阅读说明：本技术 一种油田污水中破乳剂的检测方法 (Method for detecting demulsifier in oilfield sewage ) 是由 王雨 宫兆波 王兴华 任召言 林莉莉 屈静 斯绍雄 吴永花 张珍珠 王华鹏 杨永 于 2021-08-24 设计创作，主要内容包括：本发明涉及化学分析技术领域,具体涉及一种油田污水中破乳剂的检测方法,所述检测方法,包括如下步骤：(1)配制标准溶液：将破乳剂用水配制成系列不同浓度标准溶液；(2)定量分析：将不同浓度标准溶液进行液相色谱分析,根据标准溶液的浓度和对应的色谱峰面积,绘制定量工作曲线；(3)样品检测：将油田污水样品过滤,进行分析,将样品色谱峰面积带入步骤(2)得到的定量工作曲线,即可获得破乳剂浓度。本发明具有灵敏度高、准确性好、测试方法简单的优点。(The invention relates to the technical field of chemical analysis, in particular to a detection method of a demulsifier in oilfield sewage, which comprises the following steps: (1) preparing a standard solution: preparing a series of standard solutions with different concentrations by using water for the demulsifier; (2) quantitative analysis: performing liquid chromatography analysis on standard solutions with different concentrations, and drawing a quantitative working curve according to the concentration of the standard solution and the corresponding chromatographic peak area; (3) sample detection: and (3) filtering and analyzing the oilfield sewage sample, and substituting the chromatographic peak area of the sample into the quantitative working curve obtained in the step (2) to obtain the concentration of the demulsifier. The invention has the advantages of high sensitivity, good accuracy and simple test method.)

1. A method for detecting a demulsifier in oilfield sewage is characterized by comprising the following steps:

(1) preparing a standard solution: preparing a series of standard solutions with different concentrations by using water for the demulsifier;

(2) quantitative analysis: performing liquid chromatography analysis on standard solutions with different concentrations, and drawing a quantitative working curve according to the concentration of the standard solution and the corresponding chromatographic peak area;

(3) sample detection: and (3) filtering and analyzing the oilfield sewage sample, and substituting the chromatographic peak area of the sample into the quantitative working curve obtained in the step (2) to obtain the concentration of the demulsifier.

2. The detection method according to claim 1, wherein the demulsifier is a fatty alcohol-based demulsifier.

3. The detection method according to claim 1, wherein the demulsifier comprises at least one of a C18 fatty alcohol or a C16 fatty alcohol head-based, polyoxyethylene and polyoxypropylene diblock, triblock, or tetrablock nonionic polyether demulsifiers.

4. The method according to claim 1, wherein the liquid chromatography in step (2) is performed using an ionic chromatography column.

5. The detection method according to claim 4, wherein the ionic chromatography column in the step (2) is a SAX ionic chromatography column.

6. The detection method according to claim 1, wherein the chromatographic column packing for the liquid chromatographic analysis in the step (2) is prepared by the following process: and (3) bonding aminopropyltriethoxysilane with hydroxyl on the surface of silica gel, and adding methyl iodide to carry out quaternization reaction to obtain the product.

7. The detection method according to claim 1, wherein in the step (2), the liquid chromatography is performed, the mobile phase is methanol and water, and the gradient elution is performed.

8. The detection method according to claim 7, wherein the conditions of the gradient elution are 0-1min, 50% methanol; 1.01min, 80% methanol; 1.01-6min, 80% methanol.

9. The detection method according to claim 1, wherein in the step (3), if the concentration of the demulsifier in the oilfield wastewater sample is more than 5mg/L, the filtration is directly carried out, and the filtrate is taken for analysis; and if the concentration of the demulsifier in the oilfield sewage sample is less than 5mg/L, filtering and concentrating the demulsifier, and then analyzing the demulsifier.

10. The detection method according to claim 9, wherein the concentration process in the step (3) is: filtering an oilfield sewage sample, concentrating the filtrate, washing with methanol, transferring flushing fluid, evaporating the solvent, and performing constant volume analysis on the methanol.

11. The detection method according to claim 1, wherein in the step (2), the liquid chromatography is performed, and the detector is an evaporative light scattering detector; the detection wavelength was 245 nm.

Technical Field

The invention relates to the technical field of chemical analysis, in particular to a method for detecting a demulsifier in oilfield sewage.

