WO2014064985A1 - System for unified quantitative determination of various forms of carbon and nitrogen which employs calibration curves based on organic compounds - Google Patents

Abstract

[Problem] To establish a method for unified analysis for the quantitative determination of TOC, IC, TC, DOC, POC, VOC, NVOC, PM_2.5, VON, DON, PON, IN, ON, and TN. [Solution] In a first oven, a sample is decomposed in accordance with the material properties such as boiling point or decomposition point. In a second oven, the organic forms are burned. Finally, the first oven is heated to a high temperature to burn the inorganic forms. The thus-obtained various forms of carbon and nitrogen are quantitatively determined all together by means of calibration curves obtained with highly purified organic compounds having a known composition. The thus-determined values are approximated by means of other highly purified organic compounds having a known composition. Thus, a system capable of easy verification is established.

Description

Unified determination system of carbon and nitrogen in the atmosphere using calibration curve with organic compounds

The present invention relates to an analyzer for CHN, TOC, IC, TC, DOC, POC, VOC, NVOC, VON, DON, PON, IN, ON, TN.

Regarding carbon contained in the sample, TOC (organic carbon), IC (inorganic carbon), TC (all carbon), DOC (dissolved organic matter), VOC (volatile organic carbon), NVOC (nonvolatile inorganic carbon) There are measurement categories such as). In the environmental field, these determinations are important measurement items such as lakes, marine floating materials, sediments, soils, sludges, exhaust gases and industrial wastes. In the industrial field, it is a quality indication item such as petroleum, coal, heavy oil, food and compost. Furthermore, in the energy field, it is necessary for biomass, business organic waste RPF, general household organic waste RDF, etc. Regarding nitrogen, classifications such as VON (volatile organic nitrogen), DON (dissolved organic nitrogen), PON (suspended organic nitrogen), IN (inorganic nitrogen), ON (organic nitrogen), TN (total nitrogen), etc. There is. Nitrogen is important as an indicator of eutrophication of the ocean and lakes. Furthermore, the ratio of carbon to nitrogen is a quality indicator for compost. It is also an important measurement in the study of marine sediments and soil organisms. In these quantifications, various measuring instruments have been developed in each field, and there are variations in the apparatus itself as variations in the process, variations due to people to measure, and variations due to pretreatment, etc., a method for establishing measurement reliability. The relevant organizations, such as the preparation of manuals, supply of standard samples, and workshops, are being carried out.

For example, in the determination of TOC (organic carbon), hydrochloric acid is added to the sample to acidify it, and inorganic carbon (IC) is decomposed and then the concentration of soot is determined by combustion oxidation method and NDIR (infrared gas detector) Many things are widespread. The calibration of sputum is in accordance with the specified standard. Total carbon (TC) is also measured by combustion oxidation and NDIR samples. Calibration in this case uses an inorganic compound such as calcium carbonate. For determination of IC (inorganic form carbon), hydrochloric acid is added to the sample to acidify the sample, aeration treatment is performed to determine the soot concentration with NDIR (infrared gas detector), or phosphoric acid is added and heated to 150 ° C for determination The former standard sample uses potassium hydrogen phthalate and the latter uses sodium carbonate. The NDIR method requires frequent calibration because the intensity of the infrared source and the detector fluctuate.

For example, quantification of DOC (dissolved organic matter) is carried out with a TOC meter: 1) wet oxidation method, 2) wet ultraviolet oxidation method, 3) combustion oxidation method, and 3 methods, 1) and 3) NDIR method 2 2.) According to the conductivity detection method, it is reported that the combustion oxidation method shows lower values due to loss of non-volatile DOC as compared with the first two methods. It is pointed out that the standard solution for calibrating the TOC meter is easily oxidized and dissolved in water, there are no interfering substances in the NDIR detector, and whether the IC and DOC are completely separated. ing. Also, DOC is an extremely small value compared to IC and TC, and it is unclear whether there is measurement accuracy that can verify this.

For the measurement of nitrogen, combustion analyzers are mainly used for TN (total nitrogen) and ON (organic nitrogen), but in the determination of a very small amount, a numerical value less than 2 digits of comma as a% content, in other words, detection of several μg It is unclear whether or not it is accurate. Since the calibration of several μg is close to the fluctuation value of the apparatus itself, it can not be distinguished from the simple output value if it is not sufficiently considered. There is a situation that has not been established for the calibration of measuring instruments for the measurement of trace amounts of nitrogen

There is no unified and simple way of carbon and nitrogen in this way. The confidence of the analysis values depends on the specifications and standards of the analyzer, each standard and the environmental conditions of the laboratory. In other words, the analysis value is defined in the official law as being based on a certain method, and the task of procurement such as procuring standard solutions or purchasing expensive commercial reagents for calibration is complicated and analytical operation is complicated and work efficiency is poor Can be mentioned. Under the present circumstances, it is difficult to evaluate a detection amount of several μg as, for example, a measurement value that can be compared and compared among countries.

