Internal Standard / Deuterated Standard
Definition
A chemically similar (often perdeuterated) compound spiked into the sample to correct for matrix effects and ionisation suppression. Standard practice in forensic LC-MS quantitation.
- Field
- Forensic LC-MS quantitation
- Nature
- Chemically similar compound, often perdeuterated
- Purpose
- Corrects for matrix effects and ionisation suppression
- Usage
- Spiked into the sample before analysis
Common questions
Why is a deuterated version of the target analyte preferred as the internal standard?+
A deuterated analogue behaves almost identically to the target compound during extraction, chromatographic separation, and ionisation, since it shares the same chemistry, but its added mass lets the mass spectrometer distinguish it from the analyte, allowing accurate correction for losses and suppression at each step.
What happens to quantitation accuracy if no internal standard is used?+
Without a matched internal standard, matrix components in blood, urine, or tissue can suppress or enhance the analyte's ionisation efficiency unpredictably between samples, making reported concentrations less reliable and harder to compare across a batch.
Related terms
- Atmospheric Pressure Chemical Ionisation (APCI)
- A complementary atmospheric-pressure source that vaporises the LC eluent and uses a corona discharge to ionise a reagent gas, which transfers charge...
- Electrospray Ionisation (ESI)
- A soft atmospheric-pressure ionisation source that sprays the LC eluent through a charged capillary into a heated counter-current gas, producing protonated or...
- Hyphenation
- Online coupling of a separation technique (GC, LC, ICP) with a spectrometric detector (MS, FTIR) so identification happens within the same run....
- ICP Plasma
- Inductively coupled argon plasma at 6,000 to 10,000 K that atomises and ionises samples in ICP-MS, generating singly charged elemental ions for...
- Interface
- The hardware bridge that transfers analyte from the separation stage to the detector while removing the unwanted mobile phase (carrier gas, solvent,...
- Isotope Ratio Mass Spectrometry (IRMS)
- Specialised MS that measures precise ratios of light stable isotopes (delta values of 2H, 13C, 15N, 18O, 34S) on a continuous-flow combustion...
- Jet Separator
- Early GC-MS interface (Ryhage, 1964) that used differential pumping through a nozzle to enrich analyte and bleed helium. Replaced by direct capillary...