Method for detecting anti-aging agents CPPD and IPPD in tap water sample

Abstract

The invention belongs to the field of analytical chemistry, and provides a method for detecting antioxidants CPPD and IPPD in a tap water sample, which comprises the following steps: collecting the tap water sample, adding an acetonitrile / acetone mixed solution and an internal standard 13C6-CPPD, extracting through oscillation, ultrasonic and centrifugal operation to obtain a supernatant, concentrating and purifying, and fixing the volume with methanol to obtain a tap water CPPD-IPPD methanol solution to be detected; the method comprises the following steps: injecting a to-be-detected methanol solution of tap water CPPD-IPPD into a liquid chromatography system with set parameters, separating out a target compound through a specific liquid phase gradient elution program, converting the target compound into target ions by using a mass spectrometer under set ion source parameters, detecting an ion intensity signal according to a multi-reaction monitoring scanning mode MRM, and determining the concentration of the target ions according to the ion intensity signal. The concentration of a target compound is calculated, the accuracy and the relative standard deviation of the detection method are calculated through a labeled sample, the operation normalization is judged according to the accuracy and the relative standard deviation, the detection result of the tap water sample is obtained by combining the detection limit and the quantitation limit, and accurate detection of CPPD and IPPD in the tap water sample is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and particularly relates to a method for detecting anti-aging agents CPPD and IPPD in tap water samples. Background Art

[0002] In modern society, the safety of drinking water is of utmost importance. Water quality detection is a crucial link in ensuring drinking water safety. As common chemical substances, anti-aging agents CPPD and IPPD may enter the tap water source through industrial wastewater discharge and chemical product leakage. Anti-aging agents CPPD and IPPD have potential biological toxicity, and long-term intake may endanger human health. Therefore, accurately detecting CPPD and IPPD in tap water samples is of great significance.

[0003] Traditional tap water detection methods mostly focus on common microorganisms, heavy metals, and conventional chemical pollutants, and there are limitations in detecting trace organic pollutants such as anti-aging agents CPPD and IPPD. Conventional detection means lack sufficient sensitivity and are difficult to detect target substances at extremely low concentrations, prone to missed detections. At the same time, there is a lack of targeted separation and detection technologies, and it is impossible to effectively exclude the interference of complex water sample matrices, resulting in poor accuracy of detection results. Therefore, how to achieve highly sensitive, highly accurate, and effectively anti-interference detection of the concentrations of CPPD and IPPD in tap water samples is an urgent problem to be solved. Based on this, a method for detecting anti-aging agents CPPD and IPPD in tap water samples is proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for detecting anti-aging agents CPPD and IPPD in tap water samples to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A method for detecting anti-aging agents CPPD and IPPD in tap water samples, comprising the following steps:

[0007] S1. Collect tap water samples, obtain the supernatant by solvent extraction treatment of the tap water samples, concentrate and purify the supernatant, and make a constant volume with methanol to obtain the methanol solution to be detected for CPPD-IPPD in tap water;

[0008] S2. Process the methanol solution to be detected for CPPD-IPPD in tap water through a liquid chromatography system to obtain the target compound;

[0009] S3. Convert the target compound into target ions through a mass spectrometer, detect the target ions through the multiple reaction monitoring (MRM) scanning mode of the mass spectrometer, obtain the target ion intensity signal, and obtain the concentration of the target compound in the tap water sample according to the target ion intensity signal;

[0010] S4. Calculate the accuracy and relative standard deviation of the detection method for the tap water sample. Based on the accuracy and relative standard deviation, determine whether to perform judgment processing on the concentration of the target compound in the tap water sample to obtain the detection result of the tap water sample.

