A method for detecting cyclohexylamine in soil

Abstract

The application discloses a method for detecting cyclohexylamine in soil, which comprises the following steps: step A: sample treatment, foreign matters such as leaves and stones are removed from the soil sample, and an appropriate amount of diatomite is added and mixed thoroughly until the soil sample becomes granular; and the PH value is adjusted to 11 by using ammonia water; step B: extraction, the soil sample is extracted by using a fast solvent extractor, chloroform is selected as the solvent, and the extraction liquid is concentrated to about 1 mL after water is removed; step C: purification, the concentrated liquid is purified by using a magnesium silicate purification column, and the concentrated liquid is concentrated and fixed to 1 mL; and step D: detection, gas chromatography mass spectrometry is used for detection, and the internal standard method is used for quantification; the application has the advantages that the use amount of organic reagents is greatly reduced by using the pressurized fluid extraction method; the extraction of a single sample can be completed in a short time; the detection limit of the cyclohexylamine detection method is 0.04 mg / kg, the precision is 8.2% to 8.7%, and the accuracy is 68.3% to 74.5%; and the method can meet the determination requirements.

Description

Technical Field

[0001] This invention relates to the field of environmental testing, and specifically to a method for detecting cyclohexylamine in soil. Background Technology

[0002] Cyclohexylamine is an organic compound with the chemical formula C6H13N. It is soluble in water and most organic solvents. As an important raw material for food additives and rubber additives, and a fine chemical intermediate, cyclohexylamine has experienced rapid growth in recent years, with demand exceeding supply. Driven by market demand, the market prospects for cyclohexylamine are very broad. Against this backdrop, a large number of factories have sprung up.

[0003] Recent field investigations of soil have revealed residual cyclohexylamine pollution in some sites. Cyclohexylamine is a major characteristic pollutant in soil. Determining the cyclohexylamine content in soil is used to determine the pollution level and distribution of cyclohexylamine, which helps in conducting detailed site investigations and risk assessments.

[0004] Currently, there is no method in China for determining cyclohexylamine in soil. Therefore, a method for detecting cyclohexylamine in soil is urgently needed to effectively control its residual levels. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for detecting cyclohexylamine in soil, which can detect the content of cyclohexylamine in soil.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for detecting cyclohexylamine in soil, comprising the following steps:

[0007] Step A: Sample preparation. First, remove foreign objects such as leaves and stones from the soil sample. Add an appropriate amount of diatomaceous earth and mix thoroughly until it becomes granular. Adjust the pH value to 11 with ammonia.

[0008] Step B: Extraction. The soil sample was extracted using a rapid solvent extractor with chloroform as the solvent. After removing water, the extract was concentrated to about 1 mL.

[0009] Step C: Purification. The concentrate is purified using a magnesium silicate purification column and then concentrated to a final volume of 1 mL.

[0010] Step D: Detection. Gas chromatography-mass spectrometry (GC-MS) is used for detection, and the internal standard method is employed for quantification.

[0011] Preferably, in step A, the diatomaceous earth is 60-100 mesh, and the mass ratio of soil to diatomaceous earth is 8:2. The ammonia solution has a concentration of W(NH3·H2O) = 26%. Sample pH values ​​of 8, 9, 10, 11, and 12 were selected. Through comparative experiments, the highest recovery rate of cyclohexylamine was observed at a sample pH of 11.

[0012] Preferably, in step B, the extraction solvent is selected from acetone, n-hexane, dichloromethane, and chloroform. Through comparative experiments, chloroform extraction showed the highest spike recovery rate, so chloroform was chosen as the extraction solvent. Then, anhydrous sodium sulfate was used to remove water.

[0013] Preferably, the specific method of the rapid solvent extraction instrument in step B is as follows: the temperature of the extraction cell is 100°C, the pressure of the extraction cell is 100 bar, the carrier gas pressure is 0.7 MPa, the nitrogen washing time is 2 min, the static extraction time is 5 min, and the number of extractions is 2.

