Method for detecting multiple chelating agents in daily chemical products

Abstract

The invention relates to the field of analysis and detection, and discloses a method for detecting multiple chelating agents in daily chemical products, which comprises the following steps: methylating a to-be-detected sample by using a diazomethane methylation reagent to obtain a to-be-detected solution; carrying out liquid chromatography-mass spectrometry detection on the to-be-detected liquid by adopting a specific elution program to obtain a chromatogram; and performing qualitative and / or quantitative analysis on the chelating agent in the to-be-detected sample according to the chromatogram. By adopting the detection method disclosed by the invention, efficient detection of various chelating agents (including DTPA, DTPMP, EDTMPA, HDTEPA, EGTA, HEDP, EDTA, NTA, GLDA, PBTC, MGDA, IDS, HEEDTA, HPAA, DTPA-OH, CA and ATMP) can be realized, meanwhile, interference of other components in daily chemical products on detection can be avoided, and relatively high detection sensitivity and accuracy of the chelating agents can be realized.

Description

Technical Field

[0001] The present invention relates to the field of analysis and detection, and in particular to a method for detecting multiple chelating agents in daily chemical products. Background Art

[0002] Chelating agents are a class of compounds that can form complexes with metal ions. They typically possess electron donors capable of coordinating with metal ions, resulting in a range of special effects, including softening, descaling, rust prevention, efficiency enhancement, and stabilization. Chelating agents are widely used in the daily chemical industry. For example, adding chelating agents to hydrogen peroxide and hypochlorous acid bleaches effectively inhibits the catalytic decomposition of metal ions on hydrogen peroxide and hypochlorous acid components, improving bleaching efficiency, conserving bleaching liquid, and reducing bleaching costs. Adding chelating agents to detergents can effectively adjust water hardness and improve cleaning performance.

[0003] Common chelating agents include phosphates, carboxylates, and organophosphines. Currently, methods for detecting trace chelating agents primarily include ion exchange chromatography and metal ion complexation liquid chromatography. Ion exchange chromatography is suitable for carboxylic acid chelating agents, phosphate chelating agents, and some organophosphorus chelating agents. Its disadvantage is that qualitative analysis relies primarily on peak elution time and chromatographic peak shape, but the elution time of chelating agents is prone to drift during analysis, making qualitative analysis difficult. Metal ion complexation liquid chromatography utilizes a complex formed between a color-forming metal and a chelating agent, followed by detection using a UV detector. It is suitable for chelating agents (primarily carboxylate chelating agents) that react with copper and iron ions to produce color. For example, patent CN112326850A uses this method to detect trisodium nitrilotriacetate in water. This method has a low detection limit, short detection time, and is less susceptible to matrix influence. However, the peak elution times and absorption wavelengths of the chelating agents are relatively close, resulting in a narrow range of applications. The above-mentioned test methods only cover a maximum of 5 to 9 types of chelating agents during analysis, and the types of chelating agents involved are limited. In addition, no detection method for chelating agents in complex daily chemical systems has been reported. However, there are some special interfering substances in daily chemical systems that can easily affect the detection of chelating agents. In addition, the content of chelating agents in daily chemical systems is low, and high detection sensitivity is required. Summary of the Invention

[0004] To address the aforementioned technical issues, namely that existing chelating agent detection methods can only detect a limited number of chelating agents, and that no method for detecting chelating agents in complex daily chemical systems has been reported, the present invention provides a method for detecting multiple chelating agents in daily chemical products. The present method enables efficient qualitative and quantitative detection of 17 chelating agents while avoiding interference from other ingredients in the daily chemical products. It also achieves high detection sensitivity and accuracy for all 17 chelating agents.

[0005] The specific technical solutions of the present invention are: A method for detecting multiple chelating agents in daily chemical products comprises the following steps: S1: using a diazomethane methylation reagent to methylate the sample to be tested to obtain a test solution; S2: The test liquid is subjected to liquid chromatography-mass spectrometry to obtain a chromatogram. The elution procedure is as follows: 1) At minute 0, the eluent composition was: 94-96% v / v formic acid aqueous solution, the balance formic acid acetonitrile solution; this remained unchanged until minute 4-5; 2) The eluent composition ratio gradually changed to: 60-70% v / v formic acid aqueous solution, the balance formic acid acetonitrile solution at 8-10 minutes; this ratio remained unchanged until 13-14 minutes; 3) The eluent composition ratio gradually changes to: 94-96% v / v formic acid aqueous solution, with the remainder being formic acid acetonitrile solution at the 14th to 15th minute; the subsequent formulation remains unchanged for an unlimited period of time; S3: Perform qualitative and / or quantitative analysis on the chelating agent in the sample according to the chromatogram.

[0006] In the above detection method, if the elution procedure is expressed in the conventional way in liquid chromatography, it can be summarized in the following table:

[0007] The specific meaning of the elution program shown in the above table is as follows (the elution program in each embodiment below is expressed in the same way): at the start (0 min), the eluent used is composed of the following components, calculated by volume percentage: 94-96% v / v formic acid aqueous solution, the balance being formic acid acetonitrile solution; the eluent formula remains unchanged until the 4th to 5th minute, and then the distribution ratio of each group gradually changes until it changes to: 60-70% v / v formic acid aqueous solution, the balance being formic acid acetonitrile solution at the 8th to 10th minute; the eluent formula remains unchanged until the 13th to 14th minute, and then the distribution ratio of each group gradually changes until it changes to: 94-96% v / v formic acid aqueous solution, the balance being formic acid acetonitrile solution at the 14th to 15th minute; the subsequent eluent formula remains unchanged for an unlimited period of time.

[0008] In the process of detecting trace chelating agents in daily chemical products, if the sample is directly tested by liquid chromatography-mass spectrometry, the chelating agent has high polarity and low ionization efficiency. For example, EDTA, NTA, etc. contain multiple carboxylic acid groups and dissociate into multi-charged negative ions in the solution (such as EDTA 4-), which leads to charge dispersion and difficulty in forming stable single-charged ions. During mass spectrometry analysis, the signal is easily dispersed to multiple low-abundance mass-to-charge ratio (m / z) positions, and the detection threshold cannot be reached. In addition, the highly polar chelating agent is tightly combined with the water and other solvents in the sample to be tested to form a solvation layer, which requires additional energy for desolvation before entering the gas phase. However, during mass spectrometry analysis, the desorption efficiency of such molecules is low, and the number of effective ions is insufficient. In response to the above problems, the present invention methylates the sample to be tested before detection by liquid chromatography-mass spectrometry. The methylated chelating agent can form stable single-charged ions during mass spectrometry analysis, and the number of effective ions is relatively large, thereby improving the detection sensitivity and facilitating the detection of trace chelating agents in daily chemical products.

