CN114324691B - Method for improving sulfide detection precision - Google Patents
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- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 title claims abstract description 73
- 238000001514 detection method Methods 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 44
- 239000007789 gas Substances 0.000 claims abstract description 101
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 42
- 239000011593 sulfur Substances 0.000 claims abstract description 42
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 39
- WQOXQRCZOLPYPM-UHFFFAOYSA-N dimethyl disulfide Chemical compound CSSC WQOXQRCZOLPYPM-UHFFFAOYSA-N 0.000 claims abstract description 36
- JJWKPURADFRFRB-UHFFFAOYSA-N carbonyl sulfide Chemical compound O=C=S JJWKPURADFRFRB-UHFFFAOYSA-N 0.000 claims abstract description 32
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910000037 hydrogen sulfide Inorganic materials 0.000 claims abstract description 28
- 150000003568 thioethers Chemical class 0.000 claims abstract description 28
- 238000002347 injection Methods 0.000 claims abstract description 27
- 239000007924 injection Substances 0.000 claims abstract description 27
- QMMFVYPAHWMCMS-UHFFFAOYSA-N Dimethyl sulfide Chemical compound CSC QMMFVYPAHWMCMS-UHFFFAOYSA-N 0.000 claims abstract description 25
- YTPLMLYBLZKORZ-UHFFFAOYSA-N Thiophene Chemical compound C=1C=CSC=1 YTPLMLYBLZKORZ-UHFFFAOYSA-N 0.000 claims abstract description 20
- QGJOPFRUJISHPQ-NJFSPNSNSA-N carbon disulfide-14c Chemical compound S=[14C]=S QGJOPFRUJISHPQ-NJFSPNSNSA-N 0.000 claims abstract description 12
- 229930192474 thiophene Natural products 0.000 claims abstract description 10
- 238000002444 silanisation Methods 0.000 claims abstract description 9
- RAOIDOHSFRTOEL-UHFFFAOYSA-N tetrahydrothiophene Chemical compound C1CCSC1 RAOIDOHSFRTOEL-UHFFFAOYSA-N 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims description 54
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 47
- LSDPWZHWYPCBBB-UHFFFAOYSA-N Methanethiol Chemical compound SC LSDPWZHWYPCBBB-UHFFFAOYSA-N 0.000 claims description 38
- 238000005070 sampling Methods 0.000 claims description 28
- 229910052757 nitrogen Inorganic materials 0.000 claims description 23
- DNJIEGIFACGWOD-UHFFFAOYSA-N ethanethiol Chemical compound CCS DNJIEGIFACGWOD-UHFFFAOYSA-N 0.000 claims description 16
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- BDFAOUQQXJIZDG-UHFFFAOYSA-N 2-methylpropane-1-thiol Chemical compound CC(C)CS BDFAOUQQXJIZDG-UHFFFAOYSA-N 0.000 claims description 10
- WQAQPCDUOCURKW-UHFFFAOYSA-N butanethiol Chemical compound CCCCS WQAQPCDUOCURKW-UHFFFAOYSA-N 0.000 claims description 10
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- LJSQFQKUNVCTIA-UHFFFAOYSA-N diethyl sulfide Chemical compound CCSCC LJSQFQKUNVCTIA-UHFFFAOYSA-N 0.000 claims description 7
- 239000001257 hydrogen Substances 0.000 claims description 7
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- 238000007781 pre-processing Methods 0.000 abstract 1
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- QGJOPFRUJISHPQ-UHFFFAOYSA-N Carbon disulfide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 description 23
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- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical compound S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 10
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 231100000739 chronic poisoning Toxicity 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000010779 crude oil Substances 0.000 description 2
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
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- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 1
- 208000033962 Fontaine progeroid syndrome Diseases 0.000 description 1
- 239000005864 Sulphur Substances 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
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- 239000003245 coal Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 150000001879 copper Chemical class 0.000 description 1
- 229910001431 copper ion Inorganic materials 0.000 description 1
- OBBCYCYCTJQCCK-UHFFFAOYSA-L copper;n,n-diethylcarbamodithioate Chemical compound [Cu+2].CCN(CC)C([S-])=S.CCN(CC)C([S-])=S OBBCYCYCTJQCCK-UHFFFAOYSA-L 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- XYWDPYKBIRQXQS-UHFFFAOYSA-N di-isopropyl sulphide Natural products CC(C)SC(C)C XYWDPYKBIRQXQS-UHFFFAOYSA-N 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
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- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- XLTBPTGNNLIKRW-UHFFFAOYSA-N methyldisulfanylethane Chemical compound CCSSC XLTBPTGNNLIKRW-UHFFFAOYSA-N 0.000 description 1
- WXEHBUMAEPOYKP-UHFFFAOYSA-N methylsulfanylethane Chemical compound CCSC WXEHBUMAEPOYKP-UHFFFAOYSA-N 0.000 description 1
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- VOVUARRWDCVURC-UHFFFAOYSA-N thiirane Chemical compound C1CS1 VOVUARRWDCVURC-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
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- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
Abstract
The invention relates to a method for improving sulfide detection precision, which comprises the following steps: (1) pre-processing components of a focus concentrator; (2) Connecting a focusing concentrator with a gas chromatograph with a sulfur chemiluminescence detector; (3) The gas bag collects gas, samples are taken, focusing and concentration are carried out, and sulfide is detected. According to the invention, through the silanization pretreatment of the SECA focusing concentrator component and the matching of the gas chromatograph with the sulfur chemiluminescence detector, the detection precision of 16 sulfides is greatly improved, and the concentration of large-volume sample injection can be realized. The method has high precision, good reproducibility and low detection limit which can be as low as 0.07-0.15 nmol/mol, and the detection limit of hydrogen sulfide, carbonyl sulfide, methyl sulfide, dimethyl disulfide, carbon disulfide, thiophene, tetrahydrothiophene and the like is smaller than the olfactory threshold, so that the technical problem that trace sulfide in ambient air can be smelled but is not easy to detect is solved.
Description
Technical Field
The invention relates to a method for improving sulfide detection precision, and belongs to the field of analytical chemistry.
