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
GE Newsletter June 2017
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