JPS6119935B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential scanning calorimeter, which is a thermal analysis device that performs chemical analysis using the properties of a sample with respect to thermal energy, and is capable of quantitatively analyzing a small amount of sample. It is.

Generally called DSC, it is possible to precisely measure the temperature and heat amount of melting and transition of a minute sample in a short time.
Furthermore, it is well known that there are two types of differential scanning calorimeters that can easily measure the purity of chemicals and, although not as accurate as an adiabatic meter, measure specific heat: a heat compensation type and a heat flow type. The former is an internal heating method in which the sample container is equipped with a heater and a temperature sensor, and the heating part has a small heat capacity and can accurately measure exothermic reactions with a quick response. As a result, as the scanning temperature changes, the efficiency of heat dissipation between the two containers, the sample and reference sample, becomes different, causing the thermal equilibrium between the two containers to be broken and heat to flow in and out of the sample. The disadvantage is that the experimental baseline of the thermogram gradually shifts in one direction even though no phenomenon accompanied by this has occurred, and measurements must be made while correcting this. Another disadvantage is that in a liquid sample, the uniformity of temperature distribution is reduced due to the generation of convection by the heater inside the container, resulting in low measurement accuracy.
The latter type of heat flow is generally called differential thermal analysis (DTA), which uses an external heating method in which the sample and reference sample are arranged in a heating furnace with good temperature distribution and heated at a constant rate.
It is a DSC, and the sample and reference sample containers are thermally connected using thermocouples, etc., so the thermal equilibrium is high and the baseline is stable, but because the heating furnace has a large heat capacity, it is difficult to measure fast reactions. cannot follow,
Furthermore, if the heat of reaction is large, heat leakage occurs between the reaction and the outside world, so there is a limit to measurement.