[0014] Preferably, the concentration method used in steps B and C is a parallel evaporation concentrator. Specifically, the heating temperature is 40°C, the rotation speed is 160 rpm, and the vacuum degree is slowly reduced from atmospheric pressure to 300 mbar.

[0015] Preferably, in step C, the magnesium silicate purification column has a specification of 1000 mg / 6 ml.

[0016] Preferably, in step C, the purification device uses a solid-phase extraction device, and the organic solvents used are dichloromethane and n-hexane.

[0017] Preferably, 1,4-dichlorobenzene D4 is added as an internal standard before volume adjustment in step C.

[0018] Preferably, the gas chromatography conditions in step D of the gas chromatography-mass spectrometry system are as follows: injection port temperature is 250℃, column flow rate is 1.2 mL / min, split injection is used with a split ratio of 30:1, and the column is a DB-5ms capillary column, 30m×250μm×0.25μm.

[0019] Column oven temperature program: 40℃ for 2 min, increase to 160℃ at 10℃ / min and hold for 1 min, then increase to 300℃ at 20℃ / min and hold for 7 min. Mass spectrometry conditions: ion source temperature 230℃, quadrupole temperature 150℃, transfer line temperature 300℃, electron impact source EI, full scan mode, mass scan range 45 amu to 450 amu.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The advantages of this invention, which utilizes pressurized fluid extraction, are that it significantly reduces the amount of organic reagents used; it can complete the extraction of a single sample in a shorter time; and the method for detecting cyclohexylamine provided by this invention has a detection limit of 0.04 mg / kg, a precision of 8.2%~8.7%, and an accuracy of 68.3%~74.5%, which meets the requirements for determination. Attached Figure Description

[0022] Figure 1 The total ion chromatogram of cyclohexylamine and 1,4-dichlorobenzene-D4 of the present invention is shown below.

[0023] Figure 2 The mass spectrum of cyclohexylamine of the present invention is shown below.

[0024] Figure 3 This is the mass spectrum of the internal standard 1,4-dichlorobenzene-D4 of this invention;

[0025] Figure 4 This is a standard curve diagram of cyclohexylamine according to the present invention;

[0026] Figure 5 This is a graph showing the recovery rate of cyclohexylamine spiked at different pH values ​​according to the present invention;

[0027] Figure 6 The graph shows the recovery rate data of cyclohexylamine spiked under different extraction solvents according to the present invention. Detailed Implementation

[0028] The present invention will now be described with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. The purpose of these embodiments is to enable those skilled in the art to fully understand the invention.

[0029] Example 1:

[0030] Weigh 10g of the soil sample and add 2g of diatomaceous earth, stirring until it reaches a fine, quicksand-like consistency. Adjust the pH to 11 with ammonia water, then transfer the mixture to an extraction tank. Place a dedicated filter membrane at the bottom and top of the extraction tank. Use chloroform as the solvent. The specific method for rapid solvent extraction is as follows: heat the extraction tank to 100℃, maintain a pressure of 100 bar, set the carrier gas pressure to 0.7 MPa, perform nitrogen purging for 2 minutes, conduct ACE extraction for 5 minutes, and repeat the extraction process twice. Collect the extract in a collection bottle at the bottom of the rapid solvent extractor.

[0031] After extraction, the extract in the collection flask is dehydrated through a cylindrical funnel containing anhydrous sodium sulfate, and then transferred to a parallel evaporation flask. The collection flask is rinsed with chloroform solvent at least three times to ensure that all the extract is transferred to the parallel evaporation flask. Then, the extract is concentrated to about 1 mL using a parallel evaporation concentrator. The specific method for using the parallel evaporation concentrator is as follows: heating temperature is 40℃, rotation speed is 160 rpm, and the vacuum degree is slowly reduced from atmospheric pressure to 300 mbar.