On the other hand, organic elemental analysis (CHN analysis) is to measure the content (w / w%) of the CHN element in a sample. It was developed for drug structure determination, but is currently used for the determination of carbon, nitrogen and hydrogen in many fields. It is possible to measure TC (total carbon), TN (total nitrogen) and C / N ratio which overlap with the above. For example, the procedure is performed as described below.
1.
Helium is flowed at a constant speed as a carrier gas into the measurement system.
2.
The weight of the sample is about 1 to 100 mg in μg units.
3.
Oxygen is fed into the combustion tube to completely burn the sample to a gas at about 950 ° C. At that time, C is CO ₂ , N is NO ₂ and H is H ₂ O. Pump the combustion gas into the measurement system.
4.
Remove excess oxygen from the reduction pipe of the reduction tube as copper oxide. Here, NO ₂ is reduced to N ₂ . If it contains halogen or sulfur, trap it as silver halide or silver sulfide in the silver grain column in the system.
5.
The remaining gas is a mixed gas of CO ₂ , N ₂ , H ₂ O and helium.
6.
The mixed gases are measured for their respective quantities through a TCD detector. The TCD detector has a filament. TCD detector measures the thermal conductivity, but helium is a gas with good thermal conductivity. If other gases are mixed there, the thermal conductivity will decrease, and the electric resistance will move accordingly. A count value corresponding to the change in resistance value is recorded.
7.
First, the gas is passed through the H ₂ O absorber to remove H ₂ O. The TCD detector is placed before and after it to convert changes in electrical resistance into counts.
8.
Then through the absorption of CO _2, removing the CO _2. Convert the change before and after to count.
Such a detection method is called differential thermal conductivity method.
9.
Finally, compare N ₂ with helium and convert the difference to a count value.
10.
A calibration curve for each element is prepared using the standard sample for organic element analysis, and the numerical value of the measurement sample is calculated.

Among the organic element analysis methods (CHN analysis) mentioned above, the TCD detector has two sets of filaments, and the mixed component gas of helium gas and combustion gas is measured with a filament on one side, and then the gas to be measured is It has the principle that it is possible to know the concentration of the component gas absorbed from the difference of 其 by measuring the remaining passing gas with the other side of the filament by chemically capturing it through the absorption tube filled with the reagent capable of absorbing and capturing . The content is determined using the correlation between the mass (μg) defined in the International System of Units (SI) and the change in the electrical resistance (Ω) of the gas generated by the chemical reaction. Furthermore, the correctness of the standard curve of the crucible can be verified by other organic compounds having different compositions.

The face of the CHN coder Keiichiro Hozumi supervised by Yanako Analytical Industry Co., Ltd.

The current analyzers for quantifying various types of carbon (TOC, IC, TC, DOC, POC, VOC, NVOC) and nitrogen (VON, DON, PON, IN, ON, TN)
1. There are various ways to use standard samples.
2. There are many measurement methods and each problem has not been established.
3. The lower limit of detection, the lower limit of quantification, etc. depend on the analysis model, and the limits of detected amounts of carbon and nitrogen can not be grasped correctly.
4. There is a problem unique to each instrument in calibration, and there is no chemical verification data on concentrations that are considered important in the environment, such as low concentration detection, which is a research issue.
5. Parts of important numerical calculations are black-boxed by the device manufacturer, and it is possible to verify the method in accordance with the procedure but the verification as the true value is insufficient.
And other problems can be raised. There are divisions, definitions and analysis methods of each state in each field,
There is a problem that the means for securing the reliability is complicated.

Furthermore, it is important to be able to demonstrate the measurements used in industry, and it is desirable that the sample handle the amount that can be demonstrated. Analyzers that use an extremely small amount of sample, such as spectrum analysis or absorption of wavelength, are effective and important in the research area, but they are objective in quantities that can be easily demonstrated for calibration of the measuring instrument and estimation of uncertainty. It should be improved to a method that can be verified

In addition, it seems important that measurement data has wide compatibility across countries and time. For this reason, research on equivalence evaluation is actively conducted in which the reliability of data is expressed in a common manner, but in the current situation, it seems difficult to establish a unified evaluation method for each device analysis.