[0009] On this basis, the present invention adopts a specific elution procedure in the process of liquid chromatography, which can achieve the elution of various chelating agents commonly used in daily chemical products (including diethylenetriamine pentaacetic acid, diethylenetriamine penta (methylene phosphonic acid), ethylenediamine tetramethylene phosphonic acid, hexamethylenediamine tetramethylene phosphonic acid, ethylene glycol ditetraacetic acid, hydroxyethyl diphosphonic acid, ethylenediamine tetraacetic acid, nitrilotriacetic acid, tetrasodium glutamate diacetate, phosphonobutane tricarboxylic acid, methylglycine diacetic acid, iminodisuccinic acid, N-β-hydroxyethyl ethylenediamine triacetic acid, 2-hydroxyphosphonoacetic acid, diethylenetriamine tetraacetic acid, 1,2-dimethylamino ... The method can separate triaminepentaacetic acid, citric acid, and nitrilotrimethylenephosphonic acid, while avoiding interference from other ingredients in daily chemical products (including high ionic strength, complex surfactant components, and oxidizing components). It can also achieve high detection sensitivity and accuracy for each chelating agent, thus enabling qualitative and quantitative detection of various chelating agents, including various carboxylic acid chelating agents and various organophosphorus chelating agents. This breaks through the limitation of existing detection methods that can only detect a limited number of chelating agents, and can meet the detection needs of trace chelating agents in complex matrices of daily chemical products.

[0010] Preferably, the chelating agent includes at least one of diethylenetriaminepentaacetic acid (DTPA), diethylenetriaminepenta(methylenephosphonic acid) (DTPMP), ethylenediaminetetramethylenephosphonic acid (EDTMPA), hexamethylenediaminetetramethylenephosphonic acid (HDTMPA), ethylene glycol ditetraacetic acid (EGTA), hydroxyethyl diphosphonic acid (HEDP), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), tetrasodium glutamate diacetate (GLDA), phosphonobutanetricarboxylic acid (PBTC), methylglycine diacetic acid (MGDA), iminodisuccinic acid (IDS), N-β-hydroxyethylethylenediaminetriacetic acid (HEDTA), 2-hydroxyphosphonoacetic acid (HAPP), diethylenetriaminepentaacetic acid (DTPA-OH), citric acid (CA) and nitrilotrimethylenephosphonic acid (ATMP).

[0011] Preferably, the specific process of step S1 includes: dissolving the sample to be tested in a solvent to obtain a sample solution, mixing the sample solution, methanol and a diazomethane methylation reagent, performing a methylation treatment, and passing the solution through a microporous filter membrane to obtain a test solution; the volume ratio of the sample solution to methanol is 1:0.5~2; and the solvent is methanol or a methanol aqueous solution with a methanol volume fraction of 75~95%.

[0012] Furthermore, the pore size of the microporous filter membrane is 0.1-0.3 μm.

[0013] Furthermore, the sample to be tested contains hydrogen peroxide and / or hypochlorite; in the process of preparing the test solution, the sample to be tested is dried and then dissolved in a solvent to obtain a sample solution.

[0014] When the sample to be tested contains hydrogen peroxide and / or hypochlorite, if it is directly dissolved in a solvent to prepare a sample solution, the subsequent methylation will fail. By drying the sample to be tested and then dissolving it, the methylation reaction of the chelating agent can proceed smoothly.

[0015] Preferably, in step S1, the diazomethane methylation reagent is trimethylsilylated diazomethane; and the methylation treatment is carried out in the dark for 2 to 36 hours.

[0016] Within a certain range, extending the methylation treatment time can lead to a more complete methylation reaction, thereby improving detection sensitivity. However, as the methylation treatment time increases, the methyl group exists as a free radical, an unstable structure that is significantly affected by environmental factors (such as temperature and pH), and the product may undergo hydrolysis, resulting in a decrease in detection sensitivity. The present invention further improves detection sensitivity by controlling the methylation treatment time within the range of 2 to 36 hours.

[0017] Preferably, in step S1, the chelating agent content in the sample to be tested is not higher than 0.05 wt %, and the mass volume ratio of the sample to be tested to the diazomethane methylating agent is 1 g: 1-2 mL.

[0018] Preferably, in step S2, the specific process of performing liquid chromatography-mass spectrometry detection on the test liquid includes: injecting the test liquid into the chromatographic column for liquid chromatography, using the elution program to perform gradient elution to separate each chelating agent, and performing mass spectrometry detection on the eluate to obtain a chromatogram; the conditions of the liquid chromatography are as follows: the chromatographic column is waters BEHC18, the column temperature is 30~35°C, the injection volume is 1~5 μL, and the flow rate is 0.1~0.3 mL / min.

[0019] Preferably, in step S3, during the qualitative and / or quantitative analysis, the type of chelating agent is determined according to the following criteria: Diethylenetriaminepentaacetic acid: retention time 10-11 min, parent ion mass-to-charge ratio 464.1-464.3; Diethylenetriamine penta (methylene phosphonic acid): retention time 9-10 min, parent ion mass-to-charge ratio 714.0-714.2; Ethylenediaminetetramethylenephosphonic acid: retention time 3~4min, parent ion mass-to-charge ratio 549.0~549.2; Hexamethylenediaminetetramethylenephosphonic acid: retention time 9-10 min, parent ion mass-to-charge ratio 605.0-605.2; Ethylene glycol ditetraacetic acid: retention time 5-6 min, parent ion mass-to-charge ratio 423.0-423.2; Hydroxyethyl diphosphate: retention time 0.5~1min, parent ion mass-to-charge ratio 262.9~263.1; Ethylenediaminetetraacetic acid: retention time 8-10 min, parent ion mass-to-charge ratio 348.9-349.1; Nitrilotriacetic acid: retention time 8-10 min, parent ion mass-to-charge ratio 234.0-234.2; Tetrasodium glutamate diacetate: retention time 10-12 min, parent ion mass-to-charge ratio 319.9-320.1; Phosphonobutanetricarboxylic acid: retention time 10-11 min, parent ion mass-to-charge ratio 341.0-341.2; Methylglycine diacetic acid: retention time 9-11 min, parent ion mass-to-charge ratio 248.0-248.2; Iminodisuccinic acid: retention time 10-11 min, parent ion mass-to-charge ratio 306.0-306.2; N-β-Hydroxyethylethylenediaminetriacetic acid: retention time 0.5~1min, parent ion mass-to-charge ratio 307.0~307.2; 2-Hydroxyphosphonoacetic acid: retention time 1-2 min, parent ion mass-to-charge ratio 213.0-213.2; Diethylenetriaminepentaacetic acid: retention time 10-11 min, parent ion mass-to-charge ratio 392.9-393.1; Citric acid: retention time 5-6 min, parent ion mass-to-charge ratio 235.0-235.2; Nitrilotrimethylenephosphonic acid: retention time 8~9min, parent ion mass-to-charge ratio 405.9~406.1.

[0020] Preferably, in step S2, the volume fraction of formic acid in the formic acid aqueous solution is 0.1-0.2%, and the volume fraction of formic acid in the formic acid acetonitrile solution is 0.1-0.2%.

[0021] Preferably, in step S3, the specific process of the quantitative analysis includes: substituting the peak area corresponding to each chelating agent in the chromatogram into the standard curve to calculate the content of each chelating agent in the sample to be tested.

