A method for simultaneously detecting multiple impurity components in imidacloprid

Abstract

The invention discloses a method for detecting multiple impurity components in imidacloprid simultaneously, the impurity components include acrolein, acrylonitrile, dichloromethane, ethylenediamine and toluene, using gas chromatography headspace injection, imidacloprid is detected, using the capillary chromatographic column of HP-1 model, its inner diameter is 0.53mm, length is 15m, film thickness is 3μm, initial column temperature is 32~34℃ and maintains 3min, rises to 60℃ at 3℃ / min rate, then rises to 240℃ and maintains 2min at 50℃ / min rate, injection port temperature is 240~260℃, detector temperature is 240~260℃, and diluent is dimethyl sulfoxide. The method for detecting impurity components in imidacloprid simultaneously of the present invention is highly sensitive, and specificity is strong, and the content of acrolein, acrylonitrile, dichloromethane, ethylenediamine and toluene can be determined simultaneously quickly and conveniently.

Description

Technical Field

[0001] The invention relates to a method for detecting impurity components in imidacloprid, and belongs to the technical field of chemical analysis. Background Art

[0002] Imidacloprid is a nitromethylene systemic insecticide, a chlorinated nicotinyl insecticide, also known as a neonicotinoid insecticide, with a chemical formula of C9H 10 ClN5O2. It has a broad spectrum, high efficiency, low toxicity, and low residue. Pests are not likely to develop resistance, and it has multiple effects such as contact killing, stomach poisoning, and systemic absorption. After the pests come into contact with the agent, the normal conduction of the central nervous system is blocked, causing them to be paralyzed and die. The product has good rapid effect, with a high protective effect one day after the drug is applied, and the residual period is as long as about 25 days. The efficacy of the drug is positively correlated with temperature. The higher the temperature, the better the insecticidal effect. It is mainly used to control pests with piercing-sucking mouthparts. The CAS number of imidacloprid is: 105827-78-9, and the chemical formula is as follows:

[0003]

[0004] Acrolein is an organic compound, the simplest unsaturated aldehyde, with the chemical formula C3H4O. It is a colorless or light yellow liquid, soluble in water, and easily soluble in most organic solvents such as ethanol and acetone. Its vapor has strong irritation and tear-inducing properties. It is a very important synthetic intermediate in the chemical industry and is widely used in resin production and organic synthesis. The CAS number of acrolein is 107-02-8, and the chemical formula is as follows:

[0005]

[0006] Acrylonitrile is an organic compound with the chemical formula C3H3N. It is a colorless liquid with a pungent odor and is flammable. Its vapor can form an explosive mixture with air. It is easy to burn when exposed to open flames and high heat, and emits toxic gases. It reacts violently with oxidants, strong acids, strong bases, amines, and bromine. The CAS number of acrylonitrile is 107-13-1, and the chemical formula is as follows:

[0007]

[0008] Dichloromethane is an organic compound with the chemical formula CH2Cl2. It is a colorless, transparent liquid with a pungent odor similar to ether. It is slightly soluble in water, soluble in ethanol and ether. It is a non-flammable low-boiling point solvent under normal conditions of use. Its vapor will only generate a weakly burning mixed gas when it reaches a high concentration in high-temperature air. It is often used to replace flammable petroleum ether, ether, etc. The CAS number of dichloromethane is 75-09-2, and the chemical formula is as follows:

[0009]

[0010] Ethylenediamine, referred to as ethylenediamine, has a chemical formula of C2H8N2. It is a typical fatty diamine, a colorless or slightly yellow oily or watery transparent liquid, produces smoke in the air, has an ammonia-like odor, and is hygroscopic. Molecular weight 60.10, melting point 8.5℃, autoignition point 385℃. It is an alkaline substance, easily soluble in water and ethanol, slightly soluble in ether, insoluble in benzene unless absolutely dry, and can form an azeotropic mixture with water, n-butanol, and toluene. It is flammable when exposed to heat, open flames, and oxidants, and has a moderate combustion hazard. It can be sterilized by high pressure or filtration. Ethylenediamine can be used to make fuels, rubber vulcanization accelerators, drugs, etc., solvents such as fibrin, emulsifiers, epoxy resin curing agents, and intermediates for making insulating paints and coatings. Ethylenediamine can be absorbed through the digestive tract, respiratory tract, and skin. The vapor has a strong irritating effect on the skin mucosa and nasal mucosa, and the liquid is corrosive and sensitizing. The CAS number of ethylenediamine is 107-15-3, and the chemical formula is as follows:

