A C 0 ~C 2 -Characterization method and application of alkyl substituted phenols

Abstract

The present invention discloses a characterization method and application of C0-C2-alkyl-substituted phenols, relating to the technical field of environmental detection. The method includes: selecting a corresponding sample pretreatment process to prepare a test sample according to the petroleum content range in the sample; detecting the test sample by LC-MS under a mobile phase system of methanol-5.0-6.5 mmol / L ammonia water to obtain the concentration of the first component and the normalized concentrations of co-eluted 3,5-dimethylphenol and 2,6-dimethylphenol; detecting the test sample by LC-MS under a mobile phase system of methanol-7.0-11.5 mmol / L ammonia water to obtain the concentration of 3,5-dimethylphenol; detecting calibration samples of 3,5-dimethylphenol and 2,6-dimethylphenol respectively by LC-MS under a mobile phase system of methanol-5.0-6.5 mmol / L ammonia water, calculating a conversion factor, and obtaining the concentration of 2,6-dimethylphenol; and obtaining the contents of 13 single components of C0-C2-alkyl-substituted phenols based on the concentrations of the first component, 3,5-dimethylphenol and 2,6-dimethylphenol. The present invention realizes the quantitative characterization of 13 single components of C0-C2-alkyl-substituted phenols.

Description

Technical Field

[0001] The invention relates to the technical field of environmental detection, and in particular to a characterization method and application of C0-C2-alkyl substituted phenol. Background Art

[0002] The stripping water discharged from the sulfur-containing and salt-containing wastewater stripping device is oily wastewater and is the main process wastewater in oil refineries. The unit discharge volume reaches 0.2m 3 / t crude oil, volatile phenol is the main contributing component of COD (chemical oxygen demand) of this type of wastewater (Yan Song, Li Lingbo, Han Congbi, Zhou Yanhong. Study on organic components of high-sulfur and high-acid crude oil wastewater [J]. Contemporary Chemical Industry, 2015, 44(09): 2081-2083), with a content as high as 0.2-0.5 kg / m 3 The volatile phenols in stripping water come from crude oil and crude oil processing, and mainly include phenol (C0-alkyl substituted phenol), methylphenol (C1-alkyl substituted phenol), dimethyl / ethylphenol (C2-alkyl substituted phenol) and trimethyl / methylethyl / n-propyl / isopropylphenol (C3-alkyl substituted phenol).

[0003] Volatile phenol components contain many isomers. When using chromatography-mass spectrometry technology for quantification, it is necessary to achieve chromatographic separation of isomers. However, chromatographic separation of isomers has always been a technical difficulty in this field. In terms of gas chromatography, GC-FID or GC-MS methods are used to determine volatile phenolic components, which have been applied to the quantitative characterization of some components in C0~C2-alkyl substituted phenols in different sample matrices (Sun Ce, Jiang Yuanbo, Li Yanhong, et al. Analysis of phenolic compounds in coal liquefaction oil by heart-cutting GC-MS [J]. Chemical Bulletin, 2014, 77(09): 888-893; Song Lingyong, Zhao Qi, Huang Shijie, et al. Simultaneous determination of 15 phenolic components in mainstream cigarette smoke by gas chromatography-mass spectrometry [J]. Physical and Chemical Testing (Chemical Section), 2020, 56(10): 1085-1090; C.Barnaba, E.Dellacassa, G.Nicolini, et al. Identification and quantification of 56targeted phenols in wines, spirits, and vinegars by onlinesolid-phase extraction-ultrahigh-performance liquid chromatography-quadrupole-orbitrap mass spectrometry [J]. Journal of Physical and Chemical Testing (Chemical Section), 2020, 56(10): 1085-1090; C.Barnaba, E.Dellacassa, G.Nicolini, et al. Identification and quantification of 56targeted phenols in wines, spirits, and vinegars by onlinesolid-phase extraction-ultrahigh-performance liquid chromatography-quadrupole-orbitrap mass spectrometry, Journal of Chromatography A, 2015, 1423: 124-135); in the detection methods of C0~C2-alkyl substituted phenols based on liquid chromatography separation, methods that only test a small part of the components are occasionally seen (Y. S. Fung, Y. H. Long, Determination of phenols in soil by supercritical fluid extraction-capillary electrochromatography, Journal of Chromatography A, 2001, 907(1–2): 301-311; Liu Guihua, Su Feng, Li Wei, et al. Determination of the migration amount of 9 phenolic substances in food contact materials and products by high performance liquid chromatography [J]. Journal of Analysis and Testing, 2021, 40(11): 1619-1626), and there are few reports on the simultaneous detection of 13 C0~C2-alkyl substituted phenol single components.