A combustion system designed so that the boiling point or decomposition point of the sample can be arbitrarily set;
Using a highly purified organic compound of known composition as a standard sample, the content (μg) of each element contained in the standard sample and the electric resistance value of the detector corresponding to the concentration of each component generated by the combustion ( Characterized by having a calibration system based on the relationship with the change in Ω) and a system for verifying the detected amount of the sample in an approximate amount using another similar highly purified organic compound of known composition. It is said that.

That is, the present invention volatilizes and burns each form carbon and nitrogen in a combustion furnace set at the boiling point or decomposition point of the sample, and finally leads all forms of carbon and nitrogen to carbon dioxide gas and nitrogen to carry out the same calibration. It is characterized by quantifying with a line.

The present invention uses TOC (organic carbon), IC (inorganic carbon), TC (total carbon), DOC (dissolved organic matter) by utilizing the boiling point and decomposition point of various forms of carbon in the first furnace and arbitrarily designated temperature. ), The carbon in VOC (volatile organic carbon) and NVOC (nonvolatile inorganic carbon) are separated, and the conditions for each form carbon to go to the detection system by passing through the second intermediate temperature furnace are unified, and the same calibration It is characterized in that it is easy to determine by equation. Classification of VOC according to WHO is highly volatile organic compound (VVOC) to 50 ° C, volatile organic compound (VOC) 50 to 260 ° C, semi volatile organic compound (SVOC) 260 to 400 ° C, particulate organic compound (POM) The PRTR method is defined as having a temperature of 380 ° C. or higher, and the PRTR method has a definition of a boiling point of 150 ° C. or lower. The method of the present invention is characterized by being a method corresponding to its physical property value.

Furthermore, the present invention has the advantage of being able to measure all types of carbon and nitrogen in a unified manner in a calibration formula prepared from organic compounds of known composition with high purification. It can be proved experimentally by the oxygen concentration in the carrier and the combustion temperature whether a sufficient oxidation reaction is performed. In practice, it has been proved by experiments that the organic matter does not burn completely in the absence of oxygen at 550 ° C. When 10% of oxygen is not added, the combustion is insufficient even if the temperature is raised to 750 ° C. For example, the experimental verification is carried out as to whether the values determined by burning and removing the organic carbon in advance and burning the remaining organic carbon as inorganic carbon at high temperature are identical. It can be done correctly. This advantage makes it possible to estimate the uncertainty of measurement accurately, and has the effect of establishing traceability with international weighing standards in an easy way.

In the calibration of the present invention, the accuracy of mass of 1 mg or less is verified by using a plurality of highly purified organic compounds by using the composition ratio obtained from the molecular formula. In the case of organic elemental analysis, the calibration curve by the standard sample is characterized by measuring other organic compounds different in molecular formula and verifying whether it conforms to the theoretical value (element content%). General measurement systems are based on measurements based on a one-sided calibration curve, but the method of the present invention measures the same detection amount as that of the sample with an organic compound having similar content and verifies the uncertainty There are effects that can be done. In fact, 10 μg of both carbon and nitrogen can be verified.

It is a block diagram of the analysis system which showed the implementation method of this invention. It is a figure of a calibration curve of carbon of the present invention.

The apparatus implemented in the case of the determination of carbon and nitrogen according to the invention is shown in FIG. Three electric furnaces 4, 5, 6 and the combustion pipe 1 that spans them, the absorption pipe 8, 11 and C and N detectors 9, 10, the C detector 9, and the N detector 10 for capturing water, carbon dioxide gas And a delay coil 12. It is also possible to add an H detector in front of the C detector of this analysis system to measure H. The combustion tube is filled with a filler containing titanium oxide and a halogen-sulfur absorbent, and two electric furnaces are sufficient if they are filled with reduced copper together. The combustion tube may be made of hard glass, ceramic or other metal. The electric furnace has a precisely controllable first furnace 4 and a second furnace 5 which can be arbitrarily set at medium temperature (450-650 ° C), and the first furnace can freely change the furnace temperature from low temperature to high temperature . The third furnace 6 heats the reduction tube filled with reduced copper. The temperature is set to medium temperature (450-650 ° C.).

An example of the determination of each state carbon and nitrogen will be described in detail below with reference to the block diagram of the analysis system of FIG.