Background
The organic sulfide is an organic compound containing carbon-sulfur bonds, has the characteristics of strong chemical activity, low odor threshold and strong odor, and is a main odor-causing substance in the complaint event of resident malodor. For the detection of sulfides, the relatively wide standard methods used in the present stage are "spectrophotometry for measuring diethylamine by carbon disulfide of air quality" (GB/T14680-1993), "gas chromatography for measuring hydrogen sulfide of air quality, methyl mercaptan, methyl sulfide and dimethyl disulfide" (GB/T14678-1993), "gas chemiluminescence gas chromatography for measuring sulfide of gas analysis" (GB/T33318-2016), "measurement tank sampling of volatile organic matters of ambient air/gas chromatography-mass spectrometry" (HJ 759-2015) and "gas bag sampling of 8 sulfur-containing organic compounds such as methyl mercaptan of stationary pollution source" (HJ 1078-2019), which have the following drawbacks:
measurement of air quality carbon disulfide spectrophotometry (GB/T14680-93) uses an ethanol solution containing copper salt and diethylamine for sampling, and in the presence of copper ions, carbon disulfide reacts with diethylamine to produce copper diethyldithiocarbamate in a yellowish brown color, which is measured using spectrophotometry.
When the sampling volume is 10-30L, the lowest detected concentration is 0.03mg/m 3 The method has single form of the test component and can only measure one component of carbon disulfide.
The determination of air quality hydrogen sulfide, methyl mercaptan, dimethyl sulfide and dimethyl disulfide (GB/T14678-1993) adopts a direct sample injection or concentration tube sample injection mode to enter a gas chromatograph, and uses a Flame Photometric Detector (FPD) detector to make quantitative and qualitative analysis, and the logarithm of various sulfide contents is proportional to the logarithm of chromatographic peak height in a certain concentration range.
Measurement of air quality hydrogen sulfide, methyl mercaptan, dimethyl sulfide and dimethyl disulfide (GB/T14678-1993) an unorganized emission source malodorous gas or ambient air sample was collected from a vacuum-treated 1L gas cylinder, and a malodorous gas sample was collected from an exhaust funnel from a polyester plastic bag. The method uses different pretreatment sample injection modes to analyze samples in different concentration ranges. When the content of hydrogen sulfide, methyl mercaptan, methyl sulfide and dimethyl disulfide is higher than 1.0mg/m 3 When the gas sample is used, 1-2 mL of the gas sample can be directly sampled by a syringe, and the gas sample is injected into a gas chromatograph equipped with a Flame Photometric Detector (FPD) for analysis, wherein the detection limit range is 0.2X10 -9 ～1.0×10 -9 g. When the sample concentration is lower than 1.0mg/m 3 When in use, the 1L gas sample is concentrated and enriched under the condition of liquid oxygen refrigeration to low temperature (0-300 ℃), and then is thermally desorbed and enters gas chromatography, and the gas chromatography is carried outColumn separation, FPD detector quantitative analysis, at which the detection limit range was 0.2X10 -3 ～1.0×10 -3 mg/m 3 The method has high detection limit by a direct sampling method, is generally used for monitoring air at a pollution source or an unorganized emission monitoring point with higher concentration, and has complex sampling operation of a concentrating tube in another sampling mode, and has high inerting requirement on an analyzed pipeline due to the chemical activity and the larger water solubility of organic sulfide, otherwise, the phenomenon that components are degraded before entering an instrument is easily caused. In addition, in the analysis of the actual sample, once the flame photometric detector contains high-concentration hydrocarbon compounds, quenching effect is easy to occur, namely CO in the flame when the high-concentration hydrocarbon compounds are burnt 2 、CH 4 And other combustion products may reduce the FPD response of the sulfide, even without a sulfur signal. In addition, from the aspect of analyzing the types of sulfides, the target compounds of the method are only four, and hydrogen sulfide, methyl mercaptan, dimethyl sulfide and dimethyl disulfide cannot be used for analyzing organic sulfides such as carbon disulfide, methyl ethyl disulfide and the like, so that the requirement of monitoring work cannot be met.
Measurement of volatile organic compounds in ambient air tank sampling/gas chromatography-Mass Spectrometry (HJ 759-2015) 67 volatile organic compounds in ambient air were measured using tank sampling/gas chromatography-Mass Spectrometry, including four types of sulfides: methyl mercaptan, dimethyl sulfide, dimethyl disulfide and carbon disulfide. And (3) sampling 400mL of ambient air sample by adopting a tank sampling/gas chromatography-mass spectrometry method, collecting the ambient air sample by using a stainless steel tank with an inert treatment inner wall, concentrating by a cold trap, performing thermal analysis, then entering gas chromatography for separation, and detecting by using a mass spectrum detector in a full scanning mode. Qualitative and internal standard quantitative analysis are performed by comparing the mass spectrum with the standard substance and the retention time. The detection limits of several sulfides in the method are as follows: methyl mercaptan 0.3. Mu.g/m 3 0.5 mu g/m of methyl sulfide 3 Dimethyl disulfide 0.6. Mu.g/m 3 And carbon disulphide 0.4. Mu.g/m 3 . The method mainly aims at determining toxic and harmful volatile organic pollutants, and in the preservation and analysis of samples with larger humidity, organic sulfides and other volatile organic matters have larger differences, the organic sulfides and other volatile organic matters are easy to degrade, and the organic sulfides and other volatile organic matters are more stable.In addition, the target compound of the method only contains four organic sulfides of methyl mercaptan, methyl sulfide, dimethyl disulfide and carbon disulfide, and the types are too few and can not meet the requirements of monitoring work.
The method is used for measuring 8 sulfur-containing organic compounds such as methyl mercaptan, ethanethiol, methyl sulfide, carbon disulfide, ethylene sulfide, dimethyl disulfide and thiophene in the waste gas of the fixed pollution source. The specific method comprises the following steps: the waste gas with fixed pollution source is collected by using an air bag, concentrated by a cold trap, thermally analyzed, and then enters a gas chromatograph for separation, and is detected by a mass spectrum detector. Qualitative, internal standard quantitative by comparison with the mass spectrum and retention time of the standard substance. When the sampling amount is 50mL, the detection limit of each sulfide in the full-sweep mode is as follows: methyl mercaptan 0.01mg/m 3 0.01mg/m of ethanethiol 3 0.01mg/m of methyl sulfide 3 0.02mg/m of methyl ethyl sulfide 3 0.01mg/m of carbon disulfide 3 0.01mg/m of ethylsulfide 3 Dimethyl disulfide 0.01mg/m 3 Thiophene 0.01mg/m 3 . The method is suitable for the measurement of the waste gas of the fixed pollution source, the detection limit is far higher than the actual concentration in the ambient air, and the method is not suitable for the measurement of the ambient air.