[0004] The existing technology for quantitative characterization of C0~C2-alkyl substituted phenol isomers, whether using gas chromatography separation or liquid chromatography separation technology, still has not completely solved the problem of accurate quantification of single components of chromatographic co-eluting isomers when simultaneously detecting 13 C0~C2-alkyl substituted phenols. Summary of the invention

[0005] The present invention aims to provide a method for characterizing C0-C2-alkyl substituted phenol and its application, which adopts LC-MS detection technology, based on the characterization of each isomer in the same reverse C 18 The elution order and chromatographic co-elution in the liquid chromatography column have changed, a calculation method for the single component content of chromatographic co-elution isomers has been established, and the quantitative characterization of 13 C0-C2-alkyl substituted phenol single components has been achieved. The present invention is applicable to the quantitative characterization of 13 C0-C2-alkyl substituted phenol single components in drinking water, surface water and groundwater, and oil-containing solid waste. To achieve the above purpose, the present invention provides the following technical solutions:

[0006] In one aspect, the present invention provides a method for characterizing a C0-C2-alkyl substituted phenol, the method comprising the following steps:

[0007] According to the petroleum content range in the sample, select the corresponding sample pretreatment process to prepare the sample;

[0008] The sample is detected by LC-MS in a methanol-5.0-6.5 mmol / L ammonia water mobile phase system to obtain the concentration of the first component and the standardized concentrations of the co-eluted 3,5-dimethylphenol and 2,6-dimethylphenol;

[0009] The sample was detected by LC-MS in a methanol-7.0-11.5 mmol / L ammonia water mobile phase system to obtain the concentration of 3,5-dimethylphenol;

[0010] In the mobile phase system of methanol-5.0~6.5mmol / L ammonia water, 3,5-dimethylphenol and 2,6-dimethylphenol calibration samples were detected by LC-MS, and the conversion factor was calculated to obtain the concentration of 2,6-dimethylphenol.

[0011] Based on the concentration of the first component, the concentration of 3,5-dimethylphenol and the concentration of 2,6-dimethylphenol, the contents of 13 C0-C2-alkyl-substituted phenol single components in the sample were obtained.

[0012] Furthermore, the first component comprises:

[0013] Phenol, 2-methylphenol, 3-methylphenol, 4-methylphenol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol, 2-ethylphenol, 3-ethylphenol and 4-ethylphenol.

[0014] Furthermore, the sample preparation process of selecting a corresponding sample pretreatment process according to the petroleum content range in the sample includes:

[0015] If the petroleum content in the sample does not exceed 50 mg / L, the sample is filtered through a 0.22 μm filter membrane before sampling.

[0016] If the petroleum content in the sample exceeds 50 mg / L, the sample is alkalized with NaOH and extracted with dichloromethane-n-hexane, and the organic phase is separated by centrifugation. The aqueous phase is filtered through a 0.22 μm filter membrane, and then neutralized with formic acid before sampling and testing.

[0017] Furthermore, the elution conditions of the methanol-5.0-6.5 mmol / L ammonia water mobile phase system include:

[0018] The column flow rate was 0.20 mL / min;

[0019] Gradient elution is as follows: the initial volume ratio of methanol is 10% to 25%, zero gradient elution is maintained for 1 to 10 minutes, and then the volume ratio of methanol is increased to 40% in an isocratic manner within 30 minutes, and the volume ratio of methanol is maintained at 40% until all components flow out;

[0020] The column temperature is 35-40°C.

[0021] Furthermore, the elution conditions of the methanol-7.0-11.5 mmol / L ammonia water mobile phase system include:

[0022] The column flow rate was 0.20 mL / min;

[0023] Gradient elution is as follows: the initial volume ratio of methanol is 10% to 25%, zero gradient elution is maintained for 1 to 10 minutes, and then the volume ratio of methanol is increased to 40% in an isocratic manner within 30 minutes, and the volume ratio of methanol is maintained at 40% until all components flow out;

[0024] The column temperature is 35-40°C.

[0025] Furthermore, the calculation formula for the concentration of 2,6-dimethylphenol is:

[0026] c' 2,s =(m+1)·c' STD,s -m·c' 1,s ;

[0027] Where c' 2,s represents the concentration of 2,6-dimethylphenol; m represents the conversion factor; c' STD,s represents the normalized concentration of co-eluted 3,5-dimethylphenol and 2,6-dimethylphenol; c' 1,sIndicates the concentration of 3,5-dimethylphenol.

[0028] On the other hand, the present invention also provides an application of a method for characterizing C0-C2-alkyl substituted phenols, which is applied to the analysis of volatile phenol components in stripping water.

[0029] Furthermore, the resolution rate of the volatile phenol (in terms of phenol) index reaches more than 92.7%.

[0030] Technical effects and advantages of the present invention:

[0031] First, the quantitative characterization of 13 C0-C2-alkyl-substituted phenol single components was achieved.

[0032] Second, the water samples are not enriched or derivatized, and the detection limit of the method for 13 C0-C2-alkyl substituted phenols is 0.3-1.0 μg / L. Compared with the standard HJ744-2015 (derivation-GC-MS method) for testing phenolic compounds, the sensitivity of this method is 1-2 orders of magnitude higher.

