Method for detecting multiple chelating agents in daily chemical products

Abstract

The application relates to the field of analysis and detection, and discloses a detection method for multiple chelating agents in daily chemical products, which comprises the following steps: methylating a to-be-detected sample by using a diazomethane methylating reagent to obtain a to-be-detected solution; detecting the to-be-detected solution by using a specific elution program to obtain a chromatogram; and qualitatively and / or quantitatively analyzing the chelating agents in the to-be-detected sample according to the chromatogram. By using the detection method, multiple chelating agents (including DTPA, DTPMP, EDTMPA, HDTEPA, EGTA, HEDP, EDTA, NTA, GLDA, PBTC, MGDA, IDS, HEDTA, HPAA, DTPA-OH, CA and ATMP) can be efficiently detected, meanwhile, the detection can be prevented from being disturbed by other components in the daily chemical products, and high detection sensitivity and accuracy can be realized for the chelating agents.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analytical detection, in particular to a detection method for multiple chelating agents in daily chemical products. BACKGROUND

[0002] Chelating agents are a class of compounds that can form complexes with metal ions. They usually have electron donors that can coordinate with metal ions, thus having a series of special effects such as softening, descaling, rust prevention, synergism, and stabilization. Chelating agents are widely used in the daily chemical industry. For example, adding chelating agents to hydrogen peroxide and hypochlorous acid bleaching agents can effectively inhibit the catalytic decomposition of metal ions on hydrogen peroxide and hypochlorous acid components, improve bleaching efficiency, save bleaching solution, and reduce bleaching cost. Adding chelating agents to detergents can effectively adjust water hardness and improve washing performance.

[0003] Common chelating agents include phosphate, carboxylate, and organic phosphorus. Current detection methods for trace chelating agents mainly include ion exchange chromatography and metal ion complexing liquid chromatography. Ion exchange chromatography is suitable for carboxylic acid chelating agents, phosphate chelating agents, and some organic phosphorus chelating agents. The disadvantage is that it mainly relies on peak time and chromatographic peak shape for qualitative analysis, but the peak time of chelating agents may shift during analysis, causing difficulty in qualitative analysis. Metal ion complexing liquid chromatography uses a color-developing metal to form a complex with chelating agents, which is then detected by a UV detector. It is suitable for chelating agents that can develop color with copper ions and iron ions, mainly carboxylate chelating agents. For example, patent CN112326850A uses this method to detect trisodium nitrilotriacetate in water. This method has low detection limit, short detection time, and less influence from the matrix. However, the peak time and absorption wavelength of chelating agents are relatively close, and the scope of application is narrow. The above-mentioned test methods cover only 5-9 types of chelating agents, and the types of chelating agents involved are limited. Moreover, there is no reported detection method for chelating agents in complex daily chemical systems. Some special interferents in daily chemical systems can easily affect the detection of chelating agents, and the content of chelating agents in daily chemical systems is low, requiring high detection sensitivity. SUMMARY

[0004] To solve the above technical problems, i.e., the existing chelating agent detection methods can detect fewer types of chelating agents, and there is no reported detection method for chelating agents in complex daily chemical systems, the present application provides a detection method for multiple chelating agents in daily chemical products. The detection method of the present application can achieve efficient qualitative and quantitative detection of 17 types of chelating agents, while avoiding interference from other components in daily chemical products. Moreover, the detection method can achieve high sensitivity and accuracy for the 17 types of chelating agents.

[0005] The specific technical solutions of the present application are as follows:

[0006] A method for detecting multiple chelating agents in daily chemicals, comprising the following steps:

[0007] S1: methylating the sample to be tested with a diazomethane methylating reagent to obtain a test solution;

[0008] S2: detecting the test solution by liquid chromatography-mass spectrometry to obtain a chromatogram, and the elution program is as follows:

[0009] 1) At 0 min, the eluent composition is: 94-96% v / v formic acid aqueous solution, and the rest is formic acid acetonitrile solution; unchanged until 4-5 min;

[0010] 2) The component ratio in the eluent gradually changes, and changes to: 60-70% v / v formic acid aqueous solution, and the rest is formic acid acetonitrile solution, until 8-10 min; unchanged until 13-14 min;

[0011] 3) The component ratio in the eluent gradually changes, and changes to: 94-96% v / v formic acid aqueous solution, and the rest is formic acid acetonitrile solution, until 14-15 min; the subsequent formula is unchanged, and the maintenance time is unlimited;

[0012] S3: qualitatively and / or quantitatively analyzing the chelating agents in the sample to be tested according to the chromatogram.

[0013] In the above detection method, if the elution program uses the conventional representation method of the elution program in liquid chromatography, it can be summarized in the following table:

[0014]

[0015] The specific meaning of the elution program represented by the above table is as follows (the representation method of the elution program in each of the following embodiments is also the same): at the start (0 min), the eluent used is composed of the following components by volume percentage: 94-96% v / v formic acid aqueous solution, and the rest is formic acid acetonitrile solution; the eluent formula is unchanged until 4-5 min, and then the component ratio gradually changes until 8-10 min, which changes to: 60-70% v / v formic acid aqueous solution, and the rest is formic acid acetonitrile solution; the eluent formula is unchanged until 13-14 min, and then the component ratio gradually changes until 14-15 min, which changes to: 94-96% v / v formic acid aqueous solution, and the rest is formic acid acetonitrile solution; the subsequent eluent formula is unchanged, and the maintenance time is unlimited.

[0016] In the process of detecting trace chelating agents in daily chemicals, if the sample is directly detected by liquid chromatography-mass spectrometry, the ionization efficiency is low due to the high polarity of the chelating agent, such as EDTA, NTA, etc. containing multiple carboxylic acid groups, which are dissociated into multiple charged negative ions (such as EDTA 4-), leading to charge dispersion, difficulty in forming stable single-charge ions, signal dispersion to multiple low-abundance mass-to-charge ratio (m / z) positions in mass spectrometric analysis, and failure to reach the detection threshold; and the polar chelating agent is closely combined with solvents such as water in the sample to be detected to form a solvation layer, and additional energy is required to desolvate to enter the gas phase, and the desorption efficiency of such molecules is low in the mass spectrometric analysis process, and the number of effective ions is insufficient. In view of the above problems, the sample to be detected is subjected to methylation treatment before being detected by liquid chromatography-mass spectrometry, and the chelating agent after methylation can form stable single-charge ions in the mass spectrometric analysis process, and the number of effective ions is relatively large, so that the detection sensitivity can be improved, and the detection of trace chelating agents in daily chemical products can be realized.

