CN110455908B - Preparation method of organic sulfur isotope detection sample and detection method of organic sulfur isotope - Google Patents
Preparation method of organic sulfur isotope detection sample and detection method of organic sulfur isotope Download PDFInfo
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Abstract
The invention provides an organic sulfur isotope detection methodThe preparation method of the test sample comprises the following steps: (1) converting organic sulfur in the organic matter raw material into barium sulfate; (2) reacting barium sulfate in solid acid phosphate and hydroiodic acid to generate hydrogen sulfide gas; (3) removing hydrogen sulfide gas and absorbing with alkaline solution to obtain absorption solution, and (4) adding silver salt solution into the absorption solution to convert sulfur in the absorption solution into silver sulfide precipitate. The invention also provides a detection method for organic sulfur isotope in organic matter raw material, which comprises the steps of preparing a detection sample according to the method of the invention, and adopting SF6A method for detecting said sample.
Description
Technical Field
The invention relates to the field of geochemistry, in particular to a preparation method of an organic sulfur isotope detection sample, the organic sulfur isotope detection sample prepared by the method, and the organic sulfur isotope detection sample used for indicating organic matters33S、36Method of S isotope content.
Background
The 4 elements of carbon, sulfur, nitrogen and phosphorus participate in oxidation-reduction geochemical cycles which are related with each other globally, and the cycles are closely related with the change of the earth environment and the burying-preservation of marine organic matters.
Shale and carbonate formations rich in organic materials are widely distributed, and organic sulfur, a sulfur-containing organic compound, is an important component of the formations. Current research has recognized that sulfur in reservoir bitumen, heavy oil, condensate of oil and gas reservoirs, unlike hydrocarbon elements, can come from either dispersed organic matter (kerogen) in sedimentary rock or inorganic sulfur incorporation in later diagenesis, and organic sulfur isotope analysis is the most effective method for determining its cause. Accurate measurement of the isotopic ratios of the organic sulfur 32, 33, 34, 36 can provide reliable basis for ancient atmospheric oxygen-containing, early life origins and evolutions, fluid sources and mixing studies.
Among the four sulfur isotopes, FengAt the highest degree, the32S (95.02%), followed by34S(4.21％)，33S (0.75%) and36S(0.02％)，33S、36the abundance of S is extremely low. In isotopic geological work, usually at δ34S (‰) indicates the source of sulfur in the organic matter. Delta34S (‰) is the percentage of the sample in thousandths of its deviation from the standard, which represents the difference between the isotopic composition of the sulfur in the sample and the standard, the isotopic ratio and the δ34The relation between S (‰) is:
compared with delta34Isotope number of S, delta33S、δ36The S isotope value can be a more sensitive indicator of the source of sulfur in organic matter. However, it is possible to use a single-layer,33s and36the abundance of S is only 0.75 percent and 0.02 percent of the total sulfur respectively, and the extraction and test difficulty is extremely high; in addition, the measurement method currently in use is BaSO4In the form of a sample to measure the contents of various sulfur isotopes, as described above33S and36in the case where the abundance of S is extremely low,33s and36the S sample introduction is obviously interfered by three oxygen isotopes. Thus, it is33S and36for S content determination, BaSO4The sample needs to be further converted to eliminate the interference of the oxygen isotope with the sulfur isotope, and the difficulty of accurate measurement is relatively greater. Thus delta for testing organic sulfur33S and delta36S is rarely studied.
It has been described to convert sulfur in a sample to silver sulfide by SF6Gas method for gas source mass spectrometric detection33S and36method of S content. The method requires that a silver sulfide sample without oxygen element is used as a sample introduction to avoid oxygen isotope pair with low abundance33S and36interference of the S isotope. But the organic sulfur in the sample cannot be directly converted to silver sulfide, requiring conversion to barium sulfate first, followed by conversion of the barium sulfate to silver sulfide. The process is used for the conversion of organic sulfur to silver sulfide33S、36The S isotope sample preparation is one of the obvious difficulties in sulfur fractionation in the process of converting barium sulfate into silver sulfide, namely, the obtained silver sulfide sample33S and36s content in barium sulfate33S and36the S content is greatly different, so that the prepared silver sulfide sample still does not have indication organic matter33S and36the reliability and application value of S content.