[0033] Third, it is applied to the characterization of the main components of volatile phenols in stripping water, and the resolution rate of the volatile phenol (measured in phenol) index reaches more than 92.7%, realizing the accurate analysis of volatile phenol components in stripping water.

[0034] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of a method for characterizing C0-C2-alkyl substituted phenol of the present invention;

[0036] Figure 2 [MH] is the chromatographic separation of 9 C2-alkyl substituted phenol isomers under 3 different elution conditions in the present invention. - Extracted ion map;

[0037] Figure 3 [MH] is the chromatographic separation of 9 C2-alkyl substituted phenol isomers when the ammonia concentration is 4.0 to 11.5 mmol / L in the embodiment of the present invention. - Extracted ion map;

[0038] Figure 4 13 kinds of C0~C2-alkyl substituted phenols [MH] in the methanol-6.0mmol / L ammonia mobile phase system in the present invention - Extracted ion map of

[0039] Figure 5 The [MH] of 13 C0-C2-alkyl substituted phenols in the methanol-11.5 mmol / L ammonia mobile phase system according to the present invention is shown in FIG. - Extracted ion map. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] In order to solve the deficiencies of the prior art, the present invention discloses a method for characterizing C0-C2-alkyl substituted phenols. Figure 1 is a flow chart of a method for characterizing a C0-C2-alkyl substituted phenol of the present invention, such as Figure 1 As shown, the method comprises the following steps:

[0042] According to the petroleum content range in the sample, select the corresponding sample pretreatment process to prepare the sample;

[0043] The sample is detected by LC-MS in a methanol-5.0-6.5 mmol / L ammonia water mobile phase system to obtain the concentration of the first component and the standardized concentrations of the co-eluted 3,5-dimethylphenol and 2,6-dimethylphenol;

[0044] The sample was detected by LC-MS in a methanol-7.0-11.5 mmol / L ammonia water mobile phase system to obtain the concentration of 3,5-dimethylphenol;

[0045] In the mobile phase system of methanol-5.0~6.5mmol / L ammonia water, 3,5-dimethylphenol and 2,6-dimethylphenol calibration samples were detected by LC-MS, and the conversion factor was calculated to obtain the concentration of 2,6-dimethylphenol.

[0046] Based on the concentration of the first component, the concentration of 3,5-dimethylphenol and the concentration of 2,6-dimethylphenol, the contents of 13 C0-C2-alkyl-substituted phenol single components in the sample were obtained.

[0047] Preferably, the first component comprises:

[0048] Phenol, 2-methylphenol, 3-methylphenol, 4-methylphenol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol, 2-ethylphenol, 3-ethylphenol and 4-ethylphenol.

[0049] The specific steps of the characterization method of the present invention are as follows:

[0050] Step S1: According to the petroleum content range in the oily wastewater sample, select the corresponding sample pretreatment process to prepare the sample.

[0051] When the petroleum in the sample does not exceed 50 mg / L, the sample is filtered through a 0.22 μm filter membrane and then injected for testing;

[0052] When the petroleum in the sample exceeds 50 mg / L, the sample is alkalized with NaOH, extracted with dichloromethane and n-hexane, and the organic phase is separated by centrifugation. The aqueous phase is filtered through a 0.22 μm filter membrane and then neutralized with formic acid before sampling and testing.

[0053] Step S2: LC-MS is performed to detect the sample under a methanol-5.0-6.5 mmol / L ammonia water mobile phase system to obtain the concentrations of 11 components in the sample, including phenol, 2-methylphenol, 3-methylphenol, 4-methylphenol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol, 2-ethylphenol, 3-ethylphenol and 4-ethylphenol, as well as the standardized concentrations of co-eluted 2,6-dimethylphenol and 3,5-dimethylphenol.

[0054] In step S2 of the present invention, the elution conditions of the methanol-5.0-6.5mmol / L ammonia water mobile phase system include: a chromatographic column flow rate of 0.20mL / min; gradient elution: the initial volume ratio of methanol is 10%-25%, maintaining zero gradient elution for 1-10min, and then increasing the volume ratio of methanol to 40% in an isocratic manner within 30min, maintaining the volume ratio of methanol at 40% until all components flow out.

[0055] Preferably, the elution conditions include: a chromatographic column flow rate of 0.20 mL / min; a gradient elution of: 0-1 min, 20% methanol; 1-31 min, 20%-40% methanol; 31-32 min, 40% methanol; 32-32.1 min, 40%-90% methanol; 32.1-37 min, 90% methanol; 37-37.1 min, 90%-20% methanol; 37.1-42 min, 20% methanol; and a chromatographic column temperature of 35-40°C; preferably 40°C.

[0056] Step S3: LC-MS is performed to detect the sample in a methanol-7.0-11.5 mmol / L ammonia water mobile phase system to obtain the concentration of 3,5-dimethylphenol in the sample.