[0017] On this basis, in the process of liquid chromatography, a specific elution program is used, which can realize the separation of multiple chelating agents commonly used in daily chemical products (including diethylene triamine pentaacetic acid, diethylene triamine pentamethylene phosphonic acid, ethylenediamine tetramethylene phosphonic acid, hexamethylene diamine tetramethylene phosphonic acid, ethylene glycol bis-tetraacetic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, glutamic acid diacetic acid tetrasodium, phosphono butane tricarboxylic acid, methyl glycine diacetic acid, imino disuccinic acid, N-β-hydroxyethyl ethylenediamine triacetic acid, 2-hydroxyphosphonoacetic acid, diethylene triamine pentaacetic acid, citric acid and nitrilotrimethylene phosphonic acid), and can avoid the interference of other components (including high ionic strength and complex surfactant components and oxidizing components) in daily chemical products on the detection, and can realize high detection sensitivity and accuracy for each chelating agent, so as to realize the qualitative and quantitative detection of each chelating agent including multiple carboxylic acid chelating agents and multiple organic phosphorus chelating agents, break through the limitation that the existing detection method can detect limited types of chelating agents, and meet the detection needs of trace chelating agents in complex matrix of daily chemical products.

[0018] As preferred, the chelating agent includes at least one of diethylene triamine pentaacetic acid (DTPA), diethylene triamine pentamethylene phosphonic acid (DTPMP), ethylenediamine tetramethylene phosphonic acid (EDTMPA), hexamethylene diamine tetramethylene phosphonic acid (HDTMPA), ethylene glycol bis-tetraacetic acid (EGTA), hydroxyethylidene diphosphonic acid (HEDP), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), glutamic acid diacetic acid tetrasodium (GLDA), phosphono butane tricarboxylic acid (PBTC), methyl glycine diacetic acid (MGDA), imino disuccinic acid (IDS), N-β-hydroxyethyl ethylenediamine triacetic acid (HEDTA), 2-hydroxyphosphonoacetic acid (HAPP), diethylene triamine pentaacetic acid (DTPA-OH), citric acid (CA) and nitrilotrimethylene phosphonic acid (ATMP).

[0019] Preferably, 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-based methylating agent; performing methylation treatment; and filtering through a microporous membrane to obtain the test solution; wherein the volume ratio of the sample solution to methanol is 1:0.5~2; and wherein the solvent is methanol or an aqueous solution of methanol with a volume fraction of 75~95%.

[0020] Furthermore, the pore size of the microporous filter membrane is 0.1~0.3 μm.

[0021] 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.

[0022] When the sample to be tested contains hydrogen peroxide and / or hypochlorite, directly dissolving it in a solvent to prepare a sample solution will cause subsequent methylation failure. Drying the sample before dissolving it can ensure that the methylation reaction of the chelating agent proceeds smoothly.

[0023] Preferably, in step S1, the diazomethane methylating agent is trimethylsilanized diazomethane; the methylation treatment is carried out in the dark for 2-36 hours.

[0024] Within a certain range, extending the methylation treatment time can make the methylation reaction more complete, thereby improving detection sensitivity. However, during the methylation treatment process, the methyl group exists in the form of a free radical, which is an unstable structure and is greatly affected by environmental factors (such as temperature and pH). Furthermore, the product may undergo hydrolysis, thus causing a decrease in detection sensitivity. This invention controls the methylation treatment time within the range of 2–36 hours, which can further improve detection sensitivity.

[0025] Preferably, in step S1, the chelating agent content in the sample to be tested is not higher than 0.05 wt%, and the mass-to-volume ratio of the sample to be tested to the diazomethane methylating reagent is 1 g: 1~2 mL.

[0026] Preferably, in step S2, the specific process of detecting the test solution using liquid chromatography-mass spectrometry includes: injecting the test solution into a 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 eluent to obtain a chromatogram; the conditions for liquid chromatography are as follows: the chromatographic column is a Waters BEHC18, the column temperature is 30~35℃, the injection volume is 1~5 μL, and the flow rate is 0.1~0.3 mL / min.

[0027] Preferably, in step S3, during the qualitative and / or quantitative analysis, the type of chelating agent is determined according to the following criteria:

[0028] Diethylenetriaminepentaacetic acid: retention time 10-11 min, parent ion mass to charge ratio 464.1-464.3;

[0029] Diethylenetriaminepentamethylene phosphonic acid: retention time 9-10 min, parent ion mass to charge ratio 714.0-714.2;

[0030] Ethylene diamine tetramethylene phosphonic acid: retention time 3-4 min, parent ion mass to charge ratio 549.0-549.2;

[0031] Hexamethylene diamine tetramethylene phosphonic acid: retention time 9-10 min, parent ion mass to charge ratio 605.0-605.2;

[0032] Ethylene glycol bis-tetraacetic acid: retention time 5-6 min, parent ion mass to charge ratio 423.0-423.2;

[0033] Hydroxyethylidene diphosphonic acid: retention time 0.5-1 min, parent ion mass to charge ratio 262.9-263.1;

[0034] Ethylene diamine tetraacetic acid: retention time 8-10 min, parent ion mass to charge ratio 348.9-349.1;

[0035] Nitrilotriacetic acid: retention time 8-10 min, parent ion mass to charge ratio 234.0-234.2;

[0036] Glutamic acid diacetic acid tetrasodium: retention time 10-12 min, parent ion mass to charge ratio 319.9-320.1;

[0037] Phosphonobutanetricarboxylic acid: retention time 10-11 min, parent ion mass to charge ratio 341.0-341.2;

[0038] Methylglycinediacetic acid: retention time 9-11 min, parent ion mass to charge ratio 248.0-248.2;

[0039] Imidodisuccinic acid: retention time 10-11 min, parent ion mass to charge ratio 306.0-306.2;

[0040] N-β-hydroxyethyl ethylenediamine triacetic acid: retention time 0.5-1 min, parent ion mass to charge ratio 307.0-307.2;

[0041] 2-Hydroxyphosphonooxyacetic acid: retention time 1-2 min, parent ion mass to charge ratio 213.0-213.2;

[0042] Diethylenetriaminepentaacetic acid: retention time 10-11 min, parent ion mass to charge ratio 392.9-393.1;

[0043] Citric acid: retention time 5-6 min, parent ion mass-to-charge ratio 235.0-235.2;

[0044] Nitrilotrimethylene phosphonic acid: retention time 8-9 min, parent ion mass-to-charge ratio 405.9-406.1.

[0045] Preferably, in step S2, the volume fraction of formic acid in the aqueous formic acid solution is 0.1-0.2%, and the volume fraction of formic acid in the formic acid acetonitrile solution is 0.1-0.2%.

[0046] Preferably, in step S3, the specific process of quantitative analysis comprises: according to the peak area corresponding to each chelating agent in the chromatogram, substituting into the standard curve to calculate the content of each chelating agent in the sample to be measured.

[0047] Preferably, the daily chemical product is a color bleaching solution, a dishwashing detergent, a glass cleaner, a laundry detergent, a shampoo, a laundry condensation bead or a softener.

[0048] Compared with the prior art, the present application has the following advantages:

[0049] (1) The present application designs a specific detection method according to the characteristics of the various chelating agents commonly used in daily chemical products and the interfering substances possibly present in daily chemical products. By methylating the sample to be measured and using specific eluents and elution procedures, high-efficiency qualitative and quantitative detection of the 17 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, while avoiding the interference of other components in daily chemical products on the detection, and high detection sensitivity and accuracy can be achieved for these chelating agents.

