Application Spotlight
An example of a complete High TDS application kit for the Agilent
5100 SVDV ICP-OES is shown in Figure 1. Below we will describe
in detail the characteristics of each of these essential high TDS
components.
Figure 1. Glass Expansion High TDS Package for Agilent 5100 ICP-OES.
Argon Humidifier
The ElegraTM argon humidifier
was released in February 20163,
offering an upgraded design to
the CapricornTM. The elegant
design of the Elegra results in a
very compact accessory (Figure
2), making it easy to fit every
ICP model without overcrowding
the sample compartment and
providing simple installation. The
Elegra utilizes highly efficient
membrane technology to add
moisture to the argon as it flows
through the inert metal-free
construction. The device runs at atmospheric pressure and does not
require heating or electric power, as required by other manufacturers.
The Elegra is also configured with a bypass switch so that the
operator can turn humidification on and off without connecting or
disconnecting any tubing.
To evaluate the performance of the Elegra, a nebulizer stress test
was completed aspirating a 25% NaCl solution while monitoring the
nebulizer gas flow with and without the Elegra (Figure 3). A decrease
in gas flow is a good indicator of a nebulizer that is clogging. Note
a nebulizer with a TDS tolerance rating of only 5% was used to
illustrate the advantage of the Elegra. As a worst case test, the salt
solution was aspirated continuously, with no rinsing. As expected,
without the Elegra, the nebulizer was completely clogged after
only 5 min. In contrast, the same nebulizer with the Elegra, held a
relatively constant gas flow throughout the entire test (over 30 min).
A similar result was also observed with the injector, which is detailed
elsewhere.3
Figure 3. Elegra Nebulizer High TDS Stress Test (25% NaCl)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Time (seconds)
Nebulizer Gas Flow (%)
0
120%
100%
80%
60%
40%
20%
0%
Nebulizer without Elegra Nebulizer with Elegra
Even when a proper high TDS nebulizer is chosen, some matrices
like lithium metaborate fusions can pose a challenge due to the very
high amount of TDS. The stability of three internal standard (IS) lines
were compared with and without the Elegra (Figure 4) by an ICP
contract laboratory running a lithium metaborate method. Without the
Elegra the IS signals begin to drift after 35 min, eventually resulting
in a failed analysis (> 10% drift). With the Elegra there is negligible
variation in IS signal over a period of 4 hours. A significant reduction
in the required nebulizer maintenance was also observed, going over
two months without cleaning as opposed to weekly cleaning without
the Elegra.
Figure 4. Internal Standard Stability in 0.5% Lithium Metaborate
Analysis Failed
0:32 1:15 1:57 2.40 3:16 4:00
Time (hh:mm)
Normalized Intensity (%)
Normalized Intensity (%)
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
IS 1 IS 2 IS 3
1.4
1.3
1.2
1.1
1.0
0.9
0.8
Analysis Completed
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
A Dual Channel Elegra is also available which provides the ability
to humidify both the nebulizer gas and an auxiliary or dilution gas.
A dilution gas accessory is now a standard option on some ICP-MS
instruments4,5,6 (this is an alternative approach to an inline or offline
liquid dilution of the samples). High TDS samples need to be diluted
for ICP-MS analysis to prevent the rapid build-up of salt deposits
on the interface cones, which would otherwise result in signal drift
and frequent cleaning. The inline aerosol dilution of the sample
prior to introduction into the plasma, allows for improved analysis of
high matrix samples by ICP-MS. The dual channel Elegra prevents
nebulizer and injector blockage due to salt build-up and as a bonus,
the moisture of the dilution gas reportedly ensures a high thermal
conductivity resulting in improved ionization.5
Figure 2. Elegra Argon Humidifier
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
www.geicp.com Glass Expansion Newsletter | Issue 43 2
Analysis Without Elegra Argon Humidifier
Signal drifts after 35 mins
With Elegra Stable for 0.7
0.6
0:32 1:15 IS 1 Time (hh:mm)
Normalized Intensity (%)
Normalized Intensity (%)
Analysis Failed
0:32 1:15 1:57 2.40 3:16 4:00
0.6
IS 1 IS 2 IS 3
Time (hh:mm)
Without Elegra Argon Humidifier
Signal drifts after 35 mins
With Elegra Argon Humidifier
Stable for greater than 4 hours
0:32 1:15 1:57 2.40 3:16 4:00
0.6
IS 1 IS 2 IS 3
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