CN115901914A - Soil invertebrate carbon stabilization isotope testing device and using method - Google Patents
Soil invertebrate carbon stabilization isotope testing device and using method Download PDFInfo
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- CN115901914A CN115901914A CN202211407641.XA CN202211407641A CN115901914A CN 115901914 A CN115901914 A CN 115901914A CN 202211407641 A CN202211407641 A CN 202211407641A CN 115901914 A CN115901914 A CN 115901914A
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Abstract
The invention discloses a carbon stable isotope testing device for soil invertebrates and a using method thereof, belonging to the technical field of environmental monitoring; comprises an air extraction component, an automatic sample injector, a sample injection valve, a high-temperature combustion furnace, a water trap and a six-way valve which are sequentially connected in series; an air inlet valve is externally connected between the sample injection valve and the high-temperature combustion furnace; the six-way valve is provided with an air inlet port and an air outlet port; the two ends of the stainless steel column are respectively communicated with the six-way valve; one end of the capillary column is communicated with the six-way valve; and the liquid nitrogen cup is arranged below the capillary column and the stainless steel column. The invention realizes that the sample quantity requirement is reduced by two orders of magnitude compared with the commercial EA-IRMS under the condition of ensuring the data precision and accuracy.
Description
Technical Field
The invention relates to the technical field of environmental monitoring, in particular to a carbon stable isotope testing device for soil invertebrates and a using method thereof.
Background
Photosynthesis is a unidirectional reaction in the atmosphere 12 CO 2 Key ratio 13 CO 2 Is easily broken, so that the plant tissue is preferentially absorbed during photosynthesis 12 CO 2 Under the action of enzyme 12 CO 2 Preferentially transferring to take part in biochemical reaction to enrich organic substances 12 C。CO 2 In the course of participating in biochemical reactions in the body, different components of the body also have different isotopic composition characteristics due to different metabolic pathways, e.g. lipids are more enriched than proteins and cellulose 12 C. And as the biological nutrition level is increased, the tissues are slightly enriched compared with the previous nutrition level organisms 13 C, which is also widely used in the study of the recognition of the ecological nutritional chain.
Soil invertebrates, as an important component in soil ecosystems, are important links in the processes of overground and underground ecology, and play an important role in litter decomposition, nutrient mineralization, biodiversity protection and biogeochemical cycle processes. More and more studies indicate that the diversity of the underground ecosystem determines the biological diversity on the ground, the function of the terrestrial ecosystem and its response to environmental changes, and is an important content for monitoring the soil ecosystem process and evaluating the health of the soil ecosystem. The soil animal food net characterizes the feeding relationship among various species in the soil animal community, is also a network formed by various organisms and nutrition relationships thereof in an ecosystem, describes the complex nutrition relationship among different organisms in the biological community, and is an important form of material and energy flow in the soil ecosystem. Food net studies can indicate the composition, association and integrity of communities, and are of great significance in exploring energy flow and material circulation in ecosystems.
The stable isotope technology is an important research means which is raised in ecology in recent decades, and provides quantitative indexes for researching the nutritional relationship among species from a new perspective. Different organisms have C isotopes with different ratios, the C isotope ratio of the organisms is determined by foods, the isotope ratios of different foods are different, and the long-term and short-term isotope ratios of different tissues and organs of the organisms can be judgedWhat is the main food in the composition, the carbon stable isotope ratio delta 13 C( 13 C/ 12 C) To indicate the source of the food.
Isotopic abundance of carbon is typically achieved using pure gaseous CO 2 Measured on an isotope ratio mass spectrometer. Continuous flow systems have significantly lower sample size requirements than off-line preparation because most or all of the analyte gas is fed into the mass spectrometer source. Continuous flow analysis of the C isotope composition of bulk organic materials is routinely performed using Elemental Analyzers (EA) and Isotope Ratio Mass Spectrometers (IRMS). These assays typically require at least 2. Mu. MolCO 2 . Although EA-IRMS is useful, in many cases the amount of available samples is much less than the requirements of the technique.
Due to the high split ratio of carrier gas to ion source, the EA-IRMS sample size requirement in commercial systems increases. Elemental analyzers typically use a helium gas flow rate of 50-150ml min-1, but only about 0.2ml min-1 is transferred to the ion source of the IRMS. The lower limit on the sample volume is limited by the minimum acceptable helium flow in the EA and the maximum flow rate that the ion source pump can accommodate. Finally, the ionization efficiency of the mass spectrum and the relative abundance of the rare isotopes govern the minimum sample size required for acceptable accuracy of analysis.
