Sample Preparation, and Matrices

In order to facilitate the reader, the chapter is split into various sections. Section 15.2 deals with instrumentation, sample preparation, and matrices, remaining sections deal with the analysis of ultrapure polymers, polymer mixtures in which backbones are identical, and polymer mixtures in which backbones are different, respectively. The final section deals with the determination of average molar masses. 

The laser induces instantaneous vaporization of a microvolume (called a plume), and a mixture of ionized matrix and analyte molecules is released into the vacuum of the ion source. The relationship between the laser irradiance, I ascn and the number of molecules formed, Gma di, is most peculiar. There exists a threshold irradiance, peculiar to each matrix, below which ionization is not observed. Above this level, the ion production increases in a very strong, nonlinear, manner (often Gma di grows as Ilaser is raised to the eighth power). 

The choice of a matrix tailored for a particular kind of polymer sample is cmcial for successful characterization of the sample. Therefore, it is useful to discuss the properties of some common matrices [4—6], 3-Amino-4-hydroxybenzoic acid and POPOP need high laser power, since they possess a high threshold. Alpha-cyanocynnamic acid is 

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