Differential Scanning Calorimetry is a key technique used by nearly all members of my research group. We like to calibrate the DSC frequently, and indium is one of our go to calibration materials. As it is a stable metal, and heated under nitrogen within the calorimetry we tend to re-use the indium containing DSC pans. I have suggested re-use not to exceed 20 heating cycles, however I don't really have any data to support this. Thus I am interested in finding out how many times other workers re-use their indium pans, and to learn if there is any data showing when indium DSC pans begin to fail or degrade.
Another related question, I used Sn in Aluminium pan as one of the material for calibration of my DSC/TGA instrument (heated upto 450 °C). But it resulted in making a whole in the pan and the alloy (or Sn) get stuck to thermocouple of the instrument. If you are aware which materials should not be used with Aluminium pan for calibration kindly let me know (Indium worked fine win aluminium crucibles/pans).
We usually use mercury (melting point, −38.8 °C), water (melting point, 0.0 °C),gallium (melting point, 29.8 °C) and indium (melting point, 156.6 °C) for calibration with aluminium pans. But I am not sure how many times the indium pans could be re-used.
In my previous lab, we use it up to 8 times including the 1st pre-melt. Personally, I have used it for up to 5-6 times and it still produces desirable results for calibration. I would be interested to know the experiences from other researchers.
I have used indium several times to calibrate DSC.It is really a stable material. The problem appears with zinc broadly. So indium can be used many times under inert atmosphere
Thanks Runjing, Choon and Djalal,
for your interesting replies, so I think the things to capture when calibrating a DSC, use a range of calibrants, introduce a pre-melt and perhaps limit repeats to 10 times. However a little more research is required to support this.
Cheers all
As long as one is getting the reasonably same value for melting point and enthalpy of melting, reuse should be fine. But as such I don't have any idea about how many number of cycles.
We normally use it only one time to eliminate the factors related to the thermal history of the calibrant which might affect the quality of calibration.
Best wishes,
I used In, Sn, Pb, Zn, and single crystal quartz to calibrate my DSC with Al pans in air. I never had any problems with any of them. I never had any reason to reuse the pans more than a few times. Most of the time, I'd use a new pan. This worked well for me and produced extremely reproducible calibration curves.
Muqdad, James & Gunther,
Many thanks for your superb replies.
Gunther the attached papers are excellent, just the ticket. I was aware of the issue with Indium and gold pans, however pre-oxidisation Al step is new to me, however it will be incorporated from now on.
Regards Paul
Depending on the instrument make and model and the experimental procedure you are wanting to use. You should not have to calibrate every time.. only load up appropriate calibration file and perform verification. With respect to indium, do a present to allow indium to make a good contact over a wider area if the pan then use to calibrate or verify. At the most use 15 times but most likely 10. If the indium is exposed to air their is potential for oxidation so in this case the number of uses will reduce. I would suggest if in doubt do a verification with indium first to check if the "working" standard is still suitable instead of potentially using a standard that may have been compromised.
The main requirement for a reference material is purity, which must be at least 99.998 % mol. This may be verified by using the DSC, for which the indium sample must be heated at 2 C/min, from 140 C up to 165 C, and with the obtained thermogram calculate purity by the Van’t Hoff method. It was mentioned, the purity must be at least 99.998 % mol. If you obtain this kind of purity you may continue using your sample, otherwise you must use a new one. I have indium samples that I had been using for more than five years. Is it worth noting that this method may be used for all metal standards.
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