[0022] Preferably, the daily chemical product is bleaching liquid, detergent, glass cleaner, laundry detergent, shampoo, laundry beads or softener.

[0023] Compared with the prior art, the present invention has the following advantages: (1) The present invention designs a specific detection method based on the characteristics of various chelating agents commonly used in daily chemical products and possible interferences in daily chemical products. By performing methylation pretreatment on the test samples and adopting specific eluents and elution procedures, efficient qualitative and quantitative detection of various chelating agents (including DTPA, DTPMP, EDTMPA, HDTEPA, EGTA, HEDP, EDTA, NTA, GLDA, PBTC, MGDA, IDS, HEDTA, HPAA, DTPA-OH, CA and ATMP) can be achieved. At the same time, the interference of other ingredients in daily chemical products on the detection can be avoided, and high detection sensitivity and accuracy can be achieved for these chelating agents.

[0024] (2) The present invention can further improve the detection sensitivity of 17 chelating agents by controlling the amount of methylation reagent and the methylation treatment time.

[0025] (3) Using the method of the present invention, the qualitative detection limit of 17 chelating agents commonly used in daily chemical products is between 0.3 and 0.8 μg / mL, and the quantitative detection limit is between 0.8 and 2.0 μg / mL, which can achieve high detection sensitivity.

[0026] (4) Using the method of the present invention, the linear range of EDTA among 17 chelating agents commonly used in daily chemical products is 2~50 μg / mL, the linear range of HPAA and ATMP is 1~20 μg / mL, and the linear range of several other chelating agents is 1~50 μg / mL. The wide linear range enables the detection method of the present invention to have a wider applicability and can meet the detection needs of daily chemical products with different chelating agent contents.

[0027] (5) The method of the present invention has a detection precision of 0.68% to 3.47% for 17 chelating agents commonly used in daily chemical products, which has a high detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The total ion current of 17 chelating agent standards.

[0029] Figure 2The chromatograms were obtained for the blank samples.

[0030] Figure 3 This is a trend diagram of the peak area changes of DTPA, DTPMP, EDTMP and HDTEPA measured at different methylation reaction times (0.25-6 h) in Example 1.

[0031] Figure 4 This is a trend diagram of the peak area changes of EGTA, HEDP, EDTA, NTA and PBTC measured at different methylation reaction times (0.25~6h) in Example 1.

[0032] Figure 5 1 is a graph showing the trend of peak area changes of HPAA, ATMP, and DTPA-OH measured at different methylation reaction times (0.25-6 h) in Example 1.

[0033] Figure 6 This is a trend diagram of the peak area changes of MGDA, IDS, HEDTA, citric acid and GLDA measured at different methylation reaction times (0.25-6 h) in Example 1.

[0034] Figure 7 This is a trend diagram of the peak area changes of DTPA, DTPMP, EDTMP and HDTEPA measured at different methylation reaction times (6-84 h) in Example 2.

[0035] Figure 8 This is a trend diagram of the peak area changes of EGTA, HEDP, EDTA, NTA and PBTC measured at different methylation reaction times (6-84 h) in Example 2.

[0036] Figure 9 This is a trend diagram of the peak area changes of HPAA, ATMP and DTPA-OH measured at different methylation reaction times (6-84 h) in Example 2.

[0037] Figure 10 This is a trend diagram of the peak area changes of MGDA, IDS, HEDTA, citric acid and GLDA measured at different methylation reaction times (6-84 h) in Example 2.

[0038] Figure 11 This is a trend diagram of the peak area changes of DTPA, DTPMP, EDTMP and HDTEPA measured at different amounts of trimethylsilylated diazomethane in Example 3.

[0039] Figure 12 This is a trend diagram of the peak area changes of MGDA, IDS, HEDTA, citric acid and GLDA measured at different amounts of trimethylsilylated diazomethane in Example 3.

[0040] Figure 13 This is a trend diagram of the peak area changes of HPAA, ATMP and DTPA-OH measured at different amounts of trimethylsilylated diazomethane in Example 3.

[0041] Figure 14 This is a trend diagram of the peak area changes of EGTA, HEDP, EDTA, NTA and PBTC measured at different amounts of trimethylsilylated diazomethane in Example 3.

[0042] Figure 15 HEDP chromatograms obtained from different experimental groups in Example 4. Figure 15 A in the figure is the HEDP chromatogram obtained in experimental group 1; Figure 15 B in the figure is the HEDP chromatogram obtained from experimental group 3.

[0043] Figure 16 This is the HEDTA chromatogram obtained by different experimental groups in Example 4. Figure 16 A in the figure is the HEDTA chromatogram obtained in experimental group 1; Figure 16 B in the figure is the HEDTA chromatogram obtained from experimental group 3.

[0044] Figure 17 This is the chromatogram obtained from testing the color bleaching liquid sample.

[0045] Figure 18 Chromatogram obtained for a glass cleaner sample.

[0046] Figure 19 Chromatogram obtained for the testing of dishwashing liquid samples. DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to the examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, any changes and advantages that may occur to a person skilled in the art are intended to be included in the present invention, and the scope of protection of the present invention is defined by the appended claims and any equivalents thereof.

[0048] The tables involving elution procedures in the following examples and comparative examples all adopt the conventional representation of elution procedures in liquid chromatography.

[0049] The following provides information on the main instruments and reagents used in each embodiment and comparative example, but the scope of protection of the present invention is not limited thereto: (1) Main instruments: 1) Liquid chromatography-mass spectrometry (LC-MS): 6120 Quadrupole LC / MS, manufactured by Agilent Technologies, USA; 2) Chromatographic column: Waters BEH C18 100×2.1 mm 1.7 μm, manufactured by Waters, USA; 3) Electronic balance: accurate to 0.001 mg, manufactured by METTLER TOLEDO, Switzerland; 4) Vortex apparatus: VORTEX 3, manufactured by IKA, Germany; 5) Water Purifier: ELGA flex2, manufactured by Veolia, UK; 6) Microporous membrane: 0.22 μm, manufactured by Shanghai Anpu Scientific Instrument Co., Ltd. 7) Pipette: 10 mL, 1 mL, 100 μL, manufactured by Eppendorf, Germany; 8) Syringe: 2 mL.