[0057] In step S3 of the present invention, the elution conditions of the methanol-7.0-11.5 mmol / L ammonia water mobile phase system include: a mobile phase flow rate of 0.20 mL / min; gradient elution: an initial volume ratio of methanol of 10%-25%, maintaining zero gradient elution for 1-10 min, and then increasing the proportion of methanol to 40% isogradiently within 30 min, and maintaining the proportion of methanol at 40% until all components flow out.

[0058] Preferably, the elution conditions include: a chromatographic column flow rate of 0.20 mL / min; a gradient elution of: 0-1 min, 20% methanol; 1-31 min, 20%-40% methanol; 31-32 min, 40% methanol; 32-32.1 min, 40%-90% methanol; 32.1-37 min, 90% methanol; 37-37.1 min, 90%-20% methanol; 37.1-42 min, 20% methanol; and a chromatographic column temperature of 35-40°C, preferably 40°C.

[0059] Step S4: performing LC-MS detection on calibration samples of 2,6-dimethylphenol and 3,5-dimethylphenol respectively in a methanol-5.0-6.5 mmol / L ammonia water mobile phase system, calculating the conversion factor of 2,6-dimethylphenol to 3,5-dimethylphenol, and obtaining the concentration of 2,6-dimethylphenol.

[0060] The LC-MS detection conditions of step S4 of the present invention are consistent with the LC-MS detection conditions of step S2.

[0061] As described in step S4 above, after long-term repeated testing, if the conversion factor m value remains unchanged, the previous m value can be used to calculate the concentration of 2,6-dimethylphenol.

[0062] Step S5: Calculate the contents of 13 C0-C2-alkyl-substituted phenol single components in the sample.

[0063] Step S5 of the present invention comprises the following steps:

[0064] Step S51: Calculate the concentration of 2,6-dimethylphenol in the sample according to formula (11).

[0065] c 2,s =(m+1)·c STD,s -m·c 1,s ; (11)

[0066] In the formula, c 2,srepresents the concentration of 2,6-dimethylphenol; m represents the conversion factor; c STD,s represents the normalized concentration of co-eluted 3,5-dimethylphenol and 2,6-dimethylphenol; c 1,s Indicates the concentration of 3,5-dimethylphenol.

[0067] Step S52: Calculate the content of each component in the sample based on the sample amount, sample volume, dilution factor, etc., and the concentration value of each component in the sample.

[0068] It should be noted that the test order of the above step S2, step S3 and step S4 of the present invention can be arbitrarily changed.

[0069] Based on the above method, on the other hand, the present invention also provides an application of a method for characterizing C0~C2-alkyl substituted phenol, which is mainly used for the analysis of volatile phenol components in stripping water, and the analysis rate of the volatile phenol (calculated as phenol) index reaches more than 92.7%.

[0070] The following is a detailed description of the method and application of characterizing 13 C0-C2-alkyl substituted phenols using the method of the present invention through specific examples in conjunction with the accompanying drawings.

[0071] Example 1

[0072] This example provides two sample pretreatment methods for LC-MS injection testing.

[0073] 1. Oily wastewater with petroleum content ≤50mg / L

[0074] The water sample was filtered through a 0.22 μm filter membrane. Depending on the volatile phenol content, 10 μL to 500 μL of the filtrate was taken to prepare the test sample.

[0075] This process is not only applicable to stripping water samples, but also to the preparation of cleaner water samples such as drinking water, groundwater and surface water.

[0076] 2. Oily wastewater with petroleum content > 50mg / L

[0077] Take 10.00mL of water sample in a 20mL round-bottom screw-mouth sample bottle (with a sample cap of polytetrafluoroethylene liner), add the substitute, add 100μL of 2.5mol / L NaOH to adjust the pH ≥ 12, add 1-3mL of dichloromethane-n-hexane (2+1) mixed solvent, and tighten the cap. Shake for 30 minutes and centrifuge. Take the aqueous phase and add formic acid to neutralize it, pass the aqueous phase through a 0.22μm filter membrane, and take 10μL-500μL of the filtrate to prepare the sample according to the volatile phenol content.

[0078] It should be noted that this process can still be used to prepare samples for oily wastewater with petroleum content ≤50mg / L.

[0079] Example 2

[0080] This example is to optimize the chromatographic elution conditions of 9 C2-alkyl substituted phenols.

[0081] The chromatographic mobile phase used was methanol-ammonia system, and the ACQUITY UPLC BEH C 18 Chromatographic column (1.7μm, 2.1mm×150mm). Under the initial conditions of 10% methanol mobile phase volume ratio, 6.0mmol / L ammonia concentration and 40℃ column temperature, the four C0~C1-alkyl substituted phenols can be well chromatographically separated, so the chromatographic separation effect of the mobile phase elution conditions on C2-alkyl substituted phenols was investigated.

[0082] The results showed that when the initial volume ratio of methanol was 10%, maintaining zero gradient elution for 1, 5 and 10 min respectively and then eluting with the same gradient did not improve the chromatographic separation of 9 C2-alkyl substituted phenols much. Therefore, it was sufficient to maintain the initial ratio of the mobile phase for 1 min.