Sulfur chemiluminescence gas chromatography for measuring sulfide by gas analysis (GB/T33318-2016), which uses a gas chromatograph equipped with a sulfur chemiluminescence detector to measure sulfide and total sulfur in gases such as industrial gases, natural gases, liquefied petroleum gases, coke oven gases, food-grade carbon dioxide gases, air, automobile exhaust gases, biomass gases, and coal-derived synthetic natural gases. The specific method comprises the following steps: introducing sample through six-way valve, separating sulfur compounds from sample by gas chromatographic column, introducing into sulfur chemiluminescence detector, burning to obtain sulfur monoxide and other products in hydrogen-rich environment, pumping the combustion products into a low pressure reaction tank by vacuum pump, adding excessive ozone, and reacting sulfur monoxide with ozone to obtain excited SO 2 ，SO 2 And when the light returns to the ground state, a blue fluorescent signal can be emitted. Hair brushThe light energy is proportional to the sulfur content in the sample, the photomultiplier is used for detecting the intensity of the reaction emitted light, and the intensity of the reaction emitted light is compared with the intensity of the standard sample emitted light to calculate the sulfide content in the sample. The twelve sulfides mentioned in the standard, hydrogen sulfide, carbon oxysulfide, methyl mercaptan, ethyl mercaptan, methyl sulfide, carbon disulfide, isopropyl mercaptan, n-propyl mercaptan, thiophene, ethyl sulfide, dimethyl disulfide, tetrahydrothiophene, etc., can be separated under appropriate conditions. The measurement range of the organic sulfide is 0.1mg/m 3 To 1000mg/m 3 . The scope of application in this standard, while containing air, lacks investigation into each sulfide, mainly focuses on the description of total sulfur in gases such as liquefied gas, natural gas, pipeline gas, and the like. And the sample injection mode adopts a six-way valve for quantitative sample injection, the sampling amount is 1mL, and the detection limit can be limited by the sample injection mode when various sulfide substances in the ambient air are measured, so that the detection limit can not be close to the olfactory threshold of various sulfides.
In summary, the existing monitoring methods for various sulfides are not comprehensive in practice, and particularly, hydrogen sulfide, methyl mercaptan, etc. with a low olfactory threshold value have not yet reached the level of the olfactory threshold value. The most common substance hydrogen sulfide in sulfides is easy to react, the water solubility of the sulfide is extremely high, the conventional concentration mode and means can remove the hydrogen sulfide together or react with stainless steel pipelines and valves in the instrument to disappear when the concentration and the dehydration are carried out in the pretreatment concentration process, so that the hydrogen sulfide cannot be effectively detected, and sulfide with the concentration lower than the human olfactory threshold has great hidden danger to the life and health of people, for example, the imported high-sulfur crude oil processed by petrochemical enterprises is rapidly increased, and the chronic poisoning of low-concentration hydrogen sulfide is a common health threat. Therefore, finding a method for improving the detection accuracy of sulfides is an urgent problem to be solved.
Disclosure of Invention
In order to solve the problems, the invention provides a method for improving the detection precision of sulfides, which mainly comprises the following steps: the SECA focusing concentrator component is preprocessed, and then is connected with a gas chromatograph with a sulfur chemiluminescence detector to realize accurate detection of sulfide.
The SECA focusing concentrator is a gas pre-concentration device and has the characteristics of short pre-concentration treatment process time, high concentration efficiency, less loss of components to be detected and strong operability. The principle is that the gas quantitative loop is used for quantitative sample injection, after the sample is concentrated and trapped by cold trap physical focusing at low temperature, the cold trap is heated again to transfer the sample to a gas automatic sampler of GC or GCMS. However, the object of the present invention cannot be achieved by using the above-mentioned focus concentrator, and the focus concentrator is improved, especially the focus concentrator tube is improved, and a heating device with a specific structure is further provided on the focus concentrator, so as to heat the focus concentrator. The improvement described above is the key innovation of the present invention.
Sulfur Chemiluminescence Detectors (SCD) are currently accepted as the most sensitive and selective detector for detecting sulfur. SCD uses the chemiluminescence reaction generated by the reaction of ozone and sulfur monoxide (SO) generated by the combustion of the element to be detected to generate sulfur dioxide (SO) 2 ) Oxygen (O) 2 ) The pressure difference from the characteristic spectrum < 300-400nm (hgamma) of light, generated by a vacuum pump, transfers the combustion products to a reaction cell, where an excess of ozone is added. The light (hgamma) generated by the subsequent reaction is optically filtered and detected by a blue-sensitive photomultiplier, and the signal is amplified for display or output to a data system, thereby realizing the detection of sulfur. SCD has better sulfur selectivity, simple operation and lower use and maintenance cost, and is the sulfur selectivity detector with the most application potential at present. Similarly, the sulfur chemiluminescence detector can be matched with a specific structure of the invention to achieve the purpose of accurately detecting sulfide.
The invention uses the sniffing threshold as the contrast of the sulfide detection precision, on one hand, the invention embodies the application of improving the sulfide detection precision in practice, solves the technical problem that the detection cannot be realized by sniffing, and on the other hand, the invention more intuitively highlights the technical advantage of extremely low detection limit.
Specifically, the technical scheme of the invention is as follows:
a method for improving the detection accuracy of sulfides, comprising the steps of:
(1) The focusing concentrator adopts a silanized pipeline and a valve (commercially available), wherein the silanized pipeline comprises a focusing concentration pipe and other pipelines through which the sample passes; a focusing concentration heating device is additionally arranged, and an arc-shaped focusing concentration pipe is used;
(2) Connecting the focus concentrator described in (1) to a gas chromatograph with a sulfur chemiluminescence detector;
(3) The air bag collects gas, and pressure balance sample injection is carried out until the quantitative ring is full;
(4) And (3) filling carrier gas, focusing a cold trap, heating the gas, focusing a concentration tube, desorbing sulfide, and detecting the sulfide by a gas chromatograph.
Wherein, no water removal or adsorption filler is adopted in the process of focusing the gas sample on the cold trap;
(3) During sample injection, the pressure balance device is used for controlling the pressure balance time to be 0.5min, and the pressure of the quantitative ring is 1 atmosphere after the sample injection is finished;
(4) In the method, N is adopted for heating and focusing the concentration tube by gas 2 Heating, N after heating 2 The temperature is 65 to 75℃and preferably 70 ℃.
Sulfides detected by the present invention include, but are not limited to, the following species: any one of hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, methyl sulfide, ethyl sulfide, dimethyl disulfide, carbon disulfide, tertiary butyl mercaptan, isopropyl mercaptan, n-propyl mercaptan, thiophene, methyl isopropyl sulfide, isobutyl mercaptan, n-butyl mercaptan and tetrahydrothiophene.
