Sampling is the initial stage in any quality control laboratory testing. It is also a critical step, as any errors made during sampling can invalidate any results obtained.

In some situations, such as an erroneous sampling of an incorrect batch, but of an otherwise correct material, would in all probability go undetected.

In light of this, the instructor advocates measures to verify correct sampling at the point of source, such as confirmation by a second person, as happens with other critical steps in a manufacturing process, which rely on human judgement and are susceptible to error.

Purpose of Sampling

The purpose of sampling is to obtain a truly representative sample of the bulk material. It should be carried out according to scientifically valid sampling plans, and based on statistical principals. The sampling plans should also address factors to be controlled, to ensure the validity of the samples taken.

The procedures should also address any precautions to be taken to prevent contamination or deterioration of the sample, such precautions could include:

• Sampling in specified locations
• Use of personal protective equipment
• Use of dedicated sampling or single use tools

Deviations

Any deviations from established sampling plans should be documented, and justified, which should include an assessment on any impact the deviation may have on the validity of the sample.

All deviations must be approved by laboratory management, and authorised by the quality assurance department.

Information for Sampling

All sampling operations should be documented with the following information:

• Material identity
• Material stock reference
• Batch number
• Sampling procedure used
• Statistical principles on which sampling is based (if appropriate)
• Environmental conditions (if appropriate)
• Identification of sampling locations (if appropriate)
• Identity of the person(s) performing the sampling