[0083] The initial volume proportion of methanol in the mobile phase was set to 10%, 20% and 25%, respectively, and zero gradient elution was maintained for 1 min. The volume proportion of methanol was then increased to 40% isocratically within 30 min, and the volume proportion of methanol was maintained at 40% until all components were eluted. Figure 2 [MH] is the chromatographic separation of 9 C2-alkyl substituted phenol isomers under 3 different elution conditions in the present invention. - Extracted ion map, where Figure 2 The specific elution conditions of A include: 0-1min, 10% methanol; 1-31min, 10%-40% methanol; 31-35min, 40% methanol; the specific elution conditions of B include: 0-1min, 20% methanol; 1-31min, 20%-40% methanol; 31-35min, 40% methanol; the specific elution conditions of C include: 0-1min, 25% methanol; 1-31min, 25%-40% methanol; 31-35min, 40% methanol. Figure 2 As shown in the figure, under these three different elution conditions, the nine C2-alkyl substituted phenols all present a set of eight continuous chromatographic peaks that can be integrated. When the initial volume ratio of the methanol mobile phase is 10%, the separation of the first eluted components is relatively poor, while the separation of the later eluted components is relatively good; when the initial volume ratio of the methanol mobile phase is 25%, the separation of the first eluted components is relatively good, while the separation of the later eluted components is relatively poor, so the elution condition with an initial volume ratio of methanol of 20% is selected.

[0084] The effects of column temperatures of 30, 35, 40 and 45°C on the chromatographic separation of C2-alkyl substituted phenols were further compared. The chromatographic separation of C2-alkyl substituted phenols deteriorated at column temperatures of 30 and 45°C, and better chromatographic separation was obtained at column temperatures of 35 and 40°C. When the column temperature was 40°C, the column pressure decreased by about 4-5 MPa and the analysis process was shortened by about 1.5 min. Therefore, the preferred column temperature was 40°C.

[0085] Example 3

[0086] This example investigates the effect of ammonia mobile phase concentration in the range of 4.0 to 11.5 mmol / L on the chromatographic separation of C2-alkyl substituted phenols.

[0087] ACQUITY UPLC BEH C 18 Chromatographic column (1.7 μm, 2.1 mm×150 mm). Figure 3 [MH] is the chromatographic separation of 9 C2-alkyl substituted phenol isomers when the ammonia concentration is 4.0 to 11.5 mmol / L in the embodiment of the present invention. - Extracted ion map, where Figure 3 A corresponds to an ammonia concentration of 4.0mmol / L, B is 5.0mmol / L, C is 6.0mmol / L, D is 7.0mmol / L, E is 8.0mmol / L, and F is 11.5mmol / L; the corresponding chromatographic peaks are: 1, 3,4-dimethylphenol; 2, 3-ethylphenol; 3, 3,5-dimethylphenol; 4, 2,6-dimethylphenol; 5, 2,3-dimethylphenol; 6, 4-ethylphenol; 7, 2,5-dimethylphenol; 8, 2-ethylphenol; 9, 2,4-dimethylphenol. Figure 3 As shown, 7 peaks were separated from 9 C2-alkyl substituted phenols when the ammonia concentration was 4.0mmol / L; 8 peaks were separated when the ammonia concentration was 5.0-6.0mmol / L, and the peak shape was better; 8 peaks were also separated when the ammonia concentration was 7.0mmol / L, but at the same time, a slowly rising step and an upward inflection point were observed when the 4th peak began to elute, which was an obvious feature of the co-elution of components; only 7 peaks were separated when the ammonia concentration was 8.0mmol / L, and when the ammonia concentration was further increased to 11.5mmol / L, only 6 peaks could be separated.

[0088] The retention time and elution order of C2-alkyl substituted phenols at different ammonia concentrations were confirmed by a single calibration method, and the co-elution between components was determined. Figure 3As shown in the figure, when the ammonia concentration is 5.0-6.0mmol / L, only 3,5-dimethylphenol and 2,6-dimethylphenol co-elute; when the ammonia concentration is 7.0-11.5mmol / L, 3,5-dimethylphenol is eluted alone, while 2,6-dimethylphenol co-elutes with other components. This provides a basis for the quantification of the co-eluting C2-alkyl substituted phenol single component.

[0089] Further experiments showed that when the column temperature was 35 and 40°C and the ammonia concentration was 5.0-6.5 mmol / L, 9 C2-alkyl substituted phenols were separated into 8 peaks with excellent peak shapes and only 3,5-dimethylphenol and 2,6-dimethylphenol co-eluted.

[0090] In summary, the problem of quantitative characterization of single components of chromatographic co-eluting isomers can be solved by testing samples separately under two different mobile phase systems. That is, the standardized concentrations of co-eluting 3,5-dimethylphenol and 2,6-dimethylphenol are measured under the mobile phase system of methanol-5.0-6.5mmol / L ammonia, and then the concentration of 3,5-dimethylphenol is measured under the mobile phase system of methanol-7.0-11.5mmol / L ammonia, so as to calculate the concentration of 2,6-dimethylphenol.