In the case of simultaneous measurement of IC, TOC, and TC, the second furnace 4 is set to an intermediate temperature (450-650 ° C.), and the sample is inserted to the middle of the second furnace 5 using the introduction rod 2. The organic carbon in the sample is burned and oxidized here, and the absorbent in the furnace traps gases other than the detection gas (halogen, sulfur, etc.) and sends it to the detection system. The detected value at this time is A (TOC). Subsequently, the first furnace 4 is raised to an arbitrary high temperature (650 ° C. or higher), and the remaining inorganic carbon is completely burned and sent to the detection system. Let B (IC) be the detected value at this time. A and B are calculated in advance by a calibration curve (a signal count representing a difference between μg / response electric signal value Ω) prepared by using a standard sample of an organic compound. TC is obtained by summing A (TOC) and B (IC).

In the case of VOC measurement, the first furnace 4 is set to a low temperature (temperature for volatilizing the sample), and the second furnace 5 is set to an intermediate temperature (450-650 ° C.). The component gas volatilized in the first furnace 4 is combusted and oxidized in the second furnace 5, and the water absorbent 8 removes moisture and is sent to the detection system. The calculation method is omitted below.

When TOC is determined from IC and TC When the sample is in an inorganic state, the first furnace 4 is set to a low temperature (room temperature) and the second furnace 5 is set to a medium temperature (450-650 ° C.). A sample is placed in the first furnace 4, hydrochloric acid is added, carbon in inorganic carbon is converted to carbon dioxide gas, and combustion oxidation is performed in the second furnace 5. The moisture is removed by the moisture absorbent 8 and sent to the detection system, and the soot detection value is taken as A (IC). The detection method is omitted below. Subsequently, the first furnace 4 is set to an arbitrary temperature of high temperature (650 ° C. or higher), and the sample is put into the first furnace 4 for combustion oxidation. The moisture is removed by the moisture absorbent 8 and sent to the detection system, and the soot detection value is taken as B (TC). The calculation method is omitted below. TOC is obtained by subtracting A from B.

A sample is introduced into the second furnace 5 after removing the inorganic carbon as carbon dioxide gas by setting the measurement sample of TOC alone to PH 4 or less. The sample is combusted and oxidized in the second furnace 5, the moisture absorbent 8 removes moisture, and is sent to the detection system. The calculation method will be described later.

In the case of measurement of IC alone, the second furnace 5 is set to an intermediate temperature (450-650 ° C.), and a sample is introduced to burn and remove organic carbon. This gas passes through the detection system and is exhausted. The first furnace 4 is set to an arbitrary temperature of high temperature (650 ° C. or higher) to burn the gas generated from the sample, remove moisture with the moisture absorbent 8 and send it to the detection system for detection. The calculation method will be described later.

For VON, NVON, TN, PON, nitrogen dioxide generated by combustion is reduced copper filled in a combustion tube in a furnace set at a second intermediate temperature (450-650 ° C.) or the third furnace of FIG. 1 After being reduced to nitrogen by 6, water is removed by a water absorbent together with carbon dioxide gas, and the resultant is sent to a detection system, and is detected by a nitrogen detector following a carbon detector. The calculation method will be described later.

The calibration system in the present invention creates a calibration equation derived from the automatic output value (μg) by the electronic balance and the output value from the analyzer (signal count representing the difference in the quantity of electricity Ω), and generates another standard sample or calibration The reliability is verified with an organic compound having a composition ratio necessary for FIG. 2 is a diagram of a calibration curve of carbon of the present invention. The following is a method of preparing a calibration curve performed by the elemental analyzer Yanako CHN coder MT-5.

The organic compounds of the standard sample are accurately measured by means of precision balances, introduced into the above-mentioned analyzer for practical use, and thermally decomposed in a first furnace. The gas generated by combustion in the second furnace is removed from the moisture with a moisture absorbent, and the difference between the electrical quantities (Ω) measured by the TCD detector is determined from the numerical value (signal count) and the theoretical value of the standard sample The calibration formula is prepared from the correlation with the content (μg) of The TCD detector has a very linear response, and in the case of carbon, the correlation coefficient is R ² = 0.9999969 as shown in FIG. This linearity indicates that the detection method is extremely accurate. The TCD detector, which has a detection limit of 10 ^-8 g and a dynamic range of 10 ⁵ , can be said to be sufficient for measurement.

