Method for detecting phthalic acid esters in seawater

Abstract

The invention relates to a method for detecting phthalic acid esters in seawater, which specifically comprises the following steps: (1) treating a to-be-detected sample: collecting the to-be-detected sample, and respectively carrying out liquid-liquid extraction under alkaline and acidic conditions to obtain extract liquor; (2) carrying out rotary evaporation concentration on the extract to obtain a concentrated solution; (3) purifying by adopting an alumina small column concentrated solution to obtain a to-be-detected solution; (4) establishment of a standard curve: preparing a mixture standard product of the phthalate compounds into a solution with the mass concentration of 5.0-500 [mu] g / L; and (5) detecting by adopting gas chromatography-mass spectrometry. The invention can effectively prevent the plastic product from interfering with the phthalic acid esters in the seawater, and provides a rapid and accurate detection method.

Description

Technical Field

[0001] The invention relates to the technical field of detection of phthalates, in particular to a method for detecting phthalates in seawater. Background Art

[0002] Phthalates (PAEs), also known as titanates, are mainly used as plasticizers and are widely used in industrial production such as rubber, coatings, printing and dyeing, toys, medical and cosmetics. Under certain conditions, they are easily released into water, atmosphere, food, soil, sediment, animals and plants, human tissues and body fluids. Studies have shown that PAEs can interfere with the normal secretion of endogenous hormones after entering the human body, while damaging the reproductive and immune systems. High concentrations can also cause liver and kidney damage. Therefore, PAEs pose potential risks to the environment and human health and are listed as environmental estrogens. The impact of PAEs has received widespread attention from environmental science, public health, the media and even the general public. Countries have successively introduced policies, regulations and pollutant limit regulations. PAEs can be determined by gas chromatography, gas chromatography-tandem mass spectrometry, liquid chromatography, ultra-high performance liquid chromatography, etc.

[0003] Invention patent application CN107607648B discloses a solid phase extraction-gas chromatography mass spectrometry detection method for phthalate ester compounds in sediments, which discloses that the sediment bottom mud is placed in a centrifuge tube and soaked with dichloromethane / cyclohexane, mixed and extracted with a vortex oscillator, the extract is transferred to a heart-shaped bottle after centrifugation, extracted with dichloromethane and repeated the above operation, the extract is combined, the extract is concentrated by rotary evaporation for purification, the sample is chemically treated with a neutral alumina column, the alumina column is first activated with dichloromethane, the effluent is discarded, the sample is passed through the column, and eluted with n-hexane / acetone and dichloromethane in turn. The eluent is dehydrated with anhydrous sodium sulfate and then rotary evaporated in a water bath to near dryness, and the volume is fixed with n-hexane to be tested on the machine, and gas chromatography-mass spectrometry is performed for quantitative analysis, and the external standard method is used for quantification. However, the extraction of sediments adopts the principle of solid-liquid extraction, that is, the target substance in the solid (soil) is extracted with an organic phase. The devices, equipment and operation methods used for the preparation of the test samples are different from those for the determination of phthalates in seawater. Invention patent application CN10764334A also discloses a solid phase membrane extraction-gas chromatography-mass spectrometry detection method for phthalates in water, using C 18 The solid phase extraction membrane is used to enrich phthalates in water, and gas chromatography-tandem mass spectrometry is used for detection. Since phthalates are used as plasticizers and widely exist in plastic products, they may interfere with phthalates in seawater, thus affecting the detection results. Summary of the invention

[0004] The purpose of the present invention is to overcome the existing shortcomings and adopt a liquid-liquid extraction-gas chromatography tandem mass spectrometry detection method to detect phthalate compounds in seawater, providing a simple, convenient, fast and accurate method for determining phthalate compounds in seawater, so as to realize the detection of phthalate compounds in seawater.

[0005] In the method provided by the present invention, in the process of preparing and purifying the sample to be tested, the spare parts, devices and consumables that are in direct contact with the sample are all made of non-plastic products, which can effectively prevent the interference of plastic products on phthalates in seawater, and the detection result is more accurate.

[0006] The specific plan is as follows:

[0007] A method for detecting phthalates in seawater comprises the following steps:

[0008] (1) Sample processing: After the sample is collected, it is extracted under acidic and alkaline conditions to obtain an extract; specifically, the following steps are included:

[0009] First, the pH of the sample to be tested is adjusted to >11, and the dichloromethane is added in a ratio of 100:2-4 by volume to perform liquid-liquid extraction. After shaking during the extraction process, the mixture is allowed to stand for stratification, the alkaline organic phase is collected, and the aqueous phase is retained;

[0010] Then, the sulfuric acid solution is mixed with the aqueous phase extracted under alkaline conditions in a volume ratio of 1-3:1-3, the pH of the mixed solution is adjusted so that the pH of the mixed solution is less than 2, and dichloromethane is added in a volume ratio of 100:2-4 between the mixed solution and dichloromethane to perform liquid-liquid extraction again, and the acidic organic phase is collected;

[0011] Mixing the alkaline organic phase and the acidic organic phase to obtain an extract;

[0012] (2) Concentrating the extract: dehydrating the extract with anhydrous sodium sulfate, repeatedly eluting the anhydrous sodium sulfate with the dichloromethane, and collecting the eluent; mixing the dehydrated extract with the eluent, and concentrating the extract with the eluent by rotary evaporation at 55-70° C. to 2-3 mL to obtain a concentrated solution;

