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ISO 19929:2017 pdf free

ISO 19929:2017 pdf free.Plastics一Determination of average molecular mass and mixture ratio of poly and its derivatives by MALD I-TOF-MS
The MALDI process involves the ablation and the ionization of an analyte dispersed in a small organic molecule matrix. The matrix shall be able to absorb the laser energy. A metal salt may be added to cationize the analyte. A polymer is co-crystallized or co-mixed with the matrix molecule and deposited on the target. A short duration UV laser pulse is used to ablate the matrix and the analyte. The laser energy is transferred to the matrix molecules, causing them to vaporize. Analyte and matrix molecules leave the target surface in a plume. Due to the very short desorption time, polymer molecules do not degrade. The polymer in the ablation plume gains a cation and is accelerated by a high voltage, drifts down the field free flight tube and is detected at the end of the flight tube. The time-of-flight of the species depends on their molecular masses, and needs to be calibrated with standards of known molecular masses. Biopolymers such as proteins are often used to this end.
Ideally, the product of the ratio between the total sum of peak areas and that between number-average molecular mass is proportional to the mass ratio, i.e.
The laser system comprises a pulsed laser, an attenuator which allows for the adjustment of the laser power, and a lens and mirror system to direct the laser beam onto the MALDI target. Some commercial instruments have beam splitters to direct a fraction of the laser light to a photodiode to start the timing for the TOF measurement. The wavelength of the laser should be in the absorption range of the matrices.Typically, UV-lasers are used.
The target is at a high voltage of several kV and just behind the acceleration optics. The analyte/matrix/salt mixture is deposited on this target and exposed to the pulsed laser beam. Thereby, gaseous analyte ions are formed which are accelerated by the electric field, exit the source and pass through into the flight tube. The flight tube is a field free drift region.ISO 19929 pdf download.


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