Gas chromatography method for detecting content of trioctyl phosphate product and impurities

Abstract

The invention discloses a gas chromatography method for detecting the content of trioctyl phosphate products and impurities, and belongs to the technical field of organic chemical detection. The core of the method is that (trimethylsilyl) diazomethane (TMSCH2N2) is adopted as a derivatization reagent, and dioctyl phosphate (P204) in a sample is subjected to rapid and safe derivatization at room temperature; an optimized dichloromethane-hexane mixed solvent system is adopted for dilution, so that the solubility is remarkably improved, and the toxicity is reduced; a first-order heating rapid screening method (17min) is suitable for industrial quality control, a multi-order heating accurate quantification method (29min) is suitable for small-scale test process research and development, and trioctyl phosphate (TOP), P204, isooctyl alcohol, isooctyl ether and chloro-isooctane can be accurately quantified at the same time. The method solves the problems of high toxicity, low efficiency, narrow detection range, single mode and the like in the prior art, and has the remarkable advantages of safety, high efficiency, accuracy, environmental protection and wide adaptability.

Description

Technical Field

[0001] This invention relates to the field of precision detection technology for organic chemical products, specifically to a method for simultaneously detecting the content of trioctyl phosphate (TOP) and its key impurities dioctyl phosphate (P204), isooctyl alcohol, isooctyl ether, and chloroisooctane based on (trimethylsilyl)diazomethane derivatization coupled with dual-mode gas chromatography. Background Technology

[0002] Trioctyl phosphate (TOP), a high-performance organophosphate, has applications spanning anthraquinone solvent production from hydrogen peroxide, cold-resistant plasticizers and flame retardants for plastics and rubber, rare earth metal extractants, and electrolyte additives for electronic materials. The purity of TOP and the types and amounts of impurities it contains directly determine its performance in these high-end applications. For example, impurities can lead to decreased hydrogen peroxide extraction efficiency, deterioration of the low-temperature flexibility of PVC products, corrosion of extraction equipment, or insulation failure in electronic materials.

[0003] Industrially, TOP is mainly synthesized via the esterification reaction of phosphorus oxychloride and isooctanol. This process inevitably produces various impurities due to incomplete reactions or side reactions, primarily including: the incompletely esterified product dioctyl phosphate (P204), residual isooctanol, isooctyl ether formed from the dehydration of isooctanol, and chloroisooctane generated from the chlorination side reaction of phosphorus oxychloride. Therefore, establishing a method capable of simultaneously, rapidly, and accurately detecting the TOP bulk and these key impurities is crucial for monitoring the production process, optimizing reaction conditions, and ensuring the quality of the final product.

[0004] Currently, industry-specific detection methods for TOP and impurities have the following limitations: 1) Acid-base titration has a limited range of substances that can be detected and cannot meet the purity requirements of many fields. Existing literature (such as HG / T 5155-2017 and CN114441258B) uses acid-base titration methods that can only quantify P204 and monoisooctyl phosphate, but cannot detect non-acidic impurities such as isooctyl alcohol, isooctyl ether, and chloroisooctane. Furthermore, the titration process requires manual operation, resulting in significant human error (relative deviation ≥3%), and the testing time for a single sample exceeds 40 minutes, generating 50 mL of waste liquid per sample, which does not align with the trends of environmentally friendly and efficient detection.

[0005] 2) Existing derivatization reagents for gas chromatography have shortcomings such as safety risks, low efficiency, and limited application. T / CIESC 51-2023 describes the derivatization of P204 using a diazomethane-ethyl ether solution. Diazomethane is highly toxic and explosive (exploding immediately upon vibration or high temperature), posing an extremely high operational risk. It must be prepared and used immediately, and its purchase and storage are strictly controlled. CN110618226A discloses a gas chromatography method for derivatizing P204 using bis(trimethylsilyl)trifluoroacetamide (BSTFA), but the derivatization reaction requires aging at 60-70℃ for 0.5-1.5 hours, resulting in insufficient efficiency in online detection of hydrogen peroxide production. CN109212053B and CN112326848B disclose the application of TMSCH2N2 in the detection of phytic acid and glyphosate, confirming its lower toxicity than diazomethane and superior stability compared to BSTFA. However, these methods do not address the simultaneous multi-component detection of phosphate esters, nor do they design dual-mode gas chromatography schemes for TOP and five impurities, failing to meet the specific requirements of industrial TOP detection.

[0006] 3) Existing gas chromatography methods have poor adaptability to solvents and detection modes. Existing methods often use chloroform as a solvent (e.g., T / CIESC 51-2023), but it has high toxicity (oral LD50 in rats). 50 It contains only 909 mg / kg, and its solubility for P204 derivatives is only 30-40 mg / mL (DOI: 10.1007 / s00216-016-9785-3), which easily leads to sample crystallization. In addition, its purchase and storage are strictly controlled. Furthermore, most existing gas chromatography methods are single detection modes and cannot detect impurities such as isooctyl ether and chloroisooctane (e.g., T / CIESC 51-2023). Moreover, due to the overlap of chromatographic peaks of isooctyl alcohol and chloroisooctane in existing methods, the content of isooctyl alcohol cannot be accurately quantified, which cannot meet the quantitative requirements of isooctyl alcohol, isooctyl ether, and chloroisooctane in fields such as hydrogen peroxide production solvents, rare earth extractants, and electronic materials.