[0011]

[0012] Toluene is an organic compound with the chemical formula C7H8. It is a colorless, volatile liquid with a special aroma. It has strong refractive index. It is miscible with ethanol, ether, acetone, chloroform, carbon disulfide and glacial acetic acid, and is very slightly soluble in water. It is flammable, and its vapor can form an explosive mixture with air. The mixture can explode when the volume concentration is in a low range. It has low toxicity, and the median lethal dose (rat, oral) is 5000mg / kg.

[0013] High concentrations of gas are anesthetic and irritating. The CAS number of toluene is 108-88-3, and the chemical formula is as follows:

[0014]

[0015] During the synthesis and preparation of imidacloprid, it is necessary to control the amount of impurity residues in the final product. Acrolein and acrylonitrile are used in the synthesis process of 2-chloro-5-chloromethylpyridine, and a sufficiently sensitive detection method should be used to prove that there are no residues of these two impurities in the final product imidacloprid. The ethylenediamine impurity in the imidacloprid starting material N-nitroimidazole may remain in the final product imidacloprid, and it should be proved by experiments that there is no residue in the final product imidacloprid. The residual solvents dichloromethane and toluene are used in the synthesis process of the starting material 2-chloro-5-chloromethylpyridine, and it should be proved by experiments that there is no residue in the final product imidacloprid. The current prior art cannot detect the content of the above five impurities at the same time. Summary of the invention

[0016] The technical problem to be solved by the present invention is to provide a method for simultaneously detecting impurity components in imidacloprid with high sensitivity, strong specificity and rapidity and convenience.

[0017] The present invention proposes a technical solution to solve the above technical problems: a method for simultaneously detecting multiple impurity components in imidacloprid, wherein the impurity components include acrolein, acrylonitrile, dichloromethane, ethylenediamine and toluene, and adopts gas chromatography headspace injection to detect imidacloprid. A HP-1 capillary chromatographic column is used, which has an inner diameter of 0.53 mm, a length of 15 m, a film thickness of 3 μm, an initial column temperature of 32-34° C. maintained for 3 min, increased to 60° C. at a rate of 3° C. / min, and then increased to 240° C. at a rate of 50° C. / min and maintained for 2 min. The injection port temperature is 240-260° C., the detector temperature is 240-260° C., and the diluent is dimethyl sulfoxide.

[0018] The above detector is a hydrogen flame ionization detector.

[0019] The carrier gas is nitrogen or helium, with a flow rate of 7.8 to 8.2 ml / min.

[0020] The injection volume was 1 mL.

[0021] The vaporization time is 10 to 20 minutes.

[0022] The vaporization chamber temperature was 130°C, the quantitative loop temperature was 140°C, and the transfer line temperature was 150°C.

[0023] The split ratio is 4:1 to 6:1.

[0024] The present invention has positive effects: under specific chromatographic conditions, the method for simultaneously detecting the impurity components in imidacloprid of the present invention can completely separate the five component peaks-acrolein, acrylonitrile, dichloromethane, ethylenediamine and toluene, and the blank peak has no interference with the five component peaks. The RSD of acrolein in the repeatability test is 6.6% (n=6), the RSD of acrylonitrile is 2.6% (n=6), the RSD of dichloromethane is 2.5% (n=6), the RSD of ethylenediamine is 3.9% (n=6), and the RSD of toluene is 3.0% (n=6). The method for simultaneously detecting the impurity components in imidacloprid of the present invention is simple to operate, saves detection time, and reduces detection costs. The method for simultaneously detecting the impurity components in imidacloprid of the present invention is verified by multiple verifications of the spiked sample solution prepared by mixing the imidacloprid sample standard with an appropriate amount of acrolein, acrylonitrile, dichloromethane, ethylenediamine and toluene, and has strong specificity, high linearity and accuracy, good durability, and can be used for the needs of daily detection of pet medicines. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the gas chromatogram of the blank solution of dimethyl sulfoxide;

[0026] Figure 2 This is the gas chromatogram of ethylenediamine solution detected by DB-624 chromatographic column;