In scientific research, many soil invertebrate samples are small in quantity and cannot be detected by using a traditional commercial system EA-IRMS, so that a carbon stability isotope testing device suitable for a trace soil invertebrate sample and a using method thereof are urgently needed.
Disclosure of Invention
In order to achieve the purpose, the invention adopts the following technical scheme:
a carbon stable isotope testing device for soil invertebrates comprises an air extraction component, an automatic sample injector, a sample injection valve, a high-temperature combustion furnace, a water trap and a six-way valve which are sequentially connected in series;
an air inlet valve is externally connected between the sample injection valve and the high-temperature combustion furnace;
the six-way valve is provided with an air inlet port and an air outlet port;
the two ends of the stainless steel column are communicated with the six-way valve;
one end of the capillary column is communicated with the six-way valve;
and the liquid nitrogen cup is arranged below the capillary column and the stainless steel column.
Further, the air extraction assembly comprises an air extraction valve and a vacuum pump, one end of the air extraction valve is communicated with the vacuum pump, and the other end of the air extraction valve is communicated with the automatic sample injector; and a vent valve is arranged between the air suction valve and the vacuum pump.
Furthermore, a first port, a second port, a third port, a fourth port, a fifth port and a sixth port are sequentially arranged on the six-way valve;
the water trap is communicated with the first port;
one end of the stainless steel column is communicated with the sixth port, and the other end of the stainless steel column is communicated with the third port;
one end of the capillary column is communicated with the fourth port;
the second port is used for discharging gas;
the fifth port is used for externally connecting helium.
Further, the number of the liquid nitrogen cups is 2, and the 2 liquid nitrogen cups are respectively arranged below the capillary column and the stainless steel column.
A method of using a soil invertebrate carbon stable isotope testing device, the method of use comprising the steps of:
s1, sample preparation
Packing the sample into regular small blocks by using 5X 3.3mm silver cups, placing the small blocks in sample holes of a sample plate of a zero-air white sample injector, and fastening a cover of the sample injector for sealing;
s2, vacuumizing
Rotating the sample injection valve to an off state, opening the air extraction valve to vacuumize the sample injector, closing the air extraction valve after 5min, rotating the sample injection valve to an on state, and communicating the sample injector with the reaction tube;
S3，CO 2 enriching;
s4, sample testing
The six-way valve is switched to the Load mode, the capillary column is lifted, and CO released 2 The C stable isotope ratio was tested by bringing it into the Conflo IV Lw interface of the stable isotope mass spectrometer with helium.
Further, step S3 specifically includes the following steps:
s31, setting the six-way valve in a Load mode, opening an air inlet valve, introducing helium, then rotating a sample introduction plate, introducing a sample into a high-temperature combustion furnace tube to start oxidation, and removing water vapor in the gas through a water trap after the sample is oxidized at high temperature, wherein a stainless steel column falls into liquid nitrogen;
s32, the carbon dioxide gas enters the sixth port from the first port of the six-way valve and is discharged out under the drive of the helium carrier gas, then the carbon dioxide gas is roughly enriched in the stainless steel column, and then the helium gas enters the third port of the six-way valve and is discharged from the second port; the capillary column enriched with carbon dioxide falls into a liquid nitrogen cup filled with liquid nitrogen;
s33, the six-way valve is switched to the Inject mode, the stainless steel column is lifted, and then heating is started to release the enriched carbon dioxide, and then the carbon dioxide enters the third port of the six-way valve, flows out from the fourth port, and is again finely enriched in the capillary column.
The invention has the following beneficial effects: the carbon stable isotope testing device for the soil invertebrates and the using method thereof are combined by utilizing the C enrichment device and the improved commercial combustion EA, can be applied to C with the content of only 25-40 nmol, reduce the requirement on the sample size, and reduce two orders of magnitude compared with the requirement on the commercial EA-IRMS sample size under the condition of ensuring the precision and accuracy of data.