[0007] In summary, existing methods suffer from problems such as low derivatization efficiency, high reagent toxicity, poor solvent solubility, limited detection modes, and incomplete impurity identification coverage. There is an urgent need to develop a safe, efficient, and multi-scenario-adaptable detection method. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention constructs a complete detection system through a combination of techniques including "derivative reagent optimization, solvent system improvement, and dual-mode GC method development," providing a safe, efficient, and multi-scenario-adaptive detection method. The technical solution adopted by this invention is as follows: A gas chromatography method for detecting the content of impurities such as trioctyl phosphate and dioctyl phosphate is used. P204 is derivatized with TMSCH2N2-hexane solution at room temperature. After dilution and filtration, two different gas chromatography methods can be selected according to the detection requirements. After removing the solvent peak, the content of impurities such as TOP and P204 is quantified by area normalization or external standard method.

[0009] The specific steps are as follows: 1) Derivatization: Accurately weigh an appropriate amount of TOP sample (accurate to 0.0001 g) into a 10 mL sample bottle with a cap, and add a 1.5~2.0 mol / L (trimethylsilyl)diazomethane-hexane solution (when the P2O4 content in the TOP sample is 0.05%~10%, the volume ratio of the sample to the derivatization reagent is 1000:1~2:5); react at room temperature for 3~20 min, and shake until the solution is pale yellow and no bubbles are generated (indicating complete reaction); place the sample bottle in a fume hood and let it stand for 5~30 min until the hexane completely evaporates and the solution is colorless to obtain the derivatized sample.

[0010] 2) Dilution and Filtration: Add an appropriate amount of solvent to the derivatized sample to dissolve and dilute it, then filter it through a 0.22 μm PTFE organic phase filter membrane to obtain the test solution. The solvent is a single solvent such as dichloromethane, 1,2-dichloroethane, or trichloromethane, or a mixed solvent of the aforementioned single solvent and hexane, cyclohexane, heptane, or petroleum ether. It is necessary to consider both polarity and solubility. The volume ratio of the two solvents in the mixed solvent is 1:5 to 5:1; the volume ratio of the derivatized sample to the solvent is 1:3 to 1:30.

[0011] 3) Gas chromatography detection: A gas chromatograph equipped with a flame ionization detector (FID) is used, employing HP-5, DB-5, DB-1, or equivalent columns (30m × 0.25mm × 0.25μm or equivalent). Select one of the following two methods as required: (1) Rapid screening method: The column temperature program is 150℃ for 2 min, then 10℃ / min to 280℃ for 2 min (total time 17 min); the injection port temperature is 280℃, the split ratio is 60:1, and the injection volume is 1.0 μL; the carrier gas (nitrogen) flow rate is 25 mL / min, the hydrogen flow rate is 30 mL / min, and the air flow rate is 300 mL / min; TOP and P204 can be quantified.

[0012] (2) Precise quantification method: The column temperature program is 50℃ for 1.5 min, 5℃ / min to 130℃, 20℃ / min to 230℃, 10℃ / min to 280℃ and hold for 1.5 min (total time 29 min); the injection port and detector parameters are the same as the rapid screening method; it can quantify TOP, P204, isooctyl alcohol, isooctyl ether, and chloroisooctane.

[0013] 4) Quantitative analysis: Based on the relative content range of TOP and impurities such as P2O4 and isooctyl alcohol in the sample, select one of the following two methods for quantitative analysis: A. Area normalization method: This method is used when the TOP main content is ≥99.0%. After deducting the solvent peak, the content is calculated based on the peak area ratio of each component.

[0014] B External standard method: This method is used when the TOP content is <99.0%. A series of standard solutions containing the target component are prepared, and after pretreatment in steps 1) and 2), they are detected by gas chromatography. A standard curve (R²≥0.999) is plotted, and the content is calculated by substituting the sample peak area.

[0015] Preferably, in step 1) derivatization: the amount of TOP sample taken is 2±0.0005 g; the concentration of derivatizing reagent is 2.0 mol / L; when the P2O4 content in the sample is 0.1~2%, the volume ratio of sample to derivatizing reagent is 1000:1~50:1, the reaction is carried out at room temperature for 5~8 min, and then left to stand in a fume hood for 10~15 min.

[0016] Preferably, in step 2) dilution and filtration: the solvent for dissolving is preferably a mixture of dichloromethane-hexane and dichloromethane-cyclohexane (volume ratio 2:1~1:2), and the volume ratio of the derivatized sample to the solvent is 1:10.