[0027] Figure 3 It is the gas chromatogram of ethylenediamine solution detected by HP-1 (30m*0.32mm) chromatographic column;

[0028] Figure 4 It is a gas chromatogram of ethylenediamine solution detected by HP-5MS column;

[0029] Figure 5 It is the gas chromatogram of ethylenediamine solution detected by HP-1 (15m*0.53mm) chromatographic column;

[0030] Figure 6 It is the gas chromatogram of the mixed solution using method 1 for column temperature;

[0031] Figure 7 This is the gas chromatogram of the mixed solution using method 2 for column temperature;

[0032] Figure 8 This is the gas chromatogram of the mixed solution using method three for column temperature;

[0033] Fig. 9 It is a gas chromatogram of a mixed reference solution of acrylonitrile, dichloromethane, ethylenediamine and toluene;

[0034] Fig.10 is the gas chromatogram of the acrolein control solution;

[0035] Fig.11 The standard curve is drawn based on the peak area corresponding to different concentrations of acrolein;

[0036] Fig.12 The standard curve is drawn based on the peak area corresponding to different concentrations of acrylonitrile;

[0037] Fig.13 The standard curve is drawn based on the peak area corresponding to different concentrations of dichloromethane;

[0038] Fig.14 The standard curve is drawn based on the peak area corresponding to different concentrations of ethylenediamine;

[0039] Fig.15 The standard curve is drawn based on the peak area corresponding to different concentrations of toluene. DETAILED DESCRIPTION

[0040] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention. Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art.

[0041] The sample of the present invention is a purchased high-purity imidacloprid powder standard product, which is verified by other methods to be free of impurities such as acrolein, acrylonitrile, dichloromethane, ethylenediamine and toluene.

[0042] 1. Brief description of method development

[0043] 1. Establishment of the maximum limit of impurities:

[0044] Acrolein: According to the CPDB database, acrolein is mutagenic (salmonella positive), but no increase in tumor incidence was observed in rat and mouse carcinogenicity tests. It belongs to Class 5 genotoxic impurities. The oral PDE given by searching relevant literature is 50μg / day. The above calculated PDE is for humans, not for the treated animal species, and needs to be adjusted based on the animal's weight. The calculation of the animal acrylonitrile residue limit follows the strict principle, and after calculation, a relatively small limit of 240ppm is selected.

[0045] Acrylonitrile: The Lifetime AI of acrylonitrile is 6μg / day in ICH M7(R1). The above-mentioned lifetime AI is for humans, not for the species of animals to be treated, and needs to be adjusted according to the weight of the animal. Calculation of animal acrylonitrile residue limit: According to the strict principle, a relatively small limit of 29.0ppm is selected after calculation.

[0046] Ethylenediamine: The NOEL on the ECHA website is as follows: NOEL is 9mg / kg / day. Based on the NOEL, the PDE is 450ug / day. 2) The PDE calculated above is for humans, not for the treated animal species, and needs to be adjusted based on the animal's weight. The animal ethylenediamine residue limit is calculated in accordance with the strict principle, and the smaller 2160ppm is selected after calculation.

[0047] Dichloromethane: Referring to the residual solvent determination method in Part IV of the Chinese Pharmacopoeia 2020 edition, the limit is set at 600 ppm.

[0048] Toluene: Referring to the residual solvent determination method in General Chapter 0861 of Part IV of the Chinese Pharmacopoeia 2020, the limit is set at 890 ppm.

[0049] 2. Condition Optimization

[0050] Proposed conditions: Chromatographic column: HP-1, 0.53mm (id) × 15m, 3μm

[0051] Column temperature: Temperature increase according to the program in Table 1:

[0052] Table 1 Chromatographic column heating program

[0053]

[0054] Inlet temperature: 250°C,

[0055] Detector temperature: 250°C,

[0056] Detector: FID,

[0057] Carrier gas: N2,

[0058] Split ratio: 2:1,

[0059] Flow rate: 5.0mL / min,

[0060] Vaporization chamber temperature: 130°C,

[0061] Vaporization time: 15 minutes,

[0062] Injection volume: 1mL (headspace injection),

[0063] Quantitative loop temperature: 140°C,

[0064] Transmission line temperature: 150°C,

[0065] Diluent: dimethyl sulfoxide.