[0050] (2) Main reagents and solutions: 1) Ultrapure water: deionized water produced by ELGA flex2 water purifier; 2) Trimethylsilylated diazomethane: analytical grade (Shanghai MacLean Biochemical Technology Co., Ltd.); 3) Methanol: analytical grade; 4) Sodium hydroxide (flakes): analytical grade; 5) The abbreviations and CAS numbers of the seventeen chelating agents are as follows: Diethylenetriaminepentaacetic acid: DTPA, CAS 67-43-6; Diethylenetriaminepenta(methylenephosphonic acid): DTPMP, CAS 15827-60-8; Ethylenediaminetetramethylenephosphonic acid: EDTMPA or EDTMP, CAS 1429-50-1; Hexamethylenediaminetetramethylenephosphonic acid: HDTMPA, CAS 23605-74-5; Ethylene glycol ditetraacetic acid: EGTA, CAS 67-42-5; Hydroxyethyl diphosphonic acid: HEDP, CAS 25211-86-3; Ethylenediaminetetraacetic acid: EDTA, CAS 6381-92-6; Nitrilotriacetic acid: NTA, CAS 139-13-9; Tetrasodium glutamate diacetate: GLDA, CAS 51981-21-6; Phosphonobutanetricarboxylic acid: PBTC, CAS 37971-36-1; Methylglycine diacetic acid: MGDA, CAS 23783-26-8; Iminodisuccinic acid: IDS, CAS 144538-83-0; N-β-Hydroxyethylethylenediaminetriacetic acid: HEDTA, CAS 150-39-0; 2-Hydroxyphosphonoacetic acid: HPAA, CAS 23783-26-8; Diethylenetriaminepentaacetic acid: DTPA-OH, CAS 3148-72-9; Citric acid: CA, CAS 5949-29-1; Nitrilotrimethylenephosphonic acid: ATMP, CAS 6419-19-8.

[0051] Seventeen chelating agent reference substances were all commercially available. Among them, the purity of the 2-hydroxyphosphonoacetic acid (HPAA) reference substance, the phosphonobutanetricarboxylic acid (PBTC) reference substance, the diethylenetriaminepenta(methylenephosphonic acid) (DTPMP) reference substance, and the nitrilotrimethylenephosphonic acid (ATMP) reference substance was 50%, and the concentrations of the other chelating agent reference substances were all ≥99.99%. 80% methanol-water solution: Add 20 mL of deionized water to a 100 mL volumetric flask, dilute to volume with pure methanol solution, shake well, and ultrasonically exhaust the solution for later use. 7) 10 mol / L sodium hydroxide solution: Weigh 40 g (accurate to 0.001 g) of solid sodium hydroxide into a 200 mL beaker. Add 80 mL of deionized water and sonicate for 15 mL. After cooling to room temperature, transfer the solution to a 100 mL volumetric flask and dilute to volume with deionized water.

[0052] Example 1: Effect of methylation treatment time on detection results Prepare standard solutions and perform qualitative and quantitative tests on the chelating agents in each standard solution according to the following steps: S1: Preparation and pretreatment of standard solutions Accurately weigh 0.2 g PBTC reference substance, 0.2 g DTPMP reference substance, 0.1 g DTPA reference substance, 0.1 g EDTMPA reference substance, 0.1 g HDTMPA reference substance, 0.1 g EGTA reference substance, 0.1 g HEDP reference substance, 0.1 g EDTA reference substance, 0.1 g NTA reference substance, 0.1 g GLDA reference substance, 0.1 g MGDA reference substance, 0.1 g IDS reference substance, 0.1 g HEDTA reference substance, 0.1 g DTPA-OH reference substance, 0.1 g CA reference substance, 0.08 g HPAA reference substance, and 0.08 g ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) and place them in 50 mL volumetric flasks respectively; add 40 mL 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, add 5 mL 10 mol / L sodium hydroxide solution, and sonicate for 30 min. min, and after complete dissolution, cool to room temperature and dilute to volume with 80% methanol aqueous solution to obtain the intermediate solution of the standard solution.

[0053] Pipette the intermediate solution of each standard solution into a 1.5 mL brown bottle and add methanol to 1000 μL to obtain a standard solution of each chelating agent with a concentration of 10 ppm (based on pure chelating agent). Then, add 100 μL of trimethylsilylated diazomethane and incubate in a dark place for a period of time (reaction times for each experimental group were 0 h, 0.25 h, 0.5 h, 1 h, 1.5 h, 2 h, 4 h, and 6 h, with 0 h indicating no addition of trimethylsilylated diazomethane). Then, use a 2 mL syringe to draw 1 mL of the reaction solution and filter through a 0.22 μm microporous filter to obtain the test solution.

[0054] S2: Detection of standard solution Each test solution was tested by liquid chromatography-mass spectrometry. The automatic sampler of the liquid chromatography system drew 1 μL of the standard working solution and injected it into the chromatographic column for gradient elution. The eluate entered the mass spectrometry system for mass spectrometry detection to obtain a chromatogram. In the above process, the liquid chromatography conditions were as follows: a) Chromatographic column: Waters BEH C18 100×2.1mm 1.7μm; b) Column temperature: 35°C; c) Flow rate: 0.3 mL / min; d) Mobile phase: Mobile phase A is a 0.1% formic acid solution in water; mobile phase B is a 0.1% formic acid solution in acetonitrile. e) Elution method: gradient elution. The elution program is shown in Table 1.

[0055] Table 1 Elution procedure

[0056] In this embodiment, when trimethylsilyl diazomethane was not added for methylation in step S1, the seventeen chelating agents were not detected. The reasons for the above phenomenon are analyzed as follows: ① The polarity of the unmethylated chelating agents is too high and the ionization efficiency is low. For example, EDTA and NTA contain multiple carboxylic acid groups and dissociate into multi-charged negative ions in the solution (such as EDTA 4- ), resulting in charge dispersion, making it difficult to form stable single-charged ions. In the full-scan mode of the mass spectrometer, the signal is dispersed to multiple low-abundance mass-to-charge ratio (m / z) positions, which cannot reach the detection threshold; ② Molecules with strong polarity are tightly bound to solvents such as water to form a solvation layer, which requires additional energy for desolvation before entering the gas phase. However, in the electrospray ionization (ESI) process, the desorption efficiency of such molecules is low and the number of effective ions is insufficient.

[0057] At different methylation reaction times (0.25-6 h), the peak areas of the chelating agents in the obtained chromatograms are shown in Figures 3 to 6 It can be seen that when the methylation reaction time is 2 h or less, the peak area of ​​each chelating agent increases with the extension of the methylation reaction time; when the methylation reaction time exceeds 2 h, the peak area of ​​some chelating agents (such as DTPA-OH and MGDA) decreases slightly.

[0058] Example 2: Methylation stability Prepare standard solutions and perform qualitative and quantitative tests on the chelating agents in each standard solution according to the following steps: S1: Preparation and pretreatment of standard solutions Accurately weigh 0.2 g PBTC reference substance, 0.2 g DTPMP reference substance, 0.1 g DTPA reference substance, 0.1 g EDTMPA reference substance, 0.1 g HDTMPA reference substance, 0.1 g EGTA reference substance, 0.1 g HEDP reference substance, 0.1 g EDTA reference substance, 0.1 g NTA reference substance, 0.1 g GLDA reference substance, 0.1 g MGDA reference substance, 0.1 g IDS reference substance, 0.1 g HEDTA reference substance, 0.1 g DTPA-OH reference substance, 0.1 g CA reference substance, 0.08 g HPAA reference substance, and 0.08 g ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) and place them in 50 mL volumetric flasks respectively; add 40 mL 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, add 5 mL 10 mol / L sodium hydroxide solution, and sonicate for 30 min. min, and after complete dissolution, cool to room temperature and dilute to volume with 80% methanol aqueous solution to obtain the intermediate solution of the standard solution.