Therefore, it is obvious to research and search for a preparation method of a sample for detecting organic sulfur isotopes, which avoids or reduces as much as possible the sulfur fractionation in the process of converting organic sulfur into silver sulfide.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the preparation method of the organic sulfur isotope detection sample, which can avoid sulfur fractionation in the preparation process.
The invention also provides an organic sulfur isotope detection sample and application thereof, which can accurately reflect the composition of the sulfur isotope in a detection object (organic matter raw material), and particularly can accurately detect the organic sulfur isotope in the raw material33S、36The content of the S isotope.
The invention also provides a method for detecting the organic sulfur isotope, and the detection sample can provide more reliable and definite sulfur isotope composition, especially organic sulfur isotope composition33S、36Information of the S isotope.
The first aspect of the present invention provides a method for preparing a sample for detecting an organic sulfur isotope, comprising the steps of:
(1) converting organic sulfur in the organic matter raw material into barium sulfate;
(2) reacting barium sulfate in solid acid phosphate and hydroiodic acid to generate hydrogen sulfide gas;
(3) removing the hydrogen sulfide gas and absorbing it with an alkaline solution to obtain an absorbing solution, and
(4) and adding a silver salt solution into the absorption solution to convert the sulfur element in the absorption solution into silver sulfide precipitate.
In the present invention, in the case of the present invention,the organic matter feedstock may be any sulfur-containing feedstock, and may typically include kerogen, crude oil, or reservoir bitumen, among others. The organic sulfur in the organic matter feed stock could not be directly measured without treatment. The isotopic test sample is typically provided by first removing inorganic sulfur (primarily pyrite) from the sample, leaving organic sulfur, elemental sulfur present as an organic compound, and then efficiently converting the organic sulfur to inorganic sulfur. Since barium sulfate has extremely low solubility and almost no sulfur fractionation occurs, organic sulfur is usually converted into barium sulfate, which is used as a sample to be tested. This conversion process is described in detail in CN108152099A, CN108168993A, the entire contents of which are incorporated herein by reference. Barium sulfate is used as a sample to be tested, the sample is decomposed into sulfur dioxide at high temperature, and the sulfur dioxide can be accurately measured in the form32S and34the content of S.
About33S and36testing of S isotope content for the purpose of eliminating pairs by oxygen isotopes33S、36The influence of S-S isotope (because the abundance of the S-S isotope is obviously smaller and the influence of the oxygen isotope is obviously increased) usually needs to take silver sulfide as a sample to be injected, so that the sulfur fractionation is ensured not to occur or to occur as low as possible in the conversion process, and the S-S isotope is accurately determined33S、36The key element of the S sulfur isotope.
In step (2) of the present invention, barium sulfate is reacted in solid acid phosphate and hydroiodic acid to generate hydrogen sulfide gas.
Hydriodic acid, hydrochloric acid, phosphoric acid (H) are commonly used in the traditional method3PO3) Or hypophosphorous acid (H)3PO2) The research results of the applicant show that the use of hydriodic acid (with the highest concentration) rather than hydriodic acid solution (with the low concentration) has a critical influence on the detection result, and the problem that the hydrogen sulfide gas generated by the low-concentration hydriodic acid solution provides more water environment is dissolved in water, so that the sulfur isotope is fractionated due to the generation of byproducts such as sulfur dioxide and elemental sulfur is avoided; the same considerations apply to the choice of solid acid phosphates, the rate of reaction being increased by the presence of phosphate, in particular bySodium dihydrogen phosphate is not only easy to dissolve in water, but also can generate a large amount of phosphine only at high temperature, thereby avoiding the problems of flammability and corrosivity.
Therefore, in the present invention, the reaction is carried out using strongly acidic hydriodic acid, so that a smaller amount of water can be introduced with the same acidification, further reducing the dissolution of hydrogen sulfide gas.
In one embodiment of the present invention, the solid acid phosphate in step (2) is selected from solid sodium dihydrogen phosphate.