[0032] After parallel evaporation, the concentrate was purified. A magnesium silicate purification column was fixed on the solid-phase extraction apparatus. The column was first rinsed with 5 mL of dichloromethane, then activated with 6 mL of n-hexane. The concentration flask was rinsed three times with 3 mL of n-hexane. All the concentrated liquid after rinsing was transferred to the purification column. The liquid level in the purification column was always higher than the packing. The control valve was closed. Finally, 10 mL of a mixed solvent of dichloromethane and n-hexane (volume ratio: 1:9) was added to complete the elution. All the eluent was collected and transferred to the concentration flask.

[0033] The solution was then concentrated again to approximately 1 mL using a parallel evaporator, and 10 μL of 1,4-dichlorobenzene-D4 (1000 mg / L internal standard) was added to accurately bring the volume to 1 mL. The solution was then transferred to a 2 mL vial and analyzed using gas chromatography-mass spectrometry (GC-MS).

[0034] Gas chromatography conditions: Injector temperature: 250℃, column flow rate: 1.2 mL / min, split injection, split ratio: 30:1, column: DB-5ms capillary column, 30m × 250μm × 0.25μm. Column oven temperature program: 40℃ for 2 min, ramp at 10℃ / min to 160℃ for 1 min, ramp at 20℃ / min to 300℃ for 7 min.

[0035] Mass spectrometry conditions: Ion source temperature: 230℃, quadrupole temperature: 150℃, transfer line temperature: 300℃, electron impact source: EI, full scan mode, mass scan range: 45amu~450amu.

[0036] Example 1: The chromatograms of cyclohexylamine and 1,4-dichlorobenzene-D4 obtained by gas chromatography-mass spectrometry are shown below. Figure 1 As shown.

[0037] Example 1: The mass spectrum of cyclohexylamine was obtained using gas chromatography-mass spectrometry (GC-MS) as shown below. Figure 2 As shown.

[0038] Example 1: The mass spectrum of 1,4-dichlorobenzene-D4 was obtained using gas chromatography-mass spectrometry (GC-MS) as shown below. Figure 3 As shown.

[0039] Prepare a standard series of cyclohexylamine at concentrations of 1, 5, 10, 20, and 50 mg / L. The internal standard 1,4-dichlorobenzene-D4 concentration at each standard point is 10 mg / L.

[0040] The standard curve equation for cyclohexylamine is: Y = 0.075514X + 4.442998E-004, and the correlation coefficient R of the standard curve is... 2 =0.9998. The standard curve of cyclohexylamine is shown below. Figure 4 As shown.

[0041] Method detection limit test:

[0042] A blank spiking test was conducted on the soil sample according to the method described in Example 1. 10g of quartz sand was used as the blank sample, and 20μL of cyclohexylamine standard at a concentration of 100mg / L was added to the quartz sand. Other steps were the same as the soil testing procedure. Ten blank spiking tests were performed. The detection limit requirements are derived from HJ 168-2020 "Technical Guidelines for the Formulation and Revision of Environmental Monitoring and Analysis Methods Standards".

[0043] Following all the analytical steps for the samples, 10 blank samples were taken, and 0.2 mg / kg of cyclohexylamine standard solution was added to each sample. The results were then measured. The limit of detection was calculated as the standard deviation × 2.821, and the lower limit of quantification was 4 times the limit of detection. The results are shown in Table 1.

[0044] Table 1. Detection Limit Test Data for Cyclohexylamine

[0045]

[0046] The method detection limit was calculated to be 0.04 mg / kg and the lower limit of quantitation was 0.16 mg / kg by repeating the blank spiked test 10 times.