Drawings
FIG. 1 is a schematic overall view of a soil invertebrate carbon stabilization isotope testing device and a method of use thereof according to the present invention;
wherein: 1. an air extraction valve; 2. an intake valve; 3. a sample injection valve; 4. an automatic sample injector; 5. a high temperature combustion furnace; 6. a six-way valve; 61. a first port; 62. a second port; 63. a third port; 64. a fourth port; 65. a fifth port; 66. a sixth port; 7. a vacuum pump; 8. a water trap; 9. a liquid nitrogen cup; 10. a capillary column; 11. stainless steel column.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
Example 1
Referring to fig. 1, in the present embodiment, a carbon stable isotope testing apparatus for soil invertebrates includes an air extraction assembly, an autosampler 4, a sample injection valve 3, a high temperature combustion furnace 5, a water trap 8 and a six-way valve 6, which are connected in series in sequence;
an air inlet valve 2 is externally connected between the sample injection valve 3 and the high-temperature combustion furnace 5;
the six-way valve 6 is provided with an air inlet port and an air outlet port;
the stainless steel column 11, both ends of the stainless steel column 11 communicate with six-way valve 6;
one end of the capillary column 10 is communicated with the six-way valve 6;
and the liquid nitrogen cup 9 is arranged below the capillary column 10 and the stainless steel column 11.
Example 2
In the embodiment, the air extraction assembly comprises an air extraction valve 1 and a vacuum pump 7, one end of the air extraction valve 1 is communicated with the vacuum pump 7, and the other end of the air extraction valve 1 is communicated with the automatic sampler 4; a vent valve is arranged between the air extraction valve 1 and the vacuum pump 7;
in the present embodiment, the six-way valve 6 is provided with a first port 61, a second port 62, a third port 63, a fourth port 64, a fifth port 65 and a sixth port 66 in sequence;
the water trap 8 is in communication with the first port 61;
one end of the stainless steel column 11 is communicated with the sixth port 66, and the other end of the stainless steel column 11 is communicated with the third port 63;
one end of the capillary column 10 is in communication with the fourth port 64;
a second port 62 for discharging gas;
a fifth port 65 for external access to helium;
in this embodiment, the number of the liquid nitrogen cups is 2, and the 2 liquid nitrogen cups are respectively disposed below the capillary column and the stainless steel column.
Example 3
In this embodiment, a method for using a soil invertebrate carbon stabilization isotope testing device includes:
s1, sample preparation
Firing a silver cup required by an experiment at 500 ℃ in a muffle furnace to remove trace impurities on the surface and reduce the blank of C; packaging the 5 x 3.3mm silver cups subjected to high-temperature treatment into regular small blocks for later use;
s2, vacuumizing
S21, placing the wrapped sample in a sample hole of a sample tray of a zero-air sample injector, and fastening a cover of the sample injector for sealing;
s22, rotating the sample injection valve 3 to an off state, opening the air extraction valve 1 to vacuumize the sample injector, closing the air extraction valve 1 after 5min, rotating the sample injection valve 3 to an on state, and communicating the sample injector with the reaction tube;
S3，CO 2 enrichment of
S31, setting the six-way valve 6 to be in a Load mode, opening an air inlet valve, introducing helium, then rotating a sample injection disc, enabling a sample to enter a high-temperature combustion furnace 5 tube to start oxidation, enabling the stainless steel column 11 to fall into liquid nitrogen, and removing water vapor in gas through a water trap 8 (magnesium perchlorate) after the sample is oxidized at high temperature;
s32, the carbon dioxide gas is driven by the helium carrier gas to flow from the first port 61 to the sixth port 66 of the six-way valve 6, and then is roughly enriched in the stainless steel column 11, and then the helium gas flows into the third port 63 of the six-way valve 6 and is discharged from the second port 62; the capillary column 10 enriched with carbon dioxide falls into a liquid nitrogen cup 9 containing liquid nitrogen;
s33, switching the six-way valve 6 to the Inject mode, lifting the stainless steel column 11, and then starting to heat to release the enriched carbon dioxide, and then the carbon dioxide enters the third port 63 of the six-way valve 6, flows out from the fourth port 64, and is finely enriched into the capillary column 10 again;
s4, sample testing
The six-way valve 6 is switched to Load mode, the capillary column 10 is lifted, and the released CO is 2 The C stable isotope ratio was tested by bringing helium into the Conflo IV Lw interface of the stable isotope mass spectrometer.
A blank test of the method is carried out, the measurement result is shown in table 1, and the result shows that the background blank is still controllable after the device is enriched twice, so that the requirement of the C stable isotope test is met.
