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. P/N: 30-808-2862 P/N: 31-808-2840 P/N: 31-808-2836 P/N: 31-808-2835 www.geicp.com Glass Expansion Newsletter | Issue 43 3
GE Newsletter June 2017
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