[0013] (3) Purification of the concentrated solution: the concentrated solution is passed through an alumina column to obtain a purified solution; the purified solution is subjected to rotary evaporation at 55-70° C. to a volume of 1-3 mL, and then dried with nitrogen gas, and then normal hexane is added to make the volume to 1.0 mL, and mixed to obtain a test solution;

[0014] (4) Establishment of a standard curve: Phthalate ester compounds are prepared into an aqueous solution with a mass concentration of 5.0 to 500 μg / L to obtain a standard product;

[0015] (5) using gas chromatography-mass spectrometry for detection, specifically including the following steps: setting a temperature program for the chromatographic column: the initial temperature is 40-150°C, heating to 180-220°C at a rate of 5-15°C / min, heating to 2200-250°C at a rate of 5-15°C / min, and heating to 290-320°C at a rate of 5-10°C / min; using an HP-5MS chromatographic column for component separation;

[0016] The standard substance and the test solution are measured by gas chromatography-mass spectrometry, respectively, a standard curve of phthalate compounds is drawn according to the test result of the standard substance, and the phthalate compounds in the test solution are qualitatively determined according to the retention time obtained by the test of the test solution in combination with the standard curve, and quantitatively determined by an external standard method;

[0017] The specific calculation method is: the content of phthalates in the sample to be tested μg / L=(the content of phthalates in the test liquid μg / L×the volume of the test liquid mL) / the initial sampling volume of the sample to be tested L; wherein the content of phthalates in the test liquid is calculated based on the detection result of the test liquid in combination with the standard curve.

[0018] Preferably, the sample to be tested in step (1) is collected, and the collected sample to be tested is stored in a dark place and refrigerated at a temperature below 4-6°C, and the extraction is completed within 5-10 days;

[0019] More preferably, the sample to be tested in step (1) is collected, and the collected sample to be tested is stored in a dark place and refrigerated at a temperature below 4-6°C, and the extraction is completed within 7 days;

[0020] Optionally, the dichloromethane is added in a ratio of 100:3 by volume of the sample to be tested to perform liquid-liquid extraction;

[0021] Preferably, the extract is best used within 40 days.

[0022] Furthermore, in step (1), a separatory funnel is used for the extraction; the shaking requires the separatory funnel to be inverted and shaken, the stopper of the separatory funnel is supported by the palm of the right hand, and the neck of the funnel is held to prevent the stopper from loosening, the stopper of the separatory funnel is clamped with the index finger and middle finger of the left hand, and the separatory funnel is held with the palm of the left hand to perform the shaking; during this period, gas is generated, and the stopper of the separatory funnel needs to be opened from time to time to exhaust gas;

[0023] Optionally, during the inverted shaking, the liquid level inside the separating funnel does not touch the stopcock;

[0024] Optionally, the inverted shaking time is 2-10 minutes, during which the gas is exhausted 3-20 times.

[0025] Furthermore, in the extraction in step (1), when encountering a sample with complex components, emulsification occurs during the extraction, and mechanical means are used to separate the two phases, including stirring, centrifugation, demulsification by glass wool filtration, or demulsification by freezing.

[0026] Preferably, the anhydrous sodium sulfate in step (2) needs to be pre-baked at 350-450° C. for 3-5 hours.

[0027] Furthermore, the preparation of the alumina column in step (3) comprises: first filling glass wool at the bottom of the glass column, adding 0.8-1.2 g of alumina, tapping the wall of the glass column to ensure that the alumina is evenly filled, adding 4-6 mL of dichloromethane for activation, then adding 4-6 mL of ethyl acetate for elution, passing nitrogen to dry for 1-3 min, closing the stopcock, wrapping the top and bottom of the alumina column with aluminum foil, and then storing it in a stainless steel container for sealed storage for later use.

[0028] Preferably, the chromatography-mass spectrometry detection in step (4) has the following gas phase conditions: injection port temperature: 280°C, no split; injection volume: 1.0-2.0 μL, carrier gas flow rate: 1.0-1.5 mL / min; mass spectrometry conditions: ion source: electron bombardment source; ion source temperature: 230°C; transmission line temperature: 280°C; quadrupole temperature: 150°C; ionization voltage: 70 eV; mass scanning range: 35u~450u; data acquisition mode: full scan mode or selected ion scan mode.

[0029] Preferably, the chromatographic column temperature raising program is set in step (5): the initial temperature is 130°C, the temperature is raised to 200°C at a rate of 10°C / min, the temperature is raised to 225°C at a rate of 15°C / min, and the temperature is raised to 300°C at a rate of 7°C / min.

[0030] Optionally, the phthalate compounds in seawater include: dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, di-n-butyl phthalate, diethyl phthalate, dihexyl phthalate, diethyl phthalate, dipentyl phthalate, dihexyl phthalate, butyl benzyl phthalate, diethyl phthalate, dicyclohexyl phthalate, dihexyl phthalate, di-n-octyl phthalate and dinonyl phthalate.

[0031] Furthermore, the recovery rate of the detection method is >99%, RSD<2%, and the detection limit is <0.9 μg / L.

[0032] Beneficial effects:

[0033] In the present invention, the extract collected after extraction needs to be dehydrated with anhydrous sodium sulfate. This step can not only remove water, but also adsorb a small amount of phthalates. Therefore, it is necessary to repeatedly rinse the anhydrous sodium sulfate with a small amount of organic phase to elute more phthalates and reduce the loss of the target substance.

[0034] Furthermore, some salts in seawater are ionic compounds that are soluble in water, while most neutral substances are insoluble in water. By utilizing acidic and alkaline conditions, most of the acidic and alkaline impurities can be separated and removed, which is more conducive to the extraction of the target object.