In one embodiment of the present invention, the reaction temperature in step (2) is 110-. The temperature is here the actual temperature at which the reactants are reacted. The research results of the applicant can know that the reaction temperature condition of 110-125 ℃ can be controlled to improve the reaction rate, shorten the reaction time, reduce the oxygen participating in the step (2) reaction process, and prevent the hydrogen sulfide product from dissolving in water as much as possible, so that the hydrogen sulfide can completely escape in a gas form and avoid fractionation in the solution. The temperature is controlled, so that the reducibility of the hydroiodic acid is favorably exerted, the phenomenon that hydrogen sulfide is dissolved in water at any time due to too slow reaction is avoided, and the increase of oxygen content in the system can be caused due to too long reaction time (even if a non-oxygen atmosphere is maintained, the mixing of a small amount of oxygen is inevitable); controlling the proper temperature and accelerating the reaction process are also beneficial to avoiding the interference of the decomposition of the reaction raw materials or side reactions on the result, such as the harm of releasing phosphine due to the decomposition of sodium dihydrogen phosphate. Of course, while the aforementioned benefits of accelerating the reaction and hydrogen sulfide evolution are provided by elevated temperatures, it is desirable to avoid the effects of excessive temperatures on the reaction system and results, e.g., excessive temperatures may promote rapid decomposition of sodium dihydrogen phosphate to produce large amounts of phosphine (pH)3)。
In one embodiment of the present invention, the reaction in step (2) is carried out in a non-oxygen atmosphere, thereby preventing elemental sulfur from being oxidized to an oxidized state to fractionate.
In a further embodiment of the present invention, the non-oxygen atmosphere in step (2) is nitrogen atmosphere, and other inert gases such as helium, argon, etc. can be selected. May be obtained by providing a non-oxygen atmosphere using conventional methods, such as purging with nitrogen.
According to the preparation method, sulfur in barium sulfate (wherein the sulfur comes from an organic raw material to be detected) is firstly transferred out in the form of hydrogen sulfide gas through the reaction system in the step (2), and then is absorbed by an alkaline solution in the system in the step (3).
In step (3) of the present invention, the hydrogen sulfide gas obtained in step (2) should be completely released and then introduced into a separate device to be absorbed. If hydrogen sulfide is absorbed in situ in the reaction solution and converted into silver sulfide, the conversion process not only generates silver sulfide precipitate, but also silver iodide precipitate, and subsequent separation treatment is required to separate silver iodide from silver sulfide, so that the treatment process is complex and difficult to perform.
In step (3) of the present invention, the absorption of hydrogen sulfide gas is carried out using an alkaline solution. In one embodiment of the invention, in case the solid acid phosphate in step (2) is selected from solid sodium dihydrogen phosphate, in step (3) the hydrogen sulfide gas is removed and absorbed in a non-oxygen atmosphere as a sodium hydroxide solution. That is, in the case where a sodium salt is used in step (2), the introduction of other elements can be reduced by using sodium hydroxide in step (3) accordingly.
In step (3) of the present invention, the alkaline solution is selected so that the absorption results in a solution, rather than a mixture comprising a precipitate. In other words, in step (3) of the present invention, gaseous hydrogen sulfide is absorbed by the solution.
The research of the applicant finds that the gaseous product generated by the absorption reaction by the alkaline solution contains not only hydrogen sulfide but also a small amount of phosphine and hydrogen iodide, and the key point of the invention is that the alkaline solution, such as sodium hydroxide, is selected as the absorption solution instead of directly adopting silver nitrate. If silver nitrate is directly used for collection, a large amount of black precipitates (presumed to comprise silver iodide, silver sulfide and silver oxide) are generated instantly after hydroiodic acid is added, and simple substance silver is generated, and the detection result is interfered by the unwanted reaction products. Even if the precipitation interference of silver iodide, silver oxide, etc. is prevented by a chemical process by appropriate means (e.g., adding an excess of nitric acid in advance), it will have an effect on ensuring that all of the hydrogen sulfide produced is absorbed.
The effect of the invention can also be demonstrated in alkaline environment (pH)>8) 100% absorption of hydrogen sulfide energy and measurement of HS by ultraviolet fluorescence spectroscopy-The reduction rate of the reaction is calculated, meanwhile, the interference caused by the reaction of phosphine and silver nitrate is avoided, and more chemical elements are not introduced by adopting sodium hydroxide to absorb hydrogen sulfide gas (particularly under the condition that sodium salt is used in the previous step). Therefore, the method of the present invention stores sulfur in the solution for the precipitation reaction in step (4), rather than absorbing hydrogen sulfide gas with silver salt in step (3) to directly obtain silver sulfide precipitate, which is beneficial to ensure no or little sulfur fractionation during the process while achieving complete absorption of hydrogen sulfide gas, and can be easily implemented by those skilled in the art according to practical situations, for example, by using an excessive amount of alkaline solution, such as sodium hydroxide, for hydrogen sulfide absorption according to calculation.