[0017] In step 2), the dichloromethane-hexane mixed solvent can be replaced with dichloromethane, 1,2-dichloroethane, trichloromethane, 1,2-dichloroethane-hexane, trichloromethane-hexane, dichloromethane-cyclohexane, 1,2-dichloroethane-cyclohexane, trichloromethane-cyclohexane, dichloromethane-heptane, 1,2-dichloroethane-heptane, trichloromethane-heptane, dichloromethane-petroleum ether, 1,2-dichloroethane-petroleum ether, or trichloromethane-petroleum ether, taking into account both the polarity of the solvent and the solubility of the mixture to be tested. The volume ratio of the two solvents in the above mixed solvents is 1:5 to 5:1; the volume ratio of the derivatized sample to the solvent is 1:3 to 1:30.

[0018] Preferably, the gas chromatography column in step 3) is HP-5, DB-5, DB-1 or an equivalent column, with a specification of 30m×0.25mm×0.25μm or an equivalent specification.

[0019] Step 3) Gas phase detection: HP-5 column (30m×0.25mm×0.25μm) is preferred. Precise quantification method is used for small-scale process development, and rapid screening method is used for industrial batch detection.

[0020] The temperature program for the precise quantification method in step 3) can be replaced with an equivalent program with a longer total analysis time, for example, holding at 50℃ for 1.5 min, increasing to 130℃ at 5℃ / min, increasing to 190℃ at 20℃ / min, increasing to 200℃ at 10℃ / min, increasing to 210℃ at 5℃ / min, increasing to 280℃ at 10℃ / min, and holding for 1.0 min (total time 31.5 min).

[0021] The selection of the two gas chromatography separation methods in step 3) is based on the fact that the rapid screening method can quantify TOP and P204, which is suitable for industrial quality control and factory inspection with mature processes; the precise quantification method can quantify TOP, P204, isooctyl alcohol, isooctyl ether, and chloroisooctane, which is suitable for the small-scale process development stage and strict impurity traceability analysis.

[0022] The selection criteria for the two quantitative analysis methods in step 4) are as follows: if the TOP main content is ≥99.0%, the area normalization method (A) is recommended; otherwise, the external standard method (B) is recommended.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1) Expanded detection range and improved environmental friendliness: Compared with acid-base titration, this method can detect various substances simultaneously, is easy to operate, shortens the detection time, reduces the amount of test waste liquid, reduces human error, and improves data accuracy.

[0024] 2) Improved reagent safety: (Trimethylsilyl)diazomethane replaces diazomethane, reducing toxicity by 60% (oral LD50 in rats). 50 The concentration has increased from 200 mg / kg to 1200 mg / kg, and commercial solutions can be purchased directly without the need for on-site preparation; it replaces BSTFA, derivatization does not require aging, and the efficiency is improved by 40% (derivatization time is reduced from 60 min to within 20 min).

[0025] 3) Solvent compatibility optimization: A dichloromethane-hexane mixture replaces chloroform, reducing toxicity (LD50). 50 The concentration of the reagent increased from 909 mg / kg to 1800 mg / kg, and the solubility of the P204 derivative increased from 35 mg / mL to 110 mg / mL. In addition, the reagent is readily available and the cost is reduced by 20%.

[0026] 4) Dual-mode adaptation to multiple scenarios: The rapid screening method completes the detection of 2 main components in 17 minutes, which is suitable for industrial factory inspection; the precise quantitative method completes the separation of 5 components in 29 minutes (without peak overlap), which is suitable for traceability of impurities in pilot-scale processes; switching between the two methods only requires changing the temperature program, making the operation flexible. Attached Figure Description

[0027] Figure 1 Gas chromatograms of dichloromethane, trichloromethane, n-hexane, industrial hexane, and TMSCH2N2 tested by Method 1, where A represents dichloromethane tested by Method 1, B represents dichloromethane and TMSCH2N2 tested by Method 1, C represents n-hexane tested by Method 1, and D represents industrial hexane tested by Method 1.

[0028] Figure 2 Gas chromatograms of dichloromethane, trichloromethane, n-hexane, industrial hexane, and TMSCH2N2 tested by Method 2, where A represents dichloromethane tested by Method 2, B represents dichloromethane and TMSCH2N2 tested by Method 2, C represents trichloromethane tested by Method 2, D represents n-hexane tested by Method 2, and E represents industrial hexane tested by Method 2.

[0029] Figure 3 In Example 1, gas chromatograms of two samples, "chloroisooctane" and "chloroisooctane + TMSCH2N2", were compared using methods 1 and 2. In the comparison, A represents chloroisooctane tested by method 1, B represents chloroisooctane + TMSCH2N2 tested by method 1, C represents chloroisooctane tested by method 2, and D represents chloroisooctane + TMSCH2N2 tested by method 2.

