Disclosure of Invention
The invention aims to provide a rapid and accurate preparation method of high-purity L-PFOS and the high-purity L-PFOS, which can improve the accuracy of the preparation process and ensure the success of the experiment; the experimental period is shortened, the experimental efficiency is improved, the requirement of accurate detection is met, and the method has important research significance and use value.
In order to realize the purpose, the invention provides the following technical scheme:
the preparation method of the high-purity L-PFOS provided by the invention comprises the following steps:
a separation stage and a concentration drying stage;
the separation stage comprises:
step one, selecting solid PFOS to prepare a PFOS methanol solution, wherein the concentration of the PFOS methanol solution is between 5mg/mL and 15 mg/mL;
step two, performing semi-preparative liquid chromatography-evaporative light scattering separation on the PFOS methanol solution to collect L-PFOS;
the concentrating and drying stage comprises:
step three: and concentrating and drying the collected liquid of the L-PFOS collected in the second step to obtain the L-PFOS.
Optionally, the concentration and drying treatment is:
and (3) carrying out reduced pressure distillation on the collected L-PFOS liquid collected in the second step by using a rotary evaporator until the residual liquid is not more than 2mL, stopping, transferring the concentrated liquid subjected to reduced pressure distillation to a sample bottle, freezing to ice, transferring to a freeze dryer, freezing overnight until all the concentrated liquid becomes white powder, obtaining L-PFOS freeze-dried powder solid, and standing at room temperature.
Optionally, an identification phase is also included;
dissolving the L-PFOS freeze-dried powder solid in a solvent to form an L-PFOS solution;
the identification phase comprises;
and step four, identifying the L-PFOS solution by using a nuclear magnetic resonance spectroscopy.
Optionally, the authentication phase further comprises:
before the fourth step, performing qualitative and quantitative analysis on the L-PFOS solution by using a liquid chromatography-mass spectrometry method, wherein the qualitative and quantitative analysis comprises the following steps:
calculating the purity of the L-PFOS according to a mass spectrum peak area normalization method,
purity of L-PFOS is w i %;
m i 、A i 、w i % is respectively the mass, peak area and mass fraction of the component L-PFOS' i A i Is a quantitative correction factor of the component L-PFOS;
comparison w i % and 98% size;
if w is i When the percentage is more than or equal to 98 percent, the L-PFOS is high-purity L-PFOS;
otherwise, the L-PFOS enters the separation stage and the concentration drying stage again, and the operation is repeated;
optionally, the authentication phase further comprises:
and performing anion qualitative and quantitative analysis on the L-PFOS solution by using liquid chromatography-mass spectrometry before the step four.
Optionally, the authentication phase further comprises:
before the fourth step, the L-PFOS solution is subjected to cationic qualitative and quantitative analysis by ion chromatography.
Optionally, calculating the purity of the L-PFOS according to a mass-weighing calculation method, including:
weighing the solid PFOS in the step one, wherein the mass is m 1 ;
Weighing the L-PFOS freeze-dried powder solid after the concentration and drying treatment, wherein the mass is m 2 ;
With mass m 2 Dissolving the solid L-PFOS freeze-dried powder in a solvent to form an L-PFOS solution;
performing anion qualitative and quantitative analysis on the L-PFOS solution by using liquid chromatography-mass spectrometry to obtain the anion substance with the amount n 1 Mass is m 3 ;
Performing cation qualitative and quantitative analysis on the L-PFOS solution by ion chromatography to obtain cation substance with n amount 2 Mass ofIs m 4 ;
The amount of anionic species n 1 Amount of substance n with cation 2 The ratio of (A) to (B) is K;
the purity of the L-PFOS is Q;
comparing the size of K to 1 and Q to 98%;
if K =1 and Q is more than or equal to 98%, the L-PFOS is high-purity L-PFOS;
otherwise, the L-PFOS enters the separation stage and the concentration drying stage again, and the operation is repeated.
Optionally, collecting the L-PFOS in the step two is isocratic elution, collecting the L-PFOS for multiple times, combining collected liquids, and performing the step three.
Optionally, the collecting condition of the L-PFOS collection in the step two is to utilize retention time to characterize chromatographic peaks of the L-PFOS, the collection is carried out when peak signals appear on the monitor, and the collection is stopped after the chromatographic peaks completely appear.