TABLE 1
Example 4
In this embodiment, a method for using a soil invertebrate carbon stabilization isotope testing device includes:
s1, sample preparation
Firing a silver cup required by an experiment at 500 ℃ in a muffle furnace to remove trace impurities on the surface and reduce the blank of C; adding USGS40 (L-glutamic acid) international standard samples into a high-temperature treated 5X 3.3mm silver cup and packaging the sample into regular small blocks for later use;
s2, vacuumizing
S21, placing the wrapped sample in a sample hole of a sample tray of a zero-air sample injector, and fastening a cover of the sample injector for sealing;
s22, rotating the sample injection valve 3 to an off state, opening the air extraction valve 1 to vacuumize the sample injector, closing the air extraction valve 1 after 5min, rotating the sample injection valve 3 to an on state, and communicating the sample injector with the reaction tube;
S3，CO 2 enrichment of
S31, setting the six-way valve 6 to be in a Load mode, opening an air inlet valve, introducing helium, then rotating an injection plate, enabling a sample to enter a high-temperature combustion furnace 5 tube to start oxidation, enabling the stainless steel column 11 to fall into liquid nitrogen, and removing water vapor in gas through a water trap 8 (magnesium perchlorate) after the sample is oxidized at high temperature;
s32, the carbon dioxide gas is driven by the helium carrier gas to flow out of the sixth port 66 from the first port 61 of the six-way valve 6, and then is roughly enriched in the stainless steel column 11, and then the helium gas flows into the third port 63 of the six-way valve 6, and is discharged from the second port 62; the capillary column 10 enriched with carbon dioxide falls into a liquid nitrogen cup 9 containing liquid nitrogen;
s33, switching the six-way valve 6 to the Inject mode, lifting the stainless steel column 11, then starting heating to release the enriched carbon dioxide, and then the carbon dioxide enters the third port 63 of the six-way valve 6, flows out from the fourth port 64, and is again finely enriched in the capillary column 10;
s4, sample testing
The six-way valve 6 is switched to Load mode, the capillary column 10 is lifted, and the released CO is 2 The C stable isotope ratio was tested by bringing it into the Conflo IV Lw interface of the stable isotope mass spectrometer with helium.
Using USGS40 (Lglutamic acid, standard value. Delta.) ( 13 C VPDB Mill: 26.39) the method is verified for precision and accuracy by international standard samples, and the measurement result is shown in Table 2 and shows that the method is accurate and feasible.
TABLE 2
Example 5
In this embodiment, a method for using a soil invertebrate carbon stabilization isotope testing device includes:
s1, sample preparation
Firing a silver cup required by an experiment at 500 ℃ in a muffle furnace to remove trace impurities on the surface and reduce the blank of C; adding the dried laboratory-cultivated flea beetles into a 5 x 3.3mm silver cup treated at high temperature, and packaging into regular small blocks for later use;
s2, vacuumizing
S21, placing the wrapped sample in a sample hole of a sample tray of a zero-air sample injector, and fastening a cover of the sample injector for sealing;
s22, rotating the sample injection valve 3 to an off state, opening the air extraction valve 1 to vacuumize the sample injector, closing the air extraction valve 1 after 5min, rotating the sample injection valve 3 to an on state, and communicating the sample injector with the reaction tube;
S3，CO 2 enrichment of
S31, setting the six-way valve 6 to be in a Load mode, opening an air inlet valve, introducing helium, then rotating an injection plate, enabling a sample to enter a high-temperature combustion furnace 5 tube to start oxidation, enabling the stainless steel column 11 to fall into liquid nitrogen, and removing water vapor in gas through a water trap 8 (magnesium perchlorate) after the sample is oxidized at high temperature;
s32, the carbon dioxide gas is driven by the helium carrier gas to flow out of the sixth port 66 from the first port 61 of the six-way valve 6, and then is roughly enriched in the stainless steel column 11, and then the helium gas flows into the third port 63 of the six-way valve 6, and is discharged from the second port 62; the capillary column 10 enriched with carbon dioxide falls into a liquid nitrogen cup 9 containing liquid nitrogen;
s33, switching the six-way valve 6 to the Inject mode, lifting the stainless steel column 11, and then starting to heat to release the enriched carbon dioxide, and then the carbon dioxide enters the third port 63 of the six-way valve 6, flows out from the fourth port 64, and is finely enriched into the capillary column 10 again;
s4, sample testing
The six-way valve 6 is switched to Load mode, the capillary column 10 is lifted, and the CO released 2 The C stable isotope ratio was tested by bringing it into the Conflo IV Lw interface of the stable isotope mass spectrometer with helium.