[0011] Preferably, the method for obtaining the supernatant by solvent extraction treatment of the tap water sample:

[0012] Collect 500 mL of the tap water sample, add 6 mL of an acetonitrile / acetone mixture with a ratio of acetonitrile to acetone of 7:3 and 2.0 ng of 13 C6-CPPD internal standard to the tap water sample. Shake the tap water sample added with the acetonitrile / acetone mixture and 13 C6-CPPD evenly to obtain the original mixture. Place the original mixture on an oscillator and shake the original mixture at a speed of 250 rpm for 30 min for shaking treatment. Perform ultrasonic treatment on the shaken original mixture for 25 min. Place the ultrasonically treated original mixture in a centrifuge and centrifuge the ultrasonically treated original mixture at a high speed of 4500 rpm for 15 min to obtain the preliminary precipitate and the original mixed supernatant;

[0013] Add 6 mL of an acetonitrile / acetone mixture with a ratio of acetonitrile to acetone of 7:3 and 2.0 ng of 13 C6-CPPD to the preliminary precipitate. Shake the preliminary precipitate added with the acetonitrile / acetone mixture and 13 C6-CPPD internal standard evenly to obtain the precipitate mixture. Place the precipitate mixture on an oscillator and shake the precipitate mixture at a speed of 250 rpm for 30 min for shaking treatment. Perform ultrasonic treatment on the shaken precipitate mixture for 25 min. Place the ultrasonically treated precipitate mixture in a centrifuge and centrifuge the ultrasonically treated precipitate mixture at a high speed of 4500 rpm for 15 min to obtain the precipitate supernatant and the final precipitate. Add the precipitate supernatant to the original mixed supernatant and shake evenly to obtain the supernatant;

[0014] Preferably, the method for concentrating and purifying the supernatant and obtaining the methanol solution to be tested for tap water CPPD-IPPD:

[0015] Blow the supernatant to a concentrated supernatant with a preset volume of 1.0 mL by high-purity nitrogen, and purify it through an Envi-Carb column (i.e., graphene column) activated with 6 mL of acetonitrile and 6 mL of acetone to generate a purified supernatant. Dry the purified supernatant to a solid state by high-purity nitrogen and add methanol to make up the volume to the preset volume to obtain 100 μL of the methanol solution to be tested for tap water CPPD-IPPD.

[0016] Preferably, the method for obtaining the target compound by processing the tap water CPPD - IPPD methanol solution to be tested through a liquid chromatography system:

[0017] Set the column temperature of the BEH Shield RP C18 column of the liquid chromatography system to 40 °C and the injection volume to 10 μL. Set mobile phase A of the liquid chromatography system for separating and analyzing the mixture to be water containing 2.5 mM NH4Ac with a pH value of 7.0, mobile phase B to be methanol, and the flow rate of the mobile phase to be 0.3 mL / min. Inject the tap water CPPD - IPPD methanol solution to be tested into the set liquid chromatography system, and obtain the target compound including the CPPD compound and the IPPD compound through a specific liquid phase gradient elution program. The BEH Shield RP C18 column, that is, the chromatographic column, is produced by Sigma - Aldrich Company, USA;

[0018] The specific liquid phase gradient elution program is to achieve the separation operation of the target compound by changing the proportion of mobile phase B. The operation steps of the specific liquid phase gradient elution program are as follows:

[0019] In the initial stage from 0 to 1.0 min, the proportion of mobile phase B is set to 40%, and the proportion of mobile phase A is 60%;

[0020] In the linearly rising stage from 1.0 to 5.0 min, the proportion of mobile phase B slowly rises linearly from 40% to 65%;

[0021] In the continuously rising to maintaining stage from 5.0 to 22 min, in the first 5.0 to 20 min, the proportion of mobile phase B rises linearly from 65% to 100%, and in the subsequent 20 to 22 min, the proportion of mobile phase B remains 100%;

[0022] In the restoring initial stage from 22 to 25 min, in the first 22 to 23 min, the proportion of mobile phase B linearly drops from 100% to 40%, and in the subsequent 23 to 25 min, the proportion of mobile phase B continues to remain 40% for 2 minutes.