[0091] Example 4

[0092] This embodiment provides a method for calculating the single component content of co-eluting isomers from two chromatograms.

[0093] In the same mobile phase system, two isomers, component 1 and component 2, are co-eluted. The linear calibration relationships of component 1, component 2 and the mixed co-eluting components are established, as shown in formulas (1) to (3):

[0094] A1=k1·c1 (1)

[0095] A2=k2·c2 (2)

[0096] A=k·c STD (3)

[0097] Where A, A1 and A2 are the response values ​​of the co-eluting component, component 1 and component 2, k, k1 and k2 are the calibration coefficients of the co-eluting component, component 1 and component 2, c1 and c2 are the concentrations of component 1 and component 2, c STD Defined as the normalized concentration of the coeluting components.

[0098] The responses of the coeluting components are simply additive, with:

[0099] A=A1+A2 (4)

[0100] k.c STD=k1·c1+k2·c2 (5)

[0101] When the prepared concentrations of the co-eluting components at each calibration point are equal (i.e., c1 = c2), and c STD =c1=c2, then:

[0102] k=k1+k2 (6)

[0103] For components 1 and 2 in the sample,

[0104] A s =A 1,s +A 2,s (7)

[0105] k.c STD,s =k1·c 1,s +k2·c 2,s (8)

[0106]

[0107] In the formula, A s , A 1,s and A 2,s is the response value of the co-eluting component, component 1 and component 2 in the sample, c STD,s 、c 1,s and c 2,s is the standardized concentration of the co-eluting components in the sample, the concentration of component 1 and component 2.

[0108] Assume m = k1 / k2, where m is defined as the conversion factor of component 1 to component 2,

[0109]

[0110] c 2,s =(m+1)·c STD,s -m·c 1,s (11)

[0111] Under the same experimental conditions, the m value remains unchanged within the linear calibration range; the m value can be obtained by testing two co-eluting single-component calibration sample series or the intermediate concentration point of the calibration sample sequence in the first mobile phase system. STD,s , the sample was tested in another mobile phase system to obtain c 1,s According to formula (11), c 2,s .

[0112] Example 5

[0113] This embodiment provides a method for quantitatively characterizing 13 C0-C2-alkyl substituted phenol single components in stripping water using ultra-performance liquid chromatography-orbitrap high-resolution mass spectrometry (UPLC-Orbitrap HRMS).

[0114] 1. Test samples

[0115] The stripping water samples were collected in 40mL VOA sample bottles with polytetrafluoroethylene liners. No headspace and no protective agent were required during sampling. The samples were refrigerated at 4-6℃ and the sample preparation was completed within 24 hours. The composition of the stripping water samples for testing was complex, and the petroleum was ≤50mg / L.

[0116] 2. Instrument conditions

[0117] UPLC-Orbitrap HRMS: Vanquish C-H10 ultra-high performance liquid chromatograph, Q-Exactive Plus electrostatic field orbitrap high-resolution mass spectrometer. Chromatographic column: ACQUITY UPLC BEH C 18 Chromatographic column (1.7 μm, 2.1 mm×150 mm).

[0118] (1) Liquid chromatography conditions

[0119] Method 1: Mobile phase system: methanol-6.0mmol / L ammonia water. Column temperature: 40℃; Flow rate: 0.20mL / min. Sample chamber temperature: 6℃; Injection volume: 2μL. Gradient elution: 0-1min, 20% methanol; 1-31min, 20%-40% methanol; 31-32min, 40% methanol; 32-32.1min, 40%-20% methanol; 32.1-37min, 20% methanol.

[0120] Method 2: Mobile phase system: methanol-11.5mmol / L ammonia water, other conditions and parameters are the same as method 1.

[0121] (2) Orbitrap HRMS conditions

[0122] Heated electrospray ion source: negative ion mode; sheath gas flow rate: 30Arb; auxiliary gas flow rate: 10Arb; spray voltage: 2.5kV; ion transfer tube temperature: 320℃; S-lens RF voltage: 50V; auxiliary gas heater temperature: 380℃. MS acquisition mode: one-stage full scan; acquisition range: m / z90~155; resolution: 70000; C-trap maximum injection time: 200ms; C-trap ion number maximum capacity (AGC Target): 1×10 6 .

[0123] 3. Preparation of calibration standard solution and sample preparation

[0124] Thirteen phenols (C0-C2-alkyl substituted phenols) with a purity of more than 98% and an internal standard (phenol- 13 C6) and surrogate (phenol-D5, 2-methylphenol-D8, 2,4-dimethylphenol-3,5,6-D3) standard samples were used to prepare single standard stock solutions. The single standard stock solutions were diluted step by step with methanol to prepare 13 kinds of phenol mixed working solutions, 3 kinds of surrogate mixed working solutions and internal standard working solutions.

