Calibration Ratio
Quantitative gas chromatography relies on mathematical coefficients to correct for sensitivity variations between internal reference compounds and target mineral oil hydrocarbons. Analysts calculate the cholestane response factor by comparing peak areas generated by known concentrations of 5-alpha-cholestane and target alkanes. This numerical value adjusts raw integration areas to prevent mass underestimation during food packaging compliance audits.
Response characteristics depend on detector temperature and carrier gas purity during flame ionization detection.
Quantification Drift
Daily instrument performance fluctuates due to column degradation and liner contamination during routine paperboard extract runs. Applying the cholestane response factor corrects for instrumental drift without requiring full multi-point recalibrations for every sample set. Sterane structures yield detector signals that closely match the ionization behavior of branched saturated hydrocarbons.
Inconsistent split ratios or syringe wear alter peak area ratios and invalidate current calibration curves. Recalibration becomes necessary whenever response values shift beyond standard five percent control limits. Flame ionization detectors require stable hydrogen and air flows to maintain uniform response across high-boiling hydrocarbon ranges.
Internal Standard
Chemical stability makes 5-alpha-cholestane an ideal surrogate for mineral oil analysis in paper substrates. The cholestane response factor remains valid only when the internal standard undergoes complete recovery during preliminary extraction steps. Fatty acid esters and natural wood resin constituents can co-elute with the internal standard if cleanup columns fail.
Such chromatographic interference distorts the calculated factor and compromises migration assessment accuracy. Verification of baseline resolution ensures accurate quantification across diverse recycled paperboard grades.