[0023] Preferably, the method for converting the target compound into target ions by a mass spectrometer:

[0024] Set the ion source temperature of the mass spectrometer to 380 °C, the capillary voltage to 3.0 kV, the cone voltage to 50 V, the lens voltage to 1.2 V, the gas pressure of Gas1 (atomizing gas of the ion source) to 0.45 MPa, the gas pressure of Gas2 (auxiliary gas of the ion source) to 0.35 MPa, and the electrospray ionization source mode to the negative ion mode. Generate target ions including CPPD ions and IPPD ions from the target compound through the electrospray ionization source (ESI) of the mass spectrometer. CPPD ions include CPPD quantitative ions and CPPD qualitative ions, and IPPD ions include IPPD quantitative ions and IPPD qualitative ions. The CPPD and IPPD quantitative ions are used in MRM to obtain the CPPD and IPPD ion intensity signals, and the CPPD and IPPD qualitative ions are used in MRM to distinguish CPPD and IPPD compounds;

[0025] The method for the MRM to distinguish CPPD and IPPD compounds and obtain the CPPD and IPPD ion intensity signals is as follows:

[0026] Under the action of the electrospray ionization source (ESI), the target compound is converted into CPPD ions and IPPD ions. The CPPD ions are converted into CPPD parent ions, and the CPPD parent ions generate CPPD quantitative ions with a mass-to-charge ratio of 267 / 107 and CPPD qualitative ions with a mass-to-charge ratio of 267 / 84 through fragmentation; the IPPD ions are converted into IPPD parent ions, and the IPPD parent ions further fragment to generate IPPD quantitative ions with a mass-to-charge ratio of 227 / 184 and IPPD qualitative ions with a mass-to-charge ratio of 227 / 107. The mass spectrometer uses the multiple reaction monitoring scan mode (MRM) to detect the CPPD ion pair and the IPPD ion pair, determines the corresponding CPPD and IPPD quantitative ions through the CPPD and IPPD qualitative ions, and the mass spectrometer determines the CPPD and IPPD ion intensity signals based on the detected CPPD and IPPD quantitative ions, achieving the exclusion of interference from other compounds, improving the specificity of detection, and accurately confirming the presence of the target compound.

[0027] Preferably, the method for obtaining the concentration of the target compound in the tap water sample based on the target ion intensity signal:

[0028] The target ion intensity signal includes the CPPD ion intensity signal and the IPPD ion intensity signal. The CPPD ion intensity signal and the IPPD ion intensity signal are respectively used to obtain the CPPD concentration and the IPPD concentration through the CPPD regression equation and the IPPD regression equation. The CPPD concentration and the IPPD concentration are collectively referred to as the target compound concentration;

[0029] The CPPD regression equation is:

[0030] Among them, y is the CPPD ion intensity signal, and x is the CPPD concentration;

[0031] The IPPD regression equation is as follows:

[0032] where y is the IPPD ionic strength signal and x is the IPPD concentration.

[0033] Preferably, the method for calculating the accuracy and relative standard deviation of the tap water sample detection method:

[0034] The tap water sample detection methods are S1, S2, and S3. Take a 500 mL tap water sample without the target compound as the blank matrix. Add CPPD and IPPD standard solutions to the blank matrix to prepare three spiked samples with CPPD and IPPD concentrations of 0.5 ng / mL, 2.0 ng / mL, and 20 ng / mL respectively. Process the three spiked samples through the tap water sample detection method to obtain the concentrations of the target compounds in the spiked samples. Calculate the accuracy and relative standard deviation of the tap water sample detection method for the concentrations of the target compounds in the spiked samples respectively through the recovery rate calculation formula and the relative standard deviation calculation formula;

[0035] The recovery rate calculation formula is as follows:

[0036] where the added concentration is 0.5 ng / mL, 2.0 ng / mL, or 20 ng / mL;

[0037] The relative standard deviation calculation formula is as follows:

[0038] where RSD is the relative standard deviation, SD is the standard deviation, and the average value is the average value of the concentrations of the target compounds in the spiked samples.