[0050] (2) By controlling the amount of methylating reagent and the methylating treatment time, the detection sensitivity of the 17 chelating agents can be further improved.

[0051] (3) Using the method of the present application, the qualitative detection limit of the 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.

[0052] (4) The linear range of EDTA in the 17 kinds of 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 other several kinds of chelating agents is 1-50 μg / mL, so that the detection method has wider applicability and can meet the detection needs of daily chemical products with different chelating agent contents.

[0053] (5) The detection precision of the 17 kinds of chelating agents commonly used in daily chemical products is between 0.68-3.47%, and the detection accuracy is higher. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is the total ion chromatogram of the seventeen kinds of chelating agent standard products.

[0055] Figure 2 It is the chromatogram obtained by detecting the blank sample.

[0056] Figure 3 It is the peak area change trend chart of DTPA, DTPMP, EDTMP and HDTEPA measured under different methylation reaction times (0.25-6h) in Example 1.

[0057] Figure 4 It is the peak area change trend chart of EGTA, HEDP, EDTA, NTA and PBTC measured under different methylation reaction times (0.25-6h) in Example 1.

[0058] Figure 5 It is the peak area change trend chart of HPAA, ATMP and DTPA-OH measured under different methylation reaction times (0.25-6h) in Example 1.

[0059] Figure 6 It is the peak area change trend chart of MGDA, IDS, HEDTA, citric acid and GLDA measured under different methylation reaction times (0.25-6h) in Example 1.

[0060] Figure 7 It is the peak area change trend chart of DTPA, DTPMP, EDTMP and HDTEPA measured under different methylation reaction times (6-84h) in Example 2.

[0061] Figure 8 It is the peak area change trend chart of EGTA, HEDP, EDTA, NTA and PBTC measured under different methylation reaction times (6-84h) in Example 2.

[0062] Figure 9This is a graph showing the peak area variation trends of HPAA, ATMP, and DTPA-OH measured at different methylation reaction times (6~84h) in Example 2.

[0063] Figure 10 This is a graph showing the peak area variation trends of MGDA, IDS, HEDTA, citric acid, and GLDA at different methylation reaction times (6~84h) in Example 2.

[0064] Figure 11 This is a graph showing the peak area variation trends of DTPA, DTPMP, EDTMP, and HDTEPA measured under different amounts of trimethylsilyl diazomethane in Example 3.

[0065] Figure 12 This is a graph showing the peak area variation trends of MGDA, IDS, HEDTA, citric acid, and GLDA under different amounts of trimethylsilyl diazomethane in Example 3.

[0066] Figure 13 This is a graph showing the peak area variation trends of HPAA, ATMP, and DTPA-OH measured under different amounts of trimethylsilyl diazomethane in Example 3.

[0067] Figure 14 This is a graph showing the peak area variation trends of EGTA, HEDP, EDTA, NTA, and PBTC measured under different amounts of trimethylsilyl diazomethane in Example 3.

[0068] Figure 15 The images show the HEDP chromatograms obtained from different experimental groups in Example 4. Wherein: Figure 15 In the figure, A represents the HEDP chromatogram obtained from experimental group 1; Figure 15 B in the figure represents the HEDP chromatogram obtained from experimental group 3.

[0069] Figure 16 The images show HEDTA chromatograms obtained from different experimental groups in Example 4. Wherein: Figure 16 In the figure, A is the HEDTA chromatogram obtained from experimental group 1; Figure 16 B in the figure represents the HEDTA chromatogram obtained from experimental group 3.

[0070] Figure 17 The chromatogram obtained from the testing of color bleach samples.

[0071] Figure 18 The chromatogram obtained from the analysis of a glass cleaner sample.

[0072] Figure 19 The chromatogram is obtained from the analysis of a dishwashing liquid sample. Detailed Implementation

[0073] The application will be further described in connection with the following examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application, and the changes and advantages that can be thought of by those skilled in the art without departing from the spirit and scope of the application are included in the application, and the appended claims and any equivalents thereof are the protection scope of the application.

[0074] The tables related to the elution procedure in the following examples and comparative examples all adopt the conventional representation of the elution procedure in liquid chromatography.

[0075] The following provides the main instrument and reagent information used in the examples and comparative examples, but the protection scope of the application is not limited thereto:

[0076] (1) Main instruments:

[0077] 1) Liquid chromatograph-mass spectrometer (LC-MS): 6120 Quadrupole LC / MS, produced by Agilent Technologies, USA;

[0078] 2) Chromatographic column: waters BEH C18 100x2.1 mm 1.7 μm, produced by waters, USA;

[0079] 3) Electronic balance: accurate to 0.001 mg, produced by METTLER TOLEDO, Switzerland;

[0080] 4) Vortex: VORTEX 3, produced by IKA, Germany;

[0081] 5) Pure water instrument: ELGA flex2, produced by WILKINSON, UK;

[0082] 6) Microporous filter membrane: 0.22 μm, produced by Shanghai Amp Scientific Instrument Co., Ltd;

[0083] 7) Pipette gun: 10 mL, 1 mL, 100 μL, produced by Eppendorf, Germany;

[0084] 8) Syringe: 2 mL.

[0085] (2) Main reagents and solutions:

[0086] 1) Ultra-pure water: deionized water produced by pure water instrument ELGA flex2;

[0087] 2) Trimethylsilyl diazomethane: analytical pure, (Shanghai Maikelin Biochemical Technology Co., Ltd.);

[0088] 3) Methanol: analytical pure;

[0089] 4) Sodium hydroxide (flaky): analytical pure;

[0090] 5) The abbreviations and CAS numbers of the seventeen chelating agents are as follows:

[0091] Diethylenetriaminepentaacetic acid: DTPA, CAS 67-43-6;

[0092] Diethylenetriaminepentamethylene phosphonic acid: DTPMP, CAS 15827-60-8;

[0093] Ethylenediaminetetramethylene phosphonic acid: EDTMPA or EDTMP, CAS 1429-50-1;

[0094] Hexamethylenediaminetetramethylene phosphonic acid: HDTMPA, CAS 23605-74-5;

[0095] Ethylene glycol bis-tetraacetic acid: EGTA, CAS 67-42-5;

[0096] Hydroxyethylidene diphosphonic acid: HEDP, CAS 25211-86-3;

[0097] Ethylenediaminetetraacetic acid: EDTA, CAS 6381-92-6;

[0098] Nitrilotriacetic acid: NTA, CAS 139-13-9;

[0099] Glutamic acid diacetic acid tetrasodium: GLDA, CAS 51981-21-6;

[0100] Phosphonobutanetricarboxylic acid: PBTC, CAS 37971-36-1;

[0101] Methylglycinediacetic acid: MGDA, CAS 23783-26-8;

[0102] Iminodisuccinic acid: IDS, CAS 144538-83-0;

[0103] N-β-hydroxyethyl ethylenediaminetriacetic acid: HEDTA, CAS 150-39-0;

[0104] 2-Hydroxyphosphonooxyacetic acid: HPAA, CAS 23783-26-8;

[0105] Diethylenetriaminepentaacetic acid: DTPA-OH, CAS 3148-72-9;

[0106] Citric acid: CA, CAS 5949-29-1;

[0107] Nitrilotrimethylenephosphonic acid: ATMP, CAS 6419-19-8.