[0035] Furthermore, the present application fully oscillates when extracting the sample to be tested, which can effectively increase the contact between the organic phase and the aqueous phase and improve the extraction efficiency.

[0036] In conclusion, the method for determining phthalate compounds in seawater provided by the present invention can quickly and accurately determine phthalate compounds in seawater. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0038] Figure 1 The TIC chromatogram (100 μg / L) of 15 phthalate standard solutions provided in Example 1 of the present invention is as follows: 1. dimethyl phthalate (DMP); 2. diethyl phthalate (DEP); 3. diisobutyl phthalate (DIBP); 4. di-n-butyl phthalate (DBP); 5. di(2-methoxy)ethyl phthalate (DMEP); 6. di(4-methyl-2-pentyl)hexyl phthalate (BMPP); 7. di-n-butyl phthalate (DBP); 8. di-(2-methoxy)ethyl phthalate (DMEP); 9. di-(4-methyl-2-pentyl)hexyl phthalate (BMPP); 10. 8. di(2-oxy)ethyl phthalate (DEEP); 9. dipentyl phthalate (DPP); 10. dihexyl phthalate (DHXP); 11. butyl benzyl phthalate (BBP); 12. di(2-butoxy)ethyl phthalate (DBEP); 13. dicyclohexyl phthalate (DCHP); 14. di(2-ethyl)hexyl phthalate (DEHP); 15. di-n-octyl phthalate (DNOP); 16. dinonyl phthalate (DNP).

[0039] Figure 2The SIM chromatograms of 15 phthalate standard solutions provided in Example 1 of the present invention (100 μg / L) are as follows: 1. dimethyl phthalate (DMP); 2. diethyl phthalate (DEP); 3. diisobutyl phthalate (DIBP); 4. di-n-butyl phthalate (DBP); 5. di(2-methoxy)ethyl phthalate (DMEP); 6. di(4-methyl-2-pentyl)hexyl phthalate (BMPP); 7. di-n-butyl phthalate (DBP); 8. di-(2-methoxy)ethyl phthalate (DMEP); 9. di-(4-methyl-2-pentyl)hexyl phthalate (BMPP); 10. 8. di(2-oxy)ethyl phthalate (DEEP); 9. dipentyl phthalate (DPP); 10. dihexyl phthalate (DHXP); 11. butyl benzyl phthalate (BBP); 12. di(2-butoxy)ethyl phthalate (DBEP); 13. dicyclohexyl phthalate (DCHP); 14. di(2-ethyl)hexyl phthalate (DEHP); 15. di-n-octyl phthalate (DNOP); 16. dinonyl phthalate (DNP). DETAILED DESCRIPTION

[0040] The following are definitions of some terms used in the present invention. Other terms not mentioned here have definitions and meanings known in the art:

[0041] TIC chromatogram: total ion current chromatogram;

[0042] SIM chromatogram: selected ion scan chromatogram;

[0043] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. In the embodiments, if specific techniques or conditions are not indicated, the techniques or conditions described in the literature in this area or the product specifications are carried out. The reagents used or the instruments that are not indicated by the manufacturer are all conventional products that can be obtained commercially. In the following embodiments, if not specifically stated, "%" refers to weight percentage, and parts refer to weight parts.

[0044] Seawater: comes from the sea area near Xiamen Island, Fujian Province.

[0045] Example 1

[0046] A method for detecting phthalates in seawater comprises the following steps:

[0047] (1) Sample processing: Take 1000 mL of seawater and extract it under acid and alkaline conditions (after the seawater is collected, store it in a dark place at 3°C ​​and complete the extraction within 7 days) to obtain an extract; specifically, the following steps are included:

[0048] First, the pH of the sample to be tested is adjusted to >11, and the dichloromethane is added in a ratio of 100:3 in volume to the sample to be tested and dichloromethane for liquid-liquid extraction. A separatory funnel is used for the extraction, and the separatory funnel needs to be inverted and shaken. The stopper of the separatory funnel is supported by the palm of the right hand, and the neck of the funnel is held to prevent the stopper from loosening. The stopper of the separatory funnel is clamped with the index finger and middle finger of the left hand, and the separatory funnel is held with the left palm for the shaking; during this period, gas will be generated, and the stopper of the separatory funnel needs to be opened from time to time to exhaust; during the inverted shaking, the liquid surface inside the separatory funnel should not touch the stopper; the inverted shaking time is 5 minutes, and the exhaust is 10 times during the period; after shaking during the extraction process, the layers are allowed to stand, the alkaline organic phase is collected, and the aqueous phase is retained;

[0049] Then, the pure sulfuric acid solution and the aqueous phase extracted under alkaline conditions were adjusted to pH in a volume ratio of 1:1 so that the pH was less than 2, and dichloromethane was added in the same ratio as above to perform liquid-liquid extraction again, and the acidic organic phase was collected;

[0050] Mixing the alkaline and acidic organic phases to obtain an extract;

[0051] If the sample to be tested has a complex composition and emulsification occurs during the extraction, mechanical means can be used to separate the two phases, including stirring, centrifugation, and demulsification by filtering with glass wool, or freezing to demulsify.

