Extraction fibers, choosing

In practice, either a pole figure has been measured in a texture-goniometer setup, or a 2D SAXS pattern with fiber symmetry has been recorded. In the first case we take the measured intensity g (pole figure. In the second case we can choose a reflection that is smeared on spherical arcs and project in radial direction over the range of the reflection. From the measured or extracted intensities I (orientation parameter by numerical integration and normalization... 

The variables involved in choosing extraction conditions include the fiber coating and coating thickness, whether derivatizing is necessary, selection of an extraction mode and agitation method, automation options, and injection (desorption)... 

The main issues in choosing an extraction mode and an agitation method involve the nature of the sample and matrix volatility and affinity to the matrix. From the point of view of fiber lifetime, headspace extraction is preferred, but samples must be at least somewhat volatile and not very strongly bound to the matrix. For samples with lower volatility, direct immersion is preferred, although fiber lifetime is a consideration if the matrix is especially dirty. The second consideration in choosing the extraction mode is equilibrium versus exhaustive extraction. In SPME, equilibrium extraction is much simpler to perform, so it is generally... 

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