The method for improving the sulfide detection precision is realized by matching with a focusing concentration-gas chromatography sulfide detection system; the structure of the system is shown in fig. 2 and 3, wherein the focusing concentration-gas chromatography sulfide detection system comprises a pressure balancing device, a sample injection system, a focusing concentration instrument, a focusing concentration heating device and a gas chromatograph.
Wherein, heating of focus concentration pipe adopts the mode of high temperature gas heating, just can improve the temperature of focus pipe in the twinkling of an eye (the schematic diagram is see fig. 3), focus concentration pipe heating flow is as follows:
1) Laboratory nitrogen at about 20 ℃ enters from an inlet and passes through a spiral heating pipe (the temperature of the heating pipe is 120 ℃);
2) When the nitrogen is discharged from the nitrogen outlet, the nitrogen is heated from about 20 ℃ to about 70 ℃.
Parameters of the focusing and heating device:
pipeline shape: spiral shape;
pipeline length: 12cm;
inner diameter: 6cm;
flow rate: 10L/min;
heating: inlet N 2 The temperature of the mixture is 15-25 ℃;
outlet temperature: 65-75 ℃;
the material of the heat conduction pipe: metal aluminum;
the focusing and heating device has the beneficial effects that:
1. the heat exchange can be completed rapidly, the nitrogen temperature of a laboratory is increased to be heated gas, and the temperature of the focusing tube is increased rapidly by means of temperature conduction in the heating mode.
2. Liquid nitrogen left in the focusing module can be taken away fast, and compared with the liquid nitrogen which is directly heated by an electric heating wire on the focusing tube, the liquid nitrogen focusing device has high efficiency and is not easy to leak electricity.
The arc focusing concentration tube is of an arc tubular structure, is made of stainless steel, is 65mm in length, is 0.15mm in wall thickness, is 0.5mm in inner diameter, is 0.8mm in outer wall diameter, is 135 degrees in radian (see the structure shown in fig. 1), is used for capturing sulfide components to be detected in a liquid nitrogen refrigerating state, and is used for achieving desorption of a gas sample after heating.
The arc focusing concentration tube has radian and has the following advantages:
1. the speed and time for the components in the tested sample to pass through the focusing concentration tube are slowed down, and when the passing speed of the tested component molecules is slowed down, the temperature is lowered more easily and the components are captured at low temperature;
2. the occupied space of the focusing tube in the instrument is reduced, the contact area is increased to the maximum extent, and the cooling or heating effect is effectively improved;
3. the cooling effect is showing, there is the focus concentrator pipe of radian better than straight-line focus concentrator pipe effect, in theory, spiral pipe cooling is better, but spiral though area of contact grow, catch and the effect of heating up and cooling is better, but because there is spiral centrifugal effect, the drop of water that congeals after the heating up is difficult to blow out immediately in the focus pipe, cause water smoke to enrich gradually at the minimum of focus pipe and form the drop of water easily, adsorb the sulphide for the sulphide of water-soluble nature is adsorbed by the drop of water, consequently, the focus concentrator pipe of radian is the body of optimum shape.
In the step (3), the air bag collects gas, and the pressure is controlled by the pressure balancing device during sample injection, and the specific flow is as follows:
control schematic figure 2:
1) Sampling: sampling from the upper layer C1 of the 16-hole valve, wherein the power is from Pump at the rear end of MFC (electronic flow controller);
2) Pressure balance: come to the No. 4 position of the 8-way valve through the com common port, then pass through the No. 3 position, and go to the 5mL dosing ring. The outlet of the quantitative ring is at the position 8 and then enters the pressure balancing device of the blue square frame, the public end is connected with the external environment, the pressure gauge (P) detects the gas pressure and has the alarm prompting function, and the gas pressure is ensured to be maintained at 1 atmosphere.
3) Sampling, pressure balance sampling for 20s, and finishing the filling of 5mL quantitative loops.
The pressure balancing device of the invention has the following advantages:
1. accurately controlling the air pressure: the pressure gauge (P) with alarming and prompting functions can monitor the gas pressure in real time, maintain the pressure balance, and can also adjust in real time due to the air pressure change caused by the reasons of topography and the like, so that the complexity of subsequent data conversion is avoided, and the rapid and accurate detection is realized;
2. preventing air pump load: when the air bag is pumped and injected, the air bag is contracted, if the pumping speed is too high or the sample is pumped out, negative pressure is easily caused, the load of the pump is increased, and finally the air bag is overheated and damaged. Thus, the sample can be kept to be sampled under one atmosphere, and the damage caused by overlarge pump load is avoided.
In the step (3), the focusing and concentrating workflow is as follows:
as shown in the figure 3 of the drawings,
1) Introducing laboratory nitrogen into the position 1 on the eight-way valve, taking out the sample in the quantitative ring through the position 8 and the position 3, and introducing the sample into a focusing tube cooled to-165 ℃ through the position 2;
2) The sample to be measured is concentrated and enriched in the focusing tube.
Wherein, sixteen-hole valve is divided into upper and lower two-layer, totally 32 sampling positions. C1 is the upper layer, C2 is the lower layer, and the position No. 6 on the eight-way valve in the figure is a non-through plug.
According to the invention, the pipeline and the valve are silanized by using the silanization technology on the transfer of the sample to be detected, so that the sulfide and the copper pipe or the stainless steel pipe are prevented from reacting, the whole substance sample injection of the component to be detected is realized by adopting a substance freezing focusing mode on the concentration of the sample to be detected, the sulfide characteristic detector is selected, the sulfide is ensured not to be lost due to the adsorption of water removal or adsorption filler in the concentration process, the sensitivity of detecting the sulfur-containing compound is improved, and the stable air pressure during sample injection is realized by using the air bag in combination with the pressure balancing device in the aspect of sampling, so that the aim of accurate detection is fulfilled.
The instrument parameter settings of the invention are as follows:
sulfide detected by gas chromatograph: 16 sulfur-containing compounds mixed with standard gas (5. Mu. Mol/mol) nitrogen balance, the components include, but are not limited to, the following: hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, methyl sulfide, ethyl sulfide, dimethyl disulfide, carbon disulfide, t-butyl mercaptan, isopropyl mercaptan, n-propyl mercaptan, thiophene, methyl isopropyl sulfide, isobutyl mercaptan, n-butyl mercaptan, and tetrahydrothiophene.
The parameters of the gas chromatograph were set as follows:
base temperature: 250 ℃;
burner temperature: 800 ℃;
upper hydrogen flow rate: 38mL/min;
lower limit of hydrogen flow: 8mL/min;
oxidizer flow (air): 50mL/min;
combustor pressure: 380Torr;
ozone flow rate: 30mL/min.