Optionally, the liquid chromatography-mass spectrometry is used for carrying out anion qualitative and quantitative analysis on the L-PFOS solution, and the particle size of a chromatographic column packing is 3 μm; the length of the chromatographic column is 150mm, and the inner diameter of the chromatographic column is 2.1mm; the pore diameter of the filler is
The mobile phase is formed by mixing a phase A and a phase B according to the ratio of 7: 3, wherein the phase A is methanol, and the phase B is a mixed solution of 60mmol/L ammonia water and 20mmol/L formic acid aqueous solution.
The invention also provides high-purity L-PFOS which is prepared by the preparation method of the high-purity L-PFOS as claimed in the above claim.
In the technical scheme provided by the invention, solid PFOS is prepared into a methanol solution of PFOS, and the methanol solution is separated by a semi-preparative liquid chromatography-evaporative light scattering method to collect L-PFOS; and concentrating and drying the collected L-PFOS collecting liquid to obtain the L-PFOS. The L-PFOS provided by the invention is a rapid and accurate preparation method of high-purity L-PFOS, and can improve the accuracy of the preparation process and ensure the success of the experiment; the method has the advantages of shortening the experiment period, improving the experiment efficiency, meeting the requirement of accurate detection and having important research significance and use value.
In the preferable scheme of the invention, the L-PFOS solution is identified by using a nuclear magnetic resonance spectroscopy in the identification stage, and the content of impurities is simultaneously determined, so that the experimental period is shortened, the experimental efficiency is improved, and the requirement of accurate detection is met.
In a preferable scheme of the invention, the method also comprises a liquid chromatography-mass spectrometry method and an ion chromatography method, so that the liquid chromatography-mass spectrometry method is used for carrying out anion qualitative and quantitative analysis on the L-PFOS solution to obtain the quantity and the quality of anion substances; performing cation qualitative and quantitative analysis on the L-PFOS solution by using ion chromatography to obtain the amount and the mass of a cation substance, and judging whether the L-PFOS is high-purity L-PFOS or not by comparing the ratio of the amount of the anion substance to the amount of the cation substance and the proportion of the sum of the masses of the anion and the cation in the solid of the L-PFOS freeze-dried powder after concentration and drying treatment; when the ratio of the amount of the anionic substance to the amount of the cationic substance is 1 and the proportion of the sum of the masses of the anions and the cations in the L-PFOS freeze-dried powder solid after concentration and drying is more than or equal to 98 percent, the L-PFOS is high-purity L-PFOS; otherwise, the L-PFOS enters the separation stage and the concentration and drying stage again, and the steps are repeated until the conditions are met, so that the accuracy of the preparation process can be improved, and the success of the experiment is ensured; the experimental period is shortened, the experimental efficiency is improved, the requirement of accurate detection is met, and the method has important research significance and use value.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without making any creative effort, shall fall within the protection scope of the present invention.
The research on L-PFOS and B-PFOS is rarely reported in China, the preparation method of the PFOS isomer monomer is not reported, and related standard substances are not on the market. Research and application related to PFOS requires high purity reference substances and standard substances purchased from foreign countries, which are affected by international relations, price fluctuations, time periods, and the like. The invention provides a preparation method of high-purity L-PFOS, wherein the L-PFOS is English abbreviation of linear perfluorooctane sulfonate, and the PFOS is English abbreviation of perfluorooctane sulfonate.
As shown in fig. 1 to 7, the preparation method of the high-purity L-PFOS comprises:
a separation stage and a concentration drying stage;
the separation stage comprises:
step one, selecting solid PFOS to prepare a PFOS methanol solution, wherein the concentration of the PFOS methanol solution is between 5mg/mL and 15 mg/mL;
step two, carrying out semi-preparative liquid chromatography-evaporative light scattering separation on the PFOS methanol solution to collect L-PFOS;
the concentrating and drying stage comprises:
step three: and concentrating and drying the collected liquid of the L-PFOS collected in the step two to obtain the L-PFOS.
In the second step, the PFOS methanol solution is separated by a semi-preparative liquid chromatography-evaporative light scattering method to collect L-PFOS; the method has the advantages of strong passing ability, large magnitude of prepared chromatographic columns, flexible and diverse mobile phase compositions, combination of advantages of response of evaporative light scattering detection to a target substance, and difficulty in separation and detection of PFOS isomers and large-scale preparation by optimizing experimental conditions.