In the present invention, for example, a reaction generator, a hydrogen sulfide gas transfer line (around which a condenser for cooling the hydrogen sulfide gas is disposed), and a hydrogen sulfide gas absorber may be sequentially provided, and these three elements are hermetically connected, and nitrogen gas is introduced from the reaction generator and purged with nitrogen gas, thereby obtaining a non-oxygen atmosphere required for performing the steps (2) and (3).
In step (4) of the present invention, a silver salt solution is added to the absorbing solution to convert sulfur in the absorbing solution into a silver sulfide precipitate.
In the step (4) of the invention, the sulfur element in the absorption liquid is completely converted into silver sulfide precipitate, and the sulfur fractionation can be effectively prevented.
In a specific embodiment, the reaction for converting the sulfur in the absorption solution into silver sulfide precipitate is performed at room temperature, for example, 18 to 25 ℃. If heated, the nitric acid may react with silver sulfide to form, for example, a sulfur precipitate, causing sulfur fractionation. In addition, an excess of silver nitrate solution or silver chloride solution is added to the absorbing solution, that is, the amount of silver nitrate or silver chloride added should be in excess relative to the amount of elemental sulfur in the absorbing solution, so that elemental sulfur is entirely precipitated as silver sulfide. Meanwhile, pure nitric acid is added dropwise in the reaction to prevent the formation of silver iodide or silver oxide precipitate.
Another aspect of the present invention provides a detection sample for detecting an organic sulfur isotope, the detection sample being prepared according to the method of the present invention. The preparation process of the detection sample realizes the high-efficiency conversion of organic sulfur into barium sulfate and the non-fractionation conversion of barium sulfate into silver sulfide, so that the obtained detection sample can more accurately and truly reflect the existence forms of various organic sulfur isotopes in the organic matter raw material.
Still another aspect of the present invention provides the use of the organic sulfur isotope detection sample of the present invention for indicating the content of organic sulfur isotopes in organic matter.
Further, the organic sulfur isotope detection sample of the invention is provided for indicating organic sulfur in organic matter33S、36Use of S isotope content.
In another aspect of the present invention, there is provided a method for detecting organic sulfur isotopes in an organic material, comprising preparing a detection sample according to the method of the present invention, and using SF6A method for detecting said sample.
The detection method of the invention can be applied to sulfur-containing organic materials, for example, the organic materials can include kerogen, crude oil or reservoir asphalt, etc. which are commonly used.
According to the scheme of the invention, through the selection and combined utilization of reactants, reaction conditions and reaction flow, sulfur fractionation does not occur in the conversion process of barium sulfate to silver sulfide. Specifically, 1, in terms of reactant selection, solid acid phosphate and strong hydriodic acid are used, thereby reducing the dissolution of hydrogen sulfide gas in the reaction solution. If the aim is not to prevent the fractionation of sulfur, only the dissolution of barium sulfate to obtain a silver sulfide precipitate, the in-situ dissolution of hydrogen sulfide and the in-situ introduction of silver salt in the reaction solution are possible. The scheme of the invention reduces the amount of water introduced by reactants as much as possible to obtain hydrogen sulfide gas, and the gas form ensures that elemental sulfur is thoroughly separated from the reactant solution, which is an important step for avoiding sulfur fractionation in the process of converting barium sulfate into silver sulfide. 2. The method of the invention is designed into two steps of absorbing hydrogen sulfide by alkaline solution to form absorbing solution and converting to form silver sulfide precipitate, and researches prove that the operation is another important step which is beneficial to avoiding sulfur fractionation in the process of converting barium sulfate into silver sulfide. 3. Ensuring that the sulfur element is finally converted into silver sulfide, and the precipitation product in the preparation system is only silver sulfide, which is also one of the control points of the invention, in the specific operation, pure nitric acid can be additionally added and the reaction temperature can be controlled to prevent the formation of precipitate besides silver sulfide while the silver salt (silver nitrate or silver chloride) is in excess.