The precision of the method is verified by using the springtail (one of the micro arthropods) cultivated in a laboratory, the measurement result is shown in table 3, and the test result shows that the method is accurate and feasible.
TABLE 3
The invention relates to a carbon stable isotope testing device for soil invertebrates and a using method thereof, wherein a C enrichment device is combined with improved commercial combustion EA, the carbon stable isotope testing device can be applied to C with the content of only 25-40 nmol, the requirement on the sample size is reduced, and the sample size requirement is reduced by two orders of magnitude compared with that of commercial EA-IRMS under the condition of ensuring the precision and accuracy of data.
The above-described embodiments are only intended to illustrate the preferred embodiments of the present invention, and not to limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims (6)
1. A carbon stable isotope testing device for soil invertebrates is characterized by comprising an air extraction component, an automatic sample injector, a sample injection valve, a high-temperature combustion furnace, a water trap and a six-way valve which are sequentially connected in series;
an air inlet valve is externally connected between the sample injection valve and the high-temperature combustion furnace;
the six-way valve is provided with an air inlet port and an air outlet port;
the two ends of the stainless steel column are respectively communicated with the six-way valve;
one end of the capillary column is communicated with the six-way valve;
and the liquid nitrogen cup is arranged below the capillary column and the stainless steel column.
2. The soil invertebrate carbon stabilization isotope testing apparatus of claim 1, wherein the pumping assembly comprises a pumping valve and a vacuum pump, one end of the pumping valve is in communication with the vacuum pump, and the other end of the pumping valve is in communication with the autosampler; and a vent valve is arranged between the air suction valve and the vacuum pump.
3. The soil invertebrate carbon stabilization isotope testing device of claim 1, wherein the six-way valve is provided with a first port, a second port, a third port, a fourth port, a fifth port and a sixth port in sequence;
the water trap is communicated with the first port;
one end of the stainless steel column is communicated with the sixth port, and the other end of the stainless steel column is communicated with the third port;
one end of the capillary column is communicated with the fourth port;
the second port is used for discharging gas;
the fifth port is used for externally connecting helium.
4. The soil invertebrate carbon stabilization isotope testing device of claim 1, wherein the number of liquid nitrogen cups is 2, and 2 liquid nitrogen cups are respectively arranged below the capillary column and the stainless steel column.
5. A method for using the carbon stable isotope testing apparatus for soil invertebrates according to any one of claims 1 to 4, the method comprising the steps of:
s1, sample preparation
Packing the sample into regular small blocks by using 5X 3.3mm silver cups, placing the small blocks in sample holes of a sample plate of a zero-air white sample injector, and fastening a cover of the sample injector for sealing;
s2, vacuumizing
Rotating the sample injection valve to an off state, opening the air exhaust valve to vacuumize the sample injector, closing the air exhaust valve after 5min, rotating the sample injection valve to an on state, and communicating the sample injector with the reaction tube;
S3，CO 2 enriching;
s4, sample testing
The six-way valve is switched to the Load mode, the capillary column is lifted, and the released CO 2 The C stable isotope ratio was tested by bringing it into the Conflo IV Lw interface of the stable isotope mass spectrometer with helium.
6. The use method of the soil invertebrate carbon stabilization isotope testing device of claim 5, wherein the step S3 specifically comprises the following steps:
s31, setting the six-way valve in a Load mode, opening an air inlet valve, introducing helium, then rotating a sample injection plate, enabling a sample to enter a high-temperature combustion furnace tube to start oxidation, enabling a stainless steel column to fall into liquid nitrogen, and removing water vapor in the gas through a water trap after the sample is subjected to high-temperature oxidation;
s32, the carbon dioxide gas enters the sixth port from the first port of the six-way valve and is discharged out under the drive of the helium carrier gas, then the carbon dioxide gas is roughly enriched in the stainless steel column, and then the helium gas enters the third port of the six-way valve and is discharged from the second port; the capillary column enriched with carbon dioxide falls into a liquid nitrogen cup filled with liquid nitrogen;
s33, the six-way valve is switched to the Inject mode, the stainless steel column is lifted, and then heating is started to release the enriched carbon dioxide, and then the carbon dioxide enters the third port of the six-way valve, flows out from the fourth port, and is again finely enriched in the capillary column.
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