[0030] Figure 4 In Example 1, gas chromatograms of two samples, "isooctanol" and "isooctanol + TMSCH2N2", were compared using methods 1 and 2. In the comparison, A represents isooctanol tested by method 1, B represents isooctanol + TMSCH2N2 tested by method 1, C represents isooctanol tested by method 2, and D represents isooctanol + TMSCH2N2 tested by method 2.

[0031] Figure 5 In Example 1, gas chromatograms of two samples, "isooctyl ether" and "isooctyl ether + TMSCH2N2", were compared using methods 1 and 2. In the comparison, A represents isooctyl ether tested by method 1, B represents isooctyl ether + TMSCH2N2 tested by method 1, C represents isooctyl ether tested by method 2, and D represents isooctyl ether + TMSCH2N2 tested by method 2.

[0032] Figure 6In Example 1, gas chromatograms of two samples, “TOP” and “TOP + TMSCH2N2”, tested by Method 1 and Method 2 are compared. A is TOP tested by Method 1, B is TOP + TMSCH2N2 tested by Method 1, C is TOP tested by Method 2, and D is TOP + TMSCH2N2 tested by Method 2.

[0033] Figure 7 In Example 1, gas chromatograms of two samples, “P204” and “P204 + TMSCH2N2”, were compared using methods 1 and 2. In the comparison, A represents P204 tested by method 1, B represents P204 + TMSCH2N2 tested by method 1, C represents P204 tested by method 2, and D represents P204 + TMSCH2N2 tested by method 2.

[0034] Figure 8 In Example 2, the gas chromatogram of the mixed sample of "chloroisooctane + isooctyl alcohol + isooctyl ether + P204 + TOP" was tested according to Method 1.

[0035] Figure 9 In Example 2, the gas chromatogram of the mixed sample of "chloroisooctane + isooctyl alcohol + isooctyl ether + P204 + TOP" was tested according to Method 2.

[0036] Figure 10 Example 3: Gas chromatogram of group 1 (P204 to TMSCH2N2 volume ratio 1:1.0).

[0037] Figure 11 Example 3: Gas chromatogram of group 2 (P204 to TMSCH2N2 volume ratio 1:1.2).

[0038] Figure 12 Example 3: Gas chromatogram of group 3 (P204 to TMSCH2N2 volume ratio 1:1.4).

[0039] Figure 13 In Example 4, the gas chromatogram of the mixed sample in Group I (solvent: dichloromethane) was tested.

[0040] Figure 14 In Example 4, the gas chromatogram of the mixed sample was tested using Group II (solvent: chloroform).

[0041] Figure 15 In Example 4, the gas chromatogram of the mixed sample in Group III (solvent: dichloromethane-hexane 3:1) was tested.

[0042] Figure 16 In Example 4, the gas chromatogram of the mixed sample in Group IV (solvent: dichloromethane-hexane 1:1) was tested.

[0043] Figure 17 In Example 5, the gas chromatogram of the mixture sample was tested using a temperature program T1.

[0044] Figure 18 In Example 5, the gas chromatogram of the mixture sample was tested using a temperature program T2.

[0045] Figure 19 In Example 5, the gas chromatogram of the mixture sample was tested using a temperature program T3.

[0046] Figure 20 Comparative Example 4 shows the gas chromatograms of the mixed samples tested with methanol and ethanol as solvents. In this example, A represents methanol tested in Method 2, B represents methanol and TMSCH2N2 tested in Method 2, C represents dichloromethane tested in Method 2, D represents dichloromethane and TMSCH2N2 tested in Method 2, E represents ethanol tested in Method 2, and F represents ethanol and TMSCH2N2 tested in Method 2. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited thereto. Those skilled in the art can make various modifications and variations without departing from the spirit of the present invention.

[0048] Example 1: Dual-method detection of single-component samples (TOP or P204 or isooctyl alcohol or isooctyl ether or chloroisooctane) 1.1 Experimental Objective The retention times of individual components of the TOP synthesis and product system were determined using both rapid screening (Method 1) and precise quantification (Method 2) methods.

[0049] 1.2 Sample Preparation Derivatization: Weigh 2.00 g of sample (accurate to 0.0001 g) into a 10 mL capped sample vial, and add 0.0–2.0 mL of 2.0 mol / L TMSCH2N2-hexane solution (where 0 mL is for samples without "N", 1.0 mL for samples with "N", and 2.0 mL for samples with "NN"). React at room temperature (25 °C) for 8 min, shaking until the solution turns pale yellow and is free of bubbles (reaction complete). Let stand in a fume hood for 15 min until the hexane evaporates and the solution becomes colorless to obtain the derivatized sample. This step is omitted for samples that do not require derivatization.

[0050] Dilution and filtration: Dilute with dichloromethane or a dichloromethane-hexane mixed solvent at a volume ratio of 1:10 (in this example, take 0.1 mL of sample or derivative sample and add 1 mL of solvent), shake for 1 min, and filter through a 0.22 μm PTFE filter membrane to obtain the test solution.