In a word, the L-PFOS provided by the invention is a rapid and accurate preparation method of high-purity L-PFOS, and can improve the accuracy of the preparation process and ensure the success of the experiment; the experimental period is shortened, the experimental efficiency is improved, the requirement of accurate detection is met, and the method has important research significance and use value.
PFOS isomers are difficult to separate and detect. PFOS isomers are large in quantity, have hydrophobic and oleophobic characteristics and have no response on detectors such as ultraviolet detectors and diode arrays, so that the separation and detection of the PFOS isomers are difficult. Spectroscopy can enable PFOS total dose detection, but cannot distinguish between isomers. The combination of chromatographic techniques with various detectors and the rapid development of new separation materials have made major progress in the separation and detection of PFOS isomers, but there is a great gap between the number of PFOS isomers that can be detected and the theoretical value. At present, solid phase extraction treatment, perfluorocarboxylic acid derivatization and gas chromatography-mass spectrometry are adopted, the detection limit of the gas chromatography-mass spectrometry can reach ppb level, derivatization is not needed, high performance liquid chromatography-tandem mass spectrometry (HPLC-MS or HPCL-MS/MS) realizes separation and detection of 11 PFOS in environmental and industrial samples at most, and the sensitivity can reach ppb level or even ppt level by combining with a solid phase extraction pretreatment technology. By means of the advantages, the high performance liquid chromatography-mass spectrometry is a detection technology applied in the embodiment of the invention, so that in the specific embodiment of the invention, in the step two, the PFOS methanol solution is subjected to separation by a semi-preparative liquid chromatography-evaporative light scattering method to collect L-PFOS, the throughput capacity is high, the magnitude of a prepared chromatographic column is large, the mobile phase composition is flexible and diverse, the evaporative light scattering detection is combined with the advantage of responding to a target object, and the problems of separation, detection and mass preparation of PFOS isomers are solved by optimizing experimental conditions.
It should be noted that L-PFOS is English abbreviation of L-PFOS, and PFOS is English abbreviation of perfluorooctane sulfonate. The technical scheme of the invention is to perform semi-preparative liquid chromatography-evaporative light scattering separation on the methanol solution of the PFOS so as to collect the L-PFOS.
In an embodiment of the present invention, the concentration and drying process comprises:
and (3) carrying out reduced pressure distillation on the collected liquid L-PFOS obtained in the second step by using a rotary evaporator until the residual liquid is not more than 2mL, stopping, transferring the concentrated solution subjected to reduced pressure distillation to a sample bottle, freezing to ice, transferring to a freeze dryer, freezing overnight until the concentrated solution is completely changed into white powder, obtaining the solid L-PFOS freeze-dried powder, and standing at room temperature.
It should be noted that, the L-PFOS collected liquid collected in step two is distilled under reduced pressure until the remaining liquid has a certain volume, and in the specific embodiment of the present invention, the volume is 2mL, that is, the L-PFOS collected liquid collected in step two is distilled under reduced pressure by using a rotary evaporator until the remaining liquid does not exceed 2mL, and the distillation is stopped, but this is only one specific embodiment of the present invention, and is not limited to 2mL, and may be other volumes capable of meeting experimental requirements, and all volumes can be adjusted in real time according to actual operation requirements.
In the embodiment of the invention, the rotary evaporator in the concentration and drying treatment stage is Eyela N1100, and the apparatus is simple to operate and high in precision, so that the result is more accurate. In the embodiment of the invention, in the concentration and drying treatment stage, the concentration of the concentrated solution after the reduced pressure distillation is controlled to be 2mL, and the concentrated solution after the reduced pressure distillation is transferred to a sample bottle and frozen to ice, wherein the freezing temperature is-20 ℃.
It should be noted that the rotary evaporator in the concentration and drying process stage is not limited to the eye N1100, tokyo physical and chemical instruments co, japan, but may be rotary evaporators of other countries and models, and the eye N1100 rotary evaporator of tokyo physical and chemical instruments co, japan is only one specific example in the experimental process of the present invention, and does not affect the scope of protection of the L-PFOS production method of the present invention.
