Buying Deuterated Chloroform: Silver Foil Benefits & TMS Considerations

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Deuterated chloroform is often stabilized with silver foil to prevent the formation of chlorine-active species, such as DCl, which can arise from reactions with light and oxygen. This stabilization is particularly important for critical applications where purity is essential. The discussion also touches on the inclusion of TMS (tetramethylsilane) in the solvent, with a debate over the appropriate concentration. While 1% v/v TMS is common, it may be excessive for high-field NMR instruments, as it can produce a peak that overshadows most samples unless they are highly concentrated, a practice rooted in older low-field instrument usage.
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I was looking around to purchase some deuterated chloroform online. A few of the products offered include "stabalized with silver foil". What is the silver foil preventing the solvent from doing? FYI, this silver foil is probably inside the bottle.

One more thing, is there reason why you want to have 1% v/v TMS included in the solvent? I've seen 0.03% TMS, but 1% seems to be too many resonating protons for a 500 Mhz NMR instrument...
 
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1% is way too much for a high field instrument, IMO. Your TMS peak will be way too strong for most samples unless they are pretty concentrated, like in a C13 analysis. The 1% level has been used since low field CW instruments have been used and may be a throwback to those days.

Silver foil will scavenge any Cl- or chlorine active species from the bottle. For critical applications, it may help to remove any trace DCl. The chloroform solvent can react with light and oxygen to form phosgene and DCl.
 
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