Measurement and Results - Cleaning platinum (Pt) crucibles
I am hoping that you may be able to give me some advice on preparing a sample for ICP-MS analysis. We have capsules for analysis and due to their enteric coating the only way we have been able to produce a suitable sample solution is using HF and microwave digestion; due to health and safety concerns when using HF and the amount of analysis required we are trying to find an alternative prep method. After research on your website we would like to try ashing the sample and would you be able to advise on a procedure? The elements of interest are As, Cd, Pb, Hg, Co, V and Ni. We have Pt crucibles and a muffle furnace, can you please advise if the crucibles should be cleaned in any particular way before use and if there is anyway we can minimize contamination from the furnace?
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admin
Total posts: 529
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As your elements of interest include As, Cd and Pb, we would recommend a low temperature ashing procedure that avoids the use of H2SO4 (sulfuric acid) as an ashing aid. The As and Cd can be volatilized at higher ashing temperatures and the presence of sulfuric acid can generate insoluble lead sulfate. The low temperature (~120 C) ashing procedure involves using activated oxygen and/or a Schoeniger flask approach. For cleaning Pt crucibles there are numerous methods that primarily depend upon the nature of the potential contamination (there are many references available online from crucible manufactures). A simple approach is boiling diluted HCl (20% v/v) followed by thorough rinsing; this procedure can be supplemented by using boiling diluted HNO3. Metal and metal oxides can be removed using a fusion of potassium bisulfate. We’d suggest performing a blank study on the crucibles to determine the effectiveness of the cleaning procedure, which should hopefully help determine how aggressive a cleaning procedure may be required. Minimizing contamination from a muffle furnace can be achieved by using crucibles with lids, and a blank study could also identify the key concerns that may affect contaminant levels.
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