Animal toxicity research of PFOS currently adopts a static toxicant exposure method, namely, animal toxicity performance is observed under the exposure condition of different PFOS concentrations. And (3) obtaining the semilethal concentration and the safe concentration by observing the dose effect and time effect relationship between the PFOS exposure concentration and the animal mortality, and judging the toxicity of the PFOS to the animal. In phytotoxicity experiments, an indoor pot culture method is mostly adopted, PFOS is prepared into a solution to be added into soil, and the influence of the PFOS on plant development is investigated. The above mentioned experiment is general toxicity investigation experiment, the common PFOS's semilethal concentration is mg/L or inhibition concentration is mg/kg, both reach ppm level. However, no distinction was made between PFOS used in toxicity experiments. Based on the situation, the related data of the existing PFOS biological toxicity is the embodiment of the toxicity summation of PFOS isomer mixtures, and the specific contribution value of each PFOS isomer cannot be judged. Once the composition and content of isomers in PFOS solids used in toxicity experiments are changed, the accuracy of toxicity data is difficult to guarantee. Thus, if accurate toxicological data for PFOS is to be obtained, a high purity monomer for the isomer of PFOS is required. Therefore, in order to judge whether the prepared L-PFOS meets the requirements and whether the content of impurities in the prepared L-PFOS exceeds the standard, the method further comprises an identification stage in the specific embodiment of the invention;
dissolving the L-PFOS freeze-dried powder solid in a solvent to form an L-PFOS solution;
the identification stage comprises;
and step four, identifying the L-PFOS solution by using a nuclear magnetic resonance spectroscopy.
In the specific embodiment of the invention, the fourth step further comprises the steps of identifying the L-PFOS solution by using a nuclear magnetic resonance spectroscopy method, and simultaneously determining the content of impurities, wherein if the content of the impurities is within a certain preset range value, the requirement is met, and if the content of the impurities is outside the certain preset range value, the requirement is not met.
In the specific embodiment of the invention, the identification stage of the preparation of the high-purity L-PFOS by the mass spectrum peak area normalization method further comprises the following steps: as shown in fig. 3, fig. 3 is a detailed flow chart of the preparation of high-purity L-PFOS by mass spectrum peak area normalization method in the embodiment of the present invention, specifically:
step one, selecting solid PFOS to prepare a PFOS methanol solution, wherein the concentration of the PFOS methanol solution is between 5mg/mL and 15 mg/mL;
step two, carrying out semi-preparative liquid chromatography-evaporative light scattering separation on the PFOS methanol solution to collect L-PFOS;
step three: concentrating and drying the collected liquid of the L-PFOS collected in the step two to obtain the L-PFOS;
step four, identifying the L-PFOS solution by using a nuclear magnetic resonance spectroscopy;
before the fourth step, performing qualitative and quantitative analysis on the L-PFOS solution by using liquid chromatography mass spectrometry, wherein the qualitative and quantitative analysis comprises the following steps:
calculating the purity of the L-PFOS according to a mass spectrum peak area normalization method,
purity of L-PFOS is w i %;
m i 、A i 、w i % is respectively the mass, peak area and mass fraction of the component L-PFOS' i A i Is a quantitative correction factor (also called relative peak area percentage) of the component L-PFOS, and according to the results of multiple experiments, the single peak area is found to be larger, and the peaks of other components can beTo be ignored, therefore, in the specific embodiment of the present invention, the value of the quantitative correction factor is 1;
comparison w i % and 98% size;
if w is i When the percentage is more than or equal to 98 percent, the L-PFOS is high-purity L-PFOS;
otherwise, the L-PFOS enters the separation stage and the concentration drying stage again, and the operation is repeated;
the mass spectrum peak area normalization method is a chemical calculation method parallel to an internal standard method and an external standard method. This method can be used to calculate purity when there is no standard substance or a photograph. The method comprises the following specific steps: the area normalization method is suitable for content determination of components of a complex sample, provided that all components in the sample flow out of a chromatographic column and chromatographic peaks appear on a chromatogram. The method is simple and convenient, and the accuracy of the sample injection amount and the change of the operation conditions have little influence on the measurement result.
And (3) carrying out anion qualitative and quantitative analysis on the L-PFOS solution by using liquid chromatography-mass spectrometry before the step four.
The authentication phase further comprises:
before the fourth step, the L-PFOS solution is subjected to cation qualitative and quantitative analysis by ion chromatography.