[0059] Pipette the intermediate solution of each standard solution into a 1.5 mL brown bottle and add methanol to 1000 μL to obtain a standard solution of each chelating agent with a concentration of 25 ppm (based on pure chelating agent). Then, add 100 μL of trimethylsilylated diazomethane and react in a dark place for a period of time (reaction time for each experimental group was 6 h, 12 h, 24 h, 36 h, 48 h, 72 h, and 84 h, respectively). Then, use a 2 mL syringe to draw 1 mL of the reaction solution and filter it through a 0.22 μm microporous filter to obtain the test solution.

[0060] S2: Detection of standard solution According to the method in step S2 of Example 1, each test liquid was subjected to liquid chromatography-mass spectrometry to obtain a chromatogram.

[0061] At different methylation reaction times (6-84 h), the peak areas of the chelating agents in the chromatograms obtained are shown in Figures 7 to 10 The results show that when the methylation reaction time is between 6 and 36 hours, the peak areas of most chelating agents remain relatively stable. However, after the methylation reaction time exceeds 36 hours, the peak areas of each chelating agent show a significant downward trend as the reaction time increases. This phenomenon is attributed to the fact that during the methylation process, the methyl group exists as an unstable free radical structure, which is significantly affected by environmental factors such as temperature and pH. Furthermore, if the reaction time is too long, the product may undergo hydrolysis.

[0062] Example 3: Effect of the amount of methylation reagent on the detection effect Prepare standard solutions and perform qualitative and quantitative tests on the chelating agents in each standard solution according to the following steps: S1: Preparation and pretreatment of standard solutions Accurately weigh 0.2 g PBTC reference substance, 0.2 g DTPMP reference substance, 0.1 g DTPA reference substance, 0.1 g EDTMPA reference substance, 0.1 g HDTMPA reference substance, 0.1 g EGTA reference substance, 0.1 g HEDP reference substance, 0.1 g EDTA reference substance, 0.1 g NTA reference substance, 0.1 g GLDA reference substance, 0.1 g MGDA reference substance, 0.1 g IDS reference substance, 0.1 g HEDTA reference substance, 0.1 g DTPA-OH reference substance, 0.1 g CA reference substance, 0.08 g HPAA reference substance, and 0.08 g ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) and place them in 50 mL volumetric flasks respectively; add 40 mL 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, add 5 mL 10 mol / L sodium hydroxide solution, and sonicate for 30 min. min, and after complete dissolution, cool to room temperature and dilute to volume with 80% methanol aqueous solution to obtain the intermediate solution of the standard solution.

[0063] Pipette the intermediate solution of each standard solution into a 1.5 mL brown bottle and add methanol to 1000 μL to obtain a standard solution of each chelating agent with a concentration (based on pure chelating agent) of 5 ppm. Then, add a certain amount of trimethylsilylated diazomethane (the amount of trimethylsilylated diazomethane used in each experimental group was 10 μL, 25 μL, 50 μL, and 75 μL, 100 μL, 150 μL, and 200 μL, respectively). Incubate in a dark place for 2 h. Then, use a 2 mL syringe to draw 1 mL of the reaction solution and filter it through a 0.22 μm microporous filter to obtain the test solution.

[0064] S2: Detection of standard solution According to the method in step S2 of Example 1, each test liquid was subjected to liquid chromatography-mass spectrometry to obtain a chromatogram.

[0065] At different trimethylsilylated diazomethane dosages (10-200 μL), the peak areas of the chelating agents in each chromatogram were found in Figures 11 to 14 , it can be seen that: when the amount of trimethylsilylated diazomethane is 100 μL or less, the peak area measured for each chelating agent increases with the increase of its amount; when the amount of trimethylsilylated diazomethane is higher than 100 μL, further increasing its amount will cause the peak area of ​​some chelating agents (such as EDTMP, EGTA, and HEDP) to decrease.

[0066] Example 4: Effect of different elution procedures on detection results Prepare standard solutions and perform qualitative and quantitative tests on the chelating agents in each standard solution according to the following steps: S1: Preparation and pretreatment of standard solutions Accurately weigh 0.2 g PBTC reference substance, 0.2 g DTPMP reference substance, 0.1 g DTPA reference substance, 0.1 g EDTMPA reference substance, 0.1 g HDTMPA reference substance, 0.1 g EGTA reference substance, 0.1 g HEDP reference substance, 0.1 g EDTA reference substance, 0.1 g NTA reference substance, 0.1 g GLDA reference substance, 0.1 g MGDA reference substance, 0.1 g IDS reference substance, 0.1 g HEDTA reference substance, 0.1 g DTPA-OH reference substance, 0.1 g CA reference substance, 0.08 g HPAA reference substance, and 0.08 g ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) and place them in 50 mL volumetric flasks respectively; add 40 mL 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, add 5 mL 10 mol / L sodium hydroxide solution, and sonicate for 30 min. min, and after complete dissolution, cool to room temperature and dilute to volume with 80% methanol aqueous solution to obtain the intermediate solution of the standard solution.

[0067] Pipette the intermediate solution of each standard solution into a 1.5 mL brown bottle and add methanol to 1000 μL to obtain a standard solution of each chelating agent with a concentration of 5 ppm (based on pure chelating agent). Then, add 100 μL of trimethylsilylated diazomethane and react in a dark place for 2 h. Then, use a 2 mL syringe to draw 1 mL of the reaction solution and filter it through a 0.22 μm microporous filter to obtain the test solution.

[0068] S2: Detection of standard solution According to the method in step S2 of Example 1 (the only difference is the elution procedure), each test solution was detected by liquid chromatography-mass spectrometry. The elution degree of each experimental group in this example is shown in Tables 2 to 4, respectively, and a chromatogram was obtained.

[0069] Table 2 Elution procedure of experimental group 1

[0070] Table 3 Elution procedure of experimental group 2

[0071] Table 4 Elution procedure of experimental group 3

[0072] From the chromatogram, we can see that under the elution procedures of experimental groups 1 to 3, there is a certain separation effect on the seventeen chelating agents. Among them, the separation effect of experimental group 1 is slightly worse, while the separation effects of experimental groups 2 and 3 are better. The reasons for the above phenomenon are: Effect of the initial mobile phase ratio: The initial mobile phase A (0.1% formic acid in water) ratio in experimental group 1 was 90%, which was lower than the 95% ratios in experimental groups 2 and 3. The mobile phase B (0.1% formic acid in acetonitrile) ratio was relatively high. A high organic phase ratio will shorten the retention time of the chelating agent on the chromatographic column. Some chelating agents with similar polarity, such as HEDP and HEDTA, may be eluted before they have time to be fully separated, resulting in poor resolution and poor chromatographic peak shape (the chromatograms of HEDP and HEDTA obtained in experimental group 1 are shown in Figure 2). Figure 15 A and Figure 16 The higher initial aqueous phase ratio in experimental group 2 and experimental group 3 allows the chelating agent to be retained on the chromatographic column to a certain extent. At the same time, the chromatographic peak shape is greatly improved, laying the foundation for subsequent separation. Therefore, the separation effects of the two groups are similar (the chromatograms of HEDP and HEDTA obtained in experimental group 3 are shown in Figure 15 B and Figure 16 B in ).