[0039] Preferably, the method for judging whether to perform judgment processing on the concentration of the target compound in the tap water sample according to the accuracy and relative standard deviation:

[0040] Judge the accuracy and relative standard deviation respectively through the accuracy range threshold of 80 to 120% and the relative standard deviation range threshold of 0 to 20%;

[0041] If both the accuracy and the relative standard deviation are within the accuracy range threshold of 80 to 120% and the relative standard deviation range threshold of 0 to 20%, then perform judgment processing on the concentration of the target compound to obtain the tap water sample detection result;

[0042] If the accuracy or the relative standard deviation is outside the accuracy range threshold of 80 to 120% and the relative standard deviation range threshold of 0 to 20%, it indicates that the operation of the tap water sample detection method is not standardized, and re-obtain the concentration of the target compound in the tap water sample.

[0043] Preferably, the method for judging and processing the concentration of the target compound to obtain the test result of the tap water sample:

[0044] Judge the concentrations of CPPD and IPPD respectively through their corresponding detection limits LOD and quantification limits LOQ. The detection limit LOD is the lowest concentration at which the detection method can reliably detect the presence of the target compound.

[0045] The quantification limit LOQ is the lowest value at which the detection method can accurately determine the concentration of the target compound. The detection limit of CPPD is 0.011 ng / mL, the quantification limit of CPPD is 0.034 ng / mL, the detection limit of IPPD is 0.039 ng / mL, and the quantification limit of CPPD is 0.11 ng / mL;

[0046] If the concentration of CPPD is less than 0.011 ng / mL, the concentration of CPPD in the test result of the tap water sample is not detected;

[0047] If the concentration of CPPD is greater than or equal to 0.011 ng / mL and less than or equal to 0.034 ng / mL, the concentration of CPPD in the test result of the tap water sample is detected but less than the quantification limit;

[0048] If the concentration of CPPD is greater than 0.034 ng / mL, the concentration of CPPD in the test result of the tap water sample is the actual value of the CPPD concentration;

[0049] If the concentration of IPPD is less than 0.039 ng / mL, the concentration of IPPD in the test result of the tap water sample is not detected;

[0050] If the concentration of IPPD is greater than or equal to 0.039 ng / mL and less than or equal to 0.11 ng / mL, the concentration of IPPD in the test result of the tap water sample is detected but less than the quantification limit;

[0051] If the concentration of IPPD is greater than 0.11 ng / mL, the concentration of IPPD in the test result of the tap water sample is the actual value of the IPPD concentration;

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The present invention has achieved an improvement in the detection performance of tap water testing. Traditional tap water testing technologies have poor sensitivity and accuracy when facing trace organic pollutants. The present invention optimizes the pretreatment steps, uses a mixture of acetonitrile / acetone combined with oscillation, ultrasound, and multiple centrifugations to efficiently enrich target compounds, and cooperates with the highly sensitive detection of mass spectrometry to reduce the detection limits of CPPD and IPPD. The detection limits of CPPD and IPPD are 0.011 ng / mL and 0.039 ng / mL respectively, reducing the missed detection situation. In the separation and detection link, a specific liquid phase gradient elution program and the mass spectrometry multiple reaction monitoring scanning mode cooperate to accurately separate and identify target compounds, effectively excluding the interference of complex water sample matrices, and greatly improving the detection accuracy.

[0054] 2. The method of the present invention is scientific and perfect. Existing detection methods lack a comprehensive evaluation system. The present invention constructs a perfect quality control system, calculates the recovery rate and relative standard deviation through blank matrix spike experiments to evaluate the operation standardization, sets the accuracy range threshold from 80% to 120% and the relative standard deviation range threshold from 0% to 20%. If the detection results exceed the range, re-detection is carried out in a timely manner to ensure the reliability of the data. At the same time, the concentration of target compounds is judged based on the detection limit and quantification limit, making the detection results more scientific and persuasive, and providing a scientific and systematic detection plan for tap water quality testing.