In a specific embodiment of the present invention, the HPLC is equipped with a Waters 1525 HPLC pump and a Waters 2707 autosampler (Waters corporation, USA), with an ELSD-LTI type II evaporative light detector (Shimadzu corporation, japan), with a flow splitter (1: 15) (Waters corporation, USA); high resolution mass spectrometry (Q exact orbitrap, thermo, usa); a freeze dryer (ALPHA 1-2 plus, christ, germany); XPE105 electronic balance (d =0.01mg, mettler Toledo, switzerland); research plus adjustable range pipettor (1000. Mu.L, eppendorf, germany); milli-Q Integral 3 ultra pure water system (Millipore, USA). The main reagents used were: L-PFOS control (Liner-Perfluorooctane sulfonic Acid Potasgum Salt, wellington, canada, 5 ppm); solid PFOS (Perfluorooctance sulfonic Acid Potasidum Salt, adamas-beta, china), specific information: CAS:2795-39-3, MW:538.22, MP:277-280 ℃ and 98% +. Methanol and acetic acid (chromatographically pure, fisher scientific, USA).
In a specific embodiment of the invention, the chromatographic conditions are: fluoroSep-RP Octyl (5 μm,250 mm. Times.10 mm,
ES Industries), 65% by volume of A (phase A is methanol, phase B is acetic acid in water at pH 3.5), isocratic elution, flow rate 5mL/min; sample introduction amount: 150 μ L. ELSD-LTI type II evaporative light detector (Shimadzu corporation, japan): drift
tube temperature 40 ℃, pressure 385kPa, signal amplification: 6, carrier gas: high purity nitrogen. Collecting conditions are as follows: determining the chromatographic peak of the L-PFOS by using retention time, and starting to collect the target object when a peak signal appears on a monitor; collection was stopped after the chromatographic peak was completely present.
In the qualitative and quantitative analysis of anions of the L-PFOS solution by the liquid chromatography-mass spectrometry, the model of a liquid chromatography separation column is FluoroSep-RP Octyl, which specifically refers to: the reversed phase liquid chromatography separation column is formed by bonding the fluorooctyl groups and is called a chromatographic column for short. The grain diameter of the chromatographic column packing is 3 mu m; the length of the chromatographic column is 150mm, and the inner diameter of the chromatographic column is 2.1mm; the pore diameter of the filler is
The mobile phase is formed by mixing A phase and B phase in a ratio of 7: 3, wherein the A phase is methanol, and the B phase is a mixed solution of 60mmol/L ammonia water and 20mmol/L formic acid aqueous solution.
In one embodiment of the present invention, the flow rate of the mobile phase is 0.2mL/min. The mass spectrum conditions are electrospray negative ion mode, SIM mode: i.e. Single Ion Scan pattern (Single Ion Scan). The capillary voltage is 3.0kV; the extraction voltage is 5.0V; the ion source temperature is 150 ℃; the temperature of the desolventizing gas is 350 ℃. The flow rate of the desolventizing gas is 650L/h; the air flow rate of the taper hole is 20L/h, and the parent ion is 498.6. An important parameter for mass spectrometric detection. The cone voltage is 40V. In the embodiments of the present invention, the following are specifically mentioned: when the mass spectrum detects the L-PFOS, the mass-to-charge ratio of the L-PFOS is 498.6, and if the mass-to-charge ratio can be detected, the L-PFOS is considered to be the L-PFOS.
In a specific embodiment of the invention, the split ratio is 15: 1. The method specifically comprises the following steps: after the mobile phase comes out of the chromatographic column, it is distributed in a volume ratio of 15: 1 by means of a flow divider (similar to a three-way device). Wherein, 1 part enters the detector for detection, and is used for determining the time of a collection window; the other 15 parts were collected as materials for the next experiment. In the specific embodiment of the invention, compared with the traditional collection method, the collection method is additionally provided with the workstation, the workstation can monitor the separation process in real time, the online collection process is visualized by reasonably controlling the split ratio, the separation condition is monitored in real time by the workstation, the collection starting point is screened, the accurate collection is realized, and the collection stability is ensured.
