Method for determining content of phosphodiesters in phosphate

Abstract

The invention discloses a method for determining the content of phosphodiesters in phosphate, which comprises the following steps: dissolving a dioctyl phosphate standard substance with a solvent to prepare a series of standard solutions with different concentrations, converting dioctyl phosphate into di (2-ethylhexyl) methyl phosphate through trimethylsilyl diazomethane, and determining the content of the di (2-ethylhexyl) methyl phosphate by adopting a gas chromatography external standard method. Drawing a standard curve; the method comprises the following steps: dissolving a trioctyl phosphate sample with a solvent, adding excessive derivatization reagent trimethylsilyl diazomethane to carry out derivatization reaction, carrying out gas chromatography sample injection detection analysis, and substituting the detected chromatographic peak area into a standard curve to calculate the content of dioctyl phosphate in the sample. The relative standard deviation RSD of the determination result of the method is less than 5%, the precision is high, the analysis and test method is simple, the operation is safe, and the consumed time is short.

Description

Technical Field

[0001] The invention relates to a method for determining the content of phosphodiester in phosphate ester. Background Art

[0002] Trioctyl phosphate (TOP), chemical name tri (2-ethylhexyl) phosphate, is a colorless, transparent, oily liquid, soluble in mineral oil, gasoline, ethanol and benzene, but insoluble in water. Trioctyl phosphate is a relatively practical, excellent flame retardant and cold-resistant plasticizer, used in vinyl resin, cellulose resin, phenolic resin, polyurethane, synthetic rubber, solvent, defoamer, etc.; its low-temperature performance is better than adipic acid esters, and it has mildew resistance and flame retardant effects. Although its thermal stability and plasticizing properties are slightly poor, they can be improved by using it in combination with triphenylmethyl phosphate; it can be used in combination with DOP to obtain self-extinguishing products, and can also be used in polyvinyl chloride cable materials, coatings, etc.

[0003] In the prior art, phosphorus oxychloride and octanol (2-ethylhexanol) are mainly used as raw materials to produce trioctyl phosphate (TOP). Trioctyl phosphate is mainly used as a solvent, lubricant and antistatic agent. It has high thermal stability and chemical stability and is widely used in the fields of synthetic resins, plastics, lubricating oils and fire suppressants. It can also be used as a component of liquid-liquid extractants, extractants and catalysts.

[0004] In the process of producing TOP using phosphorus oxychloride and octanol (2-ethylhexanol) as raw materials, dioctyl phosphate is usually produced as a by-product. This by-product affects the application performance of TOP products in downstream enterprises, so the content of this by-product needs to be monitored. Since dioctyl phosphate does not contain ultraviolet absorption functional groups and has a boiling point of 393°C, it cannot be directly detected by liquid phase and gas phase methods. Currently, TCIESC 51-2023 "Trioctyl Phosphate for Industrial Use" uses diazomethane to convert dioctyl phosphate in TOP products into di(2-ethylhexyl) methyl phosphate, which is then detected by gas chromatography. However, diazomethane is unstable, explosive and carcinogenic, and cannot be purchased on the market. Summary of the invention

[0005] In view of the above technical problems existing in the prior art, the purpose of the present application is to provide a method for determining the content of phosphodiester in phosphate ester.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The method for determining the content of phosphodiester in a phosphate ester comprises the following steps:

[0008] 1) Preparation of standard curve

[0009] The dioctyl phosphate standard is dissolved in a solvent to prepare a series of standard solutions with different concentrations. The prepared standard solutions are respectively added with a derivatization reagent trimethylsilyldiazomethane for derivatization reaction to generate di(2-ethylhexyl)methyl phosphate. The reaction solution after the derivatization reaction is then analyzed by gas chromatography injection. A standard curve is drawn with the initial concentration of dioctyl phosphate in the derivatization reaction system as the abscissa and the gas chromatographic peak area of ​​the derivatization reaction product di(2-ethylhexyl)methyl phosphate as the ordinate; wherein the reaction formula of the derivatization reaction is as follows:

[0010]

[0011] 2) Determination of phosphodiester content in phosphate esters

[0012] The trioctyl phosphate sample is dissolved in a solvent, and then an excess of a derivatization reagent trimethylsilyldiazomethane is added to carry out a derivatization reaction. After that, the sample is injected and detected and analyzed by gas chromatography. The detected chromatographic peak area is substituted into the standard curve to deduce the content of dioctyl phosphate in the sample.