[0073] Example 5: Detection sensitivity test Prepare standard solutions and perform qualitative and quantitative tests on the chelating agents in each standard solution according to the following steps: S1: Preparation and pretreatment of standard solutions Accurately weigh 0.2 g PBTC reference substance, 0.2 g DTPMP reference substance, 0.1 g DTPA reference substance, 0.1 g EDTMPA reference substance, 0.1 g HDTMPA reference substance, 0.1 g EGTA reference substance, 0.1 g HEDP reference substance, 0.1 g EDTA reference substance, 0.1 g NTA reference substance, 0.1 g GLDA reference substance, 0.1 g MGDA reference substance, 0.1 g IDS reference substance, 0.1 g HEDTA reference substance, 0.1 g DTPA-OH reference substance, 0.1 g CA reference substance, 0.08 g HPAA reference substance, and 0.08 g ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) and place them in 50 mL volumetric flasks respectively; add 40 mL 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, add 5 mL 10 mol / L sodium hydroxide solution, and sonicate for 30 min. min, and after complete dissolution, cool to room temperature and dilute to volume with 80% methanol aqueous solution to obtain the intermediate solution of the standard solution.

[0074] Pipette the intermediate solution of each standard solution into a 1.5 mL brown bottle and add methanol to 1000 μL to obtain a series of low-concentration standard solutions of each chelating agent. Then, add 100 μL of trimethylsilylated diazomethane and react in a dark place for 2 h. Then, use a 2 mL syringe to draw 1 mL of the reaction solution and filter it through a 0.22 μm microporous filter to obtain the test solution.

[0075] S2: Detection of standard solution According to the method in step S2 of Example 1 (the only difference is the elution procedure), each test solution is detected by liquid chromatography-mass spectrometry to obtain a chromatogram.

[0076] The above method was used for six consecutive measurements. Based on the resulting chromatograms, the ratio of the target peak height to the blank baseline noise (S / N) was calculated. The lowest concentration meeting an S / N ≥ 3 was defined as the limit of qualitative detection (LOD), and the lowest concentration meeting an S / N ≥ 10 was defined as the limit of quantitative detection (LOQ). The measured limits of qualitative detection and quantitative detection for each chelating agent are shown in Table 5.

[0077] Table 5 Qualitative detection limits and quantitative detection limits of various chelating agents

[0078] As can be seen from Table 5, the qualitative detection limits of each chelating agent are between 0.3 and 0.8 μg / mL, and the quantitative detection limits are between 0.8 and 2.0 μg / mL, indicating that the method of the present invention can achieve high detection sensitivity and meet the detection requirements of trace chelating agents in daily chemical products.

[0079] Example 6: Actual sample detection Follow the steps below to qualitatively and quantitatively test chelating agents in seven homemade daily chemical product samples (color bleach, dishwashing liquid, glass cleaner, laundry detergent, shampoo, laundry beads, and softener): S1: Preparation of standard working solution Accurately weigh 0.2 g PBTC reference substance, 0.2 g DTPMP reference substance, 0.1 g DTPA reference substance, 0.1 g EDTMPA reference substance, 0.1 g HDTMPA reference substance, 0.1 g EGTA reference substance, 0.1 g HEDP reference substance, 0.1 g EDTA reference substance, 0.1 g NTA reference substance, 0.1 g GLDA reference substance, 0.1 g MGDA reference substance, 0.1 g IDS reference substance, 0.1 g HEDTA reference substance, 0.1 g DTPA-OH reference substance, 0.1 g CA reference substance, 0.08 g HPAA reference substance, and 0.08 g ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) and place them in 50 mL volumetric flasks respectively; add 40 mL 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, add 5 mL 10 mol / L sodium hydroxide solution, and sonicate for 30 min. min, and after complete dissolution, cool to room temperature and dilute to volume with 80% methanol aqueous solution to obtain the intermediate solution of the standard solution.

[0080] Accurately pipette 2.5 μL, 5 μL, 12.5 μL, and 25 μL of the standard solution intermediate into a 1.5 mL brown bottle, add methanol to 1000 μL, then add 100 μL of trimethylsilylated diazomethane, and react in a dark place for 2 h. Then, use a 2 mL syringe to draw 1 mL of the reaction solution, pass it through a 0.22 μm microporous filter membrane, and obtain a series of standard working solutions STD2, STD3, STD4, and STD5 with a concentration gradient. Dilute STD3 or STD4 10 times with methanol to obtain the standard working solution STD1.

[0081] The corresponding chelating agent concentrations in the above-obtained standard working solutions (the chelating agent concentration before adding trimethylsilylated diazomethane and calculated as pure chelating agent) are as follows: Standard working solutions of PBTC, DTPMP, DTPA, EDTMPA, HDTMPA, EGTA, HEDP, EDTA, NTA, GLDA, MGDA, IDS, HEDTA, DTPA-OH, and CA: the corresponding chelating agent concentrations for STD1, STD2, STD3, STD4, and STD5 are 1 μg / mL, 5 μg / mL, 10 μg / mL, 25 μg / mL, and 50 μg / mL, respectively; The standard working solutions of HAPP and ATMP: STD1, STD2, STD3, STD4, and STD5 have corresponding chelating agent concentrations of 1 μg / mL, 2 μg / mL, 4 μg / mL, 10 μg / mL, and 20 μg / mL, respectively.

[0082] S2: Testing of standard working solution Each standard working solution was tested by liquid chromatography-mass spectrometry. The automatic sampler of the liquid chromatography system drew 1 μL of the standard working solution and injected it into the chromatographic column for gradient elution. The eluent entered the mass spectrometry system. In the above process, the liquid chromatography conditions were as follows: a) Chromatographic column: Waters BEH C18 100×2.1mm 1.7μm; b) Column temperature: 35°C; c) Flow rate: 0.3 mL / min; d) Mobile phase: Mobile phase A is a 0.1% formic acid solution in water; mobile phase B is a 0.1% formic acid solution in acetonitrile. e) Elution method: gradient elution. The elution program is shown in Table 6.

[0083] Table 6 Elution procedure

[0084] In the mass spectrometry system, the electrospray ion source positive ion mode (ESI+) and full scan mode were used to determine the parent ion mass-to-charge ratio (m / z) and retention time (t) of each chelating agent. The results are shown in Table 7. The total ion current (TIC) of 17 chelating agent standards was generated. The results are shown in Table 7. Figure 1 As shown; the ion monitoring mode (SIM) was used to detect ions with specific mass-to-charge ratios for qualitative and quantitative analysis. The peak area corresponding to each chelating agent in the chromatogram was used as the ordinate (y), and the concentration of the standard working solution was used as the abscissa (x). The regression equation, i.e., the standard curve of each chelating agent, was obtained. The results are shown in Table 8.