[0051] Sample list information: For comparison, some samples were treated with TMSCH2N2-hexane solution, while others were not. Furthermore, the same sample was tested using both Method 1 and Method 2 GC conditions. Sample numbers, component information, and test methods are shown in Table 1. Table 1. Summary of Sample Numbers and Components

[0052]

[0053] 1.3 Testing Procedures Test under the GC conditions of Method 1 and Method 2 respectively (the test parameters for Method 1 and Method 2 are shown in Table 2). Table 2 Gas chromatographic test parameters for Method 1 and Method 2

[0054] The chromatograms of samples tested according to methods 1 and 2 for dichloromethane, trichloromethane, n-hexane, industrial hexane, TMSCH2N2, etc. are as follows: Figure 1-2 As shown, under Method 1, the retention times of each substance are close or even overlap (see Table 3 for details), while under Method 2, the retention times of each substance differ significantly and the separation degree is higher.

[0055] Using dichloromethane as solvent, the results of testing for isooctane chloro, isooctyl alcohol, isooctyl ether, TOP, and P2O4 with and without TMSCH2N2, according to Methods 1 and 2, are as follows: Figure 3-7 As shown. Among them, as Figure 3-6 The retention times of the four substances—chloroisooctane, isooctyl alcohol, isooctyl ether, and TOP—were consistent under both conditions with and without the addition of TMSCH2N2, being 11.16, 11.76, 21.32, and 27.73 min, respectively. Figure 7 The retention times of P204 with the addition of TMSCH2N2 were 10.98 and 24.80 min under the conditions of Method 1 and Method 2, respectively.

[0056] The retention times of each substance are shown in Table 3: Table 3. Summary of retention times for each substance under Method 1 and Method 2

[0057] 1.5 Conclusion When tested using Method 1, the retention times of chloroisooctane and isooctyl alcohol, as well as P204 derivative byproduct 1 and isooctyl ether, are the same, making separation and accurate quantification impossible. Only the TOP product and impurity P204 can be accurately quantified, meeting the needs of rapid industrial screening. Method 2 achieves complete component separation and precise quantification, accurately quantifying the TOP product and impurities P204, chloroisooctane, isooctyl alcohol, and isooctyl ether, making it suitable for impurity tracing and process optimization in the small-scale process development stage.

[0058] Example 2: Dual-method detection of multi-component mixed samples (chloroisooctane + isooctyl alcohol + isooctyl ether + P204 + TOP) 2.1 Experimental Objective To verify the separation of multiple substances using rapid screening (Method 1) and precise quantification (Method 2).

[0059] 2.2 Sample Preparation 1. Prepare a multi-component mixed sample: Weigh 0.40 g of isooctane, 0.80 g of isooctyl alcohol, 0.40 g of isooctyl ether, 0.40 g of P204 and 18.00 g of TOP (accurate to 0.0001 g) into a capped sample bottle and mix well for later use.

[0060] 2. Derivatization: Weigh 2.00 g of the mixed sample (accurate to 0.0001 g) into a 10 mL capped sample vial, and add 0.0 or 0.1 mL of 2.0 mol / L TMSCH2N2-hexane solution; react at room temperature (25℃) for 8 min, shaking until the solution turns pale yellow and is free of bubbles (reaction complete); let stand in a fume hood for 15 min until the hexane evaporates and the solution becomes colorless, obtaining the derivatized sample. This step is omitted for samples that do not require derivatization.

[0061] 3. Dilution and filtration: Dilute with dichloromethane at a volume ratio of 1:10 (in this example, take 0.1 mL of sample or derivative sample and add 1 mL of solvent), shake for 1 min, and filter through a 0.22 μm PTFE membrane to obtain the test solution.

[0062] 4. Sample List Information: For comparison, some samples were treated with TMSCH2N2-hexane solution, while others were not. Furthermore, the same sample was tested using both Method 1 and Method 2 GC conditions. Sample numbers, component information, and test methods are shown in Table 4. Table 4 Summary of Sample Numbers and Components

[0063] 2.3 Testing Procedures Test under the GC conditions of Method 1 and Method 2 respectively.

[0064] 2.4 Test Results: The retention times of each component in the mixed sample under the same test method were consistent with those of the single component in Example 1. However, as shown in Table 3 and Figure 8 (The GC test results of the mixed sample-2-1 are shown in the figure). Method 1 failed to separate isooctane and isooctyl alcohol, and P204 derivative byproduct 1 and isooctyl ether; however, as shown in Table 3 and... Figure 9 (The GC test results of the mixed sample-2-2 are shown in the figure). When tested according to method 2, each component was completely separated and the resolution was ≥2.5.

[0065] 2.5 Conclusion Method 1 meets the needs of rapid industrial screening, while Method 2 achieves accurate quantification of all components and has better separation than Method 1.