[0066] Experimental process:

[0067] (1) Dimethyl sulfoxide is used as the blank solution. Accurately measure 1 ml and inject it into the gas chromatograph. Record the chromatogram. Figure 1 shown.

[0068] (2) Four different gas chromatography columns were used for ethylenediamine control, and the results were as follows:

[0069] like Figure 2 As shown, DB-624UI (30m*0.53mm*3μm) was used, and ethylenediamine did not produce a peak, so it was not used.

[0070] like Figure 3 As shown, HP-1 (30m*0.32mm*0.25μm) was used, but the peak shape of ethylenediamine was poor, so it was not used.

[0071] like Figure 4As shown, HP-5MS (30m*0.25mm*0.25μm) was used, and the peak shape of ethylenediamine was poor, so it was not used.

[0072] like Figure 5 As shown, HP-1 (15m*0.53mm*3μm) is used, and the peak shape of ethylenediamine is good, so it can be used.

[0073] Summary: When using DB-624UI, ethylenediamine has no peak; when using HP-1 (30m*0.32mm) and HP-5MS, ethylenediamine has poor peak shape; when using HP-1 (15m*0.53mm), ethylenediamine has good peak shape and the peak time can be further optimized.

[0074] (3) Take acrolein, acrylonitrile, dichloromethane, ethylenediamine and toluene, dissolve in acetonitrile and dilute to make a mixed solution containing about 0.2 mg, 0.2 mg, 0.2 mg, 0.3 mg and 0.3 mg of the above-mentioned reference substances per 1 ml, as a mixed reference solution. Accurately measure 1 ml and inject it into a gas chromatograph using an HP-1 (15m*0.53mm*3μm) chromatographic column to record the chromatogram.

[0075] Initial conditions: Inlet: 250°C, split ratio: 2:1, flow rate: 5.0 ml / min, detector: 250°C, vaporization time: 30 min, equilibrium temperature: 130°C, quantitative loop: 140°C, transfer line: 150°C, pressurization time: 0.2 min.

[0076] Optimize column temperature:

[0077] Method 1: The column temperature is maintained at 40℃ for 3 minutes, then raised to 60℃ at a rate of 2℃ / min, and then raised to 240℃ at 50℃ / min and maintained for 2 minutes. The chromatogram is as follows: Figure 6 The results show that under this method, acrylonitrile and dichloromethane have not reached baseline separation, and it is planned to continue to lower the initial column temperature to continue to separate acrylonitrile and dichloromethane.

[0078] Method 2: The column temperature was maintained at 35°C for 3 min, then raised to 60°C at a rate of 2°C / min, and then raised to 240°C at a rate of 50°C / min and maintained for 2 min. The flow rate was adjusted to 8 ml / min, and other conditions remained unchanged. The chromatogram was as follows: Figure 7 The results show that under this method, the separation of acrylonitrile and dichloromethane has been improved, but there is still risk in the current separation, so the initial column temperature can be further reduced to further optimize the separation degree.

[0079] Method 3: The column temperature is maintained at 33℃ for 3 minutes, then raised to 60℃ at a rate of 2℃ / min, and then raised to 240℃ at 50℃ / min and maintained for 2 minutes. Other conditions remain unchanged. The chromatogram is as follows: Figure 8The results show that: under this method, the peaks of each component are suitable and the separation degree is good, so this method is adopted.

[0080] (4) By consulting the literature, acrolein was added to the mixed solution of ethylenediamine. It was found that acrolein would react with ethylenediamine. Therefore, acrolein and ethylenediamine could not be prepared together. Considering that the first three components were too dense, the mixed solution was divided into two types: one was a mixed solution of acrylonitrile, dichloromethane, ethylenediamine and toluene. The chromatogram is shown in Figure 2. Fig. 9 As shown, the other is acrolein alone, the chromatogram is as shown Fig.10 Summary: The five components have appropriate peaks, normal responses, and good separation, so this method is reasonable.

[0081] 3. Content method verification

[0082] The content method was validated by methodology. It was found that under the specified chromatographic conditions, the main peak was well separated from the impurity peaks. The validation results showed that this method had good system applicability, specificity, linearity, accuracy, precision and durability, and was suitable and accurate for detecting the content of the five components.

