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Sample Preparation - Preparing standards similar to NIST SRM 1643

 
I am a chemical engineer working in metrology, and I'm currently working on a project that involves the CRM "1643". I was wondering if you could send me some information about this CRM, like stability through time, which techniques do you use to measure properties, etc. I´m in charge of trying to emulate the "1643", and I don´t have all the element standards in order to do that. I wanted to know if you could inform me about the laboratory conditions and the procedure used in the preparation of this CRM (steps, operations, etc).
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admin Total posts: 529

We are assuming you are referring to the IV-STOCK-1643 product, which is designed to mimic fresh water and be comparable to the NIST SRM 1643. Our preparation of this product depends upon 2 critical factors: very pure starting materials, and very clean labware. With respect to the starting materials, we mix together 30 different single-element concentrates to make the final product, and if any one of those 30 single-element concentrates contains significant impurities, then those impurities could affect the certified values for other elements. Regarding the labware, this product contains many elements present at very low concentrations (<100 ppb), and if the pipettes, bottles, etc. used to make the CRM are not extremely clean, then even minor contamination from the labware can affect the final certified values (please see http://inorganicventures.com/container-material-properties for more information).  If you wish to create a version of this product yourself, the two approaches would be: 1) start with 30 different certified single element concentrates, mix them together gravimetrically (most accurate), and calculate the final concentrations based upon the weights used in the dilution, or 2) create a mixture using normal reagent-grade starting materials, and then test the final mixture extensively to determine the certified values. The first approach essentially describes how we manufacture the product, but could be expensive as it requires 30 different certified starting materials. The second approach is cheaper and simpler at the beginning of the process, but requires much more extensive testing at the end, and still would require some certified standard as part of the final testing. The most straightforward approach may be to purchase a single bottle of a commercially available certified 1643 standard (we would recommend the NIST SRM, if possible, for this approach), and use that to certify a similar solution that you prepare in your lab. In this instance you would be using small volumes of the purchased standard to certify much larger volumes of the standard you prepare, which may be the most cost-effective and suitable approach for your needs.

Posted: 09/06/18 22:37:31

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