[0108] Seventeen chelating agent control products are commercially available, among which the purity of 2-hydroxyphosphonoacetic acid (HPAA) control product, phosphono butane tricarboxylic acid (PBTC) control product, diethylene triamine penta (methylene phosphonic acid) (DTPMP) control product, and nitrilo trimethylene phosphonic acid (ATMP) control product is 50%, and the concentration of other chelating agent control products is ≥99.99%;

[0109] 6) 80% methanol aqueous solution: 20 mL of deionized water was measured in a 100 mL volumetric flask, and a pure methanol solution was used to constant volume, shaken and ultrasonically degassed before use;

[0110] 7) 10 mol / L sodium hydroxide solution: 40 g (accurate to 0.001 g) of sodium hydroxide solid was weighed in a 200 mL beaker, 80 mL of deionized water was added and ultrasonically degassed for 15 mL, and then transferred to a 100 mL volumetric flask after cooling to room temperature, and constant volume with deionized water.

[0111] Example 1: Influence of methylation treatment time on detection effect

[0112] According to the following steps, standard solutions were prepared, and the chelating agents in each standard solution were qualitatively and quantitatively detected:

[0113] S1: Preparation and pretreatment of standard solution

[0114] 0.2 g of PBTC control product, 0.2 g of DTPMP control product, 0.1 g of DTPA control product, 0.1 g of EDTMPA control product, 0.1 g of HDTMPA control product, 0.1 g of EGTA control product, 0.1 g of HEDP control product, 0.1 g of EDTA control product, 0.1 g of NTA control product, 0.1 g of GLDA control product, 0.1 g of MGDA control product, 0.1 g of IDS control product, 0.1 g of HEDTA control product, 0.1 g of DTPA-OH control product, 0.1 g of CA control product, 0.08 g of HPAA control product and 0.08 g of ATMP control product (the accurate value of each chelating agent control product is 0.001 g) were accurately weighed and placed in a 50 mL volumetric flask; 40 mL of 80% methanol aqueous solution was added to each 50 mL volumetric flask, vortexed for 2 min, then 5 mL of 10 mol / L sodium hydroxide solution was added, ultrasonically degassed for 30 min, completely dissolved and cooled to room temperature, and constant volume with 80% methanol aqueous solution to obtain the standard solution intermediate liquid.

[0115] The intermediate solution in each standard solution was taken into a 1.5 mL brown bottle, supplemented with methanol to 1000 μL to obtain a standard solution of each chelating agent with a concentration (calculated by pure chelating agent) of 10 ppm. Then 100 μL of trimethylsilyl diazomethane was added, and reacted for a period of time (the reaction time of each experimental group was 0 h, 0.25 h, 0.5 h, 1 h, 1.5 h, 2 h, 4 h, 6 h, wherein 0 h was without the addition of trimethylsilyl diazomethane), and then 1 mL of the reacted solution was taken with a 2 mL syringe and filtered through a 0.22 μm microporous filter to obtain the test solution.

[0116] S2: Detection of standard solution

[0117] Each test solution was detected by liquid chromatography-mass spectrometry. The automatic sampler of the liquid phase system took 1 μL of the standard working solution and injected it into the chromatographic column for gradient elution. The eluent entered the mass spectrometry system for mass spectrometry detection to obtain a chromatogram. In the above process, the liquid chromatography conditions were as follows:

[0118] a) Chromatographic column: waters BEH C18 100×2.1 mm 1.7 μm;

[0119] b) Column temperature: 35℃;

[0120] c) Flow rate: 0.3 mL / min;

[0121] d) Mobile phase: mobile phase A was 0.1% formic acid aqueous solution, and mobile phase B was 0.1% formic acid acetonitrile solution;

[0122] e) Elution mode: gradient elution, and the elution program was shown in Table 1.

[0123] Table 1 Elution program

[0124]

[0125] In this embodiment, when trimethylsilyl diazomethane was not added in step S1 for methylation treatment, seventeen chelating agents were not detected. The reasons for the above phenomenon were as follows: ① the un-methylated chelating agent had too high polarity and low ionization efficiency. For example, EDTA, NTA and the like contained multiple carboxylic acid groups, which were dissociated into multiple charged negative ions (such as EDTA 4- ) in the solution, resulting in charge dispersion and difficulty in forming stable single-charge ions. In the full scan mode of mass spectrometry, the signal was dispersed to multiple low-abundance mass-to-charge ratio (m / z) positions, which could not reach the detection threshold; ② the polar molecules were tightly combined with solvents such as water to form a solvation layer, which required additional energy to desolvate to enter the gas phase. In the process of electrospray ionization (ESI), the desorption efficiency of such molecules was low, and the number of effective ions was insufficient.

[0126] The peak areas of the chelating agents in each chromatogram obtained at different methylation reaction times (0.25-6 h) are shown in Table 1. Figures 3-6 As can be seen from Table 1, when the methylation reaction time is 2 h or less, the peak areas of each chelating agent increase with the extension of the methylation reaction time; when the methylation reaction time exceeds 2 h, the peak areas of some chelating agents (such as DTPA-OH and MGDA) decrease slightly.

[0127] Example 2: Methylation stability

[0128] The standard solutions were prepared according to the following procedure, and the chelating agents in each standard solution were qualitatively and quantitatively detected:

[0129] S1: Preparation and pretreatment of standard solutions

[0130] 0.2 g of PBTC reference substance, 0.2 g of DTPMP reference substance, 0.1 g of DTPA reference substance, 0.1 g of EDTMPA reference substance, 0.1 g of HDTMPA reference substance, 0.1 g of EGTA reference substance, 0.1 g of HEDP reference substance, 0.1 g of EDTA reference substance, 0.1 g of NTA reference substance, 0.1 g of GLDA reference substance, 0.1 g of MGDA reference substance, 0.1 g of IDS reference substance, 0.1 g of HEDTA reference substance, 0.1 g of DTPA-OH reference substance, 0.1 g of CA reference substance, 0.08 g of HPAA reference substance, and 0.08 g of ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) were accurately weighed and placed in 50 mL volumetric flasks, respectively; 40 mL of 80% methanol aqueous solution was added to each 50 mL volumetric flask, and after vortexing for 2 min, 5 mL of 10 mol / L sodium hydroxide solution was added, and ultrasonic treatment was performed for 30 min. After complete dissolution, the solution was cooled to room temperature, and 80% methanol aqueous solution was used for constant volume to obtain the intermediate solution of the standard solution.

