JPS587945B2 - Yukishiriyoubunkaihouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (I) BACKGROUND OF THE INVENTION This invention relates to a method for automatically decomposing organic samples.

When analyzing inorganic components in organic samples, first,
The organic sample is decomposed and an analytical sample is prepared.
Wet methods and dry methods are known as methods for decomposing organic samples.

The wet method or wet ashing method decomposes and removes organic components in an organic sample using a mixture of acid and oxidizing agent, and uses the residue as an analysis sample, and is mainly used for analyzing inorganic components. .

This wet ashing method usually heat-treats an organic sample with a mixed solution of oxygen acid and oxidizing agent to decompose the sample, and then heat-treats it while adding an oxidizing agent to completely decompose and remove organic components. The residue is then used as an analysis sample.

At present, a series of these operations, especially the dropping of the oxidizing agent, is performed manually, which has the disadvantage of not only requiring human labor and being uneconomical, but also time-consuming.

In other words, it is preferable to add the oxidizing agent when the sample is carbonized and not solidified, but when adding the oxidizing agent manually, it is necessary to add the oxidizing agent when carbonization is progressing in order to avoid time constraints and dryness of the sample. This is because a large amount of oxidizing agent is added in a state where it is not used.

SUMMARY OF THE INVENTION The present invention aims to provide a wet decomposition method that eliminates the above-mentioned drawbacks, in which the conventional manual operation can be automated, and the oxidizing agent is dripped at the most appropriate time for sample decomposition. The purpose of this project is to provide a method that allows for

Therefore, the organic sample decomposition method of the present invention is a method for decomposing an organic sample with an acid-oxide mixture, in which an organic sample is heated together with an acid-oxidant mixture consisting of an acid and an oxidizing agent having a lower boiling point or decomposition temperature. When the temperature of the system reaches the boiling point of the oxidizing agent or a set temperature selected from the range above the decomposition temperature and below the boiling point of the acid, add the oxidizing agent little by little to completely decompose the organic sample. It is characterized by the fact that it can be decomposed into

According to the organic sample decomposition method of the present invention, when the system reaches a set temperature or higher, the oxidizing agent is automatically dropped, so by appropriately setting the set temperature, the organic sample is in a state where it is most easily decomposed. Sometimes it becomes possible to add an oxidizing agent, making it possible to carry out the decomposition efficiently.

Furthermore, since the dropping of the oxidizing agent can be easily controlled, for example, by electrical equipment, automation is simple and effective in saving labor.

Sub-Detailed Description of the Invention To explain this invention in more detail, first, the organic sample to be decomposed in the method of this invention is not particularly limited and may be of any type.

For example, it can be a biological sample.

To decompose an organic sample, first, add an acid (usually an oxygen acid) to the organic sample.
This first decomposition step is carried out without heating the system.

This decomposition reaction is exothermic and the temperature of the system increases.

In this specification, the term "oxidizing agent" refers to anything that has a boiling point or decomposition temperature lower than that of the acid with which it is mixed, and has an oxidizing power that does not azeotrope with the acid when mixed.

Therefore, the concept of "oxidizing agent" is determined by its relative relationship with acid.

For this reason, an oxyacid that is considered an "oxidizing agent" in one system may be treated as an "acid" in this invention in another system.

The "acid" is an acid for dissolving the component to be measured in the organic sample, and is not azeotropic with the "oxidizing agent" to be combined, and has a boiling point higher than the "oxidizing agent".

Various such acid-oxide combinations are known, such as concentrated sulfuric acid-nitric acid, perchloric acid-nitric acid, concentrated sulfuric acid-hydrogen peroxide, and concentrated sulfuric acid-perchloric acid.

In the first stage of decomposition, an acid-oxidizing agent is added to the sample, and the temperature rise is allowed to occur naturally.

External heating may cause an extreme reaction.

Once the initial decomposition step is complete, the temperature of the system begins to drop.

This is because the exothermic decomposition reaction has ended. This first decomposition step can be omitted in some cases.

Once this decomposition step is complete, the system is heated to increase the temperature.

This temperature increase is at or above the boiling point of the oxidizing agent.

That is, this is to promote the oxidative decomposition reaction of the sample by the oxidizing agent.

When the oxidizing agent is consumed by decomposition or evaporation and the temperature of the liquid exceeds the set temperature, the oxidizing agent is added to the system.

This set temperature is above the boiling point or decomposition temperature of the oxidizing agent and below the boiling point of the acid.

When the temperature exceeds the set temperature, the method of adding the oxidizing agent is basically not limited. For example, it is best to use a control device that combines a thermometer and an electrical device. It is preferable to add the oxidizing agent in small amounts and several times. It is preferable to drop a large amount.

This is because adding a large amount of oxidizing agent lowers the boiling point of the acid-oxidizing agent mixture, lowering the reaction temperature and slowing down the oxidation reaction.