[0125] The working solution was used to prepare the calibration standard solution. The concentrations of phenol components in the calibration series were 10 μg / L, 100 μg / L, 500 μg / L, 1000 μg / L and 2500 μg / L, respectively. The concentrations of the internal standard and the surrogate were both 200 μg / L. The total amount of methanol in the calibration standard solution was 120 μL / mL.

[0126] Pre-add 100 μL of methanol to a 2 mL sample bottle. Take out the refrigerated water sample, wait for the sample temperature to return to room temperature, and filter it through a 0.22 μm nylon filter. Depending on the volatile phenol content, take 10 to 500 μL of the filtrate and add it to the sample bottle. Add 10 μL of the substitute mixed working solution and 10 μL of the internal standard working solution respectively, add pure water to make the total volume of the sample 1000 μL, shake well, and store at 4 to 6 ° C for testing.

[0127] 4. Qualitative confirmation, data collection and analysis

[0128] By [MH] - Accurate mass and retention time matching to qualitatively confirm the target compound in the sample, requiring: [MH] - The relative error between the measured value of the accurate mass number (m / z) and its theoretical value is ≤5×10 -6 ; The retention time (RT) window deviation is within ±0.1min. Table 1 shows the qualitative confirmation information of 13 phenolic components and internal standards and substitutes.

[0129] Table 1 Qualitative confirmation information of 13 phenolic components and internal standards and surrogates

[0130] Serial number Compound CAS Number RT / min <![CDATA[[M-H] - Theoretical accurate mass value (m / z)]]> 1 <![CDATA[Phenol- 13 C6]]> 89059-34-7 6.27 99.05472 2 <![CDATA[Phenol-D5]]> 4165-62-2 6.16 98.06597 3 <![CDATA[2-Methylphenol-D8]]> 203645-65-2 15.48 114.09418 4 <![CDATA[2,4-Dimethylphenol-3,5,6-D3]]> 93951-75-8 29.82 124.08472 5 phenol 108-95-2 6.26 93.03459 6 3-Methylphenol 108-39-4 14.07 107.05024 7 4-Methylphenol 106-44-5 15.40 107.05024 8 2-Methylphenol 95-48-7 15.96 107.05024 9 3,4-Dimethylphenol 95-65-8 26.04 121.06589 10 3-Ethylphenol 620-17-7 26.55 121.06589 11 3,5-Dimethylphenol 108-68-9 27.25 121.06589 12 2,6-Dimethylphenol 576-26-1 27.25 121.06589 13 2,3-Dimethylphenol 526-75-0 27.72 121.06589 14 4-Ethylphenol 123-07-9 28.30 121.06589 15 2,5-Dimethylphenol 95-87-4 28.94 121.06589 16 2-Ethylphenol 90-00-6 29.63 121.06589 17 2,4-Dimethylphenol 105-67-9 30.13 121.06589

[0131] Two sets of consistent calibration standards and test samples were prepared and tested in the mobile phase systems of methanol-6.0mmol / L ammonia and methanol-11.5mmol / L ammonia, respectively. Xcalibur 4.4 software was used to collect data, and TraceFinder 5.1 software was used for data analysis. Figure 4 The [MH] of 13 C0-C2-alkyl substituted phenols in the methanol-6.0 mmol / L ammonia mobile phase system according to the present invention -Extracted ion map, Figure 5 The [MH] of 13 C0-C2-alkyl substituted phenols in the methanol-11.5 mmol / L ammonia mobile phase system according to the present invention is shown in FIG. - Extracted ion map; Figure 4 and Figure 5 The corresponding chromatographic peaks are: 1, phenol; 2, 3-methylphenol; 3, 4-methylphenol; 4, 2-methylphenol; 5, 3,4-dimethylphenol; 6, 3-ethylphenol; 7, 3,5-dimethylphenol; 8, 2,6-dimethylphenol; 9, 2,3-dimethylphenol; 10, 4-ethylphenol; 11, 2,5-dimethylphenol; 12, 2-ethylphenol; 13, 2,4-dimethylphenol.

[0132] 5. Calibration range and detection limit

[0133] The internal standard method was used for quantification, and the correlation coefficients (R 2 ) were all greater than 0.997. As shown in Table 2, the detection limits of the 13 phenolic components were 0.3-1.0 μg / L. Compared with the derivatization-GC-MS method (HJ744-2015) for testing phenolic compounds, the sensitivity of this method was 1-2 orders of magnitude higher.

[0134] Table 2 Detection limits of phenolic components

[0135] Serial number Target compound Method detection limit (μg / L) 1 phenol 1.0 2 3-Methylphenol 0.4 3 4-Methylphenol 0.3 4 2-Methylphenol 0.5 5 3,4-Dimethylphenol 0.3 6 3-Ethylphenol 0.4 7 2,6 / 3,5-Dimethylphenol 0.4 8 2,3-Dimethylphenol 0.4 9 4-Ethylphenol 0.3 10 2,5-Dimethylphenol 0.4 11 2-Ethylphenol 0.4 12 2,4-Dimethylphenol 0.3 13 3,5-Dimethylphenol* 0.4

[0136] Note: * is tested under liquid chromatography conditions Method 2.