[0131] The intermediate solution of each standard solution was taken in a 1.5 mL brown bottle, and methanol was added to 1000 μL to obtain a standard solution of each chelating agent with a concentration (calculated as pure chelating agent) of 25 ppm. Then 100 μL of trimethylsilyl diazomethane was added, and the reaction was carried out in the dark for a period of time (the reaction times of each experimental group were 6 h, 12 h, 24 h, 36 h, 48 h, 72 h, and 84 h, respectively), and then 1 mL of the reaction solution was taken with a 2 mL syringe and filtered through a 0.22 μm microporous filter to obtain the test solution.

[0132] S2: Detection of standard solutions

[0133] The test solution was subjected to liquid chromatography-mass spectrometry detection according to the method in step S2 of Example 1, and a chromatogram was obtained.

[0134] The peak areas of the chelating agents in the chromatograms obtained at different methylation reaction times (6-84 h) are shown in Table 1. Figures 7-10 As can be seen from Table 1, when the methylation reaction time is 6-36 h, the peak areas of most chelating agents remain basically stable; when the methylation reaction time is more than 36 h, the peak areas of the chelating agents show a significant downward trend as the methylation reaction time is prolonged. The reason for the above phenomenon is that the methyl group exists in the form of a free radical during the methylation process, which is an unstable structure and is greatly affected by environmental factors (such as temperature and pH), and in addition, the product may also undergo hydrolysis when the reaction time is too long.

[0135] Example 3: Effect of the amount of methylation reagent on the detection result

[0136] The standard solutions were prepared according to the following steps, and the chelating agents in each standard solution were subjected to qualitative and quantitative detection:

[0137] S1: Preparation and pretreatment of standard solutions

[0138] 0.2 g of PBTC reference substance, 0.2 g of DTPMP reference substance, 0.1 g of DTPA reference substance, 0.1 g of EDTMPA reference substance, 0.1 g of HDTMPA reference substance, 0.1 g of EGTA reference substance, 0.1 g of HEDP reference substance, 0.1 g of EDTA reference substance, 0.1 g of NTA reference substance, 0.1 g of GLDA reference substance, 0.1 g of MGDA reference substance, 0.1 g of IDS reference substance, 0.1 g of HEDTA reference substance, 0.1 g of DTPA-OH reference substance, 0.1 g of CA reference substance, 0.08 g of HPAA reference substance, and 0.08 g of ATMP reference substance (the weighing accuracy of each chelating agent reference substance is 0.001 g) were accurately weighed and placed in 50 mL volumetric flasks; 40 mL of 80% methanol aqueous solution was added to each 50 mL volumetric flask, vortexed for 2 min, then 5 mL of 10 mol / L sodium hydroxide solution was added, and ultrasonicated for 30 min. After complete dissolution, the solution was cooled to room temperature, and 80% methanol aqueous solution was used for constant volume to obtain the standard solution intermediate solution.

[0139] The intermediate solution in each standard solution was taken into a 1.5 mL brown bottle, and methanol was added to 1000 μL to obtain a standard solution of each chelating agent with a concentration (calculated as pure chelating agent) of 5 ppm. Then a certain amount of trimethylsilyl diazomethane (the amount of trimethylsilyl diazomethane in each experimental group was 10 μL, 25 μL, 50 μL and 75 μL, 100 μL, 150 μL, 200 μL, respectively) was added, and the reaction was carried out in the dark for 2 h. Then 1 mL of the reaction solution was taken with a 2 mL syringe and filtered through a 0.22 μm microporous filter to obtain the test solution.

[0140] S2: Detection of standard solution

[0141] According to the method in step S2 of Example 1, each test solution was detected by liquid chromatography-mass spectrometry to obtain a chromatogram.

[0142] Under different amounts of trimethylsilyl diazomethane (10-200 μL), the peak areas of each chelating agent in the obtained chromatogram are shown in Table 1. Figures 11-14 From Table 1, it can be seen that when the amount of trimethylsilyl diazomethane is 100 μL or less, the peak area of each chelating agent increases with the increase of the amount of trimethylsilyl diazomethane; when the amount of trimethylsilyl diazomethane is more than 100 μL, further increasing the amount of trimethylsilyl diazomethane will cause the peak area of some chelating agents (such as EDTMP, EGTA, HEDP) to decrease.

[0143] Example 4: Effect of different elution procedures on detection results

[0144] According to the following steps, standard solutions were prepared, and the chelating agents in each standard solution were qualitatively and quantitatively detected:

[0145] S1: Preparation and pretreatment of standard solution

[0146] Accurately weigh 0.2 g of PBTC reference substance, 0.2 g of DTPMP reference substance, 0.1 g of DTPA reference substance, 0.1 g of EDTMPA reference substance, 0.1 g of HDTMPA reference substance, 0.1 g of EGTA reference substance, 0.1 g of HEDP reference substance, 0.1 g of EDTA reference substance, 0.1 g of NTA reference substance, 0.1 g of GLDA reference substance, 0.1 g of MGDA reference substance, 0.1 g of IDS reference substance, 0.1 g of HEDTA reference substance, 0.1 g of DTPA-OH reference substance, 0.1 g of CA reference substance, 0.08 g of HPAA reference substance and 0.08 g of 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 of 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, then add 5 mL of 10 mol / L sodium hydroxide solution, ultrasonic for 30 min, cool to room temperature after complete dissolution, and use 80% methanol aqueous solution to make up to the volume to obtain the standard solution intermediate solution.

[0147] Take each standard solution intermediate solution into a 1.5 mL brown bottle, and use methanol to make up to 1000 μL to obtain a standard solution of each chelating agent with a concentration (calculated as pure chelating agent) of 5 ppm. Then add 100 μL of trimethylsilyl diazomethane, and react in the dark for 2 h. Then take 1 mL of the reacted solution with a 2 mL syringe, and pass through a 0.22 μm microporous filter membrane to obtain the test solution.

[0148] S2: Detection of standard solution

[0149] According to the method in step S2 of Example 1 (the only difference is that the elution program is different), each test solution is detected by liquid chromatography-mass spectrometry. The elution degree of each experimental group in this example is shown in Tables 2-4, and the chromatograms are obtained.

[0150] Table 2 Elution program of experimental group 1

[0151]

[0152] Table 3 Elution program of experimental group 2

[0153]

[0154] Table 4 Elution program of experimental group 3

[0155]

[0156] From the chromatograms, under the elution procedures of experimental groups 1-3, all have certain separation effects on the seventeen chelating agents. The separation effect of experimental group 1 is slightly poor, and the separation effects of experimental groups 2 and 3 are both good. The reason for the above phenomenon is that:

[0157] Effect of initial proportion of mobile phase: the initial proportion of mobile phase A (0.1% formic acid aqueous solution) of experimental group 1 is 90%, which is lower than that of experimental groups 2 and 3 (95%), and the proportion of mobile phase B (0.1% formic acid acetonitrile) is relatively high. High proportion of organic phase will shorten the retention time of chelating agents on the chromatographic column, and some chelating agents with similar polarity, such as HEDP and HEDTA, may not be fully separated before being eluted, resulting in poor separation degree and poor chromatographic peak shape (the HEDP and HEDTA chromatograms obtained in experimental group 1 are shown in A of Figure 15 and A of Figure 16 respectively). The higher proportion of water phase in experimental groups 2 and 3 can make the chelating agents have a certain retention on the chromatographic column, at the same time, the chromatographic peak shape is greatly improved, laying a foundation for subsequent separation, so the separation effects of experimental groups 2 and 3 are similar (the HEDP and HEDTA chromatograms obtained in experimental group 3 are shown in B of Figure 15 and B of Figure 16 respectively).