Background

A demulsifier is a surfactant that breaks emulsions. Demulsifiers break emulsions primarily by the action of partially displacing the stabilizing membrane. The dehydrating agent is used for dehydrating crude oil and heavy oil to ensure that the water content meets the requirement; can be used in oil well to reduce the viscosity of crude oil and prevent oil well from blocking. Is easily dissolved in water, and is a yellowish or milky viscous liquid.

Crude oil extracted from oil fields must be subjected to oil-water separation before being transported to an oil refinery for further processing, and various demulsifiers are main agents for oil-water separation. The demulsifier can destroy the structure of emulsified liquid to separate the phases in the emulsion. The crude oil demulsification is that the chemical action of the demulsifier is utilized to separate oil and water in emulsified oil-water mixed liquor, so that the purpose of crude oil dehydration is achieved, and the water standard of crude oil output is ensured.

After crude oil is demulsified and dehydrated, most of demulsifier enters a water phase, and the subsequent sewage treatment difficulty is increased due to the high interfacial activity of the demulsifier, so that the concentration of the demulsifier in the water phase needs to be rapidly and accurately detected urgently, and a basis is provided for determining the dosage of sewage treatment; on the other hand, the oil field external drainage needs to reach a certain Chemical Oxygen Demand (COD) index, and the demulsifier is one of the main contributions of the COD, and needs to detect the concentration of the demulsifier in the external drainage to provide targeting data for external drainage wastewater environmental impact evaluation and COD remover screening.

However, for the detection of the demulsifier in the oilfield wastewater, the interference of chemical additives, crude oil and inorganic salts and matrix effects exist, and no mature detection method can be used for reference at present.

The fatty alcohol type demulsifier is a crude oil demulsifier widely used in oil fields, is generally prepared by taking C18 alcohol or C16 alcohol as a head group and carrying out block copolymerization on polyoxypropylene and polyoxyethylene, and belongs to a nonionic surfactant. The detection of this substance has been a difficult point in analytical work. The existing determination methods comprise a gas chromatography/mass spectrum, a liquid chromatography/mass spectrum, a capillary electrophoresis method, an ion selective electrode method, an ultraviolet spectrophotometry method, a colorimetric method and the like, and are directed to nonionic surfactants with simpler structures.

The gas chromatography method requires dissociation with HBr-HAc, belongs to an indirect determination method, and has complex operation (Song iron san. oilfield chemistry, 1989); GB/T5560-2003 (measurement of the content of polyethylene glycol as a nonionic surfactant and the content of nonionic active substances-Weilbull method) is only suitable for measuring the content of effective substances of demulsifiers of alkylphenol and fatty alcohol, and the detection object is mainly a demulsifier commodity rather than a residual demulsifier in wastewater; ammonium cobalt thiocyanate photometry is also only applicable to the determination of the active ingredients of demulsifier commercial products (Wang Xiaolin. oil field chemistry, 2015).

The literature reports a quantitative method for detecting Tween 80 and decomposition products thereof by HPLC/ELSD, but the method has the disadvantages of troublesome pretreatment, decomposition reaction for 4 hours in a water bath by NaOH and toxic acetonitrile used as a mobile phase. The principle of the method is similar to that of cracking gas Chromatography, and the content of the nonionic surfactant is calculated according to the quantity of the oxygen ethyl groups in a cracking component (Rui Zhang. journal of Chromatography A, 2013).

The literature reports that an HPLC/MS method is used for simultaneously detecting anionic surfactants and nonionic surfactants in environmental water and sediments, but the operation is troublesome, solid-phase extraction and pressurized liquid-phase extraction are required, the technical difficulty of mass spectrogram quantitative analysis is high, and the method is suitable for the analysis of scientific research samples (Pablo A. journal of Chromatography A, 2006).

