Sample preparation is the first critical step in any analytical technique as it directly impacts the quality and reliability of analytical results. The goal of effective sample preparation is to ensure that the analyte of interest is extracted from the sample matrix and presented to the analytical instrument in a form that is compatible with the technique.
Sample Collection and Storage
The initial sample collection method can significantly affect the reliability of subsequent analyses. Sample Preparation must be collected carefully in appropriate containers to avoid contamination or analyte loss. Prompt transfer to the lab and proper short-term and long-term storage conditions are necessary to preserve sample integrity until analysis. Guidelines for collection, labeling, and preservation techniques should be followed as per standard protocols for each analyte and matrix.
Sample Amount and Homogenization
The mass or volume of the initial sample needs to be sufficient to not only account for analyte variability across the sample batch but also allow for multiple preparations and repeat analyses if needed. Most techniques also require a homogeneous sample to produce reproducible results. The sample must therefore be thoroughly mixed, comminuted, dissolved, or diluted as applicable to the matrix before extraction or separation of the analyte.
Extraction and Disruption
Extracting the analyte from the sample matrix is a key step in many preparation methods. This may involve separation using liquid-liquid partitioning, solid-phase extraction, membrane filtration, dissolution, or disruption techniques like ultrasonication, microwave-assisted preparations, or enzymatic digestion. The extraction conditions must be optimized for maximum analyte recovery while minimizing co-extraction of interferences. Automated systems can improve extraction precision, throughput, and reproducibility.
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