[0083] The results of the content verification are summarized in Table 2:

[0084] Table 2 Content Methodology Verification Results

[0085]

[0086]

[0087]

[0088] As summarized in the table above, the validation results of the content analysis method show that this method has very good system applicability, specificity, linearity, accuracy, precision and durability, and is suitable and accurate for simultaneously detecting the contents of five components.

[0089] The specific verification process is as follows:

[0090] 3.1. Description of the detection method

[0091] Chromatographic column: HP-1, 0.53mm(id)×15m, 3μm

[0092] Column temperature: Temperature increase according to the program in Table 3:

[0093] Table 3 Chromatographic column heating program

[0094]

[0095] Flow rate: 1.0 mL / min,

[0096] Inlet temperature: 250°C,

[0097] Detector temperature: 250°C,

[0098] Split ratio: 5:1,

[0099] Flow rate: 8.0ml / min,

[0100] Vaporization chamber temperature: 130°C,

[0101] Quantitative loop temperature: 140°C,

[0102] Transmission line temperature: 150°C,

[0103] Vaporization time: 15min,

[0104] Diluent: dimethyl sulfoxide.

[0105] Peak order: acrolein, acrylonitrile, dichloromethane, ethylenediamine, toluene.

[0106] Acrolein reference stock solution: Accurately weigh 96.0 mg of acrolein into a 100 mL volumetric flask. Dilute to volume with diluent and mix well. (0.96 mg / ml)

[0107] Acrylonitrile reference stock solution: Accurately weigh 23.0 mg of acrylonitrile into a 100 mL volumetric flask. Dilute to volume with diluent and mix well. (0.23 mg / ml)

[0108] Dichloromethane reference stock solution: Accurately weigh 240.0 mg of dichloromethane into a 100 mL volumetric flask. Dilute to volume with diluent and mix well. (2.4 mg / ml)

[0109] Toluene reference stock solution: Accurately weigh 356.0 mg of toluene into a 100 mL volumetric flask. Dilute to volume with diluent and mix well. (3.56 mg / ml)

[0110] Ethylenediamine reference stock solution: Accurately weigh 86.4 mg of toluene into a 25 mL volumetric flask. Dilute to volume with diluent and mix well. (3.46 mg / ml)

[0111] Acrolein control solution: Accurately measure 1.0 ml of acrolein stock solution into a 100 ml volumetric flask. Dilute to scale with diluent and mix well.

[0112] Mixed control solution: Accurately measure 0.5 ml of acrylonitrile, 1 ml of toluene and dichloromethane, and 2.5 ml of ethylenediamine control stock solution into a 100 ml volumetric flask, dissolve and dilute to the scale with diluent, and mix well.

[0113] Sample solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection bottle, accurately measure 3.0 ml of diluent to dissolve and mix.

[0114] Acrolein spiked sample solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection vial, accurately measure 3.0 ml of acrolein control solution to dissolve and mix.

[0115] Mixed control spiked sample solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection bottle, accurately measure 3.0 ml of mixed control solution to dissolve and mix.

[0116] 3.2. System suitability

[0117] Chromatographic analysis procedures

[0118] Perform system suitability test according to the requirements of the analytical method. After the system is balanced, take 1 ml of acrolein control solution and acrylonitrile, dichloromethane, ethylenediamine and toluene mixed control solution, inject into the gas chromatograph, and record the chromatogram. Inject 5 injections of acrolein control solution and mixed control solution respectively, calculate the relative standard deviation (RSD), relative standard deviation (%RSD): NMT5.0%, theoretical plate number (N): NLT 3000.

[0119] The system suitability test results are shown in Table 4.

[0120] Table 4 System suitability test results

[0121]

[0122]

[0123] In summary, the RSD of 5 STD injections of acrolein is 1.2%, which is much less than 5.0%; the RSD of 5 STD injections of acrylonitrile is 3.1%, which is much less than 5.0%; the RSD of 5 STD injections of dichloromethane is 2.1%, which is much less than 5.0%; the RSD of 5 STD injections of ethylenediamine is 3.0%, which is much less than 5.0%; the RSD of 5 STD injections of toluene is 0.6%, which is much less than 5.0%; the theoretical plate number of each component is also greater than 3000, so the system applicability meets the requirements.

[0124] 3.3. Exclusivity

[0125] Specificity will be confirmed by blank interference and solvent interference.