Chinese patent application CN 109490297 a discloses a method for detecting the concentration of demulsifier in crude oil, which comprises: (1) preparing a standard solution with a concentration gradient by using a demulsifier, adding an extracting agent for extraction, developing a color by using a color developing agent, measuring the absorbance of an organic layer of the standard solution by using an ultraviolet spectrophotometry, and drawing a standard curve according to the absorbance and the concentration; (2) adding a demulsifier with known content into a sample to be detected, and separating an oil phase from a water phase in the sample to be detected to obtain a water phase layer and a crude oil layer; (3) adding an extracting agent into the aqueous phase layer obtained in the step (2) for extraction and color development of a color developing agent, measuring the absorbance of the organic layer of the sample to be detected by an ultraviolet spectrophotometry, and quantifying the concentration of the demulsifier in the aqueous phase layer obtained in the step (2) according to the standard curve drawn in the step (1); (4) and (4) obtaining the concentration of the demulsifier in the oil phase according to the concentration of the demulsifier in the water phase layer obtained in the step (3) and the known content of the demulsifier in the step (2). In the method, the concentration of the demulsifier in the crude oil is detected by using a cobalt thiocyanate colorimetric method, but the detection sensitivity is limited by the color development reaction of the color developing agent, and the contrast experiment data for detecting other types of demulsifiers by using the method is not shown.

The invention aims to develop a liquid chromatography detection method of a fatty alcohol type demulsifier aiming at a complex sewage system of an oil field, and provides an analysis means for the precise strategy of sewage treatment.

Because the detection method of the demulsifier has defects or does not cover the detection of the fatty alcohol type demulsifier in the water of the oil field, the development of the detection method which has high sensitivity, good accuracy and simple test method is necessary.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the method for detecting the demulsifier in the oilfield sewage, which has high sensitivity, good accuracy and simple test method.

The invention aims at the difficult problems that the pretreatment is troublesome, the ultraviolet absorption of main components is not strong, the separation degree of different components is not high, and whether a target peak can represent the integral demulsifier and a substrate to influence the chromatographic peak type in the quantitative detection of the demulsifier liquid chromatogram in a complex sewage system of an oil field, and develops a liquid chromatogram detection method of an aliphatic alcohol type demulsifier.

The invention is realized by the following technical scheme:

a method for detecting a demulsifier in oilfield sewage comprises the following steps:

(1) preparing a standard solution: preparing a series of standard solutions with different concentrations by using water for the demulsifier;

(2) quantitative analysis: performing liquid chromatography analysis on standard solutions with different concentrations, and drawing a quantitative working curve according to the concentration of the standard solution and the corresponding chromatographic peak area;

(3) sample detection: and (3) filtering the oilfield sewage sample, taking the filtrate for analysis, and substituting the chromatographic peak area of the sample into the quantitative working curve obtained in the step (2) to obtain the concentration of the demulsifier.

Preferably, the demulsifier is a fatty alcohol-type demulsifier.

More preferably, the demulsifier is a C16 or C18 type fatty alcohol-based demulsifier.

More preferably, the demulsifier comprises at least one of a C18 fatty alcohol or a C16 fatty alcohol head-based, polyoxyethylene and polyoxypropylene diblock, triblock, or tetrablock nonionic polyether demulsifiers.

Preferably, the demulsifier is prepared into a series of standard solutions with different concentrations of 2-1000mg/L by using water in the step (1).

In the step (1), the demulsifier is prepared into a series of standard solutions with different concentrations, such as 2, 10, 20, 50, 100, 500 and 1000mg/L by using water.

Preferably, the liquid chromatography in step (2) is performed on an ionic column.

More preferably, the chromatographic column for liquid chromatography in step (2) is a SAX ionic chromatographic column.

More preferably, the chromatographic column packing for liquid chromatography in step (2) is obtained by bonding aminopropyltriethoxysilane with hydroxyl groups on the surface of silica gel, and then adding methyl iodide for quaternization.

More preferably, the liquid chromatography column packing in step (2) has a particle size of 1-10 μm and a specific surface area of 40-500m²Per g, pore diameter

The molecular structure schematic diagram of the chromatographic column packing analyzed by the liquid chromatography in the step (2) is shown in figure 1.

The preparation process and the basic process of the chromatographic column packing are as follows:

fully acidifying fully porous silica gel with hydrochloric acid to completely activate silicon hydroxyl on the surface of the silica gel, washing with water to be neutral, drying at 120 ℃ in vacuum, taking dry toluene as a solvent, carrying out chemical bonding reaction on triethoxy aminopropyl silane and the silicon hydroxyl on the surface of the silica gel to obtain aminopropyl bonded silica gel, and carrying out quaternization reaction with methyl iodide to obtain the ionic liquid chromatographic column filler for separating anionic compounds. The specific reaction formula is as follows:

and (2) performing liquid chromatographic analysis on the standard solutions with different concentrations, testing each concentration point for 3 times, selecting a chromatographic peak capable of representing the main component of the demulsifier as a quantitative basis, and drawing a quantitative working curve according to the concentration of the standard solution and the corresponding chromatographic peak area.