Further, the parameters of the focus concentrator are set as follows:
sampling a sample port: sampling by a mass flowmeter at the speed of 30-40 mL/min until a 5mL quantitative ring is full;
pressure equilibration time: 0.48 to 0.52min;
focusing cold trap temperature: -150 to-180 ℃;
flow rate of sample transfer: 2.5mL/min;
sample transfer time: 4min;
the project Gas temperature: 30-55 ℃;
desorption time: 2min.
Preferably, the focusing cold trap temperature: -165 ℃.
Preferably, the pressure equilibration time is 0.5min.
Preferably, the temperature of the object Gas is 50 to 55 ℃.
The invention has the beneficial effects that:
(1) Simple process and easy operation
The focusing concentration pretreatment device can be used for directly sampling, and compared with the thermal desorption method, the process is simpler. The SECA focusing concentrator utilizes a silanization technology to silanize the pipeline and the valve on the transfer of the sample to be detected, so that the reaction between sulfide and a copper pipe or a stainless steel pipe is avoided, the concentration of the sample to be detected adopts a substance freezing focusing mode to realize the whole substance sample injection of the component to be detected, and the feature detector SCD of the sulfide is selected, so that the sulfide is ensured not to be lost due to the adsorption of water removal or adsorption filler in the concentration process;
meanwhile, the ultrahigh sulfide detection capability improves the sensitivity of the sulfur-containing compound, so that the measurement of the sulfide component is simple, quick and reliable.
(2) High sensitivity and stability
A gas chromatograph with a Sulfur Chemiluminescence Detector (SCD) was used in conjunction with an SECA focus concentrator, the SCD detector response to sulfur being a linear response, the response value increasing linearly with increasing sulfur concentration, and being a molar response. Regardless of the structure of the sulfur-containing compound, the same response value is produced as long as the sulfide has the same molar value. This feature makes the quantitative determination very convenient and simple. However, FPD detection is nonlinear, accuracy is insufficient in quantitative measurement, and quenching effect occurs in the FPD detector, so that when the FPD detector contains a high concentration of hydrocarbon compounds, a phenomenon that the sulfur response value is reduced or even completely disappears often occurs. The substance is the inactivation of excited state molecules, SCD has good anti-quenching effect, and the quenching effect of FPD is mostly represented by the influence of hydrocarbon on sulfide, so that the detection result of sulfide is inaccurate;
the gas chromatograph with the Sulfur Chemiluminescence Detector (SCD) is matched with the SECA focusing concentrator for use, so that the sensitivity of detecting sulfide is improved, and the stability is relatively good.
(3) The human body sniffing threshold is closed to better provide a data basis for management
For most sulfides, the detection limit in the existing detection method often cannot reach the human olfactory threshold, and the detection limit of some sulfides is far greater than the olfactory threshold. The traditional detection mode and means are not enough in sensitivity, so that the human olfactory threshold cannot be analyzed, and sulfide with the concentration lower than the human olfactory threshold has great hidden danger to life health of people, for example, petroleum chemical enterprises import processed high-sulfur crude oil is dramatically increased, and chronic poisoning of hydrogen sulfide with the concentration lower than the olfactory threshold is a common health threat.
According to the invention, a gas chromatograph with a Sulfur Chemiluminescence Detector (SCD) is matched with an SECA focusing concentrator, a detection limit measuring and calculating method of HJ168-2020 is used, the detection limit of hydrogen sulfide is as low as 0.09nmol/mol and far lower than the sniffing threshold value of 0.41nmol/mol, the safety range is reached, 16 sulfide standard gases of 0.5nmol/mol are correspondingly configured, 7 needles are continuously injected, the detection limit of 7 sulfide components in the detected detection limit result is lower than the sniffing threshold value of human beings, and compared with the graph shown in figure 4, the components are specifically as follows: hydrogen sulfide, carbonyl sulfide, dimethyl disulfide, carbon disulfide, thiophene, and tetrahydrothiophene.
Drawings
FIG. 1 is a schematic view of a focusing concentration tube;
FIG. 2 is a schematic diagram of a sample injection structure of a focus concentration-gas chromatography sulfide detection system;
FIG. 3 is a schematic diagram of the operation of a focus concentrate-gas chromatograph sulfide detection system;
wherein, MFC: an electronic flow controller;
pump: an air extracting pump;
COM: a public terminal;
NO: normally open;
the P device is a pressure gauge;
FIG. 4 is a graph showing comparison between sulfide detection limit and olfactory threshold;
FIG. 5 is a bar graph of parallel detection (3 times) of hydrogen sulfide, carbonyl sulfide and carbon disulfide in a sample;
FIG. 6 is a graph of a freeze-focus apparatus set-up equilibration time of 0.2 min;
FIG. 7 is a graph showing a comparison of the freeze-focus apparatus set-up equilibration time of 0.2min versus 0.5min;
FIG. 8 is a graph of a freeze-focus apparatus set-up equilibration time of 0.5min;
FIG. 9 is a graph showing a comparison of the freeze-focus apparatus set-up equilibration time of 0.5min versus 0.8 min;
FIG. 10 is a graph showing the comparison of the equilibrium time of the freeze-focus apparatus set for 0.2min, 0.5min and 0.8 min;
FIG. 11 is a graph showing the cold hydrazine temperature set at-150 ℃;
FIG. 12 is a graph showing the cold hydrazine temperature set at-180 ℃;
FIG. 13 is a graph showing the cold hydrazine temperature set at-170 ℃;
FIG. 14 is a graph showing the cold hydrazine temperature set at-165 ℃;
FIG. 15 is a graph of the temperature of the object Gas at 30℃to 35 ℃;
FIG. 16 is a graph of the temperature of the object Gas at 40℃to 45 ℃;
FIG. 17 is a graph of the temperature of the object Gas at 50℃to 55 ℃;
FIG. 18 is a bar graph of the detection limits of 16 sulfides;
FIG. 19 is a bar graph of precision for 16 sulfide detection limits and various concentrations;
FIG. 20 is a graph of a comparison experiment using sulfide standard gas at a concentration of 10nmol/mol for two different diluter configurations.
In the figure: 1. a pressure balancing device; 2. a sample injection system; 3. a focusing concentrator; 4. focusing, concentrating and heating device; 5. a gas chromatograph.
Detailed Description
The present invention will be better understood by those skilled in the art and will now be further described in connection with the detailed description.