[0052] (2) Concentrating the extract: using anhydrous sodium sulfate to dehydrate the extract, repeatedly eluting the anhydrous sodium sulfate with the dichloromethane, and collecting the eluent; mixing the dehydrated extract with the eluent, performing rotary evaporation at 70° C. and concentrating to 2 mL to obtain a concentrated solution; the anhydrous sodium sulfate needs to be pre-baked at 400° C. for 4 h;

[0053] (3) Purification of the concentrated solution: First, prepare an alumina column: fill the bottom of the glass column with glass wool, add 1 g of alumina, tap the wall of the glass column to ensure that the alumina is evenly filled, add 5 mL of dichloromethane for activation, then add 5 mL of ethyl acetate for elution, pass nitrogen gas to dry for 2 min, close the stopcock, wrap the top and bottom of the alumina column with aluminum foil, and store it in a stainless steel container for sealed storage; then pass the concentrated solution through the alumina column to obtain a purified solution; evaporate the purified solution at 70° C. to about 2 mL, then blow dry with nitrogen, then add n-hexane to make the volume up to 1.0 mL, mix well, and obtain a test solution;

[0054] (4) Establishment of standard curve: a mixture standard of phthalate ester compounds was prepared into solutions with mass concentrations of 5.0 μg / L, 10.0 μg / L, 20.0 μg / L, 50.0 μg / L, 100.0 μg / L, 200.0 μg / L, 400.0 μg / L and 500.0 μg / L;

[0055] (5) Gas chromatography-mass spectrometry detection is adopted, which specifically includes the following steps: setting the temperature program of the chromatographic column: the initial temperature is 130°C, the temperature is increased to 200°C at a rate of 10°C / min, the temperature is increased to 225°C at a rate of 15°C / min, and the temperature is increased to 300°C at a rate of 7°C / min; using an HP-5MS chromatographic column for component separation; gas phase conditions: injection port temperature: 280°C, no split; injection volume: 1.0 μL, carrier gas flow rate: 1.2 mL / min; mass spectrometry conditions: ion source: electron bombardment source; ion source temperature: 230°C; transmission line temperature: 280°C; quadrupole temperature: 150°C; ionization voltage: 70 eV; mass scanning range: 35u~450u; data acquisition mode: full scan mode or selected ion scan mode, and the standard solution and the test solution are measured according to the set conditions.

[0056] The standard and the test solution were determined by gas chromatography-mass spectrometry, and the standard curve of the standard phthalate esters was drawn. The phthalate esters in the test solution were qualitatively determined according to the retention time and quantitatively determined by the external standard method. The chromatogram after data collection was as follows: Figure 1 and Figure 2 As shown;

[0057] The specific calculation method is: the content of phthalates in the sample to be tested μg / L=(the content of phthalates in the sample to be tested measured by the standard curve μg / L×the volume of the test liquid mL) / the initial sampling volume L of the sample to be tested; the calculation of the content of phthalates in the sample to be tested: the abundance value of the detected target is substituted into the corresponding standard curve Y, and X is calculated according to the standard curve formula, and X is the relevant content.

[0058] (6) Perform gas chromatography-mass spectrometry detection according to steps (1)-(5) and compare with the standard curve obtained above. The concentration of the spiked seawater phthalates to be tested is finally obtained by conversion. The results are shown in Tables 1-5. The recovery rate of this method is 99.38-100.98%, RSD<2%, and the detection limit is <0.9 μg / L.

[0059] The concentrations of phthalates in seawater samples (sample) and spiked seawater to be tested (spiked at a concentration of 500 μg / L) were determined and calculated using the method provided in the present application, as shown in Table 1; the recovery rate of the detection method was 99.38-100.98%; the standard curve information of each component of the phthalate compound standard is shown in Table 2; the precision of the method is shown in Table 3; the quantitative parameters of the target in seawater are shown in Table 4; the detection limits of each component calculated by the triple signal-to-noise ratio analysis method are shown in Table 5.

[0060] Table 1 Recovery results of spiked seawater samples

[0061] Table 2 Standard curves and correlation coefficients of each component in phthalate ester standards

[0062] Serial number Components Standard curve Correlation coefficient 1 Dimethyl phthalate (DMP) Y=240X-1230 <![CDATA[r 2 =0.999]]> 2 Diethyl phthalate (DEP) Y=219X-1160 <![CDATA[r 2 =0.997]]> 3 Diisobutyl Phthalate (DIBP) Y=269X-3170 <![CDATA[r 2 =0.995]]> 4 Dibutyl phthalate (DBP) Y=271X-2480 <![CDATA[r 2 =0.998]]> 5 Di(2-methoxy)ethyl phthalate (DMEP) Y=77.8X-810 <![CDATA[r 2 =0.994]]> 6 Bis(4-methyl-2-pentyl)phthalate(BMPP) Y=78.7X-429 <![CDATA[r 2 =0.998]]> 7 Di(2-ethoxy)ethyl phthalate (DEEP) Y=40.6X-589 <![CDATA[r 2 =0.998]]> 8 Dipentyl Phthalate (DPP) Y=260X-3030 <![CDATA[r 2 =0.998]]> 9 Dihexyl Phthalate (DHXP) Y=166X-1790 <![CDATA[r 2 =0.998]]> 10 Butyl Benzyl Phthalate (BBP) Y=182X-2140 <![CDATA[r 2 =0.998]]> 11 Di(2-Butoxy)ethyl Phthalate(DBEP) Y=17.5X-156 <![CDATA[r 2 =0.997]]> 12 Dicyclohexyl phthalate (DCHP) Y=129X-558 <![CDATA[r 2 =0.999]]> 13 Di(2-ethylhexyl)phthalate (DEHP) Y=97.5X-386 <![CDATA[r 2 =0.997]]> 14 Di-n-octyl phthalate (DNOP) Y=77.2X-379 <![CDATA[r 2 =0.998]]> 15 Dinonyl Phthalate (DNP) Y=58.4X-230 <![CDATA[r 2 =0.999]]>