Preferably, the liquid chromatography in step (2) is performed by using methanol and water as mobile phases and performing gradient elution.

More preferably, the conditions of the gradient elution are 0-1min, 50% methanol; 1.01min, 80% methanol; 1.01-6min, 80% methanol.

Preferably, in the step (2), the liquid chromatography is performed, and the detector is an evaporative light scattering detector.

More preferably, the evaporative light scattering detector temperature is 80 ℃ and the gas flow rate is 2.5L/min; the amount of sample was 20. mu.L.

Preferably, the detection wavelength of the liquid chromatography in step (2) is 245 nm.

More preferably, the concentration is performed by rotary evaporation.

Preferably, the filtration in step (3) is performed using qualitative filter paper.

Preferably, in the step (3), if the concentration of the demulsifier in the oilfield sewage sample is more than 5mg/L, the filtration is directly carried out, and the filtrate is taken for analysis.

More preferably, the sample with the concentration of the demulsifier above 5mg/L is a water sample obtained after demulsification of the oilfield produced fluid, and the filtration volume is 10 mL.

Preferably, in the step (3), if the concentration of the demulsifier in the oilfield sewage sample is less than 5mg/L, the oilfield sewage sample needs to be filtered, concentrated and then analyzed.

More preferably, the concentration process in step (3) is: filtering an oilfield sewage sample, taking filtrate, performing rotary evaporation and concentration, washing with methanol, transferring flushing fluid, evaporating a solvent, and performing constant volume of methanol for analysis.

More preferably, the sample with the concentration of the demulsifier less than 5mg/L is a water sample of oil field discharged wastewater, and the filtering volume is 500mL-1000mL, preferably 1000 mL. Evaporate to near dryness on a rotary evaporator, wash with 40mL methanol 4 times, place the filtrate in a 50mL chromatography flask, blow to about 1mL with a nitrogen blower, transfer to a 2mL chromatography flask, and hold the volume with methanol.

Preferably, the detection method further comprises mass spectrometric verification of the representation of the liquid chromatographic peak: taking 2mL of the treated oilfield sewage sample, performing liquid chromatography-mass spectrometry detection, and simultaneously taking 2mL of the demulsifier standard solution, and performing liquid chromatography-mass spectrometry detection. And comparing the number of chromatographic peaks in the total ion flow graph, and determining the molecular ion peak and the corresponding molecular weight at 2.9 min.

Verification of mass spectrum representative of liquid chromatography peaks: detection wavelength: 245nm, injection volume: 20 μ L, mass ESI positive mode detection. Comparing the mass spectrogram of the actual sample with the mass spectrogram of the standard sample, if the mass bar graph at 2.9min in the total ion flow graph conforms to the R + -58 n change rule, determining that the target peak represents the fatty alcohol type demulsifier, and tracking the target with the molecular ion peak 487 in the liquid chromatography.

The compound at the chromatographic peak retention time of 2.9min represents the main component of the fatty alcohol polyether demulsifier, the chromatographic peaks at other retention times are interference peaks, and the chromatographic peak area at the chromatographic peak retention time of 2.9min is taken as the basis of quantitative detection.

The invention has the beneficial effects that:

the invention relates to an improvement of an analysis method for high-efficiency separation capacity of a complex compound based on liquid chromatography. The chromatographic column is filled with aminopropyl bonded silica gel surface iodomethane quaternization modified filler, and the demulsifier has weaker adsorption capacity on the chromatographic column due to weak hydrophobic effect, so that the separation of the main components of the demulsifier can be realized; by optimizing the mobile phase and selecting methanol/water gradient elution, the interference of other surfactants, trace oil and polymers in the sewage is avoided; selection of the detector: evaporative Light Scattering Detectors (ELSDs) are general purpose detectors that can detect organic materials without uv absorption. The response of ELSD is independent of the optical characteristics of the sample, and any sample with volatility lower than that of the mobile phase can be detected without being influenced by the functional group. The ELSD response is proportional to the mass of the sample and can be used to determine the concentration of the sample or to detect an unknown.

