Sample Availability vs Method Requirements

An important practical concern that is easily overlooked is the amount (size) of the analytical sample that is available. If this is too small given the expected concentrations of analyte(s) and the minimum size of the aliquots required per analysis in order to avoid statistical limitations on precision (see discussion of Equations [8.95-8.97, Section 8.6) it will limit the strategic options available to the analyst, e.g., number of replicate analyses, applicability of the Method of Standard Additions etc. 

The amount of available sample needs to be considered both from the perspective of how this impacts the method and LLOQ and also from the standpoint of having enough sample for re-analysis in the event of run failure or other sample re-assay directives. Even in cases where an adequate amount of sample is available for re-assay, repeated run failures could lead to depletion of the sample. This is particularly problematic with multi-analyte assays where the probability of run failure due to one or more of the analytes in the assay increases as a function of the number of analytes in the method (Dadgar 1995). 

Another example where the amount of available sample is a critical consideration with respect to method design 

Information with respect to the receipt of the sample shipment should be recorded and maintained with the study or project file. If a Chain of Custody is sent along with the sample shipment, the instructions as to how to complete the form must be reviewed and completed as prescribed. At a minimum, all shipping documentation should be retained, and the condition of the sample shipping container and the condition of the samples themselves should be recorded. For samples that are shipped 

After the required procedures (laboratory SOPs) are completed for sample receipt and documentation, the samples must be logged into the laboratory s Laboratory Information System (LIMS) database, or other method that is described in the applicable SOPs. This step is also commonly referred to as sample accessioning . If sample log-in cannot be completed upon receipt or within the time prescribed by the laboratory SOPs, an explanation for the delay should be documented in the sample receipt records. All samples should arrive with sufficient labeling for unique identification (sample ID), including any duplicates received. In many instances, the laboratory will add another label with additional information, such as a unique laboratory ID. 

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