[0047] Precision and accuracy testing:

[0048] Spiking tests were conducted on soil samples. A low concentration (0.2 mg / kg) was prepared by adding 20 μL of 100 mg / L cyclohexylamine standard to the soil sample; a medium concentration (1.2 mg / kg) was prepared by adding 120 μL of 100 mg / L cyclohexylamine standard to the soil sample; and a high concentration (2.5 mg / kg) was prepared by adding 250 μL of 100 mg / L cyclohexylamine standard to the soil sample. Six parallel samples were prepared for each concentration point, and the measurements were performed according to all analytical procedures and instrument operating conditions.

[0049] Table 2 Results of sample spike recovery experiment

[0050]

[0051] As shown in Table 2, the relative standard deviation of the cyclohexylamine determination results in soil was 8.2%–8.7%, and the average spiked recovery rate was 68.3%–74.5%, indicating that the cyclohexylamine method has good precision and accuracy and can meet the determination requirements.

[0052] In summary, the method for detecting cyclohexylamine in soil of this invention exhibits good separation and extraction effects for cyclohexylamine in soil. The method detection limit for cyclohexylamine is 0.04 mg / kg, and the precision obtained by sample spiked determination is 8.2%~8.7%, with an accuracy of 68.3%~74.5%. This method meets the requirements for determination.

[0053] The above description is merely a preferred embodiment of the present invention. Any improvements and modifications made to the substantive content of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for detecting cyclohexylamine in soil, characterized in that, Includes the following steps: Step A: Sample processing. First, remove leaves and stones from the soil sample, add 60-100 mesh diatomaceous earth, with a soil-diatomaceous earth mass ratio of 8:2, mix thoroughly until granular, and adjust the pH value to 11 with 26% ammonia water. Step B: Extraction. The treated soil was extracted using a rapid solvent extractor with chloroform as the solvent. The extraction conditions were: extraction tank temperature of 100℃, extraction tank pressure of 100 bar, carrier gas pressure of 0.7 MPa, nitrogen purging time of 2 min, static extraction time of 5 min, and extraction times of 2. After dehydration with anhydrous sodium sulfate, the extract was concentrated to approximately 1 mL using a parallel evaporator at 40℃, 160 rpm, and a vacuum that was slowly reduced from atmospheric pressure to 300 mbar. Step C: Purification. The concentrate is purified by passing it through a magnesium silicate purification column with a specification of 1000 mg / 6 mL. The column is activated with 5 mL of dichloromethane and 6 mL of n-hexane in sequence. The concentration bottle is rinsed three times with 3 mL of n-hexane. All the concentrated liquid after rinsing is transferred to the purification column. Finally, it is eluted with a mixed solvent of 10 mL of dichloromethane and n-hexane in a volume ratio of 1:9, and the eluent is collected. Step D: Detection. The eluent was concentrated again to approximately 1 mL using a parallel evaporator, and 1,4-dichlorobenzene-D4 was added as an internal standard. The volume was adjusted to 1 mL, and the eluent was detected using gas chromatography-mass spectrometry. The quantification method was the internal standard method. The gas chromatography conditions were as follows: injection port temperature 250℃, column flow rate 1.2mL / min, split injection, split ratio 30:1, column was DB-5ms capillary column, 30m×250μm×0.25μm, column temperature program: 40℃ for 2min, ramped up to 160℃ at 10℃ / min and held for 1min, ramped up to 300℃ at 20℃ / min and held for 7min; The mass spectrometry conditions were as follows: ion source temperature 230℃, quadrupole temperature 150℃, transfer line temperature 300℃, ionization method was electron impact source, scanning mode was full scan, and mass scan range was 45~450amu.

2. The detection method according to claim 1, characterized in that, The method has a detection limit of 0.04 mg / kg and a determination limit of 0.16 mg / kg for cyclohexylamine in soil.

3. The detection method according to claim 1, characterized in that, The average recoveries of the method at three spiking concentrations of 0.2 mg / kg, 1.2 mg / kg, and 2.5 mg / kg were 68.3%–74.5%, with relative standard deviations of 8.2%–8.7%.

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