ISO 17025 Laboratory Sampling Requirements – Fit the Bill!

ISO 17025 Laboratory Sampling Requirements

ISO 17025 is an international standard that outlines the requirements for the competence of testing and calibration laboratories. This standard is used by laboratories around the world to ensure that they are providing accurate and reliable testing and calibration services. The ISO 17025 laboratory sampling requirements request organizations to have a well-established sampling method and plan. This will set up any laboratory on the right path to success.

This must include all the activities that the organization will plan to sample, for example, products for calibration (thermometers, tachymeters, etc.); materials (such as weights), substances or materials for analysis (food, water, air). The laboratory would need to determine the extent of such sampling and what factors need to be controlled. This is essential to ensure validity of testing.

Organizations may need to devise a proper sampling methodology to ensure the homogeneity of samples and a sampling plan. This may involve statistical methods.

Note that sampling procedures may not just entail the physical collection of samples, such as material or products, but may also require theoretical sampling of mathematical processes and sample numbers for audits.

With the new 2017 standard, more emphasis has been done on sampling to include sampling as another laboratory activity apart from testing and calibration while also including or taking into consideration the sampling uncertainty as a significant contributing factor for the evaluation of measurement uncertainty.

The scope of this topic is to understand the ISO 17025 laboratory sampling requirements for better results and to allow the user to grasp the different roles within this activity. Even though reference to uncertainty of measurement (UM) will be made, this will be tackled in another topic.

ISO 17025 Laboratory Sampling Requirements

One important aspect of ISO 17025 laboratory sampling requirements is to have a documented sampling plan. This plan should outline the steps that the laboratory will take to ensure that samples are collected, handled, and transported in a manner that maintains their integrity and ensures the accuracy of the test results.

Some key requirements for a laboratory’s sampling plan include:

  • The plan should be written in a clear and concise manner, and should be readily available to all laboratory staff.
  • The plan should outline the procedures that the laboratory will follow for each type of sample that it collects, including details such as how the sample will be collected, the amount of sample that will be collected, and any special handling requirements.
  • The plan should include a description of the equipment and materials that will be used for sampling, and should outline any quality control measures that will be in place to ensure the accuracy and precision of the samples.
  • The plan should include a description of the procedures that the laboratory will follow for sample transport and storage, including any temperature or other environmental conditions that must be maintained.

Thus, organizations must show evidence of a sampling plan and evaluate the associated sampling uncertainty. Having said that, it’s up to the organization to evaluate if an activity’s uncertainty of measurement is significant enough to include in the final calculations. Such an example would be during sub-sampling. If the sampling methodology requires the need for sub-sampling and the sample received in the lab would not be homogenous, then consideration of sampling uncertainty is to be taken into account. Alternatively, if a larger volume can be sampled, the uncertainty would be negligible.

Sampling method shall contain:

  1. Sampling plan – E.g., Matrix showing frequency of sampling
  2. Selection of sample sites – To ensure that the sampling is representative
  3. Preparation and treatment of samples, prior to and post collection

By following a documented sampling plan, a laboratory can ensure that its samples are collected, handled, and transported in a way that maintains their integrity and ensures the accuracy of the test results. This is an essential part of meeting the ISO 17025 laboratory sampling requirements and providing reliable testing and calibration services.

1)    Sampling Plan

A sampling plan may not be necessary for many instances but would be crucial in planning out sampling frequency throughout the year. This sampling plan may include the location of sampling points, frequency and amount of sampling, and any other requirements to ensure proper sampling, depending on the point. Such sampling points may be dependent on legislation, production, or up to the client itself, provided that the client may show evidence that the sampling frequency is sufficient to achieve a good representative sampling frequency. Below is an example of a sampling plan:


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Sample Point 1 Loc. A Loc. B Loc. C Loc. A Loc. B Loc. C Loc. A Loc. B Loc. C
Sample Point 2 Loc. B Loc. C Loc. A Loc. B Loc. C Loc. A Loc. B Loc. C Loc. A

Location Sampling Point Street Address Point location Preservation / Bottle type
Loc. A Tap 1 First tap Alcohol/Flaming
Loc. B Tap 2 Tap after room Alcohol/Flaming
Loc. C Tap 3 Tap in basement Alcohol/Flaming

2)    Selection of Sampling Sites

As mentioned before, sampling can also be theoretical, with no materialistic substance. In such case the sampling plan would be consistent with the activity:

  • Define the population – What number range are you looking to select, are there any criteria for such numbers? What parameters are you testing for?
  • Define sample size – How many numbers are to be selected? As mentioned above, the larger the volume, the lower the uncertainty of measurement. In such a case the larger the data set, the more statistical integrity the number would have. How many subsamples do you need? Will this affect analysis?
  • Random number generator – This can be electronic or manually operated. Either way, such a method needs to be verified or validated by comparison. A simple question to explain this: What is the possibility of choosing a five from a hat with ten balls ranging from 1 to 10? The possibility should be the same (not statistically significant) if a random number generator (electronically) were to be used; If ten water samples are collected at random from the same point, would the analysis be different?

3)    Preparation and Treatment of Samples, Prior to and Post Collection

As discussed, sampling is one of the most crucial activities that may degrade eventual activities that come after. If a sample is not preserved in a suitable way, sample characteristics may degrade, affecting the final product and thus resulting in an erroneous result. For this reason, samples may need to be preserved, recorded, or treated in a way to maintain their longevity. Such treatment may include the use of bottles with chemicals, cold temperatures, photographs, data recording, statistical data etc.


To meet the ISO 17025 laboratory sampling requirements, companies need to identify their scope of activities. Once this is established, they would need to refer to legislation or testing standards, which may indicate the minimum sampling criteria. These criteria may include the volume of testing required, which will then indicate the minimum volume required for sampling, specific preservation criteria required and minimum limits of detection, which will indicate the level of accuracy required.

Example: Let’s assume that the criteria for chloride in concrete should not exceed 500 mg/L. In such a case, complex ion chromatography analysis with a limit of detection of 0.1mg/L would not be required, as chloride testing kits of 1 mg/L would suffice. Alternatively, if a mercury level of 0.001ug/L is required, atomic absorption analysis would not be sufficient.

Interested in learning more?

Luke Desira is an ISO management system consultant whose purpose is to make your company outshine others! Learn how to achieve ISO 17025 accreditation here! To further learn about ISO 17025 laboratory sampling requirements and software validation in ISO 17025, click here!

All management systems based on ISO Standards that are implemented should pertain directly to the organization’s objectives, and ISO 17025 – Testing and Calibration Laboratories should be no different. Have a look at the ISO Certification specialised by Industry to understand in which category your organization falls.

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