[0126] Blank solution (diluent): Take dimethyl sulfoxide and inject it directly.

[0127] Sample solution: Same as sample solution in system suitability.

[0128] Acrolein control solution: Same as acrolein control solution in system suitability.

[0129] Acrylonitrile reference solution: Accurately measure 0.25 ml of acrylonitrile reference stock solution into a 50 ml volumetric flask. Dilute to volume with diluent and mix well.

[0130] Dichloromethane reference solution: Accurately measure 0.5 ml of dichloromethane reference stock solution into a 50 ml volumetric flask. Dilute to volume with diluent and mix well.

[0131] Toluene reference solution: Accurately measure 0.5 ml of toluene reference stock solution into a 50 ml volumetric flask. Dilute to volume with diluent and mix well.

[0132] Ethylenediamine control solution: Accurately measure 0.5 ml of ethylenediamine stock solution into a 20 ml volumetric flask. Dilute to scale with diluent and mix well.

[0133] Acrolein spiked sample solution: Same as acrolein spiked sample solution in system suitability.

[0134] Mixed control spike sample solution: Same as the mixed control spike sample solution in system suitability.

[0135] The specificity study test results are shown in Tables 5 and 6.

[0136] Table 5 Specificity test results Table-1

[0137] Solution Acrolein Acrylonitrile Dichloromethane Ethylenediamine Toluene Limit (ppm) 240 28.8 600 2168 890 Retention time 0.773 0.915 1.033 2.882 5.895 Peak area 221.617 13.767 126.092 150.013 834.936

[0138] Table 6 Specificity test results table-2

[0139]

[0140] In summary, the specificity study showed that any chromatographic peaks from blanks and samples did not significantly interfere with the peaks to be measured. This study showed that this analytical method was appropriate.

[0141] 3.4. Linear

[0142] The limit concentrations of the method for simultaneously detecting multiple impurity components in imidacloprid of the present invention are 2160 ppm for ethylenediamine, 28.8 ppm for acrylonitrile, 240 ppm for acrolein, 600 ppm for dichloromethane, and 890 ppm for toluene. A linear study is conducted on the limit standard range of 50% to 150%. The linear study is conducted according to the following requirements.

[0143] Test procedures and result handling:

[0144] A standard curve y=ax+b was drawn with concentration (μg / mL) as the abscissa and peak area as the ordinate.

[0145] Calculate the correlation coefficient r of the standard curve.

[0146] Calculate the linear deviation Bias%: intercept b relative to the peak area y at 100% concentration 100％ The percentage of.

[0147]

[0148] Calculate the mean response factor (MRF):

[0149]

[0150] The linear test results are as follows:.

[0151] The linear test results of acrolein are shown in Table 7.

[0152] Table 7 Acrolein linear test results

[0153]

[0154] The linear test results of acrylonitrile are shown in Table 8.

[0155] Table 8 Acrylonitrile linear test results

[0156]

[0157] The linearity test results of dichloromethane are shown in Table 9.

[0158] Table 9 Dichloromethane linear test results

[0159]

[0160]

[0161] The linearity test results of ethylenediamine are shown in Table 10.

[0162] Table 10 Ethylenediamine linear test results

[0163]

[0164] The linearity test results of toluene are shown in Table 11.

[0165] Table 11 Toluene linear test results

[0166]

[0167] In summary, the repeatability RSD of three injections at each concentration is n＝3All are less than 10.0%, indicating that the method has good system precision at each concentration; correlation coefficient r: 0.9962 (acrolein), 0.9996 (acrylonitrile), 0.9996 (dichloromethane), 0.9926 (ethylenediamine) and 0.9994 (toluene), all are greater than 0.99, indicating that the method has good linear regression; linear deviation Bias%: 1.58% (acrolein), 2.6% (acrylonitrile), 3.37% (dichloromethane), 9.0% (ethylenediamine) and 2.35% (toluene), all are less than 10.0%, indicating that the system error of this method is small.

[0168] From the above, we can see that acrolein has good linearity and system precision at a concentration of 4.47-13.42μg / mL; acrylonitrile has good linearity and system precision at a concentration of 0.67-2.02μg / mL; dichloromethane has good linearity and system precision at a concentration of 12.3-36.89μg / mL; ethylenediamine has good linearity and system precision at a concentration of 43.7-131.11μg / mL; toluene has good linearity and system precision at a concentration of 17.81-53.44μg / mL.

