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Sample Preparation - UniSolv references and leaching LDPE bottles

 
Hi, I recently assumed a position as a lab manager at a university, and the bulk of our analytical work involves silicate rocks. We are currently using a flux fusion method, but I am interested in transitioning to acid digestions. I have two questions regarding information presented in the "ICP Operations Guide" (Gaines 2011): 1) On page 15, the publications states that your lab neutralizes HF using "the neutralization option (triethanol amine) with the addition of H4EDTA when required for chemical stabilization..." I conducted a lit search to find this methodology, but was unsuccessful. Would it be possible to get a copy of relevant literature citations for this technique? 2) On page 29, the publication recommends that, when working with silicon, solutions "should be stored in plastics known to contain no catalyst residues or that have been leached with dilute HF for 48 hours". We are using 125 mL Nalgene LDPE bottles. I contacted Nalgene and inquired as to whether these bottles contain catalyst residues, but they did not know. For cleaning purposes, what is meant by "dilute HF" (concentration)? Lastly, the publications provided on your website are extremely informative and useful. Thank you for providing these resources! Many thanks, in advance, for your time and assistance.
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admin Total posts: 529

The techniques described were developed by Dr. Paul Gaines as part of the proprietary UniSolv process for analyzing zeolites, and no peer-reviewed reference was published. If a  reference is required, we would suggest the “(P. Gaines, personal communication)” approach often cited in research literature. As for the bottles, LDPE bottles are catalyst-free whereas HDPE can contain catalyst residue, so if you use LDPE from Nalgene there should be no concerns. Regarding the HF leach concentration, we've used 0.1M HF (~0.3% v/v) mixed with 0.5M HNO3 (~3% v/v) at 60 °C for 60 hours to clean a variety of plastics (LDPE, HDPE, and polypropylene) and had good results . This or a similar approach should be suitable for your application.

 

Posted: 09/06/18 22:01:05
admin Total posts: 529

The use of triethanolamine (TEA) and EDTA to neutralize and stabilize acidic metal solutions was developed as part of our UniSolv process for zeolite determinations (https://www.inorganicventures.com/elemental-analysis-zeolites), and grew out of our own research initiatives. As a result, we reference no peer-reviewed literature sources specific for our application, but the use of TEA and EDTA in titrimetric methods for metals is well documented, and that is where much of the background information we built upon may be found. One good reference for that information is “The Analytical Uses of Ethylenediaminetetraacetic Acid” by F.J. Welcher (1958). As for the bottle choice, Nalgene LDPE is a great material, and should not contain any catalyst residues, which are more of a concern with HDPE due to differences in the polymerization process. For cleaning purposes, dilute HF refers to a solution of ~0.1 – 0.5% (v/v) HF. Lower acid concentrations can be as effective for cleaining/leaching plastics as higher acid concentrations, but usually longer leach times are necessary.

Posted: 09/06/18 21:59:27

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