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36 Pharmaceutical Technology REGULATORY SOURCEBOOK SEPTEMBER 2021 P h a r mTe c h . c o m sampling plan and is divided into three sub-processes: proce- dure, protocol, and record. The sampling process is specific to a particular material or material type as illustrated in the first part of this paper (1). It should be noted that for any given material there may be different sampling procedures dependent on the characteristic. For example, the sampling procedure for a chem- ical characteristic, such as assay, may well be different from that for physical characteristic such as particle size. The output from this sampling process is the Analytical Sam- ple (Figure 1a) which is used in conjunction with the required analytical procedure to deliver the reportable value (Figure 1b). While primarily concerned with testing, reference to sam- pling is made in the ISO standard, General Requirements for the Competence of Testing and Calibration Laboratories (6) in sections 7.3, 7.8.2, and 7.8.5. These requirements are for the sampling of substances, materials, or products for subsequent testing or calibration. In addition, it makes an important re- quirement in 7.2.2.1 f, namely that "evaluation of measure- ment uncertainty of the results based on an understanding of the theoretical principles of the method and practical experi- ence of the performance of the sampling or test method" (6). See the standard for more details for measurement uncer- tainties in sampling. Some laboratories include the sampling requirements within the analytical procedure; however, this leads to overly long pro- cedures and is not recommended. The elements of this process are described in more detail in the subsequent sections. Contents of a statistical sampling plan (Phase 0) A statistical sampling plan is a high-level master document containing all necessary definitions and structures to ensure that a representative sample from a given material popula- tion is available for testing in the laboratory. This is a critical document because sampling is always an error-generating process and that, although the reported result or value may be dependent upon the selected analytical procedure, it will always be dependent upon the sampling process (7). The suggested main terms and definitions are shown in Table I, and its position in the overall process f low for a typical high-performance liquid chromatography (HPLC) application is shown in Figure 2. Sampling process (Phase 1) For practical purposes, the sampling process terminology may be reduced to five (or sometimes fewer) stages as shown in Figure 3. For example, the combined sample could be the laboratory sample or even the analytical sample. The actual nomenclature to be used for a given material would be defined in the sampling procedure and protocol with additional terms from the Statistical Sampling Plan (Phase 0) when required. Sampling protocol. This document contains the complete sampling operations to be performed on a defined material for a specific purpose and is traceable to the SSP. Sampling record. This written record of the actual sampling operations carried out on a particular material for a defined purpose should contain: • a unique identifier for the parent material • date, time, and place of sampling • reference to the sampling protocol used • a description of the containers, with labeling instruc- tions, of the materials sampled Best Practices: Part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igure 1. Proposed structure for sampling for Phase 0 and Phase 1 (a) and testing for Phases 2 and 3 (b). FIGURES COURTESY OF THE AUTHOR.