that the particular requirements for a specific intended use are fulfilled. There are numerous documents that address the topic of validation, but there are few validation protocols for methods specific to seized drug analysis.


An analytical scheme must be comprised of validated methods that are appropriate for the analyte.


The combinations of methods chosen for a particular analytical scheme must identify the specific drug of interest, preclude false positives, and minimize false negatives.


For quantification, the method should reliably determine the amount of analyte present.


If validated methods are used from published literature or another laboratory’s protocols, then the methods must be verified in each laboratory.


Verification should, at a minimum, demonstrate that a representative set of reference materials has been carried through the process and yielded the expected results.


Each laboratory should determine whether its current standard operating procedures have been validated, verified, or require further validation and/or verification.


All methods must be validated or verified to demonstrate that they will perform in the normal operational environment when used by people expected to use the methods on casework.


The entire validation and/or verification process must be documented, and the documentation must be retained. Documentation must include, but is not limited to, the following:


Personnel involved.




Observations from the process.


Statement of conclusions and/or recommendations.


Authorization-approval signature.


To meet these requirements, the Scientific Working Group for the Analysis of Seized Drugs recommends that laboratories follow the applicable provisions of the General Validation Plan when validating seized drug analytical methods.

2. General Validation Plan


Purpose and/or Scope: This is an introductory statement that will specify what is being tested, the purpose of the testing, and the result(s) required for acceptance.


Performance specification: A list of specific objectives (e.g., trueness and precision) should be determined prior to the validation process.


Process review: After completion of the validation process, the objectives should be reviewed to ensure that they have been satisfactorily met.


Analytical Method: State exactly the method to be validated. It is essential that each step in the method is demonstrated to perform satisfactorily. Steps that constitute a method for the identification and/or quantification of seized drugs may include the following:


Visual characterization (e.g., macroscopic examination).


Determination of quantity of sample, which may include the following:



Item count.


Sampling (e.g., representative or random, dry, homogenized).


Sample preparation.

Extraction method.




Techniques for introducing sample into instrumentation.


Instrumental parameters and specifications.

List the instruments and equipment (e.g., balance and glassware) used.

Instrument conditions.


Software applications.



Equation(s) to be used.

Unit specification.

Number of measurements required.

Reference values.

Significant figure conventions.

Conditions for data rejection.

Uncertainty determination.


Validation Reference Materials: Appropriate reference material(s) must be used for qualitative and quantitative procedures.


Performance Characteristics


Selectivity: Assess the capability of the method to identify/quantify the analyte(s) of interest, whether pure or in a mixture.


Matrix effects: Assess the impact of any interfering components and demonstrate that the method works in the presence of substances that are commonly encountered in seized drug samples (e.g., cutting agents, impurities, by-products, precursors).


Recovery may be determined for quantitative analysis.



Precision (repeatability/reproducibility): Determine the repeatability and reproducibility of all routine methods. Conditions under which these determinations are made must be specified. Reproducibility determination may be limited to studies in the same laboratory.

2.1. 2.4.4.

Within the scope of the validation, determine acceptable limits for repeatability and reproducibility.

For qualitative analysis, run the qualitative method a minimum of ten times.

For quantitative analysis, run the quantitative method a minimum of ten times.

Validation criteria for nonroutine methods may differ from what is stated above.
Trueness must be determined for quantitative methods to assess systematic error. Trueness can be assessed through various methods such as the following:

Comparison of a method-generated value for the reference material with its known value using replicate measurements at different concentrations.

Performance of a standard-addition method.

Comparison to proficiency test results.

Comparison with a different validated analytical method.


Range: Determine the concentration or sample amount limits for which the method is applicable.

Limit of detection must be determined for all qualitative methods.

Determine the lowest amount of analyte that will be detected and can be identified. (AOAC in Eurachem)

The results obtained at the limit of detection are not necessarily quantitatively accurate.

Limit of quantitation must be determined for all quantitative methods. Determine the lowest concentration that has an acceptable level of uncertainty.

Linearity must be determined for all quantitative methods.

Determine the mathematical relationship (calibration curve) that exists between concentration and response over a selected range of concentrations.

The limit of quantitation effectively forms the lower end of the working range.

Determine the level of acceptable variation from the calibration curve at various concentrations.

Determine the upper limits of the working range.


Robustness must be determined for either qualitative or quantitative methods. Alter the method parameters individually and determine any changes to accuracy.


Ruggedness may be determined for either qualitative or quantitative methods. Alter the analysts, instrumentation, and environment to assess changes in accuracy.


Uncertainty: The contribution of random and systematic errors to method result uncertainty must be assessed, and the expanded uncertainty derived for quantitative methods.

3. Quality Control

Acceptance criteria for quality control parameters should be adopted prior to implementing the method.

4. References


Enigma Analytical, Validating Analytical Chemistry Methods: Enigma Analytical Training Course (Version 2000-2001), Breckenridge, Colorado, 2000, pp 8-4, 8-5.


Eurachem Working Group. Fitness for Purpose of Analytical Methods: A Laboratory Guide to Method Validation and Related Topics,. Eurachem Guide, 1998. 


Department of Health and Human Services, Food and Drug Administration. International Conference on Harmonisation: Guideline on Validation of Analytical Procedures: Definitions and Terminology. Federal Register, 60 FR 11260, Part VIII (1995) pp. 11259-11262.