JPH08327573A - Thermal analysis device - Google Patents

Abstract

PURPOSE: To accurately recognize changes in state of a sample that are hard to estimate from thermal analysis data by comparing data on two images taken before and after a peak or the like appears on a data curve. CONSTITUTION: Crystal polymorphic Form [I], Form [II] and Form [III] which sulfathiazole has, for example, have different melting points, and of endothermic peaks appearing on a differential scanning calorimeter(DSC) curve, and a large one on the high temperature side can be specified to be caused by the melting of the Form [I] with a high melting point, while a small endothermic peak on the low temperature side cannot be specified to be caused by the melting of the Form [III] having the lowest melting point or by crystal transition (phase transition). Then an image at T1 point before the endothermic peak on the low temperature side starts and an image at T2 point after the peak ends are compared, and when the image at T1 point does not show melting and the image at T2 point shows melting of a part of the sample, the endothermic peak on the low temperature side is estimated to be caused by the melting of the Form [III ], and when both of the images have no changes, this peak is estimated to be caused by crystal transition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal analysis device such as a differential thermal analysis device, a differential scanning calorimeter, a thermogravimetric measurement device or a thermomechanical analysis device.

[0002]

2. Description of the Related Art Among these thermal analysis devices, a differential scanning calorimeter (DSC) is a device for measuring the enthalpy change of a substance and is widely used in the field of materials as well as in the field of pharmaceuticals. This DSC measures the endothermic and exothermic changes that occur in the sample when the sample and the reference substance are placed at symmetrical positions in the heating furnace and the temperature of the heating furnace is raised and lowered. By plotting the data based on the temperature difference of DSC with time (temperature) as a parameter,
A curve is obtained.

In such a DSC measurement, when a change in crystal form (phase transition), a change such as melting, decomposition or sublimation occurs in the sample during the temperature raising / lowering process, a peak appears in the DSC curve, and the endothermic peak causes the phase change. It is possible to determine the temperature at which transition, melting, etc. occur, and it is also possible to calculate the amount of heat absorption and heat generation from the peak area.

[0004]

By the way, in the DSC measurement, when the DSC curve becomes complicated, it may be difficult to estimate the content of the change caused in the sample.

For example, sulfathiazole is available as Form (I),
A substance known to have three crystalline polymorphs called Form (II) and Form (III). This sulfathiazole (powder)
DSC obtained when DSC measurement was performed using
If the curve is, for example, the curve shown in Fig. 3, of the two endothermic peaks, the large peak on the high temperature side is Form (I).
It can be assumed that it is due to melting of [melting point; 201.0 ° C],
The small endothermic peak on the low temperature side is Form (III) [melting point; 173.6
It is difficult to determine that this is due to the dissolution of [° C].

That is, when Form (III) powder is heated
Since it changes to Form (I), and its crystal transition has an endothermic peak at a temperature slightly lower than the melting point of Form (III), only the DSC curve shown in FIG. It is difficult to identify whether it corresponds to the melting of III) or the phase transition.

In other thermal analyzers such as a differential thermal analyzer (DTA), a thermogravimetric analyzer (TGA), or a thermomechanical analyzer, it may be difficult to analyze the substance only with the thermal analysis data. is there.

The present invention has been made in view of such circumstances, and an object thereof is to provide a thermal analysis apparatus capable of accurately knowing a state change of a sample which is difficult to estimate only by thermal analysis data. And

[0009]

In order to achieve the above object, the thermal analyzer of the present invention arranges a sample S inside a heating furnace 1 and heats it as shown in FIG. 1 corresponding to the embodiment. Furnace 1
A thermal analysis data measuring unit (thermocouples 2a, 3a, signal processing circuit 4, etc.) for measuring expansion / contraction, weight change, temperature change, or absorption / heat generation change occurring in the sample S when the temperature is raised or lowered. An image pickup means (for example, a CCD camera 6) for picking up an image of the sample S placed in the heating furnace 1 through a filter 7 is provided, and the image data and the two data of the thermal analysis data are analyzed for characteristics of the sample. It is characterized by being configured to serve as information for.

[0010]

[Function] When the state change occurring in the sample during the temperature raising / lowering process is a phase transition, there is no change in the appearance of the sample, but when it is a change such as dissolution, decomposition or sublimation, it is before and after each change. Since there is a difference in the appearance of the sample with and, by taking an image of the sample during the thermal analysis measurement, the state change (peak) of the sample that appears on the data curve during the analysis of the thermal analysis data If it cannot be estimated whether the change is due to a change in crystal form, melting, decomposition, sublimation, etc., use the imaged image data and compare the sample images before and after peaks appear on the data curve. Then, it is possible to identify what kind of change has occurred in the sample.

In many cases, various colors are present in the sample being measured, and if a simple image of the sample is taken, even if an attempt is made to capture a minute color change in the sample, It is difficult to distinguish a specific color that shows a change from another noise color. Therefore, in the present invention, by disposing a filter between the imaging means and the sample, an image in which only a specific color in the sample is amplified or reduced can be obtained.

[0012]

1 is a block diagram of an embodiment of the present invention. Inside the heating furnace 1, aluminum cells 2 and 3 containing the sample S and the reference substance R are arranged in a symmetrical positional relationship. Thermocouples 2a and 3a capable of measuring the temperatures of the sample S and the reference substance R are arranged in the cells 2 and 3, respectively, and the signal lines of the thermocouples 2a and 3a are arranged in the signal processing circuit 4 respectively. Be led to. The signal processing circuit 4 is composed of an amplifier, an A / D converter, etc., and includes thermocouples 2a and 3a.
The temperature difference detected in a is converted into a DSC signal and output.