[0055] Description of the drawings

[0056] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0057] Figure 1 It is the flowchart of the steps of the present invention; Detailed implementation manners

[0058] To make the purpose, technical solutions, and advantages of the present invention clearer, the following will describe the technical solutions of the present invention in detail. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present invention.

[0059] Example, as Figure 1 shown, a method for detecting antioxidants CPPD and IPPD in a tap water sample includes the following steps:

[0060] S1. Collect a tap water sample, obtain a supernatant by solvent extraction of the tap water sample, concentrate and purify the supernatant, and make up the volume with methanol to obtain a methanol solution of tap water CPPD-IPPD to be tested;

[0061] S2. Process the methanol solution of tap water CPPD-IPPD to be tested through a liquid chromatography system to obtain a target compound;

[0062] S3. Convert the target compound into target ions by a mass spectrometer, detect the target ions through the multiple reaction monitoring (MRM) scanning mode of the mass spectrometer, obtain the target ion intensity signal, and obtain the concentration of the target compound in the tap water sample according to the target ion intensity signal;

[0063] S4. Calculate the accuracy and relative standard deviation of the tap water sample detection method, and judge whether to perform judgment processing on the concentration of the target compound in the tap water sample to obtain the tap water sample detection result according to the accuracy and relative standard deviation.

[0064] Furthermore, the working principle of the present invention is illustrated by the following examples:

[0065] Collect 500 mL of tap water samples from ordinary southern cities, add 6 mL of a mixture of acetonitrile / acetone, with the volume ratio of acetonitrile to acetone being 7:3. At the same time, add 2.0 ng of 13 C6-CPPD internal standard, shake well to obtain the original mixture. Place the original mixture in an oscillator, oscillate at 250 rpm for 30 min, perform ultrasonic treatment for 25 min, and centrifuge at 4500 rpm for 15 min to obtain a preliminary precipitate and the original mixed supernatant. Add the same amount of acetonitrile / acetone mixture and internal standard to the preliminary precipitate, repeat the above operations to obtain the precipitate supernatant and the final precipitate. Combine the precipitate supernatant and the original mixed supernatant, blow to 1.0 mL with high-purity nitrogen, purify through an Envi-Carb column activated with 6 mL of acetonitrile and 6 mL of acetone, then dry with high-purity nitrogen, and make up the volume to 100 μL with methanol to obtain a methanol solution of tap water CPPD-IPPD to be tested.

[0066] A liquid chromatography system was set up. A BEH Shield RP C18 column was used. The column temperature was maintained at 40 °C. The injection volume was set at 10 μL. Mobile phase A was water containing 2.5 mM NH4Ac with a pH value of 7.0, and mobile phase B was methanol. The flow rate was set at 0.3 mL / min. Separation was carried out according to a specific liquid phase gradient elution program. From 0 to 1.0 min, the proportion of mobile phase B was 40%, and the proportion of mobile phase A was 60%. From 1.0 to 5.0 min, the proportion of mobile phase B slowly increased linearly from 40% to 65%. From 5.0 to 20 min, the proportion of mobile phase B increased linearly from 65% to 100%. From 20 to 22 min, the proportion of mobile phase B remained 100%. From 22 to 23 min, the proportion of mobile phase B decreased linearly from 100% to 40%. From 23 to 25 min, mobile phase B continued to maintain a proportion of 40% for 2 minutes. The methanol solution of tap water CPPD-IPPD to be tested was injected into the set liquid chromatography system. Through the above gradient elution program, the separation of the target compounds CPPD and IPPD was achieved.

