SEC is a standard technique that is frequently used to determine MMD of polymers and the corresponding number, weight, and z averages, Mn, Mw, and Mz. As has already been mentioned in Section 2.2, the separation in SEC is governed by entropic effects, unlike other modes of liquid chromatography, where enthalpic effects are predominant. The separation mechanism is, however, not the only difference between these techniques: The main difference between SEC and other modes of LC is that the information about the samples is coded into the absolute peak position (while in LAC the relative elution order is sufficient) and the peak shape (which is generally very different from peaks in LAC). As molar masses and polydispersity of macromolecules are directly obtained from these chromatographic raw data, the requirements in data processing are considerably different from those in other chromatographic techniques. There are also consequences for instrumentation, maintenance, and operation that will be discussed in the following sections.