[0169] 3.5. Accuracy

[0170] The limit concentration of this method is 2160ppm for ethylenediamine, 28.8ppm for acrylonitrile, 240ppm for acrolein, 600ppm for dichloromethane, and 890ppm for toluene. The concentration range of the accuracy study is 50% to 150% of the limit, and three samples are required for each concentration.

[0171] 50% acrolein control solution: Accurately measure 0.5 ml of acrolein stock solution into a 100 ml volumetric flask. Dilute to scale with diluent and mix well.

[0172] 100% acrolein control solution: Accurately measure 1.0 ml of acrolein stock solution into a 100 ml volumetric flask. Dilute to scale with diluent and mix well.

[0173] 150% acrolein control solution: Accurately measure 1.5 ml of acrolein stock solution into a 100 ml volumetric flask. Dilute to scale with diluent and mix well.

[0174] 50% acrolein sample solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection bottle, accurately measure 3.0 ml of 50% acrolein control solution to dissolve and mix.

[0175] 100% acrolein sample solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection bottle, accurately measure 3.0 ml of 100% acrolein control solution to dissolve and mix.

[0176] 150% acrolein sample solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection bottle, accurately measure 3.0 ml of 150% acrolein control solution to dissolve and mix.

[0177] 50% mixed control solution: accurately measure 0.5 ml of acrylonitrile, 1 ml of toluene and dichloromethane, and 2.5 ml of ethylenediamine control stock solution into a 200 ml volumetric flask, dissolve and dilute to the scale with diluent, and mix well.

[0178] 100% mixed control solution: Accurately measure 1 ml of acrylonitrile, 2 ml of toluene and dichloromethane, and 5 ml of ethylenediamine control stock solution into a 200 ml volumetric flask, dissolve and dilute to the scale with diluent, and mix well.

[0179] 150% mixed control solution: accurately measure 1.5 ml of acrylonitrile, 3 ml of toluene and dichloromethane, and 7.5 ml of ethylenediamine control stock solution into a 200 ml volumetric flask, dissolve and dilute to the scale with diluent, and mix well.

[0180] 50% mixed control solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection bottle, accurately measure 3.0 ml of 50% mixed control solution to dissolve and mix.

[0181] 100% mixed control solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection bottle, accurately measure 3.0 ml of 100% mixed control solution to dissolve and mix.

[0182] 150% mixed control solution: Accurately weigh 0.12 g of sample into a 20 mL headspace injection bottle, accurately measure 3.0 ml of 150% mixed control solution to dissolve and mix.

[0183] Inject the reference solution, 50% spiked solution, 100% spiked solution, and 150% spiked solution in sequence. Repeat the injection of the reference solution 5 times and inject the remaining solutions once. Calculate the spiked recovery of each level of spiked sample solution by the external standard method as follows:

[0184] The recoveries of acrolein are shown in Table 12.

[0185] Table 12 Acrolein accuracy results

[0186]

[0187] The recoveries of acrylonitrile spiked with 2% NH4Cl are shown in Table 13.

[0188] Table 13 Acrylonitrile Accuracy Results

[0189]

[0190] The recoveries of dichloromethane are shown in Table 14.

[0191] Table 14 Dichloromethane accuracy results

[0192]

[0193]

[0194] The spiked recoveries of ethylenediamine are shown in Table 15.

[0195] Table 15 Ethylenediamine Accuracy Results

[0196]

[0197] The recoveries of toluene spiked are shown in Table 16.

[0198] Table 16 Toluene accuracy results

[0199]

[0200]

[0201] In summary, the spiked recoveries at concentrations of 50%, 100%, and 150% are all between 90.0 and 110.0%, indicating that there is a good recovery rate at each concentration; the %RSD of the average content recovery rate of nine test sample solutions does not exceed 10%.

[0202] From the above, we can know that acrolein is at a concentration of 44.75-134.25 μg / mL, acrylonitrile is at a concentration of 13.45-40.34 μg / mL, dichloromethane is at a concentration of 61.49-184.47 μg / mL, ethylenediamine is at a concentration of 43.71-131.12 μg / mL, and toluene is at a concentration of 89.07-267.20 μg / mL, which is equivalent to 50-150%, with good accuracy.