In the specific embodiment of the invention, a certain amount of solid PFOS is weighed to prepare a 5mg/mL-15mg/mL PFOS methanol solution as a sample, and the PFOS methanol solution is prepared fresh before each use. In order to prevent the precipitation phenomenon from occurring and influence the sample injection, in the specific embodiment of the invention, solid PFOS is selected to prepare a PFOS methanol solution, and the concentration of the PFOS methanol solution is 5mg/mL, so that the sample solution is reasonable and accurate and no precipitation phenomenon occurs.
In order to judge whether the prepared L-PFOS meets the requirements and whether the content of impurities in the prepared L-PFOS exceeds the standard, the method further comprises an identification stage in the specific embodiment of the invention;
dissolving the L-PFOS freeze-dried powder solid in a solvent to form an L-PFOS solution;
the separation stage comprises:
step one, selecting solid PFOS to prepare a PFOS methanol solution, wherein the concentration of the PFOS methanol solution is between 5mg/mL and 15 mg/mL;
step two, as shown in fig. 5-6, wherein fig. 5 is a step of separating single collection of L-PFOS by semi-preparative liquid chromatography-evaporative light scattering; FIG. 6 is a semi-preparative liquid chromatography-evaporative light scattering separation for collecting L-PFOS for a plurality of times, and the PFOS methanol solution is subjected to semi-preparative liquid chromatography-evaporative light scattering separation for collecting L-PFOS; the liquid chromatography-evaporative light scattering method is divided into two parts, wherein the liquid chromatography is a separation method in the front, and the evaporative light scattering is a detection method in the back. Liquid chromatography can be divided according to the mass of the substance of a single analysis sample. Microgram scale samples are known as liquid chromatography; the milligram scale sample is called semi-preparative chromatography and the ten milligram scale sample is preparative chromatography. In the present embodiment, the experimental sample amounts are 1-5mg, and thus the present embodiment is a semi-preparative chromatography-evaporative light scattering method.
The concentrating and drying stage comprises:
step three: and concentrating and drying the collected liquid of the L-PFOS collected in the step two to obtain the L-PFOS.
The identification stage comprises;
and step four, identifying the L-PFOS solution by using a nuclear magnetic resonance spectroscopy.
And (3) carrying out anion qualitative and quantitative analysis on the L-PFOS solution by using liquid chromatography-mass spectrometry before the step four.
The identification phase further comprises:
before the fourth step, the L-PFOS solution is subjected to cation qualitative and quantitative analysis by ion chromatography. In the embodiment of the invention, the preparation of the high-purity L-PFOS by the mass weighing calculation method further comprises the following identification stages: as shown in fig. 2: fig. 2 is a detailed flow chart of the preparation of the high-purity L-PFOS by the mass weighing calculation method in the embodiment of the present invention, specifically:
the identification phase further comprises: calculating the purity of the L-PFOS according to a mass weighing calculation method, which comprises the following steps:
weighing the solid PFOS in the step one, wherein the mass is m 1 ;
Weighing the L-PFOS freeze-dried powder solid after the concentration and drying treatment, wherein the mass is m 2 ;
With mass m 2 Dissolving the solid L-PFOS freeze-dried powder in a solvent to form an L-PFOS solution;
performing anion qualitative and quantitative analysis on the L-PFOS solution by using liquid chromatography-mass spectrometry to obtain the anion substance with the amount n 1 Mass is m 3 ;
Performing cation qualitative and quantitative analysis on L-PFOS solution by ion chromatography to obtain cation substance n 2 Mass is m 4 ;
Amount of anionic substance n 1 Amount of substance n with cation 2 The ratio of (A) to (B) is K;
the purity of the L-PFOS is Q,
comparing the size of K to 1 and Q to 98%;
if K =1 and Q is more than or equal to 98%, the L-PFOS is high-purity L-PFOS;
otherwise, the L-PFOS enters the separation stage and the concentration and drying stage again, and the operations are repeated until the amount n of the L-PFOS anion substances 1 Amount of substance n with cation 2 The ratio K =1 and the purity Q of the L-PFOS is more than or equal to 98 percent.
