JPS59166851A - Device for determining moisture - Google Patents

Abstract

PURPOSE:To measure exactly an equivalence point by interposing a constant voltage generator between electrodes and automatic potentiometric titrator, applying a prescribed voltage between the two electrodes on one hand and converting the current between the two electrodes to a voltage on the other hand then inputting the voltage signal to the automatic potentiometric titrator. CONSTITUTION:A power source part 5 which applies a prescribed potential difference between two electrodes 3 and 3 and a current/voltage converting part 6 which converts the current to a voltage when the current flows between the electrodes 3 and 3 are provided to a constant voltage generator 4. The one terminal of the part 5 is connected to the one electrode 3 via an ammeter 7, and the other terminal is connected to the other electrode 3 via the part 6. The voltage output from the part 6 is inputted to an automatic potentiometirc titrator 8. The titrator 8 processes arithmetically the potential difference signal inputted thereto and is connected to an automatic sample feeder 10 which regulates the feeding of the sample by controlling a sample feeding member 9. The titrator outputs the necessary result to recording paper 11 according to the correlation between the feeding of the sample and the input potential difference signal. The moisture is thus easily and surely determined by using the automatic potentiometric titrator.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rapid foot placement device for moisture using an automatic potentiometric titrator.

Conventionally known electrometric titration methods can be roughly divided into the following three methods based on the electrochemical properties to be measured.

(1) Potentiometric titration (voltage titration) (2) Amperometric titration (3) Conductivity titration and radiofrequency titration In the above, (1) and (2) refer to the relationship between the electrode inserted in the titration solution and the solution. They have one thing in common in that they actually perform electron transfer.

Furthermore, the Karl Fischer method is known as a method for determining water content in a sample.

This method utilizes the property of Karl Fischer reagent containing iodine, sulfur dioxide, viridi/methanol as components to specifically react with water, and the reaction Fi is as follows:

H2O+ C5H5N: I2+ C5H5N: So □ C5H5N02 #-2CsHsN<, + C5H5N<6, that is, the overall reaction is expressed by the following formula.

H20+05th 5N-12+C5H5N-5O2+C3
)-15N0CHpH-This Karl Fischer test fi
In titration using K, the end point is determined visually when the test solution is not colored. The end point is usually the point at which the sample solution changes from bright yellow to red (in the case of back titration, it is the opposite).

By the way, when the sample liquid has a layered color, the end point is conventionally determined electrically. As an electrical method for this purpose, a dead stop end point method is known.

That is, first, two platinum electrodes are immersed in the fixing solution to be grated, and a constant current (5 to 70 .mu.A) is applied by appropriately adjusting the variable resistor. Next, when Karl Fischer test solution is dropped there, the needle of the microammeter in the circuit swings wildly as the titration progresses, but returns to its original position within a few seconds. However, once the end point of γ definition is reached, the microammeter swing (S0~730 μA) persists for 30 seconds or more.

The end point of the titration is when this state is reached. (For example, see Notes on the Japanese Pharmacopoeia Law, General Test Methods, and Moisture Determination Notes) In other words, the current method was used as a known method. However, when using this method, when the end point is reached, adding one drop of Karl Fischer reagent requires a long reaction time, and since the end point is determined as described above, it takes a lot of time. there were. In addition, there was a drawback that individual differences were likely to occur depending on the person measuring the ball.

The present invention relates to a new device that easily overcomes the drawbacks of such known methods.

That is, the present invention can be applied to the conventionally used
An automatic end point made by using the filif and combining it with a constant voltage generator! It is a device.

Karl Fischer reagent The main cost of the reaction using the Karl Fischer reagent is the redox reaction + 26 1-m-→2[and 1, 1e so2-1→so&] which proceeds in the presence of water.

In the present invention, two platinum electrodes are immersed in a liquid containing a sample, and a temperature of approximately 700 to 700 ml is applied between the two platinum electrodes. It consists of applying a voltage of 200 mV and titrating with Karl Fischer reagent. However, even if titration is started, no see current will flow until the sample solution reaches the equivalence point.

This is because 1□-river is reversible, but 5o2->gawa is irreversible, so 12 in the added Karl Fischer reagent is reduced, and no current flows. However, if Karl Fischer test solution is added beyond the equivalence point, there will be an excess of 12 in the sample, and 1- will be oxidized near the anode, and 1□75S will be reduced near the lower cathode. The reaction progresses, and as a result, an electric current begins to flow. The present invention utilizes such a phenomenon to electrically determine the end point.