The invention adopts liquid chromatography, the demulsifier has good linear relation in the range of 2-1000mg/L, and the correlation coefficient is 0.9988; the obtained detection result has good repeatability, accurate quantitative result, strong anti-interference capability and higher sensitivity, and the direct sample injection can still detect the demulsifier with the content of 1 mg/L. Experimental results show that the invention provides an excellent detection method for efficient and accurate analysis of the demulsifier in the produced liquid.

Drawings

FIG. 1 is a schematic diagram of the molecular structure of the chromatographic column packing of the present invention.

FIG. 2 is a liquid chromatogram of a standard solution of example 1.

FIG. 3 is a quantitative operating curve of example 1.

FIG. 4 is a liquid chromatogram of an oilfield wastewater sample of example 1.

FIG. 5 is a liquid chromatogram of the concentrated effluent sample from the oilfield of example 4.

FIG. 6 is a total ion flow diagram of the mass spectrum of the oil extraction wastewater sample of example 5.

FIG. 7 is a molecular ion peak mass spectrum of the demulsifier of example 5.

FIG. 8 is a mass spectrum of a standard sample of the demulsifier of example 5.

FIG. 9 is a graph showing the separation effect of the demulsifier after changing to the hydrophobic column in example 6.

Detailed Description

The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. These examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.

The apparatus used in each example: liquid chromatograph, agilent 7890A, usa.

Reagent: methanol, pure chromatography, beijing mai ruida technologies ltd;

the demulsifier is a nonionic polyether demulsifier SP169, and is prepared by mixing a demulsifier dry agent serving as a main agent and a small amount of auxiliary agent by Xinjiang Sanda New technology Limited company for water treatment. The polyether demulsifier SP169 dry agent is a light yellow viscous liquid, has a hydroxyl value of less than or equal to 56, a freezing point of 30-50 ℃, a pH value of 1% aqueous solution of 9-11 and a chroma of less than or equal to 350, and is produced by Dongze chemical technology Co., Ltd.

Example 1

(1) Preparing a standard solution: preparing a demulsifier standard solution with the concentration of 1000mg/L by using distilled water; diluting the standard solution as mother solution into standard solutions with different concentrations of 2, 10, 20, 50, 100 and 500mg/L respectively;

(2) quantitative analysis: and respectively taking standard solutions with different concentrations to perform liquid chromatography analysis, testing each concentration point for 3 times, and displaying a partial liquid chromatogram as shown in figure 2, wherein a chromatographic peak of the demulsifier is a chromatographic peak at 2.9 min. In the 4 chromatographic curves in FIG. 2, the concentrations of the demulsifiers from top to bottom were 20mg/L, 10mg/L, 2mg/L, and 0mg/L, respectively. As can be seen from FIG. 2, the peak profile of the target compound is good and is not interfered by other additives in the demulsifier, thus providing a theoretical basis for accurate quantitative determination.

Drawing a quantitative working curve according to the concentration of the standard solution and the corresponding chromatographic peak area, which is specifically shown in FIG. 3; according to the relation between the peak area and the concentration of the demulsifier, performing linear regression by using a least square method, wherein the quantitative working curve of the demulsifier standard solution is as follows: Y1.613X +1.81, linear range: 2-1000mg/L, correlation coefficient: 0.9988, accurate quantitative determination lower limit of 5 mg/L. Therefore, the correlation coefficient of the quantitative regression equation of the demulsifier standard solution is good, and the demulsifier standard solution has an excellent linear relation in a wide concentration range.

The liquid chromatographic analysis conditions were: the chromatographic column is SAX ionic chromatographic column; the mobile phase is methanol and water, and is subjected to gradient elution for 0-1min, 50% methanol, 1.01min, 80% methanol, 1.01-6min and 80% methanol; the detector is an evaporative light scattering detector, the temperature is 80 ℃, and the gas flow rate is 2.5L/min; the amount of sample was 20. mu.L.

