Chapter: INJECTORS
Topic:
THERMAL DESORBEROPERATION
The SRI Thermal Soil Desorber accessory is
useful for the analysis ofvolatile and
especially semi-volatilecompoundsin soil
or other granular solids. Because the
analyte can be extracted from the soil by
heat alone, with little or no sample
preparation, field analyses can be performed
without liquid solvent extraction. In
addition, very high sensitivity for semi–
volatile compounds such as diesel fuel can
beobtained because essentiallyall the
analyte is extracted from up to a gramof
soil and deposited on column.
The SRI Thermal Soil Desorber accessory is
mounted in a heated valve oven on the left
hand side ofthe 861OCGas Chromatograph.
The glass tube which contains up to a gram
ofsoil is inserted into the hot ( 250C )
desorber cell through an opening in the top
ofthe GC's red lid, and then secured by
tightening the nut and
3/8"
graphite ferrule.
The handle ofthemanually operatedValco
10 port valve exits from the left rear ofthe
heated valve oven, and is rotated to direct
the carrier gas flow down and through the
hot soil, transporting any hydrocarbons with
boiling points below300 C onto the GC
column. The stainless steel tubing leading
fromtheValeovalveto the columnis
routed and insulated to maintain a high
temperature all along the path to the column
oven to prevent high boiling compounds
fromcondensingor tailing.
ValcoValve handle
rotates to inject
sample
Heated Valve
Oven contains
ThermalDesorber
H007.doc
Transferlinefromvalvetocolumnmustbekept as
hot as possible to avoid sample condensation.
Arrange insulation tocreate"hot pocket"
in
this area.