Therefore, the present invention can be said to be a constant voltage polarization current individual determination of water.

In the present invention, test articles having various properties can be used for measurement.

Therefore, in the case where the test article is a solid or a donated body soluble in Karl Fischer reagent, the sample g is directly used as a solvent. When using a cold bath, use a suitable dry solvent to dissolve it in solution form. Examples of such solvents include methanol, chloroform, etc. These solvents can be dehydrated. However, if there is a trace amount of water present, either measure it in advance and subtract it, or remove the water with Karl Fischer test solution before adding the sample. Furthermore, even if the test item is in the same bath as the Karl Fischer tester, if it becomes viscous, it is practical to use a smaller solution as described above.

In addition, as titration methods, there are two brands: ``direct titration method'' and ``back titration method.''
However, both can be equally employed when implementing the present invention.

Structure of the Invention The present invention is achieved by using a potentiometric titration device and inserting a constant voltage generator between the input terminal of the device and two electrodes inserted into the sample tank. be done. The automatic potentiometric titrator appears between the electrodes at 7'C.
It is known as a device that performs titration by inputting the 11-position difference and calculating the value.This automatic potentiometric titrator is connected to an automatic reagent injection device that injects the reagent into the sample tank. The rate is adjusted and titrated by controlling the titrator. However, this type of titration device uses potentiometric titration and cannot perform full bottom flow titration for determining water content.

At this point, a constant voltage generator is inserted between the electrode and the automatic potentiometric titration device, and a predetermined voltage is applied between the two electrodes at -10,000, while a current is applied between the two electrodes. When it flows, it is converted into a voltage of 1'g, η, and inputted into the automatic potentiometric titration device.

As a result, the point at which current begins to flow between the electrodes, that is, the equivalence point, can be determined reliably and quickly, and the water content in the sample can be added to 111.1 using the entire potentiometric titration device. .

Hereinafter, the non-invention will be explained in detail using the first box. In FIG. 1, a sample 2 in a sample tank 1 has Ω electrodes 3, 3.
(platinum electrode) is inserted. A predetermined potential difference is applied to this electrode 3.3 from a constant voltage generator 4.

The constant voltage generator 4 includes a power supply section 5 that provides a predetermined potential flow between the two electrodes 3, 3, and a current/voltage conversion section that converts the current into voltage when a current flows between the two electrodes 3, 3. 6 is provided, and the 10,000 end of the part 5 is connected to the 10,000 electrode 3 via an ammeter 7, for example, and the power supply part 5
The other end of is connected to the other electrode 3 via the converter 6. In addition, the voltage output from the power #L/voltage converter 6 is as follows:
It is input to the automatic reagent injection device 8. The power supply unit 5 is f1]
E is the voltage dividing resistor R that lowers the voltage of battery E and battery EcD.
1 and R2, for example, the voltage applied to the resistor R2 is set to about /QmV. Also, switch SW
may be provided to turn on or off the p constant voltage generator 5. Incidentally, since the % electrode 3 is connected to the titration device 8 at full time by the resistor R, potentiometric titration can be performed with the switch sw turned off.

Although the ammeter 7 allows the current flowing between the electrodes to be visually observed, the 11L current meter 7 is not essential and may be omitted. The current/voltage converter 6 consists of an element that converts the current flowing in the circuit into a voltage, the most well known of which is a resistor R3. Of course, this element may be any other current/voltage conversion element. Capacitor C absorbs thermal noise appearing across resistor R3,
It is intended to eliminate various noises such as external noise, and is not essential.

The automatic potentiometric titration device 8 performs arithmetic processing on the inputted sample, and also performs automatic reagent injection, which injects the entire sample into the sample tank by pressing the receptacle member 9 and vertically injecting the reagent. The device 10 is connected to the VC, and the necessary results are displayed according to the correlation between the injection of the reagent and the input potential difference signal, for example, on the recording paper 11.
It is now more than output to .

In the fc embodiment described above, the battery E't/ is an old V battery, the resistor R1 is 90 ohm, the resistor R2 is 0 ohm, the resistor Rst-/ is ohm, and the ammeter 7 is /μA 7
We will explain the operation of an example experiment using a bladder that can be removed.