[0203] 3.6. Precision

[0204] (1) Method repeatability

[0205] Six samples (mixtures of three components from the same batch) were prepared in parallel and the five components were tested according to the requirements of the test method to evaluate the repeatability of the results of this method when testing the same batch of samples under the same experimental environment.

[0206] (2) Intermediate precision of the method

[0207] The 6 sample solutions used for the intermediate precision test are the same batch of samples as those used in the repeatability test, and the sample solutions are prepared as required. The tests should be conducted by different testers on different days and with different instruments, with a time interval of at least 24 hours. This is to prove the reproducibility of the results of this method when testing the same batch of samples under a variable experimental environment. The precision test results are shown in Table 17.

[0208] Table 17 Intermediate precision results

[0209]

[0210]

[0211]

[0212] In summary, the repeatability test of the method on the same day: RSD% of the 6 test results n＝6 The results were all less than 10.0%, indicating that the method has good repeatability. Repeatability test by different testers on different days: Among the 12 test results, RSD% n＝12 The average precision was 10.0%, indicating that this method has good intermediate precision.

[0213] From the above, it can be seen that this method has good repeatability and precision.

[0214] 3.7. Durability study

[0215] Under the condition of changing one of the following chromatographic parameters while keeping other factors (instrument, people) unchanged, the key parameters are confirmed. If a large impact is found, the influencing factor needs to be strictly controlled in the analysis method settings.

[0216] Change flow rate (±0.2mL / min)

[0217] Change injection port temperature (±10°C)

[0218] Change detector temperature (±10℃)

[0219] Change vaporization time (±5min)

[0220] Change the split ratio (±1)

[0221] Change column temperature (±1℃)

[0222] Change the chromatographic column (same specification but different serial number: Column: J&W Hp-1 0.53mm×15m (3μm) SN: USP207624A).

[0223] Chromatographic analysis procedure: Each HPLC condition was tested for system suitability as described in the content analysis method, and then the content was determined on the same batch of samples. The results of the system suitability and durability test are shown in Tables 18 and 19.

[0224] Table 18 Durability Results - System Suitability

[0225]

[0226] Table 19 Durability results

[0227]

[0228]

[0229] In summary, the difference between the content of acrylonitrile measured under each change condition and the result measured under the initial condition is within 15.0%, and the difference between the content of other components measured under each change condition and the result measured under the initial condition is within 10.0%. This shows that the detection method can still ensure the consistency of the content detection results after slight changes, and the method has good durability for detecting the contents of five components.

[0230] Obviously, the above embodiments are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. However, these obvious changes or modifications derived from the spirit of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for simultaneously detecting multiple impurity components in imidacloprid, wherein the impurity components include acrolein, acrylonitrile, dichloromethane, ethylenediamine and toluene, characterized in that: Imidacloprid was detected by gas chromatography headspace injection. A HP-1 capillary column was used, with an inner diameter of 0.53 mm, a length of 15 m, and a film thickness of 3 μm. The initial column temperature was maintained at 32-34°C for 3 min, increased to 60°C at a rate of 3°C / min, and then increased to 240°C at a rate of 50°C / min and maintained for 2 min. The injection port temperature was 240-260°C, the detector temperature was 240-260°C, and the diluent was dimethyl sulfoxide.

2. A method for simultaneously detecting multiple impurity components in imidacloprid according to claim 1, characterized in that: The detector is a hydrogen flame ionization detector.

3. A method for simultaneously detecting multiple impurity components in imidacloprid according to claim 1, characterized in that: The carrier gas is nitrogen or helium, with a flow rate of 7.8 to 8.2 ml / min.

4. A method for simultaneously detecting multiple impurity components in imidacloprid according to claim 1, characterized in that: The injection volume was 1 mL.

5. A method for simultaneously detecting multiple impurity components in imidacloprid according to claim 1, characterized in that: The vaporization time is 10 to 20 minutes.

6. A method for simultaneously detecting multiple impurity components in imidacloprid according to claim 5, characterized in that: The vaporizer temperature was 130°C, the loop temperature was 140°C, and the transfer line temperature was 150°C.

7. A method for simultaneously detecting multiple impurity components in imidacloprid according to claim 1, characterized in that: The split ratio is 4:1 to 6:1.

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