Page 129 - Illustrated Pocket Dictionary of Chromatography

128 MICRORETICULAR

microreticular A microreticular resin is produced through a
cross-linking such that small pores result. See macroreticular.

migration time, t m The time required for an analyte to travel from
the injector to the detector in a capillary electrophoresis column
under an applied voltage, V:

t m ª 1 V
minimum detectability Synonymous with limit of detection,
minimum detectability defines the lowest analyte signal that can be
distinguished from system noise.

miscible Two liquid components that can be mixed together in all
proportions at a given temperature without forming two separate
layers are termed miscible.

miscibility number, M Developed to offer a quick way of deter-
mining whether or not a given pair of solvents is miscible. Each
solvent is assigned an experimentally determined miscibility number
ranging from 2 to 29; 2 is very polar and 29 is nonpolar. Any pair of
solvents that have M numbers differing by <15 are miscible at room
temperature. With a difference of >17, they are immiscible. A value of
16 means that miscibility is strongly temperature dependent around
room temperature.

mixed-bed Refers to a column (or support) that is prepared con-
taining two or more distinct types of stationary phases. An example
would be a blend of an ion-exchange packing with a reversed-phase
packing. The resulting mixed-bed column would provide a mixed-
mode separation based on ion-exchange and hydrophobic retention
mechanisms (see mixed mode).

mixed mode Refers to any separation that is the result of
more than one retention mechanism. This can be intentional or
unintentional. As an example, a column can be packed with an
ion-exchange packing mixed with a reversed-phase packing (inten-
tional mixed mode). This type of bonded phase is more difficult
to make reproducibly but offers a wide range of potential selec-
tivities not available on single-moiety bonded phases. Conversely, a
reversed-phase support can have residual silanol groups that can
lead to mixed-mode separation: hydrophobic and silanophilic (often
unintentional).