As a specific example of low concentration measurement, Table 1 shows the case of carbon and Table 2 shows the case of nitrogen. As standard samples, iodoform (sp-15 C: 3.05%, manufactured by Kishida Chemical Co., Ltd.) and commercially available reagent for research (Dioctadecylamin N 2.68%) are used. In all cases, around 10 μg is accurately measured. Further, Table 3 shows an example in which standard organic compounds are measured and verified before and after a test sample as an example, and Table 4 shows an example in which organic carbon and inorganic carbon in a general reagent calcium carbonate are separately quantified. The above example is based on the implementation apparatus, but shows the simplicity and reliability of traceability of the calibration curve system by the organic compound. Calibration of detection of 10-20 μg of carbon and nitrogen elements with errors of 0-1.8 μg and 0.08-2.07 μg, respectively, and confidence of measured values can be demonstrated by sandwiching a standard sample before and after measurement The experiment of Example 1-4 shows that organic carbon and inorganic carbon are fractionated and determined.
(Experiment)

 

 

The method of the present invention is a method in which fractionation of organic carbon and inorganic carbon, fractionation of volatile and non-volatile organic compounds, and determination of nitrogen are unified. Important analytical instruments in the environment such as floats and sediments in lakes and oceans, soil, sludge, exhaust gases, industrial wastes, etc., practical indicators, quality indication such as petroleum, coal, fuel oil, food, compost, biomass, business TOC (organic carbon), IC (inorganic carbon), TC (total carbon), DOC (dissolved organic matter), VOC (volatile organic matter) in the field of new energy development such as organic waste RPF based on household waste and RDF for general household organic waste Organic carbon), carbon in NVOC (nonvolatile inorganic carbon), IN (inorganic nitrogen), ON (organic nitrogen), TN (total nitrogen), C / N ratio (indication of compost quality), C / It can be used for N ratio (research on bottom sediment and soil organisms) and a wide range of fields. In particular, based on the International Standard System (SI unit), a clear calibration system based on chemical reactions is effective for observation of all carbon and nitrogen on the earth, and can be widely used as a measuring instrument of their follow-up observation. In addition, hydrogen can be measured by adding an H detector as an option. The H / C ratio is an important indicator of various fuels, and it is an effective indicator if it is combined with boiling point measurement as a chemical evaluation of light oil. In the sewage sludge carbonization system, the H / C ratio is a self-heating characteristic and is used in the manufacturing process of carbonized products. Production management by measurement results in the development of industry, but at present, each analysis method is developed into a high-performance and advanced analysis device and the user is limited, so that anyone practical can easily use it, measurement value There is also the possibility that the development of something that can be demonstrated robustly will lead to the spread of global use. In addition to development as a universal type including CHN measurement, there is also utilization as a small practical machine specialized for the purpose.

The present invention is capable of quantifying carbon and nitrogen in the required form by appropriately matching the temperature conditions of combustion oxidation of various forms of carbon and nitrogen, so the usability is improved compared with many widely used measuring devices, and it is widely spread. Have the potential to Instruments have various measurement standards and standards to evaluate their reliability, and it is necessary to meet the requirements of each country or global standard overseas as well. The present invention emphasizes that the compatibility of measurement values is maintained by a simple principle, and has a strategy to become a national measurement standard to be provided in a new field of certification, certification, and advanced technology development. There is.

1.
Combustion tube 2.
Sample introduction rod 3.
Sample boat 4.
Heating furnace5.
Oxidation and reduction furnace6. Reduction furnace 7. Reduction pipe
8. Water absorption tube 9. C detector 10. N detector 11. Carbon dioxide absorption tube 12. Delay coil



 

Claims (5)

An analytical measurement system characterized by comprising a combustion system designed to arbitrarily set the boiling point or decomposition point of the sample and a calibration system using a highly purified organic compound of known composition as a standard sample. The combustion system designed to arbitrarily set the boiling point or decomposition point of the sample and the calibration system with the known organic compound of the composition of the highly purified composition as a standard sample and the other similarly highly purified An analytical measurement method characterized by comprising a system for verifying an analytical value in an amount close to a detected amount of the sample using an apparent organic compound of different composition. Various forms of carbon are prepared using a calibration system using a combustion step designed to arbitrarily set the boiling point or decomposition point of the sample and an organic compound of known composition of highly purified composition as a standard sample An analytical measurement system characterized by finally introducing nitrogen into carbon dioxide gas and nitrogen and quantifying them with the same calibration curve. A combustion method characterized by setting the boiling point or decomposition point of the sample arbitrarily. Using a calibration curve with an organic compound of highly purified composition as a standard sample and other similar organic compounds of highly purified composition with similar quantities of detection of the sample Analytical measurement method characterized by verifying

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