يعد كالوريمتر المسح الضوئي التفاضلي (DSC) هو أكثر تقنيات التحليل الحراري استخدامًا. DSC measures enthalpy changes in samples, due to changes in their physical and chemical properties, as a function of temperature or time.
This video teaches you how to perform a DSC calibration and adjustment using the standard reference substance, indium. More specifically, you will learn how to:
- prepare a reference substance
- insert a sample into a DSC
- program and start a calibration in the thermal analysis software
- evaluate the resulting curve
METTLER TOLEDO's thermal analysis STARe software makes the process of calibration and adjustment simple for all DSC users.
Visit us for more information on DSC (Differential Scanning Calorimetry) and other thermal analysis solutions, as well as promotions, webinars, trainings, applications and handbooks
DSC calibration and adjustment is also detailed in our TA tips and hints guide
DSC Calibration and Adjustment
In order to achieve accurate results a DSC has to be regularly calibrated and if necessary, adjusted.
We will now show how to do a standard calibration on a DSC.
For DSC calibration you need as accessories:
- A microbalance placed on a stone table
- Two standard forty microliter crucibles with pierced lids
- A crucible sealing press
- The calibration toolbox
- ومواد مناسبة للمعايرة.
The DSC calibration measurements are carried out with a reference and a sample crucible each with pierced lid.
In order to achieve good measurement results the crucible/lid combination's weight on the sample and reference side should not differ more than zero point two milligrams.
Let’s start with the preparation of the reference substance.
We take indium as an example. يمكن ضغط حبوب الإنديوم لتصبح مسطحة. The resulting sample shape provides a better thermal contact.
For heat flow calibration it is necessary to determine the accurate weight of the sample because the melting enthalpy taken is a value normalized by weight. Place the crucible and lid on the balance, tare and remove crucible and lid from the balance. Fill in the flat indium sample.
Close the crucible using the crucible press. Place the crucible on the die of the press, apply the crucible lid, center it and rotate the lever to move the plunger down until its resistance is overcome. The lid is now cold-welded to the crucible rim.
Transfer the closed crucible back to the balance. Close the weighing compartment and let the balance stabilize. Read the weight displayed on the balance terminal and note it down onto the white board of the calibration box.
If the balance is connected to the PC the weight can be directly transferred to the experiment window of the STARe TA software with the push of a button. Place the crucible onto the crucible support.
Place the crucible support near to the DSC. Open the sample changer cover. Using tweezers place the crucible containing the indium sample on a position of the sample changer tray. Make sure that an empty reference crucible is already on the reference side of the sensor.
In the module window go to the Routine Editor. Open the method Check DSC In exo^.
أدخل اسم العينة. A good name would be Indium followed by the batch number used for the calibration. أدخل الوزن. Enter the position number on the sample changer tray.
By pressing Send Experiment, the data is sent to the instrument and database and the measurement begins.
After the measurement is finished the curve is automatically evaluated and the result is displayed inside the module window.
The curve is also validated regarding onset of sample temperature and enthalpy of fusion. If the result was out of specification, then it is recommended to run a second measurement with the same sample. If it is then still out of specifications it may be necessary to adjust the instrument.
You have seen how to
- Prepare a reference substance
- Insert the sample into the DSC
- Program and start a DSC calibration
Evaluate the resulting curve.
