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Measurement and Results - Low selenium recoveries for SW-846 6010C

 
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Brian Alexander, PhD Total posts: 4

Selenium can experience losses due to volatility during many digestion procedures (it appears that you are using Method 3050B for sample preparation). Selenium losses have been reported for acidic digestions that use H2O2, and these losses are increased if appreciable chloride is present. We recommend performing a set of digestions using only your ICP calibration standards as the sample (i.e., a recovery test). For example, you can perform one digestion that includes only the HNO3 step, a second one that includes both the HNO3 and peroxide steps, and a final digestion that includes all steps (HNO3, H2O2, and HCl). The corresponding data should indicate where any Se losses may be occuring and their significance.

Posted: 08/19/19 14:07:48
Justin Weaver Total posts: 1

I have been having difficulty obtaining acceptable (85%-115%) LCS recoveries for Se following SW-846 6010C.  We typically use a mixed standard to prepare the LCS and spikes and I do not routinely get low recoveries for the other elements in this mix.  I have even tried using a single element standard for Se and I still get low recoveries.  

I am using a Perkin-Elmer Optima 5300 DV, analyzing at 196.026 nm, axial viewing.

I have tried analyzing at 203.985 nm, but the recovery is even lower.  

The instrument parameters are the same as what I use when I analyze aqueous samples, yet my Se recoveries are always quite good for aqueous samples.  This leads me to think that the digestion procedure is problematic since the solid digestion procedure is much more vigorous than what is used for aqueous samples (EPA 200.7).  We digest environmental solids and sludges at 95C with concentrated HNO3 followed by treatment with 30% H2Oand final digestion with concentrated HCl.  The digestion is carried out in a digestion tube placed in a hot block and covered with a watchglass. I am concerned that some Se may be forming a gaseous compound and escaping the digestion vessel.  

Any help will be greatly appreciated.

Posted: 07/26/19 14:17:02

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