[0013] Furthermore, in step 1) and step 2), the solvent is methanol.

[0014] Furthermore, when preparing the standard curve in step 1), the concentration range of dioctyl phosphate in the reaction solution system for the derivatization reaction is 0.5-20 ug / mL.

[0015] Furthermore, the derivatization reaction in step 1) and step 2) is carried out under ultrasound at room temperature, and the reaction time is 4-10 minutes.

[0016] Furthermore, in the reaction solution system for the derivatization reaction in step 1) and step 2), the final concentration of the derivatization reagent trimethylsilyldiazomethane added is 5-50 mmol / L.

[0017] Furthermore, in step 1) and step 2), the chromatographic conditions of the gas chromatography are: the chromatographic column stationary phase is 100% dimethylpolysiloxane, the specification is 30m*0.32mm*1.0um, the hydrogen flame ionization detector is used for detection, the initial temperature of the heating program is 150°C, maintained for 2-3min, and heated to 300°C at a rate of 8-12°C / min, maintained for 5-10min, and the detector temperature is 300°C.

[0018] Furthermore, the trioctyl phosphate sample in step 2) is a trioctyl phosphate product produced using phosphorus oxychloride and 2-ethylhexanol as raw materials.

[0019] The beneficial effects achieved by the present invention are:

[0020] 1) The method of the present invention converts dioctyl phosphate into di(2-ethylhexyl)methyl phosphate by using trimethylsilyldiazomethane, and then uses gas chromatography external standard method to determine its content. The relative standard deviation RSD of the determination result is less than 5%, the precision is high, the analysis and testing method is simple, the operation is safe, and the time consumption is short. The results of multiple groups of parallel tests of this method are close, the repeatability is good, and the accuracy is high. The recovery rate is between 95% and 105%, and the recovery rate is stable. The method of the present invention is also applicable to the determination of the content of phosphodiester in other phosphates.

[0021] 2) Compared with the prior art using diazomethane, the present invention uses trimethylsilyldiazomethane, which greatly improves the operational safety and the raw materials are easily available.

[0022] 3) The byproduct of the derivatization reaction between dioctyl phosphate and trimethylsilyldiazomethane is TMS, which has a boiling point of 26°C-28°C and is easily volatile at room temperature. Figure 2 The peak times in the detected gas phase spectra are all within the time period of 0-3 minutes, which is quite different from the peak time of the derivatization reaction product di(2-ethylhexyl)methyl phosphate (about 11 minutes), and will not have an adverse effect on the detection results of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The standard curve drawn for Example 1 of the present invention;

[0024] Figure 2 This is a partial enlarged view of the gas chromatogram of the product of the derivatization reaction of the trioctyl phosphate sample detected in Example 1 of the present invention.

[0025] Figure 3 It is a gas chromatogram of the product of the derivatization reaction of the trioctyl phosphate sample detected in Example 2 of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] Embodiment 1:

[0028] 1. Experimental Principle

[0029] In methanol solution, dioctyl phosphate in the sample undergoes a derivatization reaction with TMSCHN2 to convert it into di(2-ethylhexyl)methyl phosphate, and its content is then determined by gas chromatography. The equation for the derivatization reaction is as follows:

[0030]

[0031] 2. Reagents and Instruments

[0032] 2.1 The gas chromatograph is equipped with a FID detector.

[0033] 2.2 Methanol (chromatographic grade).

[0034] 2.3 Derivatization reagent: 2 mol / L (trimethylsilyl)diazomethane-n-hexane solution.

[0035] 2.4 Conventional laboratory glassware.

[0036] 2.5 Gas chromatography conditions are shown in Table 1.