[0067] The parameters of the mass spectrometer were set. Among them, the ion source temperature was 380 °C, the capillary voltage was 3.0 kV, the cone voltage was 50 V, the lens voltage was 1.2 V, the gas pressure of the ion source nebulizing gas Gas1 was 0.45 MPa, the gas pressure of the ion source auxiliary gas Gas2 was 0.35 MPa, and the electrospray ionization source mode was the negative ion mode. Under the action of the electrospray ionization source ESI, the target compounds were converted into ions. Among them, the CPPD ions were converted into CPPD parent ions, and the CPPD parent ions cracked to produce the CPPD quantitative ion with a mass-to-charge ratio of 267 / 107 and the CPPD qualitative ion with a mass-to-charge ratio of 267 / 84. The IPPD ions were converted into IPPD parent ions, and the IPPD parent ions cracked to generate the IPPD quantitative ion with a mass-to-charge ratio of 227 / 184 and the IPPD qualitative ion with a mass-to-charge ratio of 227 / 107. The mass spectrometer used the multiple reaction monitoring scanning mode MRM to detect the CPPD ion pair and the IPPD ion pair. The corresponding quantitative ions were determined through the CPPD and IPPD qualitative ions, and then the CPPD and IPPD ion intensity signals were obtained. Through the detection of the mass spectrometer, the CPPD quantitative ion intensity signal y1 in the sample was 5.41, and the IPPD quantitative ion intensity signal y2 was 7.67. The CPPD concentration was calculated to be approximately 9.07 ng / ml and the IPPD concentration was calculated to be approximately 8.14 ng / ml through the corresponding regression equation.

[0068] Take 500 mL of tap water sample without the target compound as the blank matrix, and prepare three spiked samples with spiking concentrations of 0.5 ng / mL, 2.0 ng / mL, and 20 ng / mL for both CPPD and IPPD. Detect the spiked samples according to the above procedure. For the 0.5 ng / mL spiked sample, the detected CPPD concentration is 0.47 ng / mL and the IPPD concentration is 0.49 ng / mL; for the 2.0 ng / mL spiked sample, the detected CPPD concentration is 1.84 ng / mL and the IPPD concentration is 1.88 ng / mL; for the 20 ng / mL spiked sample, the detected CPPD concentration is 20.8 ng / mL and the IPPD concentration is 19.2 ng / mL. Calculate the accuracy through the recovery rate calculation formula. The accuracy of CPPD is as follows: the accuracy of the 0.5 ng / mL spiked sample is 94%, the accuracy of the 2.0 ng / mL spiked sample is 92%, and the accuracy of the 20 ng / mL spiked sample is 104%. The accuracy of IPPD is as follows: the accuracy of the 0.5 ng / mL spiked sample is 98%; the recovery rate of the 2.0 ng / mL spiked sample is 94%; the recovery rate of the 20 ng / mL spiked sample is 96%. Calculate the relative standard deviation RSD through the relative standard deviation calculation formula. The average concentration of CPPD is approximately 7.7 ng / mL, the standard deviation SD of CPPD is approximately 0.28, and accordingly, the RSD of CPPD is approximately 3.6%. The average concentration of IPPD is approximately 7.19 ng / mL, the standard deviation SD of IPPD is approximately 0.26, and accordingly, the RSD of IPPD is approximately 3.6%. Make a judgment and determine the test results based on the calculated accuracy and relative standard deviation. The recovery rate of CPPD is in the range of 80% to 120%, and the RSD is in the range of 0 to 20%. The recovery rate of IPPD is in the range of 80% to 120%, and the RSD is in the range of 0 to 20%. The operation is standard. The CPPD concentration of 9.07 ng / mL is greater than 0.034 ng / mL, and the test result of the CPPD concentration in the tap water of the southern city is 9.07 ng / mL. The IPPD concentration of 8.14 ng / mL is greater than 0.11 ng / mL, and the test result of the IPPD concentration in the tap water of the southern city is 8.14 ng / mL.