[0137] 6. Comparison with the results of spectrophotometry (HJ503-2009)

[0138] Spectrophotometry (HJ503-2009) is used to test the volatile phenol (in terms of phenol) index in water samples. The molar absorption coefficients of 13 phenolic single components were tested by spectrophotometry (HJ503-2009), and the conversion factors of C1-C2-alkyl substituted phenol to phenol were obtained. The results of 13 phenolic components were converted into the results of volatile phenol (in terms of phenol) index. The results show that the resolution rate of this method for the volatile phenol (in terms of phenol) index in stripping water is more than 92.7%, and the accurate analysis of the main components of volatile phenols is achieved.

[0139] It should be noted that this embodiment is only a preferred example. The present invention does not limit the type and specification of the chromatographic column and the type of LC-MS instrument. Other similar reverse chromatographic columns and low-resolution LC-MS can be used to implement the present invention according to the technical solution disclosed in the present invention.

[0140] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for characterizing C0-C2-alkyl-substituted phenols, characterized in that: The characterization method comprises the following steps: According to the petroleum content range in the sample, select the corresponding sample pretreatment process to prepare the sample; The sample was detected by LC-MS in a methanol-5.0-6.5 mmol / L ammonia water mobile phase system to obtain the concentration of the first component and the standardized concentrations of the co-eluted 3,5-dimethylphenol and 2,6-dimethylphenol; the first component included: Phenol, 2-methylphenol, 3-methylphenol, 4-methylphenol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol, 2-ethylphenol, 3-ethylphenol, and 4-ethylphenol; The sample was detected by LC-MS in a methanol-7.0-11.5 mmol / L ammonia water mobile phase system to obtain the concentration of 3,5-dimethylphenol; In the mobile phase system of methanol-5.0~6.5mmol / L ammonia water, LC-MS was used to detect 3,5-dimethylphenol and 2,6-dimethylphenol calibration samples respectively, and the conversion factor was calculated to obtain the concentration of 2,6-dimethylphenol; The calculation formula of the concentration of the 2,6-dimethylphenol is: c’ 2,s =(m+1)·c’ STD,s -m·c’ 1,s ; Where c' 2,s represents the concentration of 2,6-dimethylphenol; m represents the conversion factor; c' STD,s represents the normalized concentration of co-eluted 3,5-dimethylphenol and 2,6-dimethylphenol; c' 1,s Indicates the concentration of 3,5-dimethylphenol; Based on the concentration of the first component, the concentration of 3,5-dimethylphenol and the concentration of 2,6-dimethylphenol, the contents of 13 C0-C2-alkyl-substituted phenol single components in the sample were obtained.

2. The method for characterizing a C0-C2-alkyl substituted phenol according to claim 1, characterized in that: The method of selecting a corresponding sample pretreatment process to prepare the sample according to the petroleum content range in the sample includes: When the petroleum content in the sample does not exceed 50 mg / L, the sample is filtered through a 0.22 μm filter membrane before sampling and testing; When the petroleum content in the sample exceeds 50 mg / L, the sample is alkalized with NaOH and extracted with dichloromethane-n-hexane, and the organic phase is separated by centrifugation. The aqueous phase is filtered through a 0.22 μm filter membrane, and then neutralized with formic acid before sampling and testing.

3. The method for characterizing a C0-C2-alkyl substituted phenol according to claim 1, characterized in that: The elution conditions of the methanol-5.0-6.5 mmol / L ammonia water mobile phase system include: The column flow rate was 0.20 mL / min; Gradient elution is as follows: the initial volume ratio of methanol is 10% to 25%, zero gradient elution is maintained for 1 to 10 minutes, and then the volume ratio of methanol is increased to 40% in an isocratic manner within 30 minutes, and the volume ratio of methanol is maintained at 40% until all components flow out; The column temperature is 35-40°C.

4. The method for characterizing a C0-C2-alkyl substituted phenol according to claim 1, characterized in that: The elution conditions of the methanol-7.0-11.5 mmol / L ammonia water mobile phase system include: The column flow rate was 0.20 mL / min; Gradient elution is as follows: the initial volume ratio of methanol is 10% to 25%, zero gradient elution is maintained for 1 to 10 minutes, and then the volume ratio of methanol is increased to 40% in an isocratic manner within 30 minutes, and the volume ratio of methanol is maintained at 40% until all components flow out; The column temperature is 35-40°C.

5. Application of a method for characterizing C0-C2-alkyl-substituted phenols, as claimed in any one of claims 1 to 4, characterized in that: Applied to the analysis of volatile phenol components in stripping water.

6. The use of the method for characterizing C0-C2-alkyl substituted phenol according to claim 5, characterized in that: The resolution rate of the volatile phenol (in terms of phenol) index reaches more than 92.7%.

Images