[0063] Table 3 Precision test results of the detection method

[0064]

[0065]

[0066] Table 4 Quantitative parameters of target substances in seawater

[0067]

[0068] Table 5 Detection limits of each component in the target in seawater

[0069]

[0070]

[0071] Example 2

[0072] (1) Sample processing: Take 1000 mL of seawater and extract it under acid and alkaline conditions (after the seawater is collected, store it in a dark place at 4°C and complete the extraction within 7 days) to obtain an extract; specifically, the following steps are included:

[0073] First, the pH of the sample to be tested is adjusted to >11, and the dichloromethane is added in a ratio of 100:2 in volume to the sample to be tested and dichloromethane for liquid-liquid extraction. A separatory funnel is used for the extraction, and the separatory funnel needs to be inverted and shaken. The stopper of the separatory funnel is supported by the palm of the right hand, and the neck of the funnel is held to prevent the stopper from loosening. The stopper of the separatory funnel is clamped with the index finger and middle finger of the left hand, and the separatory funnel is held with the left palm for the shaking; during this period, gas will be generated, and the stopper of the separatory funnel needs to be opened from time to time to exhaust; during the inverted shaking, the liquid surface inside the separatory funnel should not touch the stopper; the inverted shaking time is 2 minutes, and the exhaust is performed 3 times during the period; after shaking during the extraction process, the layers are allowed to stand, the alkaline organic phase is collected, and the aqueous phase is retained;

[0074] Then, the pure sulfuric acid solution and the aqueous phase extracted under alkaline conditions were adjusted to pH in a volume ratio of 1:3 so that the pH was less than 2, and dichloromethane was added in the same ratio as above to perform liquid-liquid extraction again, and the acidic organic phase was collected;

[0075] Mixing the alkaline and acidic organic phases to obtain an extract;

[0076] If the sample to be tested has a complex composition and emulsification occurs during the extraction, mechanical means can be used to separate the two phases, including stirring, centrifugation, and demulsification by filtering with glass wool, or freezing to demulsify.

[0077] (2) Concentrating the extract: using anhydrous sodium sulfate to dehydrate the extract, repeatedly eluting the anhydrous sodium sulfate with the dichloromethane, and collecting the eluent; mixing the dehydrated extract with the eluent, performing rotary evaporation at 55° C. and concentrating to 3 mL to obtain a concentrated solution; the anhydrous sodium sulfate needs to be pre-baked at 350° C. for 5 h;

[0078] (3) Purification of the concentrated solution: First, prepare an alumina column: fill the bottom of the glass column with glass wool, add 0.8 g of alumina, tap the wall of the glass column to ensure that the alumina is evenly filled, add 4 mL of dichloromethane to activate it, then add 4 mL of ethyl acetate to rinse, pass nitrogen to dry for 1 min, close the stopcock, wrap the top and bottom of the alumina column with aluminum foil, and store it in a stainless steel container for sealed storage; then pass the concentrated solution through the alumina column to obtain a purified solution; evaporate the purified solution at 55°C to about 1 mL, then blow dry with nitrogen, and then add n-hexane to make the volume up to 1.0 mL, mix well, and obtain a test solution;

[0079] (4) Establishment of standard curve: a mixture standard of phthalate ester compounds was prepared into solutions with mass concentrations of 5.0 μg / L, 10.0 μg / L, 20.0 μg / L, 50.0 μg / L, 100.0 μg / L, 200.0 μg / L, 400.0 μg / L and 500.0 μg / L;

[0080] (5) Gas chromatography-mass spectrometry detection includes the following steps: setting the temperature program of the chromatographic column: the initial temperature is 40°C, the temperature is increased to 180°C at a rate of 5°C / min, the temperature is increased to 200°C at a rate of 15°C / min, and the temperature is increased to 290°C at a rate of 5°C / min; using an HP-5MS chromatographic column for component separation; gas phase conditions: injection port temperature: 280°C, no split; injection volume: 2.0 μL, carrier gas flow rate: 1.0 mL / min; mass spectrometry conditions: ion source: electron bombardment source; ion source temperature: 230°C; transmission line temperature: 280°C; quadrupole temperature: 150°C; ionization voltage: 70 eV; mass scanning range: 35u~450u; data acquisition mode: full scan mode or selected ion scan mode, and measuring the standard solution and the test solution according to the set conditions.

[0081] The standard and the test solution were determined by gas chromatography-mass spectrometry, and the standard curve of the standard phthalate esters was drawn. The phthalate esters in the test solution were qualitatively determined according to the retention time and quantitatively determined by the external standard method. The chromatogram after data collection was as follows: Figure 1 and Figure 2 As shown;

[0082] The specific calculation method is: the content of phthalates in the sample to be tested μg / L=(the content of phthalates in the sample to be tested measured by the standard curve μg / L×the volume of the test liquid mL) / the sampling volume L of the sample to be tested; the calculation of the content of phthalates in the sample to be tested: substitute the abundance value of the detected target into the corresponding standard curve Y, calculate X according to the standard curve formula, and X is the relevant content.

