Extraction
Definition
The first step in sample preparation. The analyte is pulled out of its original matrix (blood, urine, viscera, soil, paint chip) into a solvent or sorbent that the instrument can handle. Choices range from classical liquid-liquid extraction to solid-phase extraction (SPE), solid-phase microextraction (SPME), accelerated solvent extraction (ASE), Soxhlet for fats and lipids, and dilute-and-shoot for high-concentration urine work.
- Purpose
- Pulls analyte from matrix into a solvent or sorbent
- Matrices
- Blood, urine, viscera, soil, paint chip
- Methods
- LLE, SPE, SPME, ASE, Soxhlet, dilute-and-shoot
- Step order
- First step in sample preparation
Common questions
Why is dilute-and-shoot suitable only for high-concentration samples like urine drug screens?+
It skips a concentration step, so it works when the analyte is already present at a level the instrument can detect after simple dilution, but it would miss trace-level analytes in a matrix like blood or tissue that need a concentrating method such as SPE.
How does an analyst choose between liquid-liquid extraction and solid-phase extraction for a case?+
The choice depends on matrix complexity, the analyte's polarity and volatility, throughput needs, and how much cleanup the downstream instrument requires; SPE generally gives cleaner extracts with less solvent but LLE remains simpler and cheaper for straightforward matrices.
Related terms
- Bracketing Standards
- Calibration standards or quality control samples injected before, during and after a batch of case samples. They track instrument drift through the...
- Calibration Curve
- In RIA, a set of standards containing known concentrations of unlabelled analyte that are run alongside test samples. Bound radioactivity is measured...
- Certified Reference Material (CRM)
- A sample with one or more analyte concentrations established by an accredited body and traceable to a national metrology institute. NIST SRM...
- Internal Standard (IS)
- A compound chemically near-identical to the analyte, often a deuterated isotopologue (d3-morphine, d5-EDDP, d5-alprazolam, pyrene-d10), spiked into every sample at a known...
- Limit of Detection (LOD) and Limit of Quantitation (LOQ)
- LOD is the lowest concentration the instrument can reliably distinguish from blank, defined as three times the standard deviation of the blank...
- Recovery
- The fraction of analyte that survives the extraction and clean-up workflow, measured by spiking a known amount of analyte into a blank...