[0158] Example 5: Sensitivity test

[0159] According to the following steps, standard solutions are prepared, and the chelating agents in each standard solution are qualitatively and quantitatively detected:

[0160] S1: Preparation and pretreatment of standard solution

[0161] Accurately weigh 0.2 g of PBTC reference substance, 0.2 g of DTPMP reference substance, 0.1 g of DTPA reference substance, 0.1 g of EDTMPA reference substance, 0.1 g of HDTMPA reference substance, 0.1 g of EGTA reference substance, 0.1 g of HEDP reference substance, 0.1 g of EDTA reference substance, 0.1 g of NTA reference substance, 0.1 g of GLDA reference substance, 0.1 g of MGDA reference substance, 0.1 g of IDS reference substance, 0.1 g of HEDTA reference substance, 0.1 g of DTPA-OH reference substance, 0.1 g of CA reference substance, 0.08 g of HPAA reference substance and 0.08 g of 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 of 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, then add 5 mL of 10 mol / L sodium hydroxide solution, ultrasonic for 30 min, cool to room temperature after complete dissolution, and use 80% methanol aqueous solution to make up to the volume to obtain the standard solution intermediate solution.

[0162] Take each standard solution intermediate solution into a 1.5 mL brown bottle, and use methanol to make up to 1000 μL to obtain a series of low-concentration standard solutions of each chelating agent. Then add 100 μL of trimethylsilyl diazomethane, and react for 2 h in the dark. Then take 1 mL of the reacted solution with a 2 mL syringe, and pass through a 0.22 μm microporous filter membrane to obtain the test solution.

[0163] S2: Detection of standard solution

[0164] According to the method in step S2 of Example 1 (the only difference is that the elution program is different), detect each test solution by liquid chromatography-mass spectrometry to obtain a chromatogram.

[0165] According to the above method, continuously determine 6 times, according to the obtained chromatogram, calculate the ratio of the peak height of the target peak to the blank baseline noise (S / N), and determine the lowest concentration that meets S / N≥3 as the qualitative detection limit (LOD), and the lowest concentration that meets S / N≥10 as the quantitative detection limit (LOQ). The qualitative detection limit and the quantitative detection limit of each chelating agent are shown in Table 5.

[0166] Table 5: Qualitative detection limit and quantitative detection limit of each chelating agent

[0167]

[0168] As can be seen from Table 5, the qualitative detection limit of each chelating agent is between 0.3 and 0.8 μg / mL, and the quantitative detection limit is between 0.8 and 2.0 μg / mL, indicating that the method of the present application can achieve high detection sensitivity and can meet the detection requirements of trace chelating agents in daily chemical products.

[0169] Example 6: Actual sample detection

[0170] According to the following steps, the chelating agents in 7 self-made daily chemical product samples (color bleaching liquid, dishwashing detergent, glass cleaner, laundry detergent, shampoo, laundry condensation beads and softener, respectively) were qualitatively and quantitatively detected:

[0171] S1: Preparation of standard working solution

[0172] 0.2 g of PBTC reference substance, 0.2 g of DTPMP reference substance, 0.1 g of DTPA reference substance, 0.1 g of EDTMPA reference substance, 0.1 g of HDTMPA reference substance, 0.1 g of EGTA reference substance, 0.1 g of HEDP reference substance, 0.1 g of EDTA reference substance, 0.1 g of NTA reference substance, 0.1 g of GLDA reference substance, 0.1 g of MGDA reference substance, 0.1 g of IDS reference substance, 0.1 g of HEDTA reference substance, 0.1 g of DTPA-OH reference substance, 0.1 g of CA reference substance, 0.08 g of HPAA reference substance and 0.08 g of ATMP reference substance (the accurate value of each chelating agent reference substance is 0.001 g) were accurately weighed and placed in a 50 mL volumetric flask; 40 mL of 80% methanol aqueous solution was added to each 50 mL volumetric flask, vortexed for 2 min, then 5 mL of 10 mol / L sodium hydroxide solution was added, ultrasonicated for 30 min, and after complete dissolution, cooled to room temperature, and then diluted to the volume with 80% methanol aqueous solution to obtain the standard solution intermediate liquid.

[0173] 2.5 μL, 5 μL, 12.5 μL and 25 μL of the standard solution intermediate liquid were accurately pipetted into a 1.5 mL brown bottle, supplemented with 1000 μL of methanol, then 100 μL of trimethylsilyl diazomethane was added, and the reaction was carried out in the dark for 2 h, then 1 mL of the reacted solution was taken with a 2 mL syringe, filtered through a 0.22 μm microporous filter membrane to obtain a series of standard working solutions STD2, STD3, STD4 and STD5 with gradient concentrations, and STD3 or STD4 was diluted 10 times with methanol to obtain the standard working solution STD1.

[0174] The corresponding chelating agent concentrations (the chelating agent concentration before the addition of trimethylsilyl diazomethane, and calculated as pure chelating agent) in the above obtained standard working solutions are as follows:

[0175] The standard working solutions of PBTC, DTPMP, DTPA, EDTMPA, HDTMPA, EGTA, HEDP, EDTA, NTA, GLDA, MGDA, IDS, HEDTA, DTPA-OH, and CA: STD1, STD2, STD3, STD4, and STD5 correspond to the chelating agent concentrations of 1 μg / mL, 5 μg / mL, 10 μg / mL, 25 μg / mL, and 50 μg / mL, respectively.

[0176] The standard working solutions of HAPP and ATMP: STD1, STD2, STD3, STD4, and STD5 correspond to the chelating agent concentrations of 1 μg / mL, 2 μg / mL, 4 μg / mL, 10 μg / mL, and 20 μg / mL, respectively.

[0177] S2: Detection of standard working solutions

[0178] Each standard working solution was detected by liquid chromatography-mass spectrometry. The automatic sampler of the liquid phase system sucked 1 μL of the standard working solution and injected it into the chromatographic column, and gradient elution was performed. The eluent entered the mass spectrometry system. During the above process, the liquid chromatography conditions were as follows:

[0179] a) Chromatographic column: waters BEH C18 100×2.1 mm 1.7 μm;

[0180] b) Column temperature: 35℃;

[0181] c) Flow rate: 0.3 mL / min;

[0182] d) Mobile phase: Mobile phase A was 0.1% formic acid aqueous solution, and mobile phase B was 0.1% formic acid acetonitrile solution;

[0183] e) Elution mode: Gradient elution, and the elution program is shown in Table 6.