[0083] Example 3

[0084] (1) Sample processing: Take 1000 mL of seawater and extract it under acid and alkaline conditions (after the seawater is collected, store it in a dark place at 5°C and complete the extraction within 10 days) to obtain an extract; specifically, the following steps are included:

[0085] First, the pH of the sample to be tested is adjusted to>11, and the dichloromethane is added in a ratio of 100:4 in volume ratio of the sample to be tested and dichloromethane for liquid-liquid extraction. A separatory funnel is used for the extraction, and the separatory funnel needs to be inverted and shaken. The stopper of the separatory funnel is supported by the palm of the right hand, and the neck of the funnel is held to prevent the stopper from loosening. The stopper of the separatory funnel is clamped with the index finger and middle finger of the left hand, and the separatory funnel is held with the left palm for the shaking; during this period, gas will be generated, and the stopper of the separatory funnel needs to be opened from time to time to exhaust; during the inverted shaking, the liquid surface inside the separatory funnel should not touch the stopper; the inverted shaking time is 10 minutes, and the exhaust is performed 20 times during the period; after shaking during the extraction process, the layers are allowed to stand, the alkaline organic phase is collected, and the aqueous phase is retained;

[0086] Then, the pure sulfuric acid solution and the aqueous phase extracted under alkaline conditions were adjusted to pH in a volume ratio of 3:1 so that the pH was less than 2, and dichloromethane was added in the same proportion as above to perform liquid-liquid extraction again, and the acidic organic phase was collected;

[0087] Mixing the alkaline and acidic organic phases to obtain an extract;

[0088] If the sample to be tested has a complex composition and emulsification occurs during the extraction, mechanical means can be used to separate the two phases, including stirring, centrifugation, and demulsification by filtering with glass wool, or freezing to demulsify.

[0089] (2) Concentrating the extract: dehydrating the extract with anhydrous sodium sulfate, repeatedly eluting the anhydrous sodium sulfate with the dichloromethane, and collecting the eluent; mixing the dehydrated extract with the eluent, performing rotary evaporation at 60° C. and concentrating to 2 mL to obtain a concentrated solution; the anhydrous sodium sulfate needs to be pre-baked at 450° C. for 3 h;

[0090] (3) Purification of the concentrated solution: First, prepare an alumina column: fill the bottom of the glass column with glass wool, add 1.2 g of alumina, tap the wall of the glass column to ensure that the alumina is evenly filled, add 6 mL of dichloromethane to activate it, then add 6 mL of ethyl acetate to rinse, pass nitrogen to dry for 3 min, close the stopcock, wrap the top and bottom of the alumina column with aluminum foil, and store it in a stainless steel container for sealed storage; then pass the concentrated solution through the alumina column to obtain a purified solution; evaporate the purified solution at 60° C. to about 3 mL, then blow dry with nitrogen, then add n-hexane to make the volume up to 1.0 mL, mix well, and obtain a test solution;

[0091] (4) Establishment of standard curve: a mixture standard of phthalate ester compounds was prepared into solutions with mass concentrations of 5.0 μg / L, 10.0 μg / L, 20.0 μg / L, 50.0 μg / L, 100.0 μg / L, 200.0 μg / L, 400.0 μg / L and 500.0 μg / L;

[0092] (5) Gas chromatography-mass spectrometry detection is adopted, which specifically includes the following steps: setting the temperature program of the chromatographic column: the initial temperature is 150°C, the temperature is increased to 220°C at a rate of 15°C / min, the temperature is increased to 250°C at a rate of 15°C / min, and the temperature is increased to 320°C at a rate of 10°C / min; using an HP-5MS chromatographic column for component separation; gas phase conditions: injection port temperature: 280°C, no split; injection volume: 1.0 μL, carrier gas flow rate: 1.0-1.5 mL / min; mass spectrometry conditions: ion source: electron bombardment source; ion source temperature: 230°C; transmission line temperature: 280°C; quadrupole temperature: 150°C; ionization voltage: 70 eV; mass scanning range: 35u~450u; data acquisition mode: full scan mode or selected ion scan mode, and measuring the standard solution and the test solution according to the set conditions.

[0093] The standard and the test solution were determined by gas chromatography-mass spectrometry, and the standard curve of the standard phthalate esters was drawn. The phthalate esters in the test solution were qualitatively determined according to the retention time and quantitatively determined by the external standard method. The chromatogram after data collection was as follows: Figure 1 and Figure 2 As shown;

[0094] The specific calculation method is: the content of phthalates in the sample to be tested μg / L=(the content of phthalates in the sample to be tested measured by the standard curve μg / L×the volume of the test liquid mL) / the sampling volume L of the sample to be tested; the calculation of the content of phthalates in the sample to be tested: substitute the abundance value of the detected target into the corresponding standard curve Y, calculate X according to the standard curve formula, and X is the relevant content.

[0095] Example 4

[0096] The specific operation is referred to in Example 1, except that the column temperature program is set in step (5): the initial temperature is 110°C, the temperature is increased to 200°C at a rate of 12°C / min, the temperature is increased to 250°C at a rate of 15°C / min, and the temperature is increased to 310°C at a rate of 10°C / min.

[0097] Example 5

[0098] The specific operation is referred to Example 1, except that the column temperature is set in step (5): the initial temperature is 130°C, the temperature is increased to 180°C at a rate of 7°C / min, the temperature is increased to 250°C at a rate of 10°C / min, and the temperature is increased to 290°C at a rate of 10°C / min.

[0099] Example 6

[0100] The specific operation is referred to Example 1, except that the column temperature is set in step (5): the initial temperature is 130°C, the temperature is increased to 220°C at a rate of 12°C / min, the temperature is increased to 250°C at a rate of 10°C / min, and the temperature is increased to 320°C at a rate of 10°C / min.

