Preparation of Gaseous Standard Mixtures: Methods for Controlling the Amount of Components Generated in the Process of Thermal Decomposition of Immobilized Compounds

Gaseous standard mixtures play an important role in characterizing and checking the applicability of new analytical procedures. In this case gaseous standard mixtures can be treated as a special kind of reference material (validation process requires the use of so-called matrix reference materials). The selection of a method of generation of gaseous standard mixtures with the desired characteristics depends on the nature of the analyte and diluent gas, as well as on the required concentration of analytes in the mixture. Recently, dynamic methods of generation of gaseous standard mixtures are becoming more and more common. These include the method based on thermal decomposition of immobilized compounds. The generation of the measured component takes place as a result of heating of a sample of solid support with chemically modified surface. During a chemical reaction initiated by sufficiently high temperature, the immobilized compound undergoes decomposition or rearrangement accompanied by the release of a specific volatile compound. Various amounts of the analyte per unit time can be obtained by adjusting the conditions of the thermal decomposition process. This article describes the possibility of varying the amount of a measured component through the adjustment of conditions of drying the solid support or of the process of chemical modification of its surface. The principle of this technique is exemplified by the generation of a mixture containing ethene as the analyte. Porous glass was used as a solid support. The proposed technique was used for the generation of gaseous standard mixtures for the calibration of a thermal desorber-gas chromatograph-flame ionization detector (TD-GC-FID) system.