The technical scheme of the invention has the following effects:
1. the organic sulfur isotope detection sample prepared by the method of the invention has the advantages that the sulfur isotope is not fractionated basically in the process of converting barium sulfate into silver sulfide, so that the existence state of the sulfur isotope in organic matters can be accurately indicated.
2. The organic sulfur isotope detection sample prepared by the method can ensure that various sulfur isotopes are not fractionated in the preparation process, thereby indicating the organic matters for direct detection33S、36S isotope content provides a reliable method.
3. The preparation method provided by the invention is simple to operate, can be completed at one time according to the reaction sequence, and has the advantages of saving material consumption and reaction time and high reaction efficiency; the preparation method does not use heavy metal, such as chromium compound, in the reaction process, avoids irreversible influence on the environment, and has the advantage of environmental friendliness.
Drawings
FIG. 1 is a schematic view of an apparatus used in the production method of the present invention.
The reference numbers in the figures mean:
1 three-neck flask, wherein 11, 12 and 13 are respectively three-neck flask necks
2 electric heating jacket
3 cooling water circulating pipe
4 hydrogen sulfide gas absorption test tube
5 gas delivery conduit
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention.
All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The embodiments described below and the features of the embodiments can be combined with each other without conflict.
Experimental materials
The organic matter kerogen is prepared from black manganese-containing mudstone of a pond slope group in Guizhou region.
Hydroiodic acid was purchased from Shanghai under the trade name 80071017, and was analytically pure at a concentration of 57%.
Solid sodium dihydrogen phosphate was purchased from Shanghai under the trade name 20040818 Anhydrous sodium dihydrogen phosphate, and was analytically pure.
Determination of sulfur isotopes
Determination of the sulphur isotope of silver sulphide
Using conventional SF6The method is carried out. Specifically, the dried silver sulfide was put into a nickel bomb subjected to fluorination treatment, and fluorine gas was blown at 250 ℃ and 37kPa to conduct fluorination treatment for 12 hours. Collecting SF by cryogenic purification6Mixing SF6And (3) performing gas source mass spectrum detection to obtain the value of the organic sulfur isotope in the organic matter raw material kerogen.
In the method of this example, different batches of samples prepared from the organic material kerogen were subjected to parallel tests, and the results of the detection of the values of organic sulfur isotopes are shown in table 1.
Determination of the sulphur isotope of barium sulphate
For comparison, the barium sulfate obtained as described above was measured by a conventional method34An S isotope. The barium sulfate sample injection method was as follows, weighing 0.4mg barium sulfate and 0.5mg vanadium pentoxide into a tin cup, and then measuring in an MAT 253 mass spectrometer manufactured by pyroelectric Finnigan MAT Corp.
Example 1
Firstly, carrying out inorganic sulfur removal treatment, organic sulfur dissolution treatment and precipitation treatment on organic matter raw material kerogen to obtain barium sulfate (BaSO)4) And (4) precipitating. The specific process of the treatment is as follows:
sufficient zinc particles, 6N hydrochloric acid and chromium chloride are mixed in a flask, an organic raw material kerogen is added, reduction reaction is carried out at the temperature of 80 ℃, so that inorganic sulfur and sulfur elements in the organic raw material are converted into hydrogen sulfide gas to escape, and the hydrogen sulfide gas is absorbed by a test tube filled with 10% silver nitrate solution. Filtering the reaction liquid in the flask, wherein a filter cake is an organic matter without inorganic sulfur;
performing pressure oxidation on the obtained organic matters without the inorganic sulfur, adding a proper amount of deionized water by using an oxygen combustion bomb of Parr company, performing deflagration oxidation in 25atm pure oxygen, and dissolving sulfur dioxide generated by oxidation reaction in the deionized water to generate an intermediate target solution (sulfuric acid and partial sulfurous acid solution); further diluting the intermediate target solution by using deionized water, adding pure bromine water to continuously oxidize sulfurous acid in the solution into sulfuric acid, and collecting the sulfuric acid solution;
adding excess barium chloride solution with the concentration of 10% into the sulfuric acid solution to enable the reaction to be complete and generate stable precipitate, filtering and collecting precipitate, washing the precipitate with deionized water, drying, weighing, and obtaining the precipitate which is barium sulfate precipitate, wherein sulfur element in the barium sulfate is derived from organic sulfur in organic matters.