[0101] Comparative Example 1

[0102] Referring to the detection method of Example 1, the only difference is the treatment of the sample to be tested in step (1). In this comparative example, the seawater is extracted only under alkaline conditions. The specific operation is as follows:

[0103] (1) Sample processing: 1000 mL of seawater is extracted under alkaline conditions (the seawater to be tested is stored in a dark place at 3°C ​​after collection, and the extraction is completed within 7 days) to obtain an extract; specifically, the following steps are included:

[0104] First, the pH of the sample to be tested is adjusted to>11, and the dichloromethane is added in a ratio of 100:3 by volume of the sample to be tested and dichloromethane for liquid-liquid extraction. A separatory funnel is used for the extraction, and the separatory funnel needs to be inverted and shaken. The stopper of the separatory funnel is supported by the palm of the right hand, and the neck of the funnel is held to prevent the stopper from loosening. The stopper of the separatory funnel is clamped with the index finger and middle finger of the left hand, and the separatory funnel is held with the left palm for the shaking; during this period, gas will be generated, and the stopper of the separatory funnel needs to be opened from time to time to exhaust; during the inverted shaking, the liquid surface inside the separatory funnel should not touch the stopper; the inverted shaking time is 5 minutes, and the exhaust is performed 10 times during the period; after shaking during the extraction process, the layers are allowed to stand and the alkaline organic phase is collected to obtain an extract.

[0105] Comparative Example 2

[0106] Referring to the detection method of Example 1, the only difference is the treatment of the sample to be tested in step (1). In this comparative example, the seawater is extracted only under acidic conditions. The specific operation is as follows:

[0107] (1) Sample processing: 1000 mL of seawater is extracted under acidic conditions (the seawater to be tested is stored in a dark place at 3°C ​​after collection, and the extraction is completed within 7 days) to obtain an extract; specifically, the following steps are included:

[0108] The pure sulfuric acid solution and the sample to be tested are adjusted to pH < 2 in a volume ratio of 1:1, and the dichloromethane is added in a ratio of 100:3 of the acidic sample to be tested and the volume ratio of dichloromethane for liquid-liquid extraction. A separatory funnel is used for the extraction, and the separatory funnel needs to be inverted and shaken, and the stopper of the separatory funnel is supported by the palm of the right hand, and the neck of the funnel is held to prevent the stopper from loosening. The stopper of the separatory funnel is pinched with the index finger and middle finger of the left hand, and the separatory funnel is held with the left palm for the shaking; during this period, gas will be generated, and the stopper of the separatory funnel needs to be opened from time to time to exhaust; during the inverted shaking, the liquid surface inside the separatory funnel should not touch the stopper; the inverted shaking time is 5 minutes, and the exhaust is performed 10 times during this period; after shaking during the extraction process, the separation is allowed to stand and the acidic organic phase is collected to obtain an extract.

[0109] Comparative Example 3

[0110] Referring to the detection method of Example 1, the only difference is the sample treatment in step (1). In this comparative example, the seawater is not sufficiently shaken when being extracted only under acidic and alkaline conditions. The specific operation is as follows:

[0111] (1) Sample processing: Take 1000 mL of seawater and extract it under acid and alkaline conditions (after the seawater is collected, store it in a dark place at 3°C ​​and complete the extraction within 7 days) to obtain an extract; specifically, the following steps are included:

[0112] First, the pH of the sample to be tested is adjusted to >11, and the dichloromethane is added in a ratio of 100:3 by volume to perform liquid-liquid extraction. A separatory funnel is used for the extraction. After the separatory funnel is slightly shaken, it is allowed to stand for stratification, and the alkaline organic phase is collected;

[0113] Then, the pure sulfuric acid solution and the sample to be tested extracted under alkaline conditions are adjusted to pH in a volume ratio of 1:1 so that the pH is less than 2, and dichloromethane is added in the same ratio as above to perform liquid-liquid extraction again, and the acidic organic phase is collected;

[0114] The alkaline and acidic organic phases are mixed to obtain an extract.

[0115] According to the comparative example results, it can be seen from comparative example 1 that when the seawater to be tested is extracted only under alkaline conditions, it will be affected by alkaline impurities; it can be seen from comparative example 2 that when the seawater to be tested is extracted only under acidic conditions, it will be affected by acidic impurities; it can be seen from comparative example 3 that the seawater to be tested is not sufficiently shaken during extraction, which will have the effect of reducing the recovery rate.