[0066] Example 3: Investigating the effect of TMSCH2N2 dosage on P204 derivatization efficiency 3.1 Experimental Objective Verify the ratio in claim 3 where “when the P204 content in the TOP sample is 0.05%~10%, the volume ratio of the sample to the derivatizing reagent is 1000:1~2:5”, using the completeness of P204 derivatization and derivatization byproducts as evaluation indicators.

[0067] 3.2 Experimental Design Take P204 standard with a purity of 99.0%, fix the derivatization time at 20 min, use dichloromethane as solvent, and set up 3 groups of TMSCH2N2 dosages: Group 1: Volume ratio 1:1.0 (P204 1.0 mL + derivatizing agent 1.0 mL); Group 2: Volume ratio 1:1.2 (P204 1.0 mL + derivatizing agent 1.2 mL); Group 3: Volume ratio 1:1.4 (P204 1.0 mL + derivatizing agent 1.4 mL); The test solutions were prepared according to the steps in Example 1 and tested using Method 2. The sample numbers and components are shown in Table 5.

[0068] Table 5 Summary of Sample Numbers and Components

[0069] 3.3 Test Results The gas chromatograms of the above three sets of experiments are as follows: Figures 10-12 The results are shown in Table 6. Table 6. Comparison of detection results for different sample-to-TMSCH2N2 volume ratios.

[0070] 3.4 Conclusion The above three sets of results show that when the sample contains 99.0% P2O4, Group 1 (1:1.0) has 1.16% residual P2O4 (incomplete derivatization), Group 2 (1:1.2) has 0.98% residual P2O4 (nearly complete derivatization), and Group 3 (1:1.4) has no residual P2O4 but 9.64% byproducts (excess). Therefore, 1:1.2~1:1.3 is the range with complete derivatization and the fewest byproducts, and 1:1.3 is recommended, consistent with the data trend. According to the content conversion, when the sample contains 0.1% P2O4, the recommended volume ratio of sample to TMSCH2N2-hexane is 1:0.0013 (1000:1.3). These three sets of experiments show that when adding TMSCH2N2 to derivatize P2O4, TMSCH2N2 can only be slightly excess; too little will result in incomplete P2O4 derivatization, and too much will result in excessive derivatization byproducts.

[0071] Example 4: Investigating the effect of solvent type on sample solubility 4.1 Experimental Objective To verify the advantages of "using mixed solvents instead of single solvents" in claim 4, the solubility and chromatographic peak shapes of different solvent systems were compared.

[0072] 4.2 Experimental Design With a fixed TMSCH2N2 dosage of 1:10 and a derivatization time of 10 min, the following four groups of solvents were added to the mixture of five components: Group I: Dichloromethane (single solvent); Group II: Chloroform (traditional solvent, control group); Group III: Dichloromethane - Hexane 3:1; Group IV: Dichloromethane - Hexane 1:1; The test solution was prepared according to the steps in Example 1 and detected using Method 2. The sample number and composition are shown in Table 7.

[0073] Table 7 Summary of Sample Numbers and Components (IV)

[0074] 4.3 Test Results The gas chromatograms of the above four sets of experiments are as follows: Figures 13-16 The results are shown in Table 8. Table 8 Comparison of sample solubility in different solvent systems

[0075] 4.4 Conclusion Due to the principle of "like dissolves like," the polarity and hydrophobicity of the solvent, along with the matching degree between the analyte (weakly polar isooctane / isooctyl ether, moderately polar isooctyl alcohol, weakly polar P204 derivative / TOP) (see Appendix Table 1), affect the sample's solubility, peak shape integrity, and quantitative reliability. The results of the four sets of experiments above show that as the polarity of the solvents trichloromethane, dichloromethane, and the mixture of dichloromethane and hexane decreases and their hydrophobicity increases, the solubility of the weakly polar isooctane and isooctyl ether increases. Therefore, appropriate solvents can be flexibly selected based on the composition of the sample to ensure high solubility for all components. For example, dichloromethane can be used as the solvent when the TOP content is ≥99%.

[0076] Example 5: Investigating the effect of temperature program in gas chromatography acquisition method on the resolution of various substances. 5.1 Experimental Objective The heating procedure of the precise quantitative method of claim 6 can be replaced with an equivalent procedure with a longer total analysis time. In this embodiment, three equivalent heating procedures are given as examples based on the boiling point and polarity characteristics of each substance in the mixture (see Appendix Table 2 for details).

[0077] 5.2 Sample Preparation 1. Derivatization and dilution filtration: Same as in Example 2.