The preparation process of the chromatographic column packing comprises the following steps:

taking 50g of full-porous spherical silica gel (particle size is 1-10 μm, specific surface area is 40-500 m)²Per g, pore diameterPurity 99.99%), soaking in concentrated hydrochloric acid, ultrasonically dispersing for 30min, and standing for 24 h; and (3) leaching the silica gel with a proper amount of deionized water until no chloride ions can be detected in the leaching solution, and drying the purified silica gel in an oven at 140 ℃ for 4h to obtain the activated silica gel.

10g of activated silica gel is taken and dried for 15h under vacuum at 120 ℃ to remove trace water in the micropores of the silica gel. The silica gel after vacuum drying was placed in a flask equipped with a condenser, 100mL of dry toluene and 15mL of KH-560 silane coupling agent were added, refluxed for 12 hours, and the supernatant was decanted. 100mL of dry toluene and 30mL of triethoxyaminopropylsilane were added and heated under reflux for 6 hours. Standing, pouring out supernatant, leaching for 3 times by using toluene, ethanol and acetone in sequence, and drying for 2 hours in vacuum at 50 ℃ to obtain the aminopropyl bonded silica gel with hydrophobic functional groups on the surface of the silica gel.

8g of aminopropyl-bonded silica gel was placed in a flask, 100mL of toluene and 25mL of methyl iodide were added, and the mixture was heated under reflux for 2 hours. And leaching the mixture by using toluene, ethanol and acetone for 3 times in sequence, and drying the solid phase in a vacuum drying oven at 60 ℃ for 4 hours to obtain the ionic liquid chromatographic column filler for separating the anionic compound. The molecular structure of the chromatographic column packing is schematically shown in figure 1.

(3) Sample detection: taking 10mL of No. 1 water sample of the oil field thin oil sewage treatment station, filtering by using quick filter paper, taking 2mL of filtrate, and carrying out sample injection analysis; and simultaneously diluting by 5 times, carrying out sample injection analysis to obtain 2 chromatographic curves, wherein the liquid chromatogram of the oilfield sewage sample is shown in figure 4. In fig. 4, the chromatographic peak at retention time 2.95min is the chromatographic peak of the fatty alcohol-type demulsifier. And (3) substituting the target chromatographic peak area into the quantitative working curve in the step (2) to obtain a detected concentration result, and further calculating to obtain a content result of the demulsifier in the oil field water sample, wherein the test result is shown in table 1.

TABLE 1 actual sample test results

Sample (I)	Concentration (mg/L)	Actual content (mg/L)
			Oil field water 1#	35.0	35.0
Oilfield water 1# (Dilute 5 times)	6.7	33.5

Example 2

10mL of No. 2 oilfield drainage sample was obtained, and the procedure was the same as in example 1 except that the sample to be tested was different from that in example 1. The test results are shown in Table 2. Because the demulsifier concentration was low in the sample # 2, no demulsifier could be detected without the concentration method.

TABLE 2 actual sample test results

Sample (I)	Concentration (mg/L)	Actual content (mg/L)
			Oil field water 2#	-	-

Note: -indicates no detection.

Example 3

10mL of No. 3 water sample of the oil field thick oil sewage treatment station is taken, and the steps are the same as those in the embodiment 1 except that the sample to be detected is different from that in the embodiment 1. The test results are shown in Table 3.

TABLE 3 actual sample test results

Sample (I)	Concentration (mg/L)	Actual content (mg/L)
			Oil field water 3#	55.6	55.6
Oilfield water 3# (dilution 5 times)	11.4	57.0

Example 4

1000mL of No. 4 drainage sample from the oil field is taken, filtered by using quick filter paper to remove a small amount of impurities, and evaporated to be nearly dry on a rotary evaporator. Washing the evaporation bottle with 40mL of methanol for 4 times, wherein a small amount of viscous substance adhered to the wall of the evaporation bottle is not washed as much as possible during washing, transferring the washing solution into a 50mL chromatographic bottle, blowing the solution to about 1mL by using a nitrogen blowing instrument, transferring the solution into a 2mL chromatographic bottle, metering the volume to 2mL by using methanol, and performing sample injection detection. Meanwhile, three different produced waters, namely polymer flooding produced water, thin oil produced water and thick oil produced water are used as blanks respectively, and detection samples are prepared by the same concentration method. In the three produced water, the polymer in the polymer flooding produced water is mainly polyacrylamide injected in polymer flooding development, the concentration of the polyacrylamide is 100mg/L-400mg/L, and the polymer in the polymer flooding produced water is insoluble in methanol; mineral substances of thin oil produced water are mainly inorganic salts in formation water of an oil field, the mineralization degree is about 10000mg/L, and the mineralization degree of thick oil produced water is about 7000 mg/L. The quantitative analysis steps are the same as those of the example 1, the liquid chromatogram of the concentrated 4# sample of the oilfield external drainage is shown in the figure 5, and the concentration test result of the demulsifier is shown in the table 4.