1) Conversion of barium sulfate to hydrogen sulfide (H) in gaseous form2S)
The reaction and absorption apparatus used in this embodiment is shown in fig. 1, and comprises a three-neck flask 1, an electric jacket 2, a cooling water circulation pipe 3, a hydrogen sulfide gas absorption test tube 4 and a gas delivery conduit 5. The lower end of the cooling water circulating pipe 3 is hermetically connected with a port 11 in the middle of the three-neck flask and is used for cooling gas escaping from the three-neck flask, and the upper end of the cooling water circulating pipe 3 is hermetically connected with the gas conveying conduit 5; the tail end of the gas conveying conduit 5, which is far away from the cooling water circulating pipe 3, is in a tapered dropper shape, the tail end of the gas conveying conduit is inserted into the hydrogen sulfide gas absorption test tube 4 to the bottom, and in the reaction process, the hydrogen sulfide gas absorption test tube 4 is used for containing a sodium hydroxide solution and realizing liquid seal on the inserted conveying conduit 5.
0.2g of barium sulfate and 13g of solid sodium dihydrogen phosphate (NaH)2PO4Anhydrous, analytically pure) is put into a three-neck flask 1, and three bottle mouths are sealed.
In order to promote the dissolution of barium sulfate to generate hydrogen sulfide, the sulfur element is prevented from still existing in an oxidation state (for example, a sulfate radical form) in the reaction solution, and the whole reaction device is made to form a non-oxygen atmosphere. Specifically, nitrogen gas was introduced through the neck 12 of the three-necked flask for about 5 minutes until uniform generation of bubbles was observed in the sodium hydroxide solution in the hydrogen sulfide gas absorption tube 4 communicating with the three-necked flask through the neck 11, at which time it was considered that there was no gas leakage from the entire reaction and absorption apparatus.
To ensure a non-oxygen environment in the entire apparatus, 100ml of hydroiodic acid (analytically pure, 57% strength) was injected into the three-necked flask through the neck 13 using a syringe. The barium sulfate, the sodium dihydrogen phosphate and the hydroiodic acid react at a temperature of about 125 ℃ by heating with the electric heating jacket 2, and the barium sulfate is dissolved and hydrogen sulfide gas is generated as the reaction progresses. Under the control of the reaction condition, the characteristic of high reduction activity of the hydroiodic acid is favorably exerted, the reaction speed is high, the reaction time is shortened, and sulfur fractionation caused by various uncertain factors during a longer reaction time is eliminated; in addition, the hydrogen sulfide is slightly soluble in water, and the generated hydrogen sulfide gas can be promoted to completely escape from the reaction solution by heating, so that the sulfur element fractionation caused by the dissolution of the hydrogen sulfide gas in the reaction solution is avoided.
2) Absorption of hydrogen sulfide
The escaped gas is cooled and cooled by a cooling water circulating pipe 3 and then is introduced into a hydrogen sulfide gas absorption test tube 4 filled with 20ml of 10% sodium hydroxide solution by a gas conveying conduit 5. The gas delivery conduit 5 is inserted into the absorption liquid to the bottom of the test tube, and bubbles are continuously and stably generated in the sodium hydroxide solution during the absorption process. The hydrogen sulfide is absorbed by the sodium hydroxide solution (it is known that the gas introduced into the sodium hydroxide solution is hydrogen sulfide and nitrogen, and also contains a small amount of phosphine).
3) Formation of silver sulfide (Ag)2S)
After 2 hours, the barium sulfate in the three-neck flask 1 is determined to have completely reacted, the generated hydrogen sulfide product is completely absorbed in the sodium hydroxide solution, the hydrogen sulfide gas absorption test tube 4 filled with the sodium hydroxide solution is taken out from the system, 40ml of 10% silver nitrate solution is added into the hydrogen sulfide gas absorption test tube, 5-8 drops of pure nitric acid are dripped into the hydrogen sulfide gas absorption test tube, and the excessive nitric acid can redissolve the silver iodide, silver oxide and other precipitates in the solution, so that the silver sulfide precipitate is prevented from being mixed with the silver sulfide precipitate, and the silver sulfide precipitate is difficult to recover. Standing for 6 hours for precipitation, reacting the silver nitrate solution with the sodium hydroxide solution absorbing the hydrogen sulfide, and completing the re-dissolution of the precipitate except the silver sulfide to obtain the silver sulfide precipitate.
