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Sample preparation is necessary to make materials ready for analysis with scientific equipment. Different techniques are used depending on the nature of the material and the desired test. Careful handling is required to avoid contamination and ensure accuracy. Laboratories may have their own protocols and documentation to ensure consistency in testing.
Sample preparation makes the material ready for analysis with equipment such as a chromatograph, which can be used to determine the content of a compound. Raw samples usually cannot be fed directly into scientific equipment because they contain impurities or are in a form that the equipment cannot easily interpret. They must be handled and prepared with care to prepare them for testing, under controlled conditions to limit the possibility of errors. There are several techniques available for use with different types of samples.
Technicians start with a raw sample they may have collected or received for analysis. They determine which sample preparation technique to use after evaluating the nature of the material and deciding what type of test they wish to use. The sample may need to be concentrated because the material of interest is highly diluted or treated to remove contaminants that could interfere with the test. Preparing a sample may include filtering, dissolving, grinding, and other activities to convert the sample into a machine-readable format.
For example, a technician might want to use subsampling in sample preparation. This allows a small component of the original sample to be tested to preserve it so it can be used in repeated or different tests. It is important to obtain a representative sample to avoid inaccurate results, so the sample should be handled carefully to extract a good subsample for analysis.
Working conditions must be carefully controlled in sample preparation. Everything that is introduced into the sample must be known so that the technician avoids accidental contamination. For example, if a chemical must undergo a chemical reaction in order to be read in a scientific instrument, the technician must use the right reactive agent. All containers and equipment used should be clean and the bench environment clear to avoid mixing up containers and methods.
Individual laboratories may have their own sample preparation protocol. A laboratory manual discusses the techniques available and provides recommendations for handling specific materials of interest. This documentation can increase consistency in testing by ensuring that no matter which engineer performs a test, the sample is handled the same way. Laboratory customers may request documentation to ensure tests are performed appropriately; for example, a laboratory that tests athletes’ samples for doping would need to do so in a manner consistent with recommendations made by a governing body in order for its results to be valid.
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