TABLE 4 actual sample test results

Sample (I)	Concentration (mg/L)	Actual content (mg/L)
			Oil field water 4#	45.0	0.045

Example 5

Taking a sample of No. 5 oil extraction wastewater treatment station for three times in an oil field, and carrying out liquid chromatography-mass spectrometry detection under the gradient elution condition optimized in the embodiment 1. Detection wavelength: 245nm, injection volume: 20 μ L, gave a chromatographic peak similar to the ELSD assay of example 1. The molecular ion peak under the positive mode is a compound of different series of homologues; the first chromatographic peak at 2.9min had a molecular weight of 487 and was a homolog of the propylene oxide block demulsifier (R)₁58n) of the molecular ion and the mass spectrum of the standard substance are highly matched, and the first chromatographic peak (the retention time is 2.9 min) is proved to represent the chromatographic peak of the quantitative substance demulsifier. The molecular weight of the second chromatographic peak at 3.65min is 516, and the second chromatographic peak is a fatty alcohol demulsifier homologue with different carbon numbers: r₂±58n，542：R₃±58n， 571：R₄Homologues of ± 58 n. The first chromatographic peak is eluted at about 2.9min, and the second chromatographic peak is eluted after being delayed to about 3.65min, so that interference of an interfering substance on the first chromatographic peak (target substance) can be avoided, and quantitative detection of the first chromatographic peak can be realized. In this example, the total ion flow diagram, the molecular ion peak mass spectrum of the demulsifier, and the mass spectrum of the standard sample are shown in fig. 6, fig. 7, and fig. 8, respectively.

Example 6

Taking 2mL of 100mg/L standard sample, and carrying out liquid chromatography detection. For comparison with examples 1-5, the procedure was the same as in example 1 except that the liquid chromatography column was replaced with a weakly hydrophobic column and the mobile phase gradient was changed. The weak hydrophobic chromatographic column filler is a material which is modified on the surface of silica gel by a silane reagent through Si-O-Si-C bonding, namely a Diol type chromatographic filler.

Fluidity phase: a, water; b, acetonitrile; gradient: 1, 1 min: 70% B, 1.01min, 100% B. The results are shown in FIG. 9. As can be seen from FIG. 9, the separation degree of the chromatographic peak of the demulsifier is poor, the accurate quantitative integration cannot be realized, and the weak hydrophobic column is not suitable for the separation and detection of complex demulsifier samples.

Test example

Recovery rate experiment

Three SP169 demulsifier samples with known concentration were added to the oilfield water, and filtered to remove impurities, and 2mL of the filtrate was sampled and subjected to chromatography measurement in parallel three times, which was performed in the same manner as in example 1 (undiluted direct sample measurement), and the results are shown in Table 5. From the experimental results of three high, medium and low concentration groups, the recovery rate of the medium concentration group can reach 100%, and the recovery rates of the low and high concentration groups are also very high and close to 100%, which are all in an ideal range, thus the method has good stability and reproducibility.

TABLE 5 recovery test results

Precision experiment

The day and day precision of the SP169 demulsifier samples at both concentrations were determined by the same apparatus and the same tester under the chromatographic conditions of example 1 (table 6). As can be seen from the data in table 6, the daily RSD (n ═ 5) is in the range of 3.30 to 4.47%, and the daily RSD (n ═ 3) can be controlled to be 7.0% or less, indicating that the accuracy of the detection method of the present invention is good.

TABLE 6 determination of precision

Precision degree	10mg/L	20mg/L
			In-day RSD% (n is 5)	4.74	3.30
Day RSD% (n is 3)	6.77	5.52

The above detailed description is specific to one possible embodiment of the present invention, and the embodiment is not intended to limit the scope of the present invention, and all equivalent implementations or modifications without departing from the scope of the present invention should be included in the technical scope of the present invention.