[0085] Table 7 Precursor ion mass-to-charge ratio and retention time of each chelating agent

[0086] Table 8 Standard curves of various chelating agents

[0087] S3: Pretreatment of samples to be tested Weigh 0.1 g (accurate to 0.001 g) of the sample to be tested into a 15 mL centrifuge tube (samples containing hydrogen peroxide or hypochlorite should be dried before this step). Use a 10 mL pipette to transfer 10 mL of 80% methanol-water solution to the same centrifuge tube. Ultrasonicate for 10 minutes to obtain the sample solution. Use a 1 mL pipette to transfer 500 μL of the sample solution and 500 μL of the methanol solution to a 1.5 mL brown bottle. Then, use a 100 μL pipette to transfer 100 μL of trimethylsilylated diazomethane to the same bottle. Vortex thoroughly to mix, and incubate in the dark for 2 hours. Use a 2 mL syringe to transfer 1 mL of the reaction solution and filter through a 0.22 μm microporous filter to obtain the test solution.

[0088] S4: Testing of samples to be tested According to the method in step S2 of this embodiment, the liquid to be tested is subjected to liquid chromatography-mass spectrometry to obtain a chromatogram. Based on the chromatogram, the chelating agent in the sample to be tested is qualitatively and quantitatively analyzed by the following method: a) Qualitative analysis of the target compound was performed using the following two criteria to determine the type of chelating agent present in the sample: the target compound in the sample had the same retention time as the chelating agent reference standard (retention times for each chelating agent are shown in Table 7, with a deviation within ±2.5%); the parent ion mass-to-charge ratio of the target compound in the sample was consistent with that of the chelating agent reference standard, with a relative deviation within ±0.1 Da; b) Quantify each chelating agent in the sample by the following method: Detect the peak area corresponding to each chelating agent in the chromatogram, substitute it into the corresponding standard curve in Table 8, and calculate the concentration of each chelating agent in the sample.

[0089] S5: Blank sample testing The sample to be tested was replaced with 80% methanol aqueous solution, and pre-treated according to the method in step S3 of this embodiment (methylation reaction time was 2 h), and then detected by liquid chromatography-mass spectrometry according to the method in step S4 of this embodiment. The obtained chromatogram is shown in FIG. Figure 2 shown.

[0090] Each daily chemical product sample was tested five times in succession according to the above method, and the types of chelating agents detected were counted and their contents were calculated. The results are shown in Table 9 (in Table 9, “ / ” indicates not detected). Among them, when testing color bleaching liquid, glass cleaner and dishwashing liquid, the typical chromatograms obtained are as follows: Figures 17 to 19 shown.

[0091] Table 9 Actual sample test results

[0092] The sample formulas of daily chemical products prepared in this embodiment are as follows: (1) The homemade bleaching liquid is composed of the following components by mass percentage: hydrogen peroxide solution 10.00%, fatty alcohol polyoxyethylene ether-9 (AEO-9) 5.00%, DTPMP 0.08%, essence 0.10%, and the balance is deionized water.

[0093] (2) Homemade dishwashing liquid is composed of the following components by mass percentage: sodium polyoxyethylene fatty alcohol ether sulfate 8.50%, sodium dodecylbenzene sulfonate 9.00%, lauryl glucoside 1.30%, cocamidopropylamine oxide 3.00%, kasonon 0.01%, sodium chloride 0.80%, citric acid monohydrate 0.09%, fragrance 0.10%, GLDA 0.20%, and the balance is deionized water.

[0094] (3) The homemade glass cleaner is composed of the following components by mass percentage: AEO-9 0.30%, propylene glycol ethyl ether 7.00%, citric acid monohydrate 0.10%, kasonon 0.01%, phenoxyethanol 0.03%, fragrance 0.10%, and the balance is deionized water.

[0095] (4) Homemade laundry detergent consists of the following components by mass percentage: 5.00% sodium dodecylbenzene sulfonate, 6.00% sodium sulfate of fatty alcohol polyoxyethylene ether, 5.50% fatty alcohol polyoxyethylene ether, 2.50% potassium soap of fatty acid, 2.00% alkyl glycoside, 1.80% sodium chloride, 0.15% citric acid monohydrate, 0.05% kasonon, 0.30% fragrance, 0.20% MGDA, and the balance is deionized water.

[0096] (5) Homemade shampoo is composed of the following components by mass percentage: sodium laureth sulfate 15.00%, cocamidopropyl betaine 3.00%, coco-glucoside 2.00%, sorbitol 2.00%, cocamide MEA 1.50%, laureth-2 1.00%, ethylene glycol distearate 0.80%, glycerin 0.50%, sodium citrate 0.50%, menthol 0.45%, sodium chloride 0.30%, caprylyl glycol 0.25%, polyquaternium-10 0.20%, sodium benzoate 0.20%, EDTA-2Na 0.13%, hydrogenated castor oil 0.10%, fragrance 0.30%, and the balance is deionized water.

[0097] (6) Homemade laundry beads are composed of the following components by mass percentage: glycerol 24.00%, monoethanolamine 5.50%, propylene glycol 8.0%, dodecylbenzenesulfonic acid 26.0%, sodium sulfate of fatty alcohol polyoxyethylene ether 16.5%, fatty alcohol polyoxyethylene ether 23.00%, fatty acid potassium soap 6.50%, fragrance 0.50%, EDTMP-3Na 0.30%, diclosan (HP100) 0.20%, and the balance is deionized water.

[0098] (7) The homemade softener is composed of the following components by mass percentage: ester quaternary ammonium salt 3.00%, fatty alcohol polyoxyethylene ether 0.50%, lauramide propyl betaine 1.5%, polydimethylsiloxane 1.00%, ethanol 1.00%, isopropyl alcohol 0.21%, kason 0.05%, HEDP 0.10%, fragrance 0.20%, and the balance is deionized water.

[0099] Example 7: Method Precision Test Prepare standard solutions and perform qualitative and quantitative tests on the chelating agents in each standard solution according to the following steps: S1: Preparation and pretreatment of standard solutions Accurately weigh 0.2 g PBTC reference substance, 0.2 g DTPMP reference substance, 0.1 g DTPA reference substance, 0.1 g EDTMPA reference substance, 0.1 g HDTMPA reference substance, 0.1 g EGTA reference substance, 0.1 g HEDP reference substance, 0.1 g EDTA reference substance, 0.1 g NTA reference substance, 0.1 g GLDA reference substance, 0.1 g MGDA reference substance, 0.1 g IDS reference substance, 0.1 g HEDTA reference substance, 0.1 g DTPA-OH reference substance, 0.1 g CA reference substance, 0.08 g HPAA reference substance, and 0.08 g ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) and place them in 50 mL volumetric flasks respectively; add 40 mL 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, add 5 mL 10 mol / L sodium hydroxide solution, and sonicate for 30 min. min, and after complete dissolution, cool to room temperature and dilute to volume with 80% methanol aqueous solution to obtain the intermediate solution of the standard solution.

