Page 177 - Illustrated Pocket Dictionary of Chromatography

SILANOPHILE 179

shrinking The process by which a dry resin or gel expels solvent
and contracts. Particle size and pore diameter are strongly affected
by this, and so before use a resin must be fully equilibrated with the
operating solvent. See swelling.

shot noise Generated in an electrical circuit because of the current
flowing through the detector collector and proportional to the square
root of the current: shot noise =÷I. This form of noise is typically
much less than Johnson noise.

sieve A unit that has a series of precisely placed screens (or
meshes) that form apertures through which particles less than or
equal to the aperture in size. Two sieve systems are commonly used:
US Standard and Tyler. See mesh.

sieving A physical method for separating particles based on size.

signal The output of a detector that is the response to an analyte
eluting through it is the signal associated with the analyte.

silanol group Terminal hydroxyl groups on the surface of the
silica support material. The resulting pH for these groups depends
on the purity of the silica and its structure. Normally a 1% in water
suspension generates a resulting solution pH of 4–10.

Si OH
Surface O

Si OH

Silanol groups

silanophile A component that generates strong interactions with
residual silica surface groups. Basic compounds such as primary and
secondary amines are strong silanophiles. Silanophilic interactions
are usually seen as peak tailing. Competing molecules such as
triethylamine are often added to the mobile phase to diminish or
eliminate these interactions.