GMP sample preparation: workflow, traceability and controls

A preparation can have correct labels and still lose some of the analyte. It may also preserve the entire transferred quantity while starting from an unrepresentative aliquot. For a QC laboratory, the workflow must protect identity, composition and the quantitative relationship between sample and result together. Control does not end when the vial enters the instrument.

Define what the result must represent

Before handling the sample, identify the material, batch, matrix, analyte and property to be measured. Clarify whether the result concerns the whole material, a soluble fraction, a dosage unit or a defined portion. Extraction and filtration can change the fraction actually measured: their purpose belongs in the method, rather than being decided by inspecting the sample.

Connect this purpose to the approved method, concentration range and final expression of the result. Concentration in an extract does not automatically equal content in the original sample. Initial mass or volume, quantitative steps and the specified factors are needed. ICH Q14 connects development, required performance and procedure controls; ICH Q2(R2) addresses demonstration of fitness for the intended purpose. Neither replaces preparation-specific instructions.

Receive the sample and determine its status

Compare the request, container and label; record the identifier, origin, batch and relevant sampling information. Assess integrity, available quantity, transport and storage against applicable requirements. A sample that has arrived is not necessarily acceptable for testing yet.

Define who can accept it, place its use on hold or request clarification. Damage, unexpected seals, unknown conditions or conflicting information must remain visible in the record and operational status. A decision may require discussion with the person who collected it; assigning a new code does not resolve uncertain provenance. EU GMP Chapter 6 provides the framework for sampling, identification and controls in its pharmaceutical context.

Preserve representativeness in the aliquot

Identification provides a link to the origin; representativeness requires an appropriate sampling and subdivision strategy. Sedimentation, phase separation or uneven particle distribution can make two aliquots from the same container different. A shared code does not demonstrate shared composition.

Apply the specified mixing, homogenisation and subdivision arrangements, checking that they do not alter the property of interest. Specify which part of the material is sampled, the tool used and the timing relative to mixing. Do not indiscriminately remix a sample when the test is intended to assess a distribution or stratification. The analytical portion must suit the matrix, heterogeneity and method; there is no universal minimum mass.

Map the steps before performing them

The table proposes a map to adapt to the actual workflow. The roles are functions to assign within laboratory procedures, rather than additional mandatory job titles.

Not every preparation needs every operation. Reduce unnecessary transfers and make each container change explicit. For volumetric stages, select systems appropriate for the liquid; pipette–tip compatibility also concerns contact with the sample. When automating, preserve these same links through requirements and tests for the automated workflow.

Control materials, holding periods and storage

Assess containers, closures, tips and filters as parts of the analytical pathway. Chemical compatibility, adsorption, released substances and retained volume are different phenomena. A primary study by Kristensen and colleagues on cationic peptides documents adsorption losses on glass and plastic under specific conditions: it does not establish the best material for every analyte.

Define the interval between preparation and measurement from method evidence, including holding and storage conditions. Time in the vial may matter as much as time on the bench. Q14 includes preparation stability in robustness evaluation. Consider evaporation, light and temperature where relevant; do not assign a generic lifetime to all solutions. Protective measures and solvent handling follow the risk assessment and local procedures.

Record data and calculations as the work proceeds

Link each aliquot to its parent sample and each solution to the preparation from which it derives. Retain actual quantities, units, instruments, relevant reagents, critical times and method version. A code on the container can refer to a complete record; it must still provide unambiguous identification during use.

Review must be able to reconstruct dilution factors and the path from signal to result without relying on the operator’s memory. Distinguish added volume from final volume, and measured values from nominal ones. EU GMP Chapter 4 requires contemporaneous records and traceable changes that preserve the original information. Spreadsheets and forms must support this control; this article does not define a LIMS architecture.

Address the error before repeating the preparation

Simulated case. After weighing, an analyst changes the container and makes the preparation up to the specified volume. Before analysis, material is noticed in the original vessel. The recorded mass is genuine, but it does not demonstrate the amount that entered the solution. Visible residue alone cannot quantify the loss.

Stop using the affected preparation and, where safe and required, retain vessels, solutions, records and observations. Document when the problem was detected and which subsequent aliquots derive from that transfer. Do not retrospectively reduce the mass, introduce an estimated factor or add an out-of-method rinse to obtain the expected result.

The responsible person assesses the cause, impact and authorised route: investigation, possible fresh preparation and management of other affected results. An acceptable repeat does not erase the event. Review the vulnerable step, such as vessel identification and transfer verification, then check the effectiveness of the change. The Liquid handling and sample preparation area explores individual operations in greater depth.

For the related steps, see: Serial dilutions: calculations, execution and error control; Sample extraction: recovery, matrix effects and reproducibility; Syringe filters: adsorption, compatibility and analyte loss.

Sources and scope

EU GMP Chapters 4 (2011) and 6 (2014), in the applicable human medicines context. ICH Q14 Step 5 Revision 1 and Q2(R2) Step 5 Revision 2: current EMA versions consulted on 30 September 2026, effective from 14 June 2024. The public scope was checked for Q2 and relevant full-text sections for Q14. Kristensen et al., PLoS ONE, 2015, PMID 25932639: abstract of the specific study, without quantitative extrapolation. The map and case are original editorial analyses, not approved laboratory procedures.