Good Laboratory Practices and Quality Assurance

Since 1987 the European Council had adopted two basic Directives and a Decision relating to the application of the GLP principles, Directive 2004/10/EC and Directive 2004/9/EC.  These Directives lay down the obligation of the Member States to designate the authorities responsible for GLP inspections in their territory (NSAI in Ireland), comprises requirements for reporting and for the internal market (i.e., mutual acceptance of data) and gives procedures for the inspection and verification of good laboratory practice (GLP).  The standard which details the criteria in relation to good laboratory practice and quality assurance is ISO 17025 which can be obtained from the NSAI. 

Although accreditation to an NSAI standard is not a licence requirement all laboratories conducting analysis to demonstrate licence compliance with licence conditions should have in place a robust quality system. 

A laboratory quality system should cover all aspects of laboratory operations

1.     Management

2.     Measurement Traceability

3.     Accommodation & Environment

4.     Sampling

5.     Test Methods

6.     Handling and Transportation

7.     Equipment

8.     Analytical Quality Control

9.     Result Reporting


Determining Performance Characteristic

In determining the performance characteristic of a method and determining its suitability for the test matrix data the following must be obtained through method evaluation and testing.

  • Limit of Quantification: the lowest concentration that can be determined with acceptable laboratory reproducibility and trueness.
  • Accuracy: how close the measurement is to the true value expressed as the mean.
  • Precision: how close the measurement is to the mean value expressed as the standard deviation.
  • Uncertainty of Measurement: uncertainty in the measured value.

In determining the suitability of the method to the test matrix as well as investigating the method for known interferences the following analysis should be conducted:

  • Spiking: adding a predetermined sample (i.e. a sample of the licensee discharge which is to be tested) to a concentration in the range of interest or at least a minimum of 50% of this value.  Recovery of the added spike should not be significantly:
    • Less than 90%
    • Greater than 110%

In the case of testing for organic methods suitability recovery of the added spike should not be significantly:

    • Less than 80%
    • Greater than 120%

Other useful information can be found at the following sites:

The National Standards Authority of Ireland website

An OECD guidance document on principles of good laboratory practice

More information on how to determine the analytical quality control performance characteristics of the test method and its suitability for the test matrix can be found in:

ISO/TS Water Quality – Guidance on analytical quality control for chemical and physiochemical water analysis obtained from