Example 1
The method is used for detecting 16 sulfides including hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, methyl sulfide, ethyl sulfide, dimethyl disulfide, carbon disulfide, tertiary butyl mercaptan, isopropyl mercaptan, n-propyl mercaptan, thiophene, methyl isopropyl sulfide, isobutyl mercaptan, n-butyl mercaptan and tetrahydrothiophene, and comprises the following specific steps:
(1) The focusing concentrator adopts a silanization pipeline and a valve, wherein the silanization pipeline comprises a focusing concentration pipe and other pipelines through which a sample passes; the focusing concentration heating device is additionally arranged, an arc focusing concentration pipe is used, the length of the pipe is 65mm, the thickness of the pipe wall is 0.15mm, the inner diameter of the pipe is 0.5mm, the diameter of the outer wall of the pipe is 0.8mm, and the radian is 135 degrees;
(2) Connecting the focus concentrator described in (1) to a gas chromatograph with a sulfur chemiluminescence detector;
(3) Collecting sulfide gas by the air bag, balancing the pressure for 0.5min, and injecting the sulfide gas into a quantitative ring filled with 5 mL;
(4) The liquid nitrogen switch is turned on to charge N 2 And (3) carrying out carrier gas, focusing a cold trap, concentrating the sample, heating a focusing concentration tube by using nitrogen at 70 ℃, desorbing the sulfide sample, and detecting the sulfide by using a gas chromatograph.
The experimental test process comprises the condition setting of the freezing focus instrument and the gas chromatograph, and the whole process is that the test condition of the gas chromatograph is a mature method, so the experimental test is only carried out on the condition of the freezing focus instrument and the experimental test is adjusted to the optimal state.
Conditions of gas chromatograph:
16 sulfur-containing compound mixed standard gas (5. Mu. Mol/mol) nitrogen balance, component: hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, methyl sulfide, ethyl sulfide, dimethyl disulfide, carbon disulfide, t-butyl mercaptan, isopropyl mercaptan, n-propyl mercaptan, thiophene, methyl isopropyl sulfide, isobutyl mercaptan, n-butyl mercaptan, and tetrahydrothiophene.
Gas chromatograph: agilent 8890GC System;
sulphur Chemiluminescence Detector (SCD): 8355Sulfur Chemiluminescence Detector;
focus concentrator 8028L Autosampling System;
gas dynamic dilution instrument: entech 4600;
gas static diluter Entech 4700;
stainless steel soda can: 6L, the inner wall and the valve body are subjected to silanization treatment.
Chromatographic column: agilent DB-Sulfur SCD 60m 320 μm 4.2 μm temperature range: -60-250 DEG C
An air bag: materials not adsorbing sulfide components
Configuration of standard usage gas: the standard gas mixture of sulfur-containing compounds was diluted to an intermediate standard gas of 50nmol/mol by using an Entech 4600 dynamic diluter, and then 6 concentration standard gases of 0.5nmol/mol, 1.0nmol/mol, 2.5nmol/mol, 5.0nmol/mol, 10.0nmol/mol, 12.5 nmol/mol were prepared in a Suma tank by using an Entech 4700 static diluter, and were inflated to an air bag after standing for 6 hours for testing.
Analyzing system conditions:
sample inlet: 150 ℃;
column incubator: maintaining the temperature at 35 ℃ for 5min, increasing the temperature from 35 ℃ to 60 ℃ at a speed of 5 ℃/min, and then increasing the temperature from 60 ℃ to 210 ℃ at a speed of 15 ℃/min;
SCD detector: base temperature: 250 ℃;
burner temperature: 800 ℃;
upper hydrogen flow rate: 38mL/min;
lower limit of hydrogen flow: 8mL/min;
oxidizer flow (air): 50mL/min;
combustor pressure: 380Torr;
ozone flow rate: 34mL/min.
Condition setting of the freeze focussing instrument:
(1) Setting of the equilibration time of a freeze focus
Equilibrium time definition: the sample is injected under normal pressure, and the purpose is to enable the pressure of the sample in the quantitative ring to be consistent with the atmospheric pressure by setting the pressure balance time, so that the sample injection volume is more accurate and stable, and the accuracy of the sample injection volume can be influenced by excessive or insufficient pressure.
The balance time is set to be 0.2min, 0.5min and 0.8min, and the spectrograms obtained through the two condition experiment parameter settings are compared, so that the fact that the pressure balance requirement cannot be met in 0.2min (see figure 6) is obviously found, and when the pressure balance time is set to be 0.5min (see figure 7), the response of each component is obviously higher than that of the pressure balance for 0.2min.
And comparing the results of the balance time of 0.5min (see figure 8) and the results of the balance time of 0.8min (see figure 9), and finding that the result spectrograms of the two groups of balance time settings are basically consistent, so that the pressure balance is consistent with the atmospheric pressure at 0.5min.
When the resulting spectra of 0.2min, 0.5min and 0.8min were superimposed (see fig. 10), it was found that 0.5min should be the optimal pressure equilibration time.
(2) Setting of cold hydrazine temperature
The cold hydrazine temperature is set for the purpose of more forcefully grabbing the target object and transferring. The set temperature is too high, which can cause loss of light component sulfides. The temperature is too low, so that heavy components are incompletely analyzed, the phenomenon of incomplete desorption in the subsequent process is caused, and when the temperature is lower than-180 ℃, oxygen can be changed into liquid oxygen, and the blocking of a focusing pipeline can be possibly caused, so that peak abnormal phenomenon is generated on light components. Thus, in combination with theory, the discussion of cold hydrazine temperatures is expected to be set at-150 ℃, -180 ℃, -170 ℃, -165 ℃ in four steps.
a) When the temperature of the cold hydrazine is set at-150 ℃, the peak of the hydrogen sulfide and the carbonyl sulfide is unstable (see figure 11), the concentration of the light-component sulfide part advances to form a peak, and then the peak is deformed (short and fat) or is divided into two peaks;
b) When the temperature of the cold hydrazine is set at-180 ℃, most of the compounds have irregular peaks (see figure 12) due to the excessively low temperature, the phenomenon of splitting peaks occurs, and the responses of hydrogen sulfide, carbonyl sulfide and methyl mercaptan are obviously reduced;
c) When the temperature of the cold hydrazine is set at-170 ℃, the peak of the hydrogen sulfide and the carbonyl sulfide is better, and the hydrogen sulfide and the carbonyl sulfide are normally separated (see figure 13). However, the combination valve box temperature can cause incomplete desorption of cold hydrazine, so that the situation that the peak of the hydrogen sulfide and the carbonyl sulfide still exists in advance;
d) When the temperature of the cold hydrazine is set at-165 ℃, the peak of the hydrogen sulfide and carbonyl sulfide low-boiling point substances is stable, the peak shape is sharp (see figure 14), and the cold hydrazine temperature is the most suitable cold hydrazine temperature.