[0100] Pipette the intermediate solution of each standard solution into a 1.5 mL brown bottle and add methanol to 1000 μL to obtain a standard solution of each chelating agent at a concentration three times the quantitative detection limit. Then, add 100 μL of trimethylsilylated diazomethane and react in a dark place for 2 h. Then, use a 2 mL syringe to draw 1 mL of the reaction solution and filter it through a 0.22 μm microporous filter to obtain the test solution.

[0101] S2: Detection of standard solution According to the method in step S4 of Example 6 (the only difference is the elution procedure), each test solution is detected by liquid chromatography-mass spectrometry to obtain a chromatogram, and quantitative analysis is performed based on the chromatogram to obtain the concentration of the chelating agent in each standard solution.

[0102] The above method was used for 6 consecutive measurements, and the method precision (RSD) was calculated. The results are shown in Table 10.

[0103] Table 10 Method precision test results

[0104] It can be seen from Table 10 that the precision of each chelating agent is between 0.68% and 3.47%, indicating that the method of the present invention has high detection accuracy.

[0105] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this disclosure pertains. Unless otherwise specified, the raw materials and equipment used herein are conventional in the art and can be obtained from conventional commercial sources. The methods used herein are conventional in the art, unless otherwise specified.

[0106] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for detecting multiple chelating agents in daily chemical products, characterized in that: The following steps are involved: S1: using a diazomethane methylation reagent to methylate the sample to be tested to obtain a test solution; S2: The test liquid is subjected to liquid chromatography-mass spectrometry to obtain a chromatogram. The elution procedure is as follows: 1) At minute 0, the eluent composition was: 94-96% v / v formic acid aqueous solution, the balance formic acid acetonitrile solution; this remained unchanged until minute 4-5; 2) The eluent composition ratio gradually changed to: 60-70% v / v formic acid aqueous solution, the balance formic acid acetonitrile solution at 8-10 minutes; this ratio remained unchanged until 13-14 minutes; 3) The eluent composition ratio gradually changes to: 94-96% v / v formic acid aqueous solution, with the remainder being formic acid acetonitrile solution at the 14th to 15th minute; the subsequent formulation remains unchanged for an unlimited period of time; S3: Perform qualitative and / or quantitative analysis on the chelating agent in the sample according to the chromatogram.

2. The detection method according to claim 1, wherein The chelating agent includes at least one of diethylenetriaminepentaacetic acid, diethylenetriaminepentamethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, ethylene glycol ditetraacetic acid, hydroxyethyl diphosphonic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, tetrasodium glutamate diacetate, phosphonobutanetricarboxylic acid, methylglycine diacetic acid, iminodisuccinic acid, N-β-hydroxyethylethylenediaminetriacetic acid, 2-hydroxyphosphonoacetic acid, diethylenetriaminepentaacetic acid, citric acid and nitrilotrimethylenephosphonic acid.

3. The detection method according to claim 1, wherein The specific process of step S1 includes: dissolving the sample to be tested in a solvent to obtain a sample solution, mixing the sample solution, methanol and a diazomethane methylation reagent, performing a methylation treatment, and passing the mixture through a microporous filter membrane to obtain a test solution; the volume ratio of the sample solution to methanol is 1:0.5-2; and the solvent is methanol or a methanol-water solution with a methanol volume fraction of 75-95%.

4. The detection method according to claim 3, characterized in that The sample to be tested contains hydrogen peroxide and / or hypochlorite; in the process of preparing the test solution, the sample to be tested is dried and then dissolved in a solvent to obtain a sample solution.

5. The detection method according to claim 1 or 3, characterized in that In step S1, the diazomethane methylation reagent is trimethylsilylated diazomethane; the methylation treatment is carried out in the dark for 2 to 36 hours.

6. The detection method according to claim 1 or 3, characterized in that In step S1, the chelating agent content in the sample to be tested is not higher than 0.05 wt %, and the mass volume ratio of the sample to be tested to the diazomethane methylating agent is 1 g: 1-2 mL.

7. The detection method according to claim 1, wherein In step S2, the specific process of performing liquid chromatography-mass spectrometry detection on the test liquid includes: injecting the test liquid into the chromatographic column for liquid chromatography, using the elution program to perform gradient elution to separate each chelating agent, and performing mass spectrometry detection on the eluate to obtain a chromatogram; the conditions of the liquid chromatography are as follows: the chromatographic column is waters BEH C18, the column temperature is 30~35°C, the injection volume is 1~5 μL, and the flow rate is 0.1~0.3 mL / min.

8. The detection method according to claim 2, characterized in that In step S3, during the qualitative and / or quantitative analysis, the type of chelating agent is determined according to the following criteria: Diethylenetriaminepentaacetic acid: retention time 10-11 min, parent ion mass-to-charge ratio 464.1-464.3; Diethylenetriamine penta (methylene phosphonic acid): retention time 9-10 min, parent ion mass-to-charge ratio 714.0-714.2; Ethylenediaminetetramethylenephosphonic acid: retention time 3~4min, parent ion mass-to-charge ratio 549.0~549.2; Hexamethylenediaminetetramethylenephosphonic acid: retention time 9-10 min, parent ion mass-to-charge ratio 605.0-605.2; Ethylene glycol ditetraacetic acid: retention time 5-6 min, parent ion mass-to-charge ratio 423.0-423.2; Hydroxyethyl diphosphate: retention time 0.5~1min, parent ion mass-to-charge ratio 262.9~263.1; Ethylenediaminetetraacetic acid: retention time 8-10 min, parent ion mass-to-charge ratio 348.9-349.1; Nitrilotriacetic acid: retention time 8-10 min, parent ion mass-to-charge ratio 234.0-234.2; Tetrasodium glutamate diacetate: retention time 10-12 min, parent ion mass-to-charge ratio 319.9-320.1; Phosphonobutanetricarboxylic acid: retention time 10-11 min, parent ion mass-to-charge ratio 341.0-341.2; Methylglycine diacetic acid: retention time 9-11 min, parent ion mass-to-charge ratio 248.0-248.2; Iminodisuccinic acid: retention time 10-11 min, parent ion mass-to-charge ratio 306.0-306.2; N-β-Hydroxyethylethylenediaminetriacetic acid: retention time 0.5~1min, parent ion mass-to-charge ratio 307.0~307.2; 2-Hydroxyphosphonoacetic acid: retention time 1-2 min, parent ion mass-to-charge ratio 213.0-213.2; Diethylenetriaminepentaacetic acid: retention time 10-11 min, parent ion mass-to-charge ratio 392.9-393.1; Citric acid: retention time 5-6 min, parent ion mass-to-charge ratio 235.0-235.2; Nitrilotrimethylenephosphonic acid: retention time 8~9min, parent ion mass-to-charge ratio 405.9~406.

1.

9. The detection method according to claim 1, wherein In step S2, the volume fraction of formic acid in the formic acid aqueous solution is 0.1-0.2%, and the volume fraction of formic acid in the formic acid acetonitrile solution is 0.1-0.2%.

10. The detection method according to claim 1, characterized in that The daily chemical products are bleaching liquid, detergent, glass cleaner, laundry liquid, shampoo, laundry beads or softener.

Images