This invention was made in view of the above-mentioned current situation, and aims to eliminate the drawbacks of conventional heat compensation type and heat flow type differential scanning calorimeters (hereinafter referred to as DSC). The improved thermal equilibrium between the sample and reference sample vessels has been improved by incorporating the advantages of the analyzer, and a stable baseline enables highly accurate measurement of exothermic reactions with a quick response under constant temperature rise conditions. In particular, it is an object of the present invention to provide an apparatus that can improve measurement accuracy by making the temperature distribution within a liquid sample uniform.
In other words, in a differential scanning calorimeter that measures the difference in heat capacity between a sample and a reference sample by controlling scanning heating of a sample and a reference sample in the same environment within an insulated enclosure, a member with high thermal conductivity is placed outside the insulated enclosure. A heat sink portion having a heat capacity sufficiently larger than that of each container of the sample and the reference sample is provided, and each of the containers is thermally connected to the heat sink portion by a heat conduction rod, and the heat conduction of the heat sink portion is The rod is provided with means for detecting the amount of heat leaking from the container to the heat sink through the rod, and means for controlling the temperature of the heat sink to an appropriate value based on the detected value. This is related to a differential scanning calorimeter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be explained below with reference to the drawings. Figure 1 is a block diagram explaining the internal structure and configuration of the device. 1 is a sample, such as an aqueous solution of protein, 2 is water almost equivalent to 1 as a reference sample, and 3 and 4 are each sample container. It is made of a thin aluminum plate and supported by container holding rods 5 and 6, which will be described later. H ₁ and H ₂ are platinum heaters inserted into the respective sample containers 3 and 4, which also serve as temperature measuring resistance pairs, for example.
Measure the temperature between 1/50 and 1/60 seconds, then take the temperature for the next 1/50 and 1/60 seconds.
During this period, a block 7 installed outside the furnace, ie, a temperature detection and differential power compensation circuit, acts as a heater. However, the above-mentioned heating method and temperature detection method are not limited to those mentioned above, and for example, about 10μ
A thin heater of m is used for heating, and a thermopile is used for heating.
A method is also used in which the temperature difference between sample 2 and sample 2 is detected, and the temperature of sample 2 is also detected using a thermocouple. These devices are designed to increase the heat compensation sensitivity and speed up the heating response, and are almost the same as conventional DSC, but the device of this invention is designed with particular attention to the above pair of samples. The block 8, in which the containers 3 and 4 are housed symmetrically in its internal space, is made into an adiabatic enclosure (insulation block) that can control heat insulation to about 1/1000 to 1/100 degrees Celsius by using several configurations described below. It is. In other words, the block 8 is made of, for example, Monel metal, which is highly corrosion resistant, and the heater _H3 installed inside it is designed to uniformly heat the entire block 8, and the thermocouple 9 for heat insulation control has a small heat capacity and is conductive. Thin insulators are used to minimize heat loss. On the outside of the block 8, two to three heat shields 10 (the figure shows one layer for simplicity) made of a metal member with high heat reflectivity are provided.
Air 11 having low thermal conductivity is filled between the shields, and a convection prevention shield as shown at 12 is further provided. 13 is a furnace wall made of a heat insulating material such as glass fiber. With the above configuration, the influence of external temperature on sample 1 and reference sample 2 is minimized. The heater H ₃ is a heat insulation controller 14 and a programmer 1.
A series of control systems including blocks 5 and 7 adiabatically control the temperature Tc of the adiabatic block 8 to within the difference between the temperature T2 of the reference sample ₂ and the above-mentioned 1/1000 to 1/100°C. The temperature T ₁ of sample 1 is heated by the heater H ₁ mentioned above, and ideally the temperature T 1 is the same as above until sample 1 starts to react.
The temperature is raised at a constant rate according to a program at the same temperature as T ₂ . If T ₁ and T ₂ are exactly equal, the baseline will be stable and there will be no problem. However, even with the above-mentioned insulating block configuration, the temperature gradient of the thermocouple lead connected to the outside world, the heater, the sample, etc. The amount of heat loss from T ₁ and T ₂ differs due to various causes such as the difference in contact between the two (T ₁ =
T ₂ ) thermal equilibrium deteriorates. This was the main cause of baseline instability in conventional DSC, but in this invention, as shown in the figure, the pair of sample containers 3 and 4 are
13 through the insulation block (8) by the retaining rod.
The present invention differs from conventional ones in that it is thermally (including mechanically) connected to the holding rod fixing portion 22 of the heat sink 21 provided on the furnace wall. That is, the holding rods 5 and 6 are made of, for example, stainless steel thin tubes,
The holding rod fixing part 22 that supports this is made of silver or copper to improve its symmetry, and the main body 22 of the heat sink part
are made of metals with high thermal conductivity, such as copper. H ₄ is a heater that always controls the temperature To of the heat sink 21 to be lower than the above (T ₁ = T ₂ = T _s ) by a certain temperature;
H ₄ is controlled by a series of control systems including a heat sink temperature To controller 24, a programmer 15, and a temperature detector 7. With this configuration, the respective temperatures T ₁ and T ₂ of the ceremony material 1 and the reference sample 2 are controlled by the holding rod 5,
Heat leaks Q ₁ and Q ₂ of 6 are generated in the direction of the arrow, canceling out the difference in heat dissipation between both containers in the conventional device, and achieving thermal equilibrium between sample 1 and reference material 2 in which the temperature difference is kept at a constant value with respect to To. This stabilizes the measurement baseline, and is comparable to the advantage of the heat flow DSC described above, in which the thermal balance between the sample and the reference material is stable due to the large heat capacity in the heating furnace. 25 and 26 are heat flow meters that quantitatively detect the heat leaks of Q ₁ and Q ₂ mentioned above, that is, they measure the temperature difference between unit distance as a function of time and measure the heat flow value of the leak, An appropriate value for the heat reservoir temperature To (a value corresponding to the magnitude of the exothermic reaction of the sample) is determined from the detected value, and the setting is changed using the controller 24. The above is the configuration of the apparatus according to the embodiment of the present invention, and the operation of this apparatus will now be described. Now, if a constant power W is supplied from block 7 to heater _H2 on the reference material 2 side, this and the above heat leakage will occur.
The temperature increases at a rate determined by the difference between Q and ₂ and the heat capacity of 2. This temperature T ₂ of reference sample 2 and sample 1
The difference ΔT between T ₀ is detected in block 7, and the heater of H ₁ is controlled so that this value is always zero, so sample 1 is also heated at the same rate. On the other hand, since block 14 controls H ₃ so that the temperature Tc of insulation block 8 also has almost zero difference from T ₂ above, ideally heat loss to the outside world passes through container holding rods 5 and 6. Only Q ₁ and Q ₂ are left. Q ₁ and Q ₂ are (T ₁
It is determined by the difference between (T ₂ ) and the heat sink temperature To and the thermal conductivity of the holding rod, and the difference between (T ₁ = T ₂ ) and To is H ₄
It can always be kept at a constant value using a heater. Next, the effect when the temperature increases and an endothermic or exothermic reaction occurs in sample 1 will be explained with reference to FIG. The figure shows a temperature program in which the temperature is increased at a constant gradient with respect to time t, and Ts is (T ₁ =T ₂ ). The figure shows the change in the electric power W _H1 of the heater H1 supplied to the sample ₁ , and the horizontal axis is t in the above figure and the temperature _T1 raised thereby. If the sample absorbs heat, heater _H1 will receive a corresponding amount of extra power (+
ΔW) is supplied from block 7 in FIG _.
=T ₂ =T _s ) is maintained. Next, when there is an exothermic reaction, the heater _H1 responds accordingly (−Δ
The power of W)′ is also reduced in block 7 (T ₁
= T ₂ = T _s ) is maintained. The figure shows that the power W _H2 supplied to the heater _H2 of the reference sample 2 is always constant; the amplifier inside block 7 amplifies the power difference (W _H1 - W _H2 ), and The above power value is converted into an energy unit (for example, mJ/s) and recorded on a recorder. The fact that the straight line (H ₁ - _{H 1} ″) in the figure always matches the straight line (H ₂ ′ - _{H 2} ″) in the figure indicates that the baseline is stable. Even in this region where the programmed temperature is low and the adiabatic control accuracy decreases, the measurement accuracy does not decrease because the quantities Q ₁ and Q ₂ can be corrected based on the readings of the heat flow meters 25 and 26 in FIG. Also, although not shown, the outputs of 25 and 26 above
A circuit is provided to amplify the difference between Q ₁ and Q ₂ , and this is converted to (T ₁
=T ₂ =Tc) and can also be used to control the difference between the above and To.