[0037] Table 1 Gas chromatography conditions

[0038]

[0039]

[0040] 3. Experimental Procedure

[0041] 3.1 Preparation of standard curve

[0042] First-level calibration solution: Weigh 0.05 g (accurate to 0.0001 g) of dioctyl phosphate into a 100 mL volumetric flask and dilute to the mark with methanol to obtain a 500 ug / mL standard solution.

[0043] Second-level calibration solution: Pipette 5 mL of the first-level calibration solution into a 50 mL volumetric flask and dilute to the mark with methanol to obtain a 50 ug / mL standard solution.

[0044] Third-level calibration solution: Pipette 20 mL of the second-level calibration solution into a 50 mL volumetric flask, add 0.2 mL of the derivatization reagent, dilute to the scale with methanol, and react by ultrasonication at room temperature for 5 min to obtain a 20 ug / mL standard solution.

[0045] Fourth-level calibration solution: Pipette 10 mL of the second-level calibration solution into a 50 mL volumetric flask, add 0.2 mL of the derivatization reagent, dilute to the scale with methanol, and react by ultrasonication at room temperature for 5 min to obtain a 10 ug / mL standard solution.

[0046] Fifth-level calibration solution: Pipette 5 mL of the second-level calibration solution into a 50 mL volumetric flask, add 0.2 mL of the derivatization reagent, dilute to the scale with methanol, and react by ultrasonication at room temperature for 5 min to obtain a 5 ug / mL standard solution.

[0047] Sixth-level calibration solution: Pipette 2 mL of the second-level calibration solution into a 50 mL volumetric flask, add 0.2 mL of the derivatization reagent, dilute to the scale with methanol, and react by ultrasonication at room temperature for 5 min to obtain a 2 ug / mL standard solution.

[0048] Seventh-level calibration solution: Pipette 1 mL of the second-level calibration solution into a 50 mL volumetric flask, add 0.2 mL of the derivatization reagent, dilute to the scale with methanol, and react by ultrasonication at room temperature for 5 min to obtain a 1 ug / mL standard solution.

[0049] According to the gas chromatography conditions in Table 1, the third to seventh level standard solutions (from small to large concentrations) were measured to obtain the corresponding peak area A. The corresponding dioctyl phosphate concentration (ug / mL) and the peak area of ​​di(2-ethylhexyl)methyl phosphate, the derivatization reaction product of dioctyl phosphate, were used to make a standard curve. The results are shown in Figure 1 .

[0050] 3.2 Sample measurement steps

[0051] Weigh about 0.1 g (accurate to 0.0001 g) of trioctyl phosphate sample into a 10 mL volumetric flask, add 0.2 mL of derivatization reagent, dilute to scale with methanol, react at room temperature for 5 min by ultrasonication, and detect according to the gas chromatography conditions in Table 1. The content of dioctyl phosphate is obtained by the external standard method. The gas chromatogram of the detection is shown in FIG. Figure 2 , where 11.007 minutes is the peak time of di(2-ethylhexyl)methyl phosphate, the derivatization product of dioctyl phosphate.

[0052] The mass fraction of dioctyl phosphate is represented by ω, the unit is %, and is calculated as follows:

[0053]

[0054] Where:

[0055] c- the concentration of dioctyl phosphate obtained from the standard working curve in the chromatographic analysis, ug / mL;

[0056] m-mass of sample, g.

[0057] 3.3 Sample measurement results

[0058] According to the above method, 8 groups of precision experiments were carried out on 3 trioctyl phosphate samples, and the results are shown in Tables 2, 3 and 4 below.

[0059] Table 2 Measurement results of sample 1

[0060]

[0061]

[0062] Table 3 Measurement results of sample 2

[0063]

[0064] Table 4 Measurement results of sample 3

[0065]

[0066] Table 5 Sample 1 spike recovery determination results

[0067]

[0068] The method of the present invention converts dioctyl phosphate into di(2-ethylhexyl)methyl phosphate by using trimethylsilyldiazomethane, and then uses a gas chromatography external standard method to determine the content thereof. The relative standard deviation RSD of the determination result is less than 5%, the precision is high, the analysis and testing method is simple, the operation is safe, and the time consumption is short. The results of multiple groups of parallel tests of the method are close, the repeatability is good, and the accuracy is high. The recovery rate is between 95% and 105%, and the recovery rate is stable. The method of the present invention is also applicable to the determination of the content of phosphodiester in other phosphates.

