SUBJECT AREA · 22 GUIDES
Analytical Methods
How laboratories separate, identify, confirm, and measure drugs, alcohols, and other compounds.
Laboratory Sample Preparation
Sample preparation isolates target compounds and reduces material that can interfere with an instrument. The preparation chosen must fit both the analyte and the biological matrix.
Internal Standards in Toxicology
An internal standard is added in a known amount to help track preparation and instrumental variation. Its behavior should be sufficiently similar to the target analyte.
Chromatography in Toxicology
Chromatography separates compounds before detection. Retention behavior supports identification, but separation quality and potential co-elution must be evaluated.
Mass Spectrometry in Toxicology
Mass spectrometry measures ions by mass-to-charge behavior. Identification depends on validated acquisition rules, suitable reference material, and defensible acceptance criteria.
LC-MS/MS in Toxicology
Liquid chromatography tandem mass spectrometry is widely used for targeted drug measurement. Its sensitivity requires close attention to matrix effects, ion ratios, and carryover.
Matrix Effects in Toxicology
Matrix effects occur when specimen components change analytical response. In LC-MS/MS, suppression or enhancement of ionization can bias measurement.
Ion Suppression in LC-MS/MS
Ion suppression reduces mass-spectrometric response when co-eluting material competes during ionization. It may affect analyte and internal standard differently.
Qualitative vs Quantitative Toxicology
Qualitative testing answers whether a compound meets identification criteria. Quantitative testing estimates how much is present within a validated range.
Analytical Interferences
An interference is a substance or condition that affects detection, identification, or measurement. Its significance depends on the method and analyte.
Analytical Selectivity
Selectivity is the method's ability to distinguish the target from other components. It is demonstrated through relevant challenges, not assumed from instrument type.
Extraction Recovery
Recovery describes how much analyte is obtained through sample preparation. Consistent recovery may be more important than maximum recovery when calibration is matrix matched.
Isotope Dilution Toxicology
Stable isotope-labeled internal standards can closely track analyte behavior through preparation and detection, improving quantitative reliability.
High-Resolution Mass Spectrometry
High-resolution mass spectrometry measures ions with accurate mass and can support broad screening and retrospective data review.
GC-MS in Toxicology
Gas chromatography mass spectrometry combines volatile separation with mass-spectral detection. Some compounds require chemical modification before analysis.
Derivatization for GC-MS
Derivatization changes a compound to improve volatility, stability, or detectability for gas chromatography. Reaction completeness and derivative stability require control.
Hydrolysis in Toxicology
Hydrolysis can release conjugated metabolites before analysis. Enzymatic and chemical approaches differ in selectivity, completeness, and risk of degradation.
Solid-Phase Extraction
Solid-phase extraction uses a sorbent to retain or exclude compounds during cleanup. Chemistry, loading, washing, and elution determine performance.
Liquid-Liquid Extraction
Liquid-liquid extraction partitions compounds between immiscible phases. pH and solvent selection are used to favor transfer of the target compound.
Protein Precipitation
Protein precipitation is a rapid preparation method for blood, serum, or plasma. It removes proteins but may leave phospholipids and other sources of matrix effect.
Chromatogram Integration
Integration defines the area or height attributed to a chromatographic peak. Manual changes can be legitimate but should follow rules and remain auditable.
Full-Scan Toxicology
Full-scan acquisition collects a broad range of ion data and can aid library searching. It still has sensitivity, extraction, chromatography, and library limits.
Untargeted Toxicology Screening
Untargeted screening seeks compounds beyond a fixed list, often using high-resolution data. No workflow is truly capable of finding every chemical.