[0069] It should be noted that the above sequence of the embodiments of the present invention is only for description and does not represent the superiority or inferiority of the embodiments. And the above specific embodiments of this specification have been described. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0070] Each embodiment in this specification is described in a progressive manner. For the same or similar parts between each embodiment, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments.

[0071] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; any modification to the technical solutions recorded in the foregoing embodiments, or any equivalent replacement of some of the technical features, does not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application, and should all be included within the protection scope of the present application.

Claims

1. A method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The following steps are involved: S1. Collect tap water samples, extract the tap water samples by solvent to obtain supernatant, concentrate and purify the supernatant, and dilute it with methanol to obtain tap water CPPD-IPPD methanol solution to be tested; S2, treating the methanol solution of tap water CPPD-IPPD to be tested through a liquid chromatography system to obtain the target compound; S3, converting the target compound into a target ion by a mass spectrometer, detecting the target ion by a multiple reaction monitoring scanning mode (MRM) of the mass spectrometer, obtaining a target ion intensity signal, and obtaining the target compound concentration in the tap water sample according to the target ion intensity signal; S4. Calculate the accuracy and relative standard deviation of the tap water sample detection method, and determine whether to perform a determination process on the concentration of the target compound in the tap water sample to obtain the tap water sample detection result based on the accuracy and relative standard deviation.

2. According to claim 1, a method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The method for obtaining a supernatant by solvent extraction of a tap water sample: The acetonitrile / acetone mixture and 13 C6-CPPD is added to the tap water sample, and the mixture is shaken to obtain an original mixed solution, the original mixed solution is shaken by an oscillator, the original mixed solution after the shaking treatment is ultrasonically treated, and the original mixed solution after the ultrasonic treatment is passed through a centrifuge to obtain a preliminary precipitate and an original mixed supernatant; The preliminary precipitate is added to the acetonitrile / acetone mixed solution, and shaken to obtain a precipitate mixed solution, the precipitate mixed solution is shaken by an oscillator, the precipitate mixed solution after the shaking treatment is ultrasonically treated, and the precipitate mixed solution after the ultrasonic treatment is passed through a centrifuge to obtain a precipitate supernatant and a final precipitate; The supernatant of the precipitate was added to the original mixed supernatant and shaken to obtain the supernatant; Said 13 C6-CPPD is an internal standard substance used to detect CPPD and IPPD in urban tap water samples.

3. According to claim 2, a method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The method of concentrating and purifying the supernatant and obtaining the methanol solution of tap water CPPD-IPPD to be tested: The supernatant is blown with high-purity nitrogen to become a concentrated supernatant of a preset volume, and purified by a graphene column activated by acetonitrile and acetone to generate a purified supernatant. The purified supernatant is blown dry with high-purity nitrogen, and methanol is added to make the volume to a preset volume, thereby obtaining the tap water CPPD-IPPD methanol solution to be tested.

4. According to claim 3, a method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The method of treating the tap water CPPD-IPPD methanol solution to be tested by a liquid chromatography system to obtain the target compound: Setting the column temperature and injection volume of the chromatographic column of the liquid chromatography system, setting the mobile phase A of the liquid chromatography system to water, the mobile phase B to methanol, and the flow rate of the mobile phase, injecting the tap water CPPD-IPPD methanol solution to be tested into the set liquid chromatography system, and obtaining the target compounds including CPPD compounds and IPPD compounds through a specific liquid phase gradient elution program; The liquid chromatography system is an instrument used for separation and analysis of mixtures; The liquid phase gradient elution procedure is a component of a liquid chromatography system and is a key operating step for improving separation effect by changing the composition ratio of the mobile phase.

