Microcal VP-Differential Scanning Calorimeter
The VP-DSC is a differential scanning microcalorimeter. The reference and sample cells are fixed in place lollipop shaped vessels with effective volumes of approximately 0.5 ml. The cells are constructed from a tantalum alloy and protrude out of the adiabatic chamber via their 1.5 mm (inner diameter) access tubes. The approximate volume of each cell stem is 0.085 ml.
The cell material (Tantaloy 61™) has chemical properties quite similar to glass. This alloy is immune to attack by almost all acids, having been tested under widely varying concentrations/temperatures involving chlorine, bromine, hydrochloric acid, nitric acid and sulfuric acid. Please refer to the dedicated manual outlining the chemical properties of Tantaloy 61™ for more detailed information.
The VP-DSC operates in the temperature range of 1° to 110° Celsius. It is capable of both upscanning and downscanning with no external heating/cooling source. Scanrates are user selectable and fall in the range of 0°/hr to +90°/hr in the upscan mode and 0° to -60°/hr in the downscan mode. The VP-DSC can also be used at constant temperature for long periods of time (Isoscan) for shelf life studies and/or for evaluating the stability of drug or other chemical formulations. The duration of such a study is limited only by the available space on the PC hard disk.
For scanning solutions above their boiling point, the VP-DSC has a self-contained pressurizing system allowing positive pressures from 0 – 30 p.s.i. Applications requiring higher pressures can be conducted with the addition of an external pressure source and accessory pressure cap, available from MicroCal. Pressure applied to the VP-DSC cells should never exceed 80 p.s.i. or irreversible damage to the cells may be incurred!
Temperature differences between the reference cell and the sample cell are measured, calibrated to power units and displayed to the user as well as saved to disk. This data channel is referred to as the DP signal, or the differential power between the reference cell and the sample cell. Calibration of this signal is obtained electrically by administering a known quantity of power through a resistive heater element located on the sample cell.
In general, an exothermic (heat is released) event in the sample cell will cause the DP signal to deflect in the negative direction. Likewise, an endothermic (heat is absorbed) event in the sample cell will cause the DP signal to deflect in the positive direction.
VP-DSC MicroCalorimeter User's Manual, MicroCal, LLC