Analytical Technique
Quantitative chemical analysis resolves the concentration of trace contaminants in complex sample matrices. The standard addition method determines the level of specific migrants, such as residual solvents or plasticizers, in printed paperboards. Spiking the sample involves adding known quantities of the target chemical directly to aliquots of the sample extract.
By measuring the analytical response of both the spiked and unspiked samples, the analyst can construct a calibration curve that intersects the concentration axis to reveal the original concentration of the analyte in the sample. This procedure is used when the sample matrix is too complex to use a standard external calibration. Accounting for the chemical complexity of the paperboard extract allows high accuracy in food safety compliance testing.
Matrix Effect
Co-extracted compounds can suppress or enhance the detector signal of the target analyte during chromatography. When analyzing recycled board, the standard addition method overcomes these matrix effects by keeping the background components constant across all calibration points. Since each test tube contains the same amount of sample extract, any signal suppression affects the added standards and the native analyte equally.
This ensures that the calculated concentration is not underestimated.
Gas Chromatography
Instrumental configuration ensures the separation of volatile substances before detection. In migration testing of printed cartons, the standard addition method is paired with headspace gas chromatography to measure residual isopropyl alcohol or ethyl acetate. The combined method ensures that the solvent levels are below the regulatory limits.
Correct calibration is essential to prevent false positives that could delay product shipments.