The above is an explanation of the configuration and operation of the embodiment device of this invention according to FIG. 1, but this invention is not necessarily limited to that shown in FIG. 1. For example, the device of this invention can be Needless to say, it can also be measured.

Since this invention is constructed as described above, it eliminates the drawbacks of conventional differential scanning calorimeters, such as the heat compensation type and the heat flow type. A passage for leakage is provided and a heat sink with a large heat capacity improves the thermal equilibrium between the sample and the reference sample and stabilizes the baseline, allowing for fast-responsive exothermic reactions to be performed with high accuracy under constant temperature rise conditions. The present invention has provided a convenient device that can improve measurement accuracy by preventing convection from occurring in the sample container due to the one-way heat leak, which improves measurement accuracy, especially when measuring liquid samples. be.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a differential scanning calorimeter which is an embodiment of the present invention, Fig. 2 is a diagram showing a constant rate temperature increase program of this device, and the figure shows the endotherm and heat absorption of the sample under the above heating conditions. A diagram showing changes in the power supplied to the heater during an exothermic reaction, and a diagram showing the power supplied to the heater for the reference substance. 1...Sample, 2...Reference sample, 3...Sample container, 4...Reference sample container, _H1 / _H2 ...Sample and reference sample heater/temperature sensor, 5, 6...
Heat conduction rod (also serves as container holding), 8...Insulated enclosure, _H3 ...Insulated enclosure heater, 9...Thermocouple for heat insulation control, 10...Insulation shield, 11...Air layer, 12... Convection prevention shield, 13... Heating furnace outer wall, 21... Heat sink part, 22... Holding rod fixing part (part of heat sink), 23... Thermocouple for controlling heat sink temperature, H ₄ ... Heat sink Part heating heater, 25, 26...
...Heat flow meter for detecting heat leakage.

Claims (1)

[Claims] 1. In a differential scanning calorimeter that measures the difference in heat capacity between a sample and a reference sample by controlling scanning heating of a sample and a reference sample in the same environment within an insulated enclosure, a member with high thermal conductivity is placed outside the insulated enclosure. A heat sink portion having a heat capacity sufficiently larger than that of each container of the sample and the reference sample is provided, and each of the containers is thermally connected to the heat sink portion by a heat conduction rod, and the heat conduction of the heat sink portion is The rod is provided with means for detecting the amount of heat leaking from the container to the heat sink through the rod, and means for controlling the temperature of the heat sink to an appropriate value based on the detected value. Differential scanning calorimeter.