[0078] 2. GC Temperature Rise Program Examples: This example demonstrates three temperature rise programs. T1: Hold at 50℃ for 1.5 min, increase to 130℃ at 5℃ / min, increase to 230℃ at 20℃ / min, increase to 280℃ at 10℃ / min and hold for 1.5 min (total time 29 min). T2: Hold at 50℃ for 1.5 min, increase to 130℃ at 5℃ / min, increase to 190℃ at 20℃ / min, increase to 200℃ at 10℃ / min, increase to 210℃ at 5℃ / min, increase to 280℃ at 10℃ / min, and hold for 1.0 min (total time 31.5 min). T3: Hold at 50℃ for 1.5 min, increase to 130℃ at 5℃ / min, increase to 190℃ at 20℃ / min, increase to 240℃ at 10℃ / min, increase to 280℃ at 5℃ / min, and hold for 1.5 min (total time 36.0 min). 3. Sample List Information: The same small-scale sample (4.8-45 ℃ + ether) was tested using the three heating programs described above. The sample number, composition information, and test method are shown in Table 9. Table 9 Summary of Sample Numbers and Components (V)

[0079] 5.3 Test Results and Conclusions as follows Figures 17-19 As shown, all five components in the mixed sample of TOP+P204+isooctanol+isooctyl ether+chloroisooctane were completely separated under three different temperature programs. Considering time and other costs, temperature program T1 is recommended, as it achieves good separation results while saving time.

[0080] Comparative Example 1: Comparison of Method 2 of the Present Invention with the Traditional Acid-Base Titration Method 1.1 Experimental Design Using "industrial TOP sample (TOP 98.5% + P204 1.2% + isooctanol 0.3%)" as the object, the following methods were used: Method 2 of the present invention: Detection according to the steps of Example 2; Traditional acid-base titration method: Refer to HG / T 5155-2017, titrate with 0.1 mol / L NaOH standard solution, phenolphthalein indicator (endpoint pH=8.3); Compare the detection capabilities, time consumption, and environmental friendliness of the two methods.

[0081] 1.2 Test Results Table 10 Comparison of Detection Characteristics of the Two Detection Methods

[0082] 1.3 Conclusion Method 2 of the present invention is significantly superior to the traditional titration method in terms of detection range, accuracy, efficiency and environmental friendliness, and solves the problem of "limited detection types and large errors of titration method" mentioned in the instruction manual.

[0083] Comparative Example 2: Comparison of the present invention's TMSCH2N2 with traditional derivatizing agents 2.1 Experimental Design Using "P204 standard (99.0% purity)" as the target, three groups of derivatizing agents were set up: Group A: TMSCH2N2 of the present invention (2.0 mol / L, 1:10 dosage, 10 min at room temperature); Group B: Diazomethane-ether solution (traditional highly toxic reagent, 0.5 mol / L, 1:5 dosage, room temperature for 10 min); Group C: BSTFA (traditional silanization reagent, containing 1% TMCS, aged at 60℃ for 60 min); all were detected using method 2, and the derivatization efficiency, safety and ease of operation were compared.

[0084] 2.2 Test Results Table 11 Comparison of the characteristics of the three groups of derivatizing agents

[0085] 2.3 Conclusion The TMSCH2N2 derivatizing agent of this invention overcomes the shortcomings of traditional reagents: toxicity is reduced by 60% (vs. diazomethane), derivatization time is shortened by 83% (vs. BSTFA), and no heating is required. The reagent can be purchased directly, which meets the invention's objective of "safe and efficient" as stated in the specification.

[0086] Comparative Example 3: Comparison of the mixed solvent of the present invention with that of conventional chloroform solvent 3.1 Experimental Design The following two solvents were added to the mixture of the five components of Example 2: The solvent of this invention is dichloromethane - hexane 3:1; Traditional solvent: chloroform; Detect solubility, peak shape, and safety.

[0087] 3.2 Test Results Table 12 Comparison of the characteristics of the two solvents

[0088] 3.3 Conclusion The mixed solvent of this invention solves the problems of traditional chloroform: the solubility is increased by 214%, peak interference is avoided, and toxicity is reduced by 50%, which meets the technical solution of claim 4 "optimized solvent compatibility".

[0089] Comparative Example 4: Comparison of the solvent of this invention with alcohol solvents 4.1 Experimental Design The reaction of TMSCH2N2 was compared with that of methanol (MeOH), dichloromethane, and ethanol (EtOH) as solvents. The sample numbers and components are shown in Table 13.

[0090] Table 13 Summary of Sample Numbers and Components (VI)

[0091] 4.2 Test Results The gas chromatograms of the six sets of experiments are shown in Figure 20. A comparison reveals that when methanol (MeOH) and ethanol (EtOH) are used as solvents, TMSCH2N2 reacts with them to produce derivative 1 (3.20 min) and derivative 2 (3.50 min), respectively. Specifically, methanol and ethanol contain active hydrogen atoms (-OH), which react with TMSCH2N2 to form silyl ether derivatives (e.g., methanol produces trimethylmethoxysilane, RT 3.20 min; ethanol produces trimethylethoxysilane, RT 3.50 min).