On the other hand, a cover 1a of the heating furnace 1 is provided with a window 1b made of quartz glass, and a stereoscopic microscope 5 is arranged above the window 1b. This stereomicroscope 5 and window 1
A filter 7 is disposed between the filter b and b, and only light of a specific color that has passed through the filter 7 enters the stereomicroscope 5.

The stereoscopic microscope 5 is provided with a CCD camera for picking up a microscope image (image of the sample S),
Further, a light source (halogen lamp or the like) 8 for illuminating the sample S arranged in the furnace through the window 1b is arranged above the cover 1a of the heating furnace.

The arithmetic processing unit 9 is, for example, a computer, to which a printer 11 for recording measurement data, a CRT 12 for displaying measurement data, an image memory 10 such as a video tape recorder, etc. are connected, and a signal processing circuit. It is configured to take in the DSC signal from 4 and the image signal from the CCD camera 6 and display their respective data on the screen of the CRT 12.

For the data display, as shown in FIG. 2, for example, two individual display areas (windows) W1 and W2 are set on the screen of the CRT 12, and a DSC signal is displayed on the screen of one display area W1. The operation is performed by plotting and displaying an image based on the image signal from the CCD camera 6 in the other display area W2.

The arithmetic processing unit 9 sequentially stores the DSC signal in an internal memory (not shown) during measurement and outputs the image signal from the CCD camera 6 to the image memory 10.

Next, a specific analysis method will be described by taking the measurement of sulfathiazole as an example. First, it is assumed that a DSC curve as shown in FIG. 3 was obtained when the measurement was performed using the thermal analyzer (DSC) having the structure shown in FIG.

Here, sulfathiazole is a substance known to have three crystal polymorphs called Form (I), Form (II) and Form (III) as described above, and its Form
The melting points of (I), Form (II) and Form (III) are respectively 201.0
℃, 196.5 ℃, 173.6 ℃, the DS of Figure 3
Of the two endothermic peaks appearing on the C curve, the large peak on the high temperature side can be assumed to be due to the melting of Form (I). The small endothermic peak on the low temperature side is likely to be the melting of Form (III) contained in the sample.

However, since sulfathiazole causes crystal transition (change of crystal form), there is a possibility that an endothermic peak on the low temperature side is generated by the transition, and any reaction occurs only by analyzing this DSC curve. However, in such a case, the change in the state of the sample can be accurately estimated by using the image data of the sample collected during the measurement.

That is, in the DSC curve shown in FIG. 3, two image data of a point T1 before the low temperature side endothermic peak starts and a point T2 after the low temperature side endothermic peak ends are compared and examined. When the image data at time T1 does not show melting of the sample and the image data at time T2 shows dissolution in a part of the sample, the low temperature endothermic peak is due to the melting of Form (III) in the sample. On the other hand, when there is no change between the two image data at the time points T1 and T2, that is, when the sample dissolution does not appear in the image data at the time point T2, the endothermic peak on the low temperature side is It can be presumed that this is due to crystal transition.

As described above, in the embodiment of the present invention, the DSC
Even if it is difficult to estimate the transition / dissolution using only the curve, by adding the image data of the sample to the analysis,
You can grasp them accurately. Further, in addition to this, in the DSC curve, an endothermic peak is generated even when the sample is decomposed or sublimated, and it can be estimated whether the endothermic peak is caused by decomposition or sublimation or another thermal change. It is possible. For example, when decomposition occurs in an organic sample (white powder), browning occurs, so it can be inferred that decomposition occurs from the color change, while in the case of sublimation, the shape of the sample itself changes. It can be estimated that sublimation is occurring from the change in shape.

Further, in the embodiment of the present invention, since the image of the sample S is picked up through the filter 7, various colors can be obtained in the sample during the measurement process by appropriately selecting the transmission color of the filter 7. Even if they exist or the color change in the sample is minute, it is possible to capture only those color changes in an amplified form, which results in a good SN ratio with a low image baseline. It is possible to obtain various image data.

Considering only the point of making the desired color change clear, means such as arranging a diffraction grating or the like instead of the filter 7 or changing the emission color of the light source 8 is adopted. It is also possible to do so.

As a camera for taking an image of the sample, C
The present invention is not limited to the CD camera, and other known ones such as an industrial TV camera may be used. Furthermore, in the above embodiments, an example in which the present invention is applied to a differential scanning calorimeter has been described. It can be applied to all other thermal analysis devices.

[0026]

As described above, according to the thermal analysis apparatus of the present invention, the image data of the sample is collected during the measurement in addition to the thermal analysis data. Even when it is difficult to estimate the content of the change that has occurred, it is possible to accurately grasp the state change of the sample by using the image data of the sample for analysis. Further, in the apparatus of the present invention, since the image of the sample is captured via the filter, it is possible to capture only the desired color change among the colors existing in the sample during the measurement process in an amplified form. Therefore, clear image data can be obtained. This facilitates the examination of the image during the above-described analysis, and the analysis work can be performed efficiently.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a display example of thermal analysis data.

FIG. 3 is a diagram showing an example of a DSC curve.

[Explanation of symbols]

 1 heating furnace 1a cover 1b window 2 cells (for sample) 3 cells (for reference material) 2a, 3a thermocouple 4 signal processing circuit 5 stereoscopic microscope 6 CCD camera 7 filter 8 light source 9 arithmetic processing unit 10 image memory 11 printer 12 CRT S Sample R Reference substance

Claims (1)

[Claims] 1. Thermal analysis data for measuring expansion / contraction, weight change, temperature change, or endothermic / exothermic change occurring in a sample when the temperature of the heating furnace is raised or lowered while the sample is placed in the heating furnace. A measurement unit and means for capturing an image of the sample placed in the heating furnace through a filter are provided, and two data of the image data and the thermal analysis data are provided as information for analyzing the characteristics of the sample. Thermal analyzer having the following structure.