Reproducibility improvement INDEX

For MEEKC, the migration index (MI) scale is quite effective in improving the reproducibility. This was introduced by Muijselaar et al. in MEKC (44) and then modified to extend the range of the migration window of the reference compounds as follows (47) ... 

Fig. 1.8 Scheme of a CW ESR spectrometer employing magnetic field modulation.The method is employed to improve the signal/noise ratio by phase-sensitive detection. The principle for obtaining the derivative of the absorption is shown. The figure is reproduced from http //www.helmholtz-berlin.de/forschung/enma/si-pv/analytische-methoden/defektanalytik/esr/index en.html with permission from Dr. Klaus Lips... 

The reasons for the continuing use of melt flow indexers are low cost (about 10% the price of a capillary rheometer), simplicity and speed of use. Improved PID heating controls and more precise linear barrel-bore machined from a nitride-hardened steel or specially engineered ceramic has led, with recent models, to more reproducible results. Melt indexers can be obtained in a range... 

The presence of certain viscosity index improvers can cause a negative bias for one or more elements. In interlaboratory studies, this bias was found to be small relative to the reproducibility of this test method, and the bias was minimized by using smaller sample sizes (for example, a sample size of 0.050 g of a blended oil) for oils that contain viscosity index improvers. 

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