[0116] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0117] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0118] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for detecting phthalates in seawater, characterized in that: The following steps are involved: (1) Sample processing: After collecting the sample, extract it under acidic and alkaline conditions to obtain an extract; The specific steps include: First, the pH of the sample to be tested is adjusted to >11, and the dichloromethane is added in a ratio of 100:2-4 by volume to perform liquid-liquid extraction. After shaking during the extraction process, the mixture is allowed to stand for stratification, the alkaline organic phase is collected, and the aqueous phase is retained; Then, the sulfuric acid solution is mixed with the aqueous phase extracted under alkaline conditions in a volume ratio of 1-3:1-3, the pH of the mixed solution is adjusted so that the pH of the mixed solution is less than 2, and dichloromethane is added in a volume ratio of 100:2-4 between the mixed solution and dichloromethane to perform liquid-liquid extraction again, and the acidic organic phase is collected; Mixing the alkaline organic phase and the acidic organic phase to obtain an extract; (2) Concentrating the extract: dehydrating the extract with anhydrous sodium sulfate, repeatedly eluting the anhydrous sodium sulfate with the dichloromethane, and collecting the eluent; mixing the dehydrated extract with the eluent, and concentrating the extract with the eluent by rotary evaporation at 55-70° C. to 2-3 mL to obtain a concentrated solution; (3) Purification of the concentrated solution: the concentrated solution is passed through an alumina column to obtain a purified solution; the purified solution is subjected to rotary evaporation at 55-70° C. to a volume of 1-3 mL, and then dried with nitrogen gas, and then normal hexane is added to make the volume to 1.0 mL, and mixed to obtain a test solution; (4) Establishment of a standard curve: Phthalate ester compounds are prepared into an aqueous solution with a mass concentration of 5.0 to 500 μg / L to obtain a standard product; (5) using gas chromatography-mass spectrometry for detection, specifically including the following steps: setting a temperature program for the chromatographic column: the initial temperature is 40-150°C, heating to 180-220°C at a rate of 5-15°C / min, heating to 2200-250°C at a rate of 5-15°C / min, and heating to 290-320°C at a rate of 5-10°C / min; using an HP-5MS chromatographic column for component separation; The standard substance and the test solution are measured by gas chromatography-mass spectrometry, respectively, a standard curve of phthalate compounds is drawn according to the test result of the standard substance, and the phthalate compounds in the test solution are qualitatively determined according to the retention time obtained by the test of the test solution in combination with the standard curve, and quantitatively determined by an external standard method; The specific calculation method is: the content of phthalates in the sample to be tested μg / L=(the content of phthalates in the test liquid μg / L×the volume of the test liquid mL) / the initial sampling volume of the sample to be tested L; wherein the content of phthalates in the test liquid is calculated based on the detection result of the test liquid in combination with the standard curve.

2. The method for detecting phthalates in seawater according to claim 1, characterized in that: The sample to be tested in step (1) is collected, and the collected sample to be tested is stored in a refrigerated state below 4-6°C and away from light, and the extraction is completed within 5-10 days, preferably within 7 days; Optionally, dichloromethane is added in a volume ratio of 100:3 between the sample to be tested and dichloromethane for liquid-liquid extraction.

3. The method for detecting phthalates in seawater according to claim 1, characterized in that: In step (1), a separatory funnel is used for the extraction; the separatory funnel needs to be inverted for the shaking, the stopper of the separatory funnel is supported by the palm of the right hand, and the neck of the funnel is held to prevent the stopper from loosening, the stopper of the separatory funnel is clamped by the index finger and middle finger of the left hand, and the separatory funnel is held by the left palm for the shaking; during this period, gas is generated, and the stopper of the separatory funnel needs to be opened from time to time to exhaust gas; Optionally, during the inverted shaking, the liquid level inside the separating funnel does not touch the stopcock; Optionally, the inverted shaking time is 2-10 minutes, during which the gas is exhausted 3-20 times.

4. The method for detecting phthalates in seawater according to claim 1, characterized in that: In the extraction described in step (1), when encountering a sample to be tested with complex components, emulsification occurs during the extraction, and mechanical means are used to separate the two phases, including stirring, centrifugation, demulsification by glass wool filtration, or demulsification by freezing.

5. The method for detecting phthalates in seawater according to claim 1, characterized in that: The anhydrous sodium sulfate in step (2) needs to be baked at 350-450° C. for 3-5 hours in advance.

6. The method for detecting phthalates in seawater according to claim 1, characterized in that: The preparation of the alumina column in step (3) comprises: first filling glass wool at the bottom of the glass column, adding 0.8-1.2 g of alumina, tapping the wall of the glass column to ensure that the alumina is evenly filled, adding 4-6 mL of dichloromethane for activation, then adding 4-6 mL of ethyl acetate for elution, passing nitrogen to dry for 1-3 min, closing the stopcock, wrapping the top and bottom of the alumina column with aluminum foil, and then storing it in a stainless steel container for sealed storage for later use.

7. The method for detecting phthalates in seawater according to claim 1, characterized in that: The chromatographic-mass spectrometric detection in step (4) has the following gas phase conditions: injection port temperature: 280°C, no split; injection volume: 1.0-2.0 μL, carrier gas flow rate: 1.0-1.5 mL / min; mass spectrometric conditions: ion source: electron bombardment source; ion source temperature: 230°C; transmission line temperature: 280°C; quadrupole temperature: 150°C; ionization voltage: 70 eV; mass scanning range: 35u-450u; data acquisition mode: full scan mode or selected ion scan mode.

8. The method for detecting phthalates in seawater according to claim 1, characterized in that: The chromatographic column temperature program described in step (5) is set as follows: the initial temperature is 130°C, the temperature is increased to 200°C at a rate of 10°C / min, the temperature is increased to 225°C at a rate of 15°C / min, and the temperature is increased to 300°C at a rate of 7°C / min.

9. The method for detecting phthalates in seawater according to claim 1, characterized in that: Phthalate esters in seawater include: dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, di-n-butyl phthalate, diethyl phthalate, dihexyl phthalate, diethyl phthalate, dipentyl phthalate, dihexyl phthalate, butyl benzyl phthalate, diethyl phthalate, dicyclohexyl phthalate, dihexyl phthalate, di-n-octyl phthalate and dinonyl phthalate.

10. The method for detecting phthalates in seawater according to any one of claims 1 to 9, characterized in that: The recovery rate of the detection method is>99%, RSD<2%, and the detection limit is<0.9μg / L.

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