[0092] 4.3 Conclusion TMSCH2N2 (trimethylsilyldiazomethane) is a typical nucleophilic silanizing agent. Its core reaction characteristic is the substitution of hydrogen atoms in compounds containing active hydrogen (such as -OH, -COOH) by the TMS group (trimethylsilyl, -Si(CH3)3), while the diazo group (-CH2N2) releases N2 as a driving force. Methanol (CH2OH) and ethanol (CH3CH2OH) both contain hydroxyl groups (-OH, active hydrogen sites), and their reaction with TMSCH2N2 produces silyl ether derivatives, consuming the derivatizing agent and making it difficult to control the amount of derivatizing agent added. Therefore, the dilution solvent should be a compound without active hydrogen (such as -OH, -COOH), and short-chain alcohols such as methanol and ethanol containing active hydrogen are not suitable.

[0093] Summary of Invention Effects 1. Safe and efficient: TMSCH2N2 replaces diazomethane / BSTFA, reducing toxicity by 60% and shortening derivatization time to 10 minutes, solving the problems of high risk and low efficiency of traditional reagents; 2. Solvent optimization: Replacing chloroform with a dichloromethane-hexane mixture increases solubility by 214%, reduces toxicity by 50%, and lowers costs by 20%; 3. Dual-mode adaptation: The rapid method (17 minutes) is suitable for industrial batch testing, while the precise method (29 minutes) is suitable for small-scale impurity traceability, covering all scenarios; 4. Expanded detection capabilities: It can detect 4 more components than the titration method, and more than the traditional GC method, including isooctyl ether and chloroisooctane. It can also accurately quantify isooctyl alcohol content, and reduce waste liquid by 98%, meeting the requirements of environmental protection and industrial quality control.

Claims

1. A gas chromatographic method for detecting the content of trioctyl phosphate products and impurities, characterized in that, Includes the following steps: (1) Derivatization: The TOP sample of trioctyl phosphate was derivatized with a hexane solution of (trimethylsilyl)diazomethane at room temperature to obtain the derivatized sample; (2) Dilution and filtration: Add organic solvent to the derivatized sample obtained in step (1) for dilution, and filter to obtain the test solution; (3) Gas phase detection: Use a gas chromatograph equipped with a flame ionization detector, select a non-polar or weakly polar capillary column, and select a rapid screening method or a precise quantitative method for detection according to the detection requirements; (4) Quantitative analysis: After removing the solvent peak, the content of TOP and impurities was quantitatively analyzed by area normalization or external standard method.

2. The method according to claim 1, characterized in that, In step (1), the concentration of the hexane solution of (trimethylsilyl)diazomethane is 1.5~2.0 mol / L; the derivatization reaction is carried out at room temperature for 3~20 min.

3. The method according to claim 2, characterized in that, In step (1), when the content of dioctyl phosphate (P204) in the TOP sample is 0.05%~10%, the volume ratio of the sample to the derivatization reagent is 1000:1~2:

5.

4. The method according to claim 1, characterized in that, In step (2), the organic solvent is a mixture of dichloromethane and hexane, wherein the volume ratio of dichloromethane to hexane is 1:5 to 5:1; and the volume ratio of the derivatized sample to the organic solvent is 1:3 to 1:

30.

5. The method according to claim 4, characterized in that, The organic solvent may be replaced by one of dichloromethane, 1,2-dichloroethane, chloroform, or a mixed solvent formed by the aforementioned solvent and one of cyclohexane, heptane, or petroleum ether.

6. The method according to claim 1, characterized in that, In step (3), the chromatographic column is a 5% phenyl-95% methyl polysiloxane capillary column with a specification of 30 m × 0.25 mm × 0.25 μm, or an equivalent DB-5 or DB-1 chromatographic column.

7. The method according to claim 1, characterized in that, In step (3), the column temperature program of the rapid screening method is as follows: initial temperature 150℃ held for 2 min, then increased to 280℃ at a rate of 10℃ / min and held for 2 min; injection port temperature 280℃, split ratio 60:1, injection volume 1.0μL; this method is used to quantify TOP and P204.

8. The method according to claim 1, characterized in that, In step (3), the column temperature program of the precise quantification method is as follows: initial temperature 50℃ held for 1.5 min, then increased to 130℃ at a rate of 5℃ / min, then increased to 230℃ at a rate of 20℃ / min, and finally increased to 280℃ at a rate of 10℃ / min and held for 1.5 min; injection port temperature 280℃, split ratio 60:1, injection volume 1.0μL; this method is used to quantify TOP, P204, isooctyl alcohol, isooctyl ether and chloroisooctane.

9. The method according to claim 8, characterized in that, The column temperature program of the precise quantitative method can be replaced by the following equivalent program: initial temperature 50℃ held for 1.5 min, increased to 130℃ at 5℃ / min, increased to 190℃ at 20℃ / min, increased to 200℃ at 10℃ / min, increased to 210℃ at 5℃ / min, increased to 280℃ at 10℃ / min and held for 1.0 min.

10. The method according to claim 1, characterized in that, In step (4), when the TOP content is ≥99.0%, the area normalization method is used for quantification; when the TOP content is <99.0%, the external standard method is used for quantification.

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