Application Spotlight
Torch Selection
The combination of high temperature and salt deposits causes a
quartz torch outer tube to devitrify; examples are shown in Figure
5. The disadvantage of a single-piece torch is that it is a relatively
high cost consumable item that requires regular maintenance and
replacement, particularly with more demanding samples, such as
high TDS. This is because the whole torch must be replaced when
just the outer tube suffers from devitrification.
Figure 5. Common wear from high temperature and presence of high TDS.
The Glass Expansion D-Torch (Figure 6), is an economical alternative
to the single piece or semi-demountable quartz torch. The D-Torch
incorporates a ceramic intermediate tube for greater robustness and
provides the analyst with an outer tube that can be replaced when it
fails rather than replacing the entire torch. The D-Torch also features
an interchangeable injector, allowing the analyst to install a specific
injector (material and internal diameter) for each application whether
it be for aqueous, organics, high TDS or HF.
Unique to the D-Torch is an optional ceramic outer tube, which is
of particular benefit for the analysis of high TDS sample matrices
because the Sialon material does not devitrify. In Figure 7 we
compare a quartz outer tube with a ceramic outer tube, both of which
have been exposed to 6 hours of a 10% NaCl analysis. You can
clearly see that there is no change to the integrity of the ceramic
outer, whereas the quartz is severely devitrified.
Figure 7. A comparison of resistance to devitrification when exposed to high salt matrix.
Quartz Outer Tube
Ceramic Outer Tube
6 HOURS OF RUNNING 10% NaCl
A detailed performance evaluation of the fully ceramic D-Torch was
presented in a 2010 application note7 by Thermo Fisher Scientific. In
this report, the D-Torch exhibited exceptional stability in the presence
of 3 % NaCl and provided equivalent analytical performance to
the standard quartz torch on the iCAP 6000 Radial ICP-OES
(Table 1)7 In another report8 the D-Torch was utilized for a
homogeneity assessment of custom blend Certified Reference
Materials (www.inorganicventures.com). An important criterion for a
homogeneity assessment is that the CRM remain undiluted; at 100
to 10,000 ppm this matrix results in significant devitrification of the
quartz. Figure 8 highlights the improved signal stability achieved
with the ceramic D-Torch versus a quartz semi-demountable torch.
The complete report can be found in our October 2013 Newsletter.8
Table 1: Detection limit comparison between the Ceramic D-Torch
and standard quartz torch
Detection Limit (μg/L)
Element (λ) Radial EMT Torch Radial Ceramic D-Torch
Al 167 1.6 1.1
Ba 455 0.07 0.12
Cu 324 0.88 0.62
K 766 25.5 11.7
Mg 279 0.05 0.05
Mn 257 0.36 0.25
Ni 221 1.6 1.3
P 177 5.1 5.0
Zn 213 0.23 0.28
Data taken from Thermo Fisher Scientific Technical Note # 43202
Figure 6. Glass Expansion D-Torch fully demountable torch, example shown for Thermo iCAP Duo.
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