(3) Setting of desorption temperature
The desorption temperature is controlled separately, and is controlled on the freeze-focus apparatus by controlling the temperature of the object Gas. The valve box is heated to generate heated nitrogen, and the heated nitrogen elutes organic sulfide adsorbed in the cold hydrazine through the cold hydrazine, but the actual desorption temperature is controlled by precisely setting the temperature of the object Gas.
a) The temperature of the object Gas is 30-35 ℃, the tested spectrogram is shown in figure 15, most of the target objects have unsharpened peak shapes and have the phenomenon of splitting peaks;
b) The temperature of the object Gas is 40-45 ℃, the peak shape of the front-stage target object is improved, the response of the rear-stage target object is still lower, the phenomenon of splitting peak still exists, and a tested spectrogram is shown in figure 16;
c) The temperature of the subject Gas was 50-55deg.C, the peak shape of all targets was improved, the response was increased, and the spectrum of the test was shown in FIG. 17.
From the above experimental results, it can be seen that when the setting of the reject Gas temperature is too low, it is unfavorable for the analysis of sulfides with a large molecular weight, and therefore, the desorption temperature is set to be most suitable at 50-55 ℃.
Combining the results of the above condition experiments, the conditions of freeze focusing are determined as follows:
sampling a sample port: sampling with a mass flow meter at a speed of about 30mL/min-40mL/min to a 5mL quantitative ring full;
pressure equilibration time: the pressure of the quantifying ring and the pipeline is balanced for 0.5min;
focusing cold trap temperature: setting the temperature to-165 ℃;
flow rate of sample transfer: 2.5mL/min;
sample transfer time: 4min;
the project Gas temperature: 50 ℃;
desorption time: 2min, the start of the GC is triggered at the same time.
Table 1: sniff threshold and detection limit of 16 sulfides
Note that: the detection limit histogram of 16 sulfides is shown in fig. 18.
Table 2: detection limit and precision of each concentration
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Note that: the 16 sulfide detection limits and the precision bar chart of each concentration are shown in FIG. 19.
From the results, the invention obviously improves the types and the precision of sulfide detection, takes the olfactory threshold as a reference standard, 7 types of sulfide in 16 common types are obviously lower than the olfactory threshold, and the rest of sulfide detection realizes lower detection limit, thereby embodying excellent technical effects.
The structure of the detection system used in the embodiment 1 is as follows:
the pressure balancing device 1 is connected with one end of a sample injection system 2 through a pipeline, the other end of the sample injection system 2 is connected with a focusing concentrator 3 through a pipeline, a focusing concentration heating device 4 is connected to the focusing concentrator 3, the focusing concentrator 3 is connected with one end of a gas chromatograph 5 through a pipeline, and the other end of the gas chromatograph 5 is connected with a sulfur chemiluminescence detector.
The sample injection system 2 mainly comprises sixteen valves (actually 32 valve positions, each layer has 16 valve positions) and eight valves with a double-layer structure;
the eight-way valve is provided with a valve position 1, a valve position 2, a valve position 3, a valve position 4, a valve position 5, a valve position 6, a valve position 7 and a valve position 8;
two pipelines of sixteen valves of the double-layer structure are converged to a com end (public end) and then lead to a valve position 4 of the eight-way valve;
the No. 5 position of the eight-way valve is connected with the pressure balancing device 1; meanwhile, valve positions No. 5 and No. 7 of the eight-way valve are connected through pipelines; the valve position No. 2 of the eight-way valve is connected with one end of an arc-shaped focusing concentration tube in the focusing concentration instrument 3; the valve position 3 and the valve position 8 of the eight-way valve 10 are respectively connected with the two ends of the quantitative ring through pipelines; the valve 1 of the eight-way valve is connected with carrier gas, the valve 5 of the eight-way valve is communicated with the valve 6, the valve 3 is communicated with the valve 4, the valve 1 is communicated with the valve 2, and the valve 7 is communicated with the valve 8;
the above structure is conventional, is not the important protection of the present invention, and will not be described in further detail herein; the invention mainly aims to protect a heating device which adopts a focusing concentration pipe with a specific structure and a focusing concentration pipe, wherein the sampling system 2 is connected with a pressure balancing device;
the pressure balancing device 1 comprises a three-way valve, wherein the three-way valve comprises valve ports No. 1, no. 2 and No. 3; the three-way valve is provided with a cavity with a certain volume, the cavity can play a certain buffering role, a No. 1 valve port of the three-way valve is connected with an external normal pressure environment, a No. 2 valve port of the three-way valve is connected with the front end of a flow controller, the rear end of the flow controller is connected with an air pump, a No. 3 valve port of the three-way valve is connected with a No. 5 valve position of an eight-way valve of the sample injection system 2 through a pipeline, the No. 3 valve port of the three-way valve is connected with the No. 5 valve position of the eight-way valve through a pipeline, and a pressure gauge is arranged on the pipeline for reading the pressure of gas on the pipeline.
The focusing concentrator 3 comprises a square shell, a focusing concentration tube, a heat preservation layer and a liquid nitrogen inlet tube, wherein the focusing concentration tube is arranged in the shell and extends from one corner of the upper part of the shell to the opposite corner of the lower part of the shell;
the focusing concentration tube is of an arc hollow tubular structure, the tube length is 65mm, the tube wall thickness is 0.15mm, the tube inner diameter is 0.5mm, the tube outer wall diameter is 0.8mm, and the radian is 135 degrees. The upper end of focus concentrator is connected through the pipeline with the No. 2 phase of the eight-way valve of sampling system 2, and the lower extreme of focus concentrator passes through pipeline connection gas chromatograph 5, and the outside cladding of focus concentrator has the heat preservation, and the liquid nitrogen import pipe passes the upper portion of casing and is connected to between focus concentrator and the heat preservation.
The focusing, concentrating and heating device comprises the following structures: the heating box, heliciform heating pipe, heating jacket, the middle part of heliciform heating pipe is heliciform tubular structure, and both ends are straight tubular structure, and the heliciform heating pipe runs through the heating box from the both ends of heating box inside, and its one end is connected with the nitrogen gas jar, and the other end leads to between focusing dense pipe and the heat preservation, and the heliciform heating pipe outer wall is provided with the heating jacket, and the heating jacket is its inside gaseous heating with the mode of electrical heating, and this heating jacket is prior art, does not explain in more detail.