After the completion of the first decomposition step, the time from when heating is started until the set temperature is reached, that is, the time during which the sample is not dried to solidity and the decomposition reaction is sufficiently progressed, is critical for efficiently carrying out the method of the present invention. is important.

If the system is heated too rapidly, the oxidizing agent will volatilize, and if the system is heated too slowly, the oxidation reaction will proceed slowly and the time required for decomposition will become longer.

The time for such carbonization treatment of an organic sample is determined by the set temperature, heating, the state of the organic sample, and the type of acid-oxidizing agent.

Therefore, it is preferable to use an organic sample similar to the organic sample to be decomposed, perform the decomposition using a specific acid monoxidizing agent, and empirically determine the optimal heating temperature and set temperature.

In this way, once the set temperature or heating temperature (specifically, the voltage of the heater) is determined, it becomes possible to quickly decompose similar organic samples.

The method of the present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram of an apparatus embodying the method of the invention.

The organic sample is placed in the decomposition chamber 1 and treated with an acid-oxidizing agent.

In this case, the acid-oxidizing agent will be explained as concentrated sulfuric acid-nitric acid.

The graph in FIG. 2 is a graph showing the temperature of the system over time.

When concentrated sulfuric acid-nitric acid is applied to the organic sample in decomposition chamber 1,
The temperature of the system increases.

The maximum temperature of the system is in this case approximately 130°C.

When the decomposition of the organic sample in the decomposition chamber 1 subsides, the temperature of the system decreases.

In the device shown in FIG. 1, the operation start time t1 of the heater 2
The timer 3 is set so that the heater 2 is activated a certain period of time after t0 when starting to treat an organic sample with concentrated sulfuric acid-nitric acid.

By testing several samples, t1-t0 can be determined empirically.

When the heater 2 is activated, the temperature in the decomposition chamber 1 rises and remains constant at about 130°C.

At this time, the nitric acid oxidizes the sample, is consumed, a part of it evaporates, and is recovered via the condenser 4.

Once the nitric acid is consumed, the temperature in the decomposition chamber 1 begins to rise again, and when the temperature reaches the first set temperature (190°C) (time t2), the thermocouples 5 sense the temperature and transmit the information to the controller 6. , the controller 6 gives instructions to the nitric acid addition device 7.

In response to this instruction, the nitric acid addition device 7 adds nitric acid to the decomposition chamber 1.

By dropping the nitric acid, the temperature of the decomposition chamber 1 decreases slightly, but as the nitric acid decomposes the sample and generates heat, the high temperature is maintained.

In this example, the temperature is always maintained above the first set temperature, and therefore the oxidizing agent is added at regular intervals (several seconds to 3 minutes) set by a separately provided timer (not shown). It is carried out in a regular manner.

In this acid addition step, the heater 2 is adjusted so that a line like the graph A in FIG. 2 is drawn, and the adjustment of the odor can be learned from experience.

As shown by graph A in FIG. 2, there are irregularities at regular intervals.

When the recovery from the temperature drop caused by the addition of the oxidizing agent is delayed and the interval between the uneven surfaces becomes longer and the liquid temperature decreases, (second
Since the decomposition of the sample is almost complete at position B in the graph, the set temperature of the controller 6 is now set to the second set temperature (270°C) at which the oxidizing agent or its decomposed products can be removed.
).

Then, the heating of heater 2 becomes stronger (time 13).

The temperature inside the decomposition chamber 1 further increases, and after reaching the second set temperature or higher, it is maintained for a certain period of time to remove the oxidizing agent or its decomposed products, and the decomposition operation is completed.

In such a series of decomposition steps, if the first decomposition step is not necessary, that is, if it is known that the sample does not have any components that decompose at room temperature, put only the sample and sulfuric acid into the decomposition chamber 1 and immediately Heating may be started.

When using concentrated sulfuric acid-nitric acid, the first set temperature is 120~
250°C is generally suitable, and the second set temperature is generally 230-330°C.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus embodying the method of the present invention, and FIG. 2 is a graph showing the temperature change of the system over time. 1... Decomposition chamber, 2... Heater, 5...
...Thermocouple, 6...Controller, 7...
・Nitric acid addition device.

Claims (1)

[Claims] 1 In a method of decomposing an organic sample with an acid-oxidizing agent mixture, the organic sample is decomposed by heating the organic sample with an acid-oxidizing agent mixture consisting of an acid and an oxidizing agent with a lower boiling point or decomposition temperature than that of the acid, and the system is decomposed. The organic sample is completely decomposed by adding the oxidizing agent little by little when the temperature reaches a preset temperature selected in the range above the boiling point or decomposition temperature of the oxidizing agent and below the boiling point of the acid, Organic sample decomposition method.