5. According to claim 4, a method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The method for converting the target compound into the target ion by mass spectrometer: The ion source temperature, capillary voltage, cone voltage, lens voltage, ion source nebulizer gas Gas1 pressure, ion source auxiliary gas Gas2 pressure and electrospray ion source mode of the mass spectrometer are set, and the target compound is subjected to the electrospray ion source ESI of the mass spectrometer to generate target ions including CPPD ions and IPPD ions, wherein the CPPD ions include CPPD quantitative ions and CPPD qualitative ions, and the IPPD ions include IPPD quantitative ions and IPPD qualitative ions; The CPPD and IPPD quantitative ions are used for MRM to obtain CPPD and IPPD ion intensity signals; The CPPD and IPPD qualifier ions are used in MRM to distinguish CPPD and IPPD compounds.

6. According to claim 5, a method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The method for obtaining the concentration of the target compound in the tap water sample according to the target ion intensity signal: The target ion intensity signal includes a CPPD ion intensity signal and an IPPD ion intensity signal. The CPPD ion intensity signal and the IPPD ion intensity signal are respectively converted into a CPPD concentration and an IPPD concentration by using a CPPD regression equation and an IPPD regression equation. The CPPD concentration and the IPPD concentration are collectively referred to as the target compound concentration.

7. According to claim 6, a method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The method for calculating the accuracy and relative standard deviation of the tap water sample detection method is as follows: A tap water sample without added target compound was taken as a blank matrix, CPPD and IPPD standard solutions were added to the blank matrix, and three spiked samples with CPPD and IPPD concentrations of 0.5 ng / mL, 2.0 ng / mL and 20 ng / mL were prepared. The three spiked samples were processed by the tap water sample detection method to obtain the target compound concentration in the spiked samples. The target compound concentration in the spiked samples was calculated by the recovery calculation formula and the relative standard deviation calculation formula, respectively, to calculate the accuracy and relative standard deviation of the tap water sample detection method; The tap water sample detection methods are S1, S2 and S3.

8. According to claim 7, a method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The method for determining whether to perform a determination process on the concentration of a target compound in a tap water sample based on accuracy and relative standard deviation: The accuracy and relative standard deviation are judged by the accuracy range threshold and the relative standard deviation range threshold respectively; If the accuracy and the relative standard deviation are both within the accuracy range threshold and the relative standard deviation range threshold, the concentration of the target compound is judged and processed to obtain the test result of the tap water sample; If the accuracy or relative standard deviation is outside the accuracy range threshold and the relative standard deviation range threshold, it indicates that the operation of the tap water sample detection method is not standardized, and the concentration of the target compound in the tap water sample should be re-obtained.

9. According to claim 8, a method for detecting antioxidants CPPD and IPPD in tap water samples, characterized in that: The method for determining the concentration of the target compound to obtain the test result of the tap water sample: The CPPD concentration is determined by the detection limit LOD and quantification limit LOQ of CPPD; If the CPPD concentration is less than the CPPD detection limit, the CPPD concentration of the tap water sample test result is not detected; If the CPPD concentration is greater than or equal to the CPPD detection limit and less than or equal to the CPPD quantification limit, the CPPD concentration of the tap water sample test result is detected but less than the quantification limit; If the CPPD concentration is greater than the CPPD quantification limit, the CPPD concentration of the tap water sample test result is the actual value of the CPPD concentration; The IPPD concentration is determined by the detection limit LOD and quantification limit LOQ of IPPD; If the IPPD concentration is less than the IPPD detection limit, the IPPD concentration of the tap water sample test result is not detected; If the IPPD concentration is greater than or equal to the IPPD detection limit and less than or equal to the IPPD quantification limit, the IPPD concentration of the tap water sample test result is detected but less than the quantification limit; If the IPPD concentration is greater than the IPPD quantification limit, the IPPD concentration of the tap water sample test result is the actual value of the IPPD concentration; The detection limit LOD is the lowest concentration at which the detection method can reliably detect the presence of the target compound; The limit of quantitation LOQ is the lowest value at which the detection method can accurately determine the concentration of the target compound.

Images