Investigation of matrix-free generation of methyl chloride as a reference material

This article describes the results of investigating the use of fused-silica fibers with chemically-modified surfaces as a source of matrix-free reference material – methyl chloride in an inert gas. The analyte is generated in the process of thermal decomposition of (immobilized) compounds bonded to the surface. Prior to chemical modification, the fibers were coated with a thin layer of polyimide to improve their mechanical strength, followed by a metal film (Al or Ti) to obtain active sites; hydroxyl groups required for chemical modification are present on the surface because both metals are readily oxidized in air and they form a protective layer of oxide. Some fibers under study, available commercially, were coated with only a thin film of aluminum.Three different thicknesses of metal film were used for the fused-silica fibers coated with thin polyimide film. Fibers with different diameters and thicknesses of metal film were used for the fibers coated with only the layer of aluminum.For the fibers of the first type, reproducible amounts of CH3Cl released per unit length of the fiber were obtained, irrespective of the kind of metal and the layer thickness: 0.111 ± 0.032 ng/cm for the SPME device and 1.676 ± 0.014 ng/cm for the thermal desorber.For the fibers of the second type, the amounts of CH3Cl released were also reproducible and, depending on the glass-fiber parameters, were: 1.408 ± 0.015 ng/cm, 1.583 ± 0.040 ng/cm and 1.993 ± 0.040 ng/cm

Metal-coated fused silica fibers as a support for immobilized compounds yielding a volatile analyte (C2H4)

This paper presents the results of investigations of chemically modified fibers comprising an immobilized compound that yields ethene as the analyte in generated standard gaseous mixtures. Prior to chemical modification, the fibers were coated with a thin aluminum layer to improve their mechanical strength. Commercially available Al-coated fibers were used in this work. During thermal decomposition of the immobilized compound, reproducible quantities of the analyte per unit fiber length were obtained for all the investigated fibers (fiber diameter (microm)/outside diameter (microm) of the Al-coated fiber=110/146, 220/300, and 660/830), amounting to 0.685+/-0.032, 0.8300+/-0.0081, and 1.092+/-0.010 ng cm(-1), respectively. The proposed procedure can be used successfully for the generation of measured component of matrix-free reference materials