[0184] Table 6 Elution program

[0185]

[0186] In the mass spectrometry system, the positive ion mode (ESI+) and full scan mode of the electrospray ion source were adopted 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, and the total ion chromatogram (TIC) of the seventeen standard chelating agents is generated, as shown in Figure 1The ions of specific mass-to-charge ratio were detected by ion monitoring mode (SIM) for qualitative and quantitative analysis. The peak area of each chelating agent in the chromatogram was used as the vertical coordinate (y), and the concentration of the standard working solution was used as the horizontal coordinate (x) to obtain the regression equation, i.e., the standard curve of each chelating agent. The results are shown in Table 8.

[0187] Table 7. Mass-to-charge ratio and retention time of parent ions of each chelating agent

[0188]

[0189] Table 8. Standard curve of each chelating agent

[0190]

[0191] S3: Pretreatment of the sample to be tested

[0192] Weigh 0.1 g (accurately 0.001 g) of the sample to be tested in a 15 mL centrifuge tube (containing hydrogen peroxide or hypochlorite, the sample is dried before this operation), use a 10 mL pipette to take 10 mL of 80% methanol solution in the above centrifuge tube, ultrasonic for 10 min to obtain the sample solution. Use a 1 mL pipette to take 500 μL of the sample solution and 500 μL of methanol solution into a 1.5 mL brown bottle, then use a 100 μL pipette to take 100 μL of trimethylsilyl diazomethane and add it to the above brown bottle, mix well by vortex, and react in the dark for 2 h. Use a 2 mL syringe to take 1 mL of the reaction solution, pass through a 0.22 μm microporous filter membrane to obtain the test solution.

[0193] S4: Detection of the sample to be tested

[0194] According to the method in step S2 of this example, the test solution was detected by liquid chromatography-mass spectrometry to obtain a chromatogram. According to the chromatogram, the chelating agents in the sample to be tested were qualitatively and quantitatively analyzed by the following methods:

[0195] a) The target was qualitatively determined by the following two indicators to determine the type of chelating agent contained in the sample to be tested: the target in the sample to be tested had the same retention time as the chelating agent control, and the retention time of each chelating agent was shown in Table 7, with a deviation of ± 2.5%; the mass-to-charge ratio of the parent ion of the target in the sample to be tested was consistent with that of the chelating agent control, with a relative deviation of ± 0.1 Da;

[0196] b) The concentration of each chelating agent in the sample to be tested was calculated by the following method: the peak area of each chelating agent in the chromatogram was detected, and the corresponding standard curve in Table 8 was substituted to obtain the concentration of each chelating agent in the sample to be tested.

[0197] S5: Detection of the blank sample

[0198] The pretreatment (methylation reaction time is 2 h) was performed according to the method in step S3 of this example by using 80% methanol aqueous solution instead of the sample to be tested, and then the liquid chromatography-mass spectrometry detection was performed according to the method in step S4 of this example, and the obtained chromatogram is shown in Figure 2 .

[0199] Each daily chemical sample was continuously determined for 5 times according to the above method, the detected types of chelating agents were counted, and the contents were calculated, and the results are shown in Table 9 (in Table 9, " / " represents not detected). Among them, when the color bleach, glass cleaner and dishwashing detergent were detected, the typical chromatograms obtained are shown in Figures 17-19 , respectively.

[0200] Table 9. Actual sample detection results

[0201]

[0202] The self-prepared daily chemical sample formulations in this example are as follows:

[0203] (1) The self-prepared color bleach consists of the following components by mass percentage: hydrogen peroxide solution 10.00%, fatty alcohol polyoxyethylene ether-9 (AEO-9) 5.00%, DTPMP 0.08%, fragrance 0.10%, and the balance is deionized water.

[0204] (2) The self-prepared dishwashing detergent consists of the following components by mass percentage: fatty alcohol polyoxyethylene ether sodium sulfate 8.50%, sodium dodecyl benzene sulfonate 9.00%, lauryl glucoside 1.30%, cocamidopropyl betaine 3.00%, carboxin 0.01%, sodium chloride 0.80%, citric acid monohydrate 0.09%, fragrance 0.10%, GLDA 0.20%, and the balance is deionized water.

[0205] (3) The self-prepared glass cleaner consists of the following components by mass percentage: AEO-9 0.30%, propylene glycol ethyl ether 7.00%, citric acid monohydrate 0.10%, carboxin 0.01%, phenoxyethanol 0.03%, fragrance 0.10%, and the balance is deionized water.

[0206] (4) The self-prepared laundry detergent consists of the following components by mass percentage: sodium dodecyl benzene sulfonate 5.00%, fatty alcohol polyoxyethylene ether sodium sulfate 6.00%, fatty alcohol polyoxyethylene ether 5.50%, potassium fatty acid soap 2.50%, alkyl glycoside 2.00%, sodium chloride 1.80%, citric acid monohydrate 0.15%, carboxin 0.05%, fragrance 0.30%, MGDA 0.20%, and the balance is deionized water.

[0207] (5) The self-made shampoo consists of the following components by mass percentage: sodium laureth sulfate 15.00%, cocamidopropyl betaine 3.00%, cocoglycoside 2.00%, sorbitol 2.00%, cocamide MEA 1.50%, laureth-2 1.00%, ethylene glycol distearate 0.80%, glycerol 0.50%, sodium citrate 0.50%, menthol 0.45%, sodium chloride 0.30%, octanol 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.

[0208] (6) The self-made laundry condensing beads consist of the following components by mass percentage: glycerol 24.00%, monoethanolamine 5.50%, propylene glycol 8.0%, dodecylbenzenesulfonic acid 26.0%, sodium fatty alcohol polyoxyethylene ether sulfate 16.5%, fatty alcohol polyoxyethylene ether 23.00%, potassium fatty acid soap 6.50%, fragrance 0.50%, EDTMP-3Na 0.30%, dichlorophenyl biguanide (HP100) 0.20%, and the balance is deionized water.

[0209] (7) The self-made softener consists of the following components by mass percentage: ester-based quaternary ammonium salt 3.00%, fatty alcohol polyoxyethylene ether 0.50%, lauryl amido propyl betaine 1.5%, polydimethylsiloxane 1.00%, ethanol 1.00%, isopropyl alcohol 0.21%, kathon 0.05%, HEDP 0.10%, fragrance 0.20%, and the balance is deionized water.