The sample may be a powdered pharmaceutical raw material, such as an antibiotic,
Karl Fischer test solution was automatically added as a test solution. Electrical connection 3
The voltage applied between the electrodes is /, tOrnV, and when the equivalence point or end point due to the reagent injection is reached, the voltage applied between the electrodes is approximately 2oμA (JISTh/0~20μA)O
'i[tfi] flows for 30 seconds (30 to θ seconds in JIS), and the current/voltage conversion element, that is, resistor R3, has a voltage of 20 mV.
A voltage of 200 nm appeared, and the amount of water in the sample could be determined by the amount of sample solution injected at this time. Therefore, it can be seen that water content can be easily and reliably determined using an automatic potentiometric titration device.

In addition, when the output voltage of the constant voltage generator 4 is low as described above, as shown in the second section, the DC amplifier 12t-device t
4, and the device 4 and the amplifier 12 may be connected as a constant voltage generator 4'.

Hereinafter, the Lp present invention will be explained in Examples.

Example/Water capacity test for ampicillin Karl Fischer methanol 2jrmek was placed in a dry titration flask and titrated to the end point with Karl Fischer reagent to make the inside of the flask anhydrous. Next, an accurate amount of about 33 μm of ampicillin υ was quickly put into the titration flask, stirred to dissolve, and titrated with Karl Fischer test solution to the end point while stirring rapidly. The results obtained are shown in Table 1.

The results obtained using the conventional manual method are also shown.

This table shows that compared to the conventional manual method, there is no problem in the reproducibility of the present device.

Example 2 Moisture Determination Test of Water-Methanol Standard Solution ``Methanol for Karl Fischer 25-'' was placed in a dry titration flask and titrated to the end point with Karl Fischer test solution in advance to make the inside of the flask anhydrous. Next, water
Precisely add methanol standard solution to the titration flask, and add to the final point with Karl Fischer test solution while stirring vigorously. The results obtained are shown in Table 2.

It can be seen that the measured values obtained by using the apparatus of the present invention at 7f'U have no problems in terms of reproducibility and elongation.

Example 3 Moisture quantitative test of sulfur tA (CuSO4.5H20) 23 ml of Karl Fischer methanol is placed in a dry titration flask and titrated to the end point with Karl Fischer test solution to make the inside of the flask anhydrous. Next, about 30 rays of sulfuric acid steel was poured into the titration flask 10 times, stirred and dissolved, and titrated to the end point using a Karl Fischer test tube while stirring vigorously.

The resulting knots are shown in Table 3.

Temperature 2'IC Humidity
27.5% Karl Fischer test solution titer F=7.0'/33
Water/methanol standard liquid power 1 piece 7.9'9m9/M
It can be seen that there is no variation in the measured values obtained by fully utilizing the apparatus of the present invention.

Example G. Potency Verification Test of Karl Fischer Test Solution Methanol 2 for Karl Fischer! ; Put ml into a dry titration flask and titrate it with Karl Fischer test solution to the end point in advance to make the inside of the flask anhydrous. Meanwhile, water was poured to a concentration of about 3 to 100 ml, and immediately poured into a commercial flask and titrated with Karl Fischer test solution to the end point while stirring vigorously.

The results obtained are shown in Table 4.

Temperature Humidity: 30 cm From the above experiment, it is clear that there is no problem with browning.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a water positioning device according to an embodiment of the present invention, and FIG. 1 is a block diagram of a water footing device according to another embodiment of the present invention. 1... Sample tank, 2... Sample, 3... Electrode, 4...
・Constant voltage generator, 5... ridge part, 6... current/voltage converter, 8th... wJ potentiometric droplet redundant device, lO...
Automatic reagent injector, 11...recording paper, 12...amplifier.

Claims (1)

[Scope of claims] A constant voltage generator is provided between the electrode and the automatic potentiometric titration device, and the constant voltage generator is equipped with a power supply that provides a predetermined potential difference between the two electrodes. and an element that converts the current into a full voltage when a current flows between both electrodes, and the voltage output from the current/voltage exchange element is input to the automatic potentiometric titration device. Quantification device. (2) The device according to claim (1), wherein the voltage generator is provided with means for amplifying the output voltage from the current/voltage conversion member. (3) The test liquid is curled. The device according to claim (1), which is a Fischer reagent.