Sample Preparation
Definition
The set of steps between the sealed evidence container and the instrument autosampler vial: extraction, clean-up, concentration, derivatisation, dilution, internal standard addition. Sample preparation typically accounts for 60 to 70 percent of the total analysis time in a CFSL toxicology workflow and is the single largest source of variability in the final result.
- Scope
- Extraction, clean-up, concentration, derivatisation, dilution
- Time share
- 60 to 70 percent of total analysis time
- Impact
- Largest source of result variability
- Setting
- CFSL toxicology workflow
Common questions
Why does sample preparation dominate the total time of an instrumental analysis?+
The instrument run itself is often fast, but getting a complex biological or physical matrix into a clean, concentrated form the instrument can read reliably requires multiple manual and chemical steps, each of which adds time before the sample ever reaches the autosampler.
Why is sample preparation the largest source of variability rather than the instrument itself?+
Modern instruments are highly reproducible once a sample is loaded, but manual steps like extraction efficiency, derivatisation completeness, and dilution accuracy vary between analysts and batches, so most of the scatter in a final result traces back to this stage.
What is the role of an internal standard added during sample preparation?+
An internal standard added early in preparation tracks losses that occur during extraction and clean-up, letting the analyst correct the final measured value for anything lost before the instrument run, which improves accuracy despite prep-stage variability.
Related terms
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- Presumptive Test
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