[0210] Example 7: Method precision test

[0211] According to the following steps, standard solutions are prepared, and the chelating agents in each standard solution are qualitatively and quantitatively detected:

[0212] S1: Preparation and pretreatment of standard solution

[0213] Accurately weigh 0.2 g of PBTC reference substance, 0.2 g of DTPMP reference substance, 0.1 g of DTPA reference substance, 0.1 g of EDTMPA reference substance, 0.1 g of HDTMPA reference substance, 0.1 g of EGTA reference substance, 0.1 g of HEDP reference substance, 0.1 g of EDTA reference substance, 0.1 g of NTA reference substance, 0.1 g of GLDA reference substance, 0.1 g of MGDA reference substance, 0.1 g of IDS reference substance, 0.1 g of HEDTA reference substance, 0.1 g of DTPA-OH reference substance, 0.1 g of CA reference substance, 0.08 g of HPAA reference substance and 0.08 g of 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 of 80% methanol aqueous solution to each 50 mL volumetric flask, vortex for 2 min, then add 5 mL of 10 mol / L sodium hydroxide solution, ultrasonic for 30 min, cool to room temperature after complete dissolution, and use 80% methanol aqueous solution to make up to the volume to obtain the standard solution intermediate.

[0214] Take each standard solution intermediate into a 1.5 mL brown bottle, and use methanol to make up to 1000 μL to obtain a standard solution of each chelating agent at a concentration of 3 times the quantitative detection limit. Then add 100 μL of trimethylsilyl diazomethane, and react for 2 h in the dark. Then take 1 mL of the reacted solution with a 2 mL syringe, and pass through a 0.22 μm microporous filter membrane to obtain a test solution.

[0215] S2: Detection of standard solution

[0216] According to the method in step S4 in Example 6 (the only difference is that the elution procedure is different), each test solution is detected by liquid chromatography-mass spectrometry to obtain a chromatogram, and quantitative analysis is performed according to the chromatogram to obtain the concentration of each chelating agent in the standard solution.

[0217] According to the above method, 6 consecutive determinations are performed, and the method precision (RSD) is calculated. The results are shown in Table 10.

[0218] Table 10: Results of method precision test

[0219]

[0220] As can be seen from Table 10, the precision of each chelating agent is 0.68-3.47%, which indicates that the method of the present application has high detection accuracy.

[0221] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The materials, devices, and methods used in the present application are those that are conventionally employed in the art, unless otherwise specified.

[0222] The above description is only the preferred embodiment of the present application, not any limitation to the present application, any simple modification, change and equivalent transformation to the above embodiment according to the technical essence of the present application are still within the protection scope of the technical solution of the present application.

Claims

1. A method for detecting multiple chelating agents in daily chemical products, characterized in that, Includes the following steps: S1: The test sample is methylated with trimethylsilanized diazomethane to obtain the test solution; S2: The chromatogram of the test solution was obtained by liquid chromatography-mass spectrometry. The chromatographic column was Waters BEH C18, and the elution program was as follows: 1) At min 0, the eluent composition is: 94-96% v / v formic acid aqueous solution, with the remainder being formic acid acetonitrile solution; maintain this composition until min 4-5. 2) The composition ratio of the eluent gradually changes, and by the 8th to 10th minute it becomes: 60-70% v / v formic acid aqueous solution, with the remainder being formic acid acetonitrile solution; it remains unchanged until the 13th to 14th minute; 3) The composition ratio of the eluent gradually changes until it becomes: 94-96% v / v formic acid aqueous solution, with the remainder being formic acid acetonitrile solution; the subsequent formulation remains unchanged, and the maintenance time is unlimited; S3: Perform qualitative and / or quantitative analysis of the chelating agents in the test sample based on the chromatogram; the chelating agents are diethylenetriaminepentaacetic acid, diethylenetriaminepentamethylphosphonic acid, ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, ethylene glycol ditetraacetic acid, hydroxyethyl diphosphate, ethylenediaminetetraacetic acid, hypozinotriacetic acid, tetrasodium diacetate of glutamate, phosphonobutane tricarboxylic acid, methylglycine diacetic acid, iminodisuccinic acid, N-β-hydroxyethyl ethylenediaminetetraacetic acid, 2-hydroxyphosphonoacetic acid, diethylenetriaminepentaacetic acid, citric acid, and hypozinotrimethylenephosphonic acid.

2. The detection method according to claim 1, characterized in that, 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 trimethylsilyldiazomethane; performing methylation treatment; and filtering through a microporous membrane to obtain the test solution; the volume ratio of the sample solution to methanol is 1:0.5~2; and the solvent is methanol or an aqueous methanol solution with a volume fraction of 75~95%.

3. The detection method according to claim 2, 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 the sample solution.

4. The detection method according to claim 1 or 2, characterized in that, In step S1, the methylation treatment is carried out in the dark for 2 to 36 hours.

5. The detection method according to claim 1 or 2, 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-to-volume ratio of the sample to be tested to trimethylsilyldiazomethane is 1 g: 1~2 mL.

6. The detection method according to claim 1, characterized in that, In step S2, the specific process of detecting the test solution using liquid chromatography-mass spectrometry includes: injecting the test solution 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 eluent to obtain a chromatogram; the conditions of the liquid chromatography are as follows: column temperature is 30~35℃, injection volume is 1~5 μL, and flow rate is 0.1~0.3 mL / min.

7. The detection method according to claim 1, characterized in that, In step S3, during 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; Diethylenetriaminepentanephosphonic acid: retention time 9~10 min, precursor ion mass-to-charge ratio 714.0~714.2; Ethylenediaminetetramethylenephosphonic acid: retention time 3-4 min, precursor ion mass-to-charge ratio 549.0-549.2; Hexamethylenediaminetetramethylenephosphonic acid: retention time 9-10 min, precursor ion mass-to-charge ratio 605.0-605.2; Ethylene glycol ditetraacetic acid: retention time 5-6 min, precursor ion mass-to-charge ratio 423.0-423.2; Hydroxyethyl diphosphate: retention time 0.5~1 min, precursor ion mass-to-charge ratio 262.9~263.1; Ethylenediaminetetraacetic acid: retention time 8-10 min, precursor ion mass-to-charge ratio 348.9-349.1; Nitrotriacetic acid: retention time 8-10 min, parent ion mass-to-charge ratio 234.0-234.2; Tetrasodium glutamate diacetate: retention time 10-12 min, precursor ion mass-to-charge ratio 319.9-320.1; Phosphonobutane tricarboxylic acid: retention time 10-11 min, parent ion mass-to-charge ratio 341.0-341.2; Methylglycine diacetic acid: retention time 9-11 min, precursor ion mass-to-charge ratio 248.0-248.2; Iminodisuccinic acid: retention time 10-11 min, precursor ion mass-to-charge ratio 306.0-306.2; N-β-hydroxyethylethylenediaminetriacetic acid: retention time 0.5~1 min, 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, precursor ion mass-to-charge ratio 235.0-235.2; Triazine-trimethylenephosphonic acid: retention time 8-9 min, precursor ion mass-to-charge ratio 405.9-406.

1.

8. The detection method according to claim 1, characterized in that, 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%.

9. The detection method according to claim 1, characterized in that, The daily chemical products mentioned are color bleach, dishwashing liquid, glass cleaner, laundry detergent, shampoo, laundry pods, or fabric softener.

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