Page 24 - Illustrated Pocket Dictionary of Chromatography

18 BET TEST METHOD

Benzene

BET test method Named for the developers (Brunauer, Emmett,
and Teller), a technique that uses nitrogen adsorption isotherms to
determine the surface area of porous materials. Pore volume and pore
size distribution can also be derived from these test results.

bias The effect resulting from the presence of a systematic error in
the analysis. A bias consistently shifts the obtained result to a greater
or lower value than expected. A bias is particularly difficult to diag-
nose because repeated analysis does not expose bias (unlike random
error).

binary mobile phase Functionally defined as a solution that is
comprised of two major constituents (e.g., 50/50 v/v methanol/water).
Although solvents contain low–level mobile-phase modifiers such as
a buffer, the buffer by definition exists as an equilibrium between two
forms (e.g., acid and its conjugate base) and so does not technically
meet the definition of binary. Therefore, it is less confusing to refer to
the major constituents only.

biocompatible Refers to any component (i.e., mobile phase,
packing, tubing, etc) that comes into contact with a biomolecule and
does not cause irreversible adsorption or denaturation.
bleed (1) The process of release of volatile/soluble components of
a GC or HPLC stationary phase. (2) Associated with the decomposi-
tion or release of volatile materials from a septum in GC. The most
critical aspects of bleed occur in GC and LC/MS applications, where
the bonded-phase or septum breakdown leads to the appearance of
these moieties in the detector. This is not the same as baseline drift,
which is due to the overall change in detector response generated by
changes in the elution conditions.

bonded phase The part of a stationary phase that is chemically
bound to the support material. A common example is the reac-
tion of chlorodimethyloctadecylsilane with silica to produce an