temperature to achieve improved sensitivity and accuracy, especially
for the analysis of precious metals.
Figure 6. Effect of IsoMist XR Temperature on Measurement Accuracy
- Pt 214
- Pt 265
- Pt Gravimetric Value
Another advantage of utilizing the IsoMist XR at an elevated
temperature is when samples are very limited in volume. We have
shown in two separate studies2,5 that samples can be analyzed at very
low uptake rates with a heated spray chamber without the ensuing
loss in detection limits as would be realized on a conventional spray
chamber without temperature control. (Heating the spray chamber
for higher uptake rates may result in overloading the plasma.)
Heating the spray chamber can also improve the analysis of viscous
samples such as lubricants and edible oils, which would otherwise
solidify at room temperature.
Improved Detection Limits
An investigation was recently carried out using the IsoMist XR
connected to a Spectro Arcos II MV ICP-OES at a NY water treatment
facility. After optimizing the nebulizer and ICP operating conditions,
the IsoMist XR was used to finely tune the conditions for optimal
signal intensity and reduced background. Replacing the standard
cyclonic spray chamber with the IsoMist and optimizing the sample
introduction environment at 5°C provided a significant improvement
in instrument detection limits (Table 1). In contrast to the precious
metal study, a lower temperature with the water samples improved
detection limits by reducing background and yielding a more robust
and higher temperature plasma.
Improved Washout
Previous work6 highlighted the advantage of the Helix zero dead
volume nebulizer interface by comparing the time required to
washout a 10ppm Molybdenum standard with the Helix interface
and a “Brand-X” spray chamber with an o-ring interface. The results
showed the 10ppm standard washed out in 4 seconds with the Helix
interface, compared to 16 seconds with “Brand-X” (Figure 7).
Application Spotlight
compared to previous work1,2,7,8 at -10°C resulted in better precision
and accuracy and higher intensities (Figure 4). The extended
temperature range of -25°C makes the IsoMist XR the perfect tool for
analyzing volatile solvents like naphtha and gasoline without dilution.
Figure 6: Effect of Spray Chamber Temperature on Intensity
Figure 4. Effect of IsoMist XR Temperature on Signal Intensity in Naphtha
120
100
80
60
40
20
0
Cd2144
Ca3158
Ag3280
B_2088
Ba2335
Ba2347
Cr2055
Cu2477
-25oC -10oC
K_7664
Mg2790
Mn2939
Mo2816
Fe2611
P_1859
Pb2203
Ni2303
Si2516
Sn2839
V_2687
Ti3349
Zn3302
Enhanced Sensitivity and Accuracy
The sensitivity for many analyses can be enhanced by operating the
spray chamber at elevated temperatures. In a previous study4, the
IsoMist XR was used in combination with an Agilent (Varian) Vista
Radial ICP-OES instrument to investigate the effect of spray chamber
temperature on precious metal signal intensity and analytical
accuracy. The elements analyzed included: gold (Au); iridium (Ir);
palladium (Pd); platinum (Pt); rhodium (Rh); and ruthenium (Ru).
Figure 5 shows the average signal intensity of these precious metals
increasing relative to an increase in IsoMist XR temperature.
Figure 5. Effect of IsoMist XR Temperature on Signal Intensity for Precious Metals
To evaluate the effect of IsoMist XR temperature on the accuracy
of precious metal measurements, a solution of Pt was analyzed
at a range of temperatures and compared to the Pt concentration
determined gravimetrically.4 The results show the Pt concentration
is closer to the gravimetric or true value at a temperature of 40 °C
(Figure 6). The results from both experiments clearly highlight the
advantage of utilizing the IsoMist XR at a higher spray chamber
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