And (3) performing solid-liquid separation on the reaction solution by using a 0.45-micron filter membrane through a negative pressure vacuum pumping machine, and collecting the obtained precipitate silver sulfide. And washing the precipitate with deionized water, drying, and weighing to obtain the target product organic sulfur isotope detection sample. The sulfur element in the obtained silver sulfide is derived from organic sulfur in the organic matter raw material kerogen. And the obtained silver sulfide is subjected to on-machine test. The test results are shown in table 1.
TABLE 1
Barium sulfate and silver sulfide prepared by the method are respectively used as detection samples, and comparison of test data shows that barium sulfate is converted into silver sulfide by the method, and delta measured based on the same barium sulfate sample before and after conversion34The S isotope content is very close (the difference is basically not more than +/-0.20)Can be regarded as34The S isotope is not fractionated. In the light of this, it is inferred that,33S、36the S isotope is not fractionated before and after the conversion. It can be shown that the sample prepared by the method of the present invention can test organic sulfur more sensitively32S、33S、34S、36S, and moreover, SF is used6The method for detecting the organic sulfur isotope detection sample prepared by the method eliminates the influence of oxygen isotope and avoids the occurrence of33S、36And (4) S isotope fractionation, wherein the test result can accurately indicate the content of organic sulfur in organic matters.
Example 2
The same procedure as in example 1 was followed, except that the barium sulfate made from kerogen was replaced with a barium sulfate standard. The barium sulfate standard sample is obtained commercially and the brands are respectively: NBS-127, IAEA-SO-5, IAEA-SO-6.
Parallel experiment and determination are carried out on each standard sample, barium sulfate is converted into silver sulfide, and delta of the silver sulfide is respectively determined34The S value and the test results are shown in Table 2.
TABLE 2
| BaSO4Standard sample | Standard sample delta34S value | Ag2Delta of S34S value |
| NBS-127 | 20.3±0.5 | 19.8 |
| IAEA-SO-5 | 0.5±0.5 | 0.7 |
| IAEA-SO-6 | -34.1±0.5 | -34 |
Analysis of the test results in Table 2, Standard (. delta.)34S value and Ag2Delta of S34Compared with the S measured value, the deviation is within an acceptable reasonable range, and the conversion and detection processes are not considered to have obvious sulfur fractionation.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.
Claims (8)
1. A preparation method of an organic sulfur isotope detection sample comprises the following steps:
(1) converting organic sulfur in the organic matter raw material into barium sulfate;
(2) reacting barium sulfate in solid acid phosphate and hydroiodic acid to generate hydrogen sulfide gas; wherein the reaction temperature is 110-125 ℃, and the reaction is carried out in a non-oxygen atmosphere;
(3) removing the hydrogen sulfide gas and absorbing it with an alkaline solution to obtain an absorbing solution, and
(4) and at room temperature, adding an excessive silver nitrate solution or silver chloride solution into the absorption solution, dropwise adding pure nitric acid into the reaction, and converting the sulfur element in the absorption solution into silver sulfide precipitate.
2. The process according to claim 1, wherein the solid acid phosphate in step (2) is selected from solid sodium dihydrogen phosphate; in step (3), the hydrogen sulfide gas is removed and absorbed with sodium hydroxide solution in a non-oxygen atmosphere.
3. The method of claim 1 or 2, wherein the organic matter feedstock comprises kerogen, crude oil or reservoir bitumen.
4. An organic sulfur isotope test sample, wherein said test sample is prepared according to the method of any one of claims 1 to 3.
5. Use of the organic sulfur isotope detection sample of claim 4 for indicating the organic sulfur isotope content in organic matter.
6. The use according to claim 5, comprising indicating organic sulfur in organic matter33S、36Use of S isotope content.
7. A method for detecting organic sulfur isotope in organic matter raw material, comprising preparing a detection sample according to the method of any one of claims 1 to 3, and using SF6A method for detecting said sample.
8. The method of testing of claim 7, wherein the organic matter feedstock comprises kerogen, crude oil, or reservoir bitumen.
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