[0069] Embodiment 2:

[0070] Weigh about 0.1 g (accurate to 0.0001 g) of another batch of trioctyl phosphate samples into a 10 mL volumetric flask, add 0.2 mL of derivatization reagent, dilute to scale with methanol, react at room temperature for 5 min with ultrasound, and perform gas chromatography under the conditions of Table 1. The content of dioctyl phosphate is obtained by the external standard method. The gas chromatogram of the detection is shown in Figure 3. Figure 3 It can be seen that the peak time of the derivatization reagent is before 3 minutes, 10.972 minutes is the peak time of dioctyl phosphate derivatization product di(2-ethylhexyl) methyl phosphate, and the peak time of trioctyl phosphate is 15.035 minutes.

[0071] Figure 2 and Figure 3 There is a slight deviation in the peak time of the dioctyl phosphate derivative product. This is due to the experimental error of different batches of samples and different batches of operations, which is within a reasonable error range.

[0072] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims

1. A method for determining the content of phosphodiester in phosphate ester, characterized in that The following steps are involved: 1) Preparation of standard curve The dioctyl phosphate standard is dissolved in a solvent to prepare a series of standard solutions with different concentrations. The prepared standard solutions are respectively added with a derivatization reagent trimethylsilyldiazomethane for derivatization reaction to generate di(2-ethylhexyl)methyl phosphate. The reaction solution after the derivatization reaction is then analyzed by gas chromatography injection. A standard curve is drawn with the initial concentration of dioctyl phosphate in the derivatization reaction system as the abscissa and the gas chromatographic peak area of ​​the derivatization reaction product di(2-ethylhexyl)methyl phosphate as the ordinate; wherein the reaction formula of the derivatization reaction is as follows: 2) Determination of phosphodiester content in phosphate esters The trioctyl phosphate sample is dissolved in a solvent, and then an excess of a derivatization reagent trimethylsilyldiazomethane is added to carry out a derivatization reaction. After that, the sample is injected and detected and analyzed by gas chromatography. The detected chromatographic peak area is substituted into the standard curve to deduce the content of dioctyl phosphate in the sample.

2. The method for determining the content of phosphodiester in a phosphate ester according to claim 1, wherein In step 1) and step 2), the solvent is methanol.

3. The method for determining the content of phosphodiester in a phosphate ester according to claim 1, wherein When preparing the standard curve in step 1), the concentration range of dioctyl phosphate in the reaction solution system for the derivatization reaction is 0.5-20 ug / mL.

4. The method for determining the content of phosphodiester in a phosphate ester according to claim 1, wherein The derivatization reaction in step 1) and step 2) is carried out under ultrasound at room temperature, and the reaction time is 4-10 minutes.

5. The method for determining the content of phosphodiester in a phosphate ester according to claim 1, wherein In the reaction solution system for the derivatization reaction in step 1) and step 2), the final concentration of the derivatization reagent trimethylsilyldiazomethane added is 5-50 mmol / L.

6. The method for determining the content of phosphodiester in a phosphate ester according to claim 1, characterized in that In step 1) and step 2), the chromatographic conditions of the gas chromatography are: the chromatographic column stationary phase is 100% dimethylpolysiloxane, the specification is 30m*0.32mm*1.0um, the hydrogen flame ionization detector is used for detection, the initial temperature of the heating program is 150°C, maintained for 2-3min, and heated to 300°C at a rate of 8-12°C / min, maintained for 5-10min, and the detector temperature is 300°C.

7. The method for determining the content of phosphodiester in a phosphate ester according to claim 1, characterized in that The trioctyl phosphate sample in step 2) is a trioctyl phosphate product produced using phosphorus oxychloride and 2-ethylhexanol as raw materials.

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