Page 71 - Illustrated Pocket Dictionary of Chromatography

ENDFITTING 67

such as chlorotrimethylsilane [ClSi(CH 3) 3] or hexamethyldisilazane
[HN(Si(CH 3) 3) 2] are used. The small size of these reagents as com-
pared with an octyl- or octadecyl-bonded phase allows them to reach
and react with residual silanols interspersed between the larger
bonded moieties.

CH 3
Si OH Si O Si CH 3
O O CH 3
CH 3 CH 3
Surface Si O Si CH 2 (CH 2 ) 16 CH 3 + ClSi(CH 3 ) 3 Surface Si O Si CH 2 (CH 2 ) 16 CH 3 + HCl
O CH 3 O CH 3
Si OH C18 bonded phase Si OH Endcapped C18 bonded phase

endfitting A part of a column that (1) allows for column connec-
tion to the injector and detector and (2) holds frits that prevent
packing material from leaving the column when mobile phase flows
through the column.

Both columns have endfittings that attach directly to the column tube, i.e., the tube
itself is threaded. The column on the left is manufactured from stainless steel and
the column on the right from PEEK. Note that the frit for the stainless steel column
is actually press-fit into a cap that fits on top of the column, whereas the frit for
the PEEK column fits inside a deformable O ring that seals when the column end-
fitting is tightened to the column tube.