Example 2
For practical sample applications, a sample of ambient air with malodorous taste collected near a gas station was collected with an air bag.
The same parameter setting and detection procedure as in example 1 was followed to detect hydrogen sulfide, carbonyl sulfide and carbon disulfide, and the results showed (fig. 5) that all three sulfides were detected, and that the relative standard deviation of the results of the three measurements in parallel was within 10%.
Comparative example 1
In order to show the effectiveness of the silylation treatment, example 1 was compared with comparative example 1, wherein the piping in comparative example 1 was not subjected to the silylation treatment, and the rest of the method was the same as in example 1, and the experimental results were as follows:
FIG. 20 is a comparative experiment using sulfide standard gas at a concentration of 10nmol/mol for two different diluter configurations. The high response and high composition A spectrum (example 1) is inerted in all the lines used in the gas diluter, and the low response and low composition B spectrum (comparative example 1) is not inerted in the lines. The comparison result shows that the active sulfide has adsorption phenomenon after being configured by a diluter which is not subjected to inerting treatment, and 16 components of sulfide have no substance loss phenomenon after being configured by the diluter which is provided with an inerting pipeline, so that the detection effect is good.
Claims (1)
1. A method for improving the detection accuracy of sulfides, comprising the steps of:
(1) The focusing concentrator adopts a silanization pipeline and a valve, wherein the silanization pipeline comprises a focusing concentration pipe and other pipelines through which a sample passes; the focusing concentration heating device is additionally arranged, an arc focusing concentration pipe is used, the length of the pipe is 65mm, the thickness of the pipe wall is 0.15mm, the inner diameter of the pipe is 0.5mm, the diameter of the outer wall of the pipe is 0.8mm, and the radian is 135 degrees;
(2) Connecting the focus concentrator described in (1) to a gas chromatograph with a sulfur chemiluminescence detector; the gas chromatographic analysis system with the sulfur chemiluminescence detector has the following detection conditions: sample inlet temperature: 150 ℃; column incubator: maintaining the temperature at 35 ℃ for 5min, increasing the temperature from 35 ℃ to 60 ℃ at a speed of 5 ℃/min, and then increasing the temperature from 60 ℃ to 210 ℃ at a speed of 15 ℃/min; the base temperature of the sulfur chemiluminescence detector is 250 ℃, the burner temperature is 800 ℃, the upper hydrogen flow is 38mL/min, the lower limit of the hydrogen flow is 8mL/min, the oxidizer flow is 50mL/min, the burner pressure is 380Torr, and the ozone flow is 34 mL/min;
(3) Collecting sulfide gas by the air bag, balancing the pressure for 0.5min, and injecting the sulfide gas into a quantitative ring filled with 5 mL; the sulfide comprises the following 16 components: hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, methyl sulfide, ethyl sulfide, dimethyl disulfide, carbon disulfide, tertiary butyl mercaptan, isopropyl mercaptan, n-propyl mercaptan, thiophene, methyl isopropyl sulfide, isobutyl mercaptan, n-butyl mercaptan, and tetrahydrothiophene;
(4) The liquid nitrogen switch is turned on to charge N 2 A carrier gas, a focusing cold trap, a focusing concentration tube heated by nitrogen at 70 ℃ after concentrating a sample, a sulfide sample desorbed, and a gas chromatograph to detect sulfide;
wherein, any water removing filler and/or adsorption filler is not adopted in the process of focusing the gas sample on the cold trap;
the apparatus used in the above steps includes: gas chromatograph: agilent 8890GC System; detecting by adopting a sulfur chemiluminescence detector; focusing concentrator: 8028L Autosampling System; gas dynamic dilution instrument: entech 4600; gas static diluter Entech 4700; stainless steel soda can: 6, L, the inner wall and the valve body are subjected to silanization treatment; chromatographic column: agilent DB-Sulfur SCD 60 m.times.320 μm.times.4.2 μm, temperature range: -60 ℃ -250 ℃; an air bag: a material that does not adsorb sulfide components;
and (3) performing freezing focusing in the step (4), wherein the conditions are as follows:
sampling at the sample port, sampling with a mass flow meter at a speed of 30mL/min-40mL/min, and filling with 5mL quantitative ring; the pressure of the quantitative ring and the pipeline is balanced for 0.5min, the temperature of a focusing cold trap is-165 ℃, the flow rate of sample transfer is 2.5mL/min, the sample transfer time is 4min, the temperature of an object Gas is 50 ℃, the desorption time is 2min, and the starting of Gas chromatography is triggered at the same time;
the method is realized through a focusing concentration-gas chromatography sulfide detection system, and the detection system is set as follows:
the pressure balancing device (1) is connected with one end of the sample injection system (2) through a pipeline, the other end of the sample injection system (2) is connected with the focusing concentrator (3) through a pipeline, the focusing concentrator (3) is connected with the focusing concentration heating device (4), the focusing concentrator (3) is connected with one end of the gas chromatograph (5) through a pipeline, and the other end of the gas chromatograph (5) is connected with the sulfur chemiluminescence detector;
the focusing concentrator (3) comprises a square shell, a focusing concentration tube, a heat preservation layer and a liquid nitrogen inlet tube, wherein the focusing concentration tube is arranged in the shell and extends from one corner of the upper part of the shell to the opposite corner of the lower part of the shell; the focusing concentration tube is of an arc hollow tubular structure, the tube length is 65mm, the tube wall thickness is 0.15mm, the tube inner diameter is 0.5mm, the tube outer wall diameter is 0.8mm, the radian is 135 degrees, the upper end of the focusing concentration tube is connected with the No. 2 phase of the eight-way valve of the sample injection system (2) through a pipeline, the lower end of the focusing concentration tube is connected with the gas chromatograph (5) through a pipeline, the outer side of the focusing concentration tube is coated with a heat preservation layer, and the liquid nitrogen inlet tube passes through the upper part of the shell and is connected between the focusing concentration tube and the heat preservation layer;
the focusing, concentrating and heating device comprises the following structures: the heating box, heliciform heating pipe, heating jacket, the middle part of heliciform heating pipe is heliciform tubular structure, and both ends are straight tubular structure, and the heliciform heating pipe runs through the heating box from the both ends of heating box inside, and its one end is connected with the nitrogen tank, and the other end leads to between focus dense pipe and the heat preservation, and the heliciform heating pipe outer wall is provided with the heating jacket, and the heating jacket is its inside gaseous heating with the mode of electrical heating.
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