Meaning
Chemical compounds of known concentration added to analytical samples correct for material losses and signal drift during spectroscopic or chromatographic measurements. In polymer testing laboratories, an internal standard is introduced during resin extraction to measure the concentration of additives such as slip agents or antioxidants. The added compound must have chemical properties similar to the analyte but remain distinct from any component in the original resin.
Testing Mechanism
Quantification of additives involves dissolving the polymer matrix and extracting the soluble organic compounds into a solvent. During this extraction and subsequent filtration, some loss of the target analyte inevitably occurs. By adding an internal standard before sample preparation, the analyst can calculate the ratio of the analyte peak area to the standard peak area.
This ratio remains constant even if a portion of the solvent evaporates or the injection volume into the gas chromatograph fluctuates. Without this calibration method, measuring the exact concentration of stabilizers in the resin would yield inconsistent and unreliable results.
Compound Selection
Selected compounds must not interfere with the elution time of the polymer additives or the solvent peak. Frequently, deuterated variants of the analyte are used because they behave identically during extraction but separate during mass spectrometry.
Processing Consequence
Incorrect addition of this reference substance leads to inaccurate measurement of resin additives, which can mask a deficiency in thermal stabilizers. This deficit can lead to polymer degradation during subsequent extrusion or injection moulding.
