The standard testing procedure begins with sample preparation. For samples such as cream, it is necessary to allow them to equilibrate at a constant temperature within a sealed container, thereby ensuring that the nitrous oxide in the gas phase reaches partition equilibrium. Subsequently, a specific volume of gas is withdrawn from the headspace vial using a gas-tight syringe and rapidly injected into a gas chromatograph that has already been initiated.
Prior to analysis, the instrument must undergo multi-point calibration using standard gases to establish a standard curve. Specific testing steps include: the programmed setting of temperatures for the column oven, detector, and injection port; the precise control of carrier gas flow rates; and the automatic or manual injection of samples. Throughout the entire process, detailed records must be maintained regarding sample information, instrument parameters, and peak area or peak height data. Each batch of samples should be accompanied by blank tests and spiked recovery tests to monitor the accuracy of the detection process.