In the specific embodiment of the invention, the preparation of the high-purity L-PFOS by combining the mass spectrum peak area normalization method and the mass weigher algorithm further comprises the identification stage: as shown in fig. 4: FIG. 4 is a detailed flow chart of the preparation of high-purity L-PFOS in the embodiment of the invention in which a mass spectrum peak area normalization method and a mass weigher algorithm are combined, specifically:
step one, selecting solid PFOS to prepare a PFOS methanol solution, wherein the concentration of the PFOS methanol solution is between 5mg/mL and 15 mg/mL; weighing the solid PFOS in the step one, wherein the mass is m 1 ;
Step two, carrying out semi-preparative liquid chromatography-evaporative light scattering separation on the PFOS methanol solution to collect L-PFOS;
step three: concentrating and drying the collected liquid of the L-PFOS collected in the step two, weighing the solid of the freeze-dried powder of the L-PFOS after the concentration and drying treatment, wherein the mass is m 2 (ii) a Dissolving L-PFOS freeze-dried powder solid with the mass of m2 in a solvent to form L-PFOS solution;
step four, identifying the L-PFOS solution by using a nuclear magnetic resonance spectroscopy;
before the fourth step, carrying out anion qualitative and quantitative analysis on the L-PFOS solution by using a liquid chromatography-mass spectrometry method, wherein the method comprises the following steps:
calculating the purity of the L-PFOS according to a mass spectrum peak area normalization method,
purity of L-PFOS is w i %;
m i 、A i 、w i % is respectively the mass, peak area and mass fraction of the component L-PFOS' i A i The quantitative correction factor (also called as relative peak area percentage) of the component L-PFOS is used, according to multiple experimental results, the single peak area is found to be larger, and other component peaks can be ignored, so that in the specific embodiment of the invention, the value of the quantitative correction factor is 1;
comparison w i % and 98% size;
first, if w is satisfied i %≥98%:
The L-PFOS is the initially qualified high-purity L-PFOS; the preliminarily qualified high-purity L-PFOS is operated by using a mass weighing calculation method.
Carrying out anion qualitative and quantitative analysis on the initially qualified high-purity L-PFOS solution by using a liquid chromatography-mass spectrometry method to obtain the anion substance with the amount n 1 Mass is m 3 ;
Performing cation qualitative and quantitative analysis on L-PFOS solution by ion chromatography to obtain cation substance n 2 Mass is m 4 ;
Amount of anionic substance n 1 Amount of substance n with cation 2 The ratio of (A) to (B) is K;
the purity of the L-PFOS is Q,
comparing the magnitude of K to 1 and Q to 98%;
if K =1 and Q is more than or equal to 98%, identifying the L-PFOS solution by using a nuclear magnetic resonance spectroscopy method, simultaneously determining the impurity content, and if the impurity content meets the preset value range, determining that the L-PFOS is high-purity L-PFOS;
if K =1 is not satisfied and Q is more than or equal to 98%, the L-PFOS enters the separation stage and the concentration and drying stage again, and the operations are repeated until the amount n of the substances of the L-PFOS anions is reached 1 Amount of substance n with cation 2 The ratio K =1 and the purity Q of the L-PFOS is more than or equal to 98 percent,
second, if w is not satisfied i The percent is more than or equal to 98 percent, the L-PFOS enters the separation stage and the concentration drying stage again, and the operation is repeated until the purity w of the collected L-PFOS is more than or equal to 98 percent i % satisfies w i %≥98%。
In a word, the preparation method of the high-purity L-PFOS provided by the embodiment of the invention is a rapid and accurate preparation method of the high-purity L-PFOS, and can improve the accuracy of the preparation process and ensure the success of the experiment; the requirements of accurate detection are met, the mobile phase composition, screening, impurity removal and drying conditions are optimized, the requirements of good stability and high purity are met, the experimental period is shortened, the experimental efficiency is improved, and the method has important research significance and use value.
Performing anion qualitative and quantitative analysis on the L-PFOS solution by using a liquid chromatography-mass spectrometry method and an ion chromatography method to obtain the quantity and the quality of anion substances; performing cation qualitative and quantitative analysis on the L-PFOS solution by using ion chromatography to obtain the amount and the mass of cation substances, and judging whether the L-PFOS is high-purity L-PFOS or not by comparing the ratio of the amount of anion substances to the amount of cation substances and the proportion of the sum of the masses of anion and cation to the proportion of L-PFOS freeze-dried powder solid after concentration and drying treatment; when the ratio of the amount of the anionic substance to the amount of the cationic substance is 1 and the proportion of the sum of the masses of the anions and the cations in the L-PFOS freeze-dried powder solid after concentration and drying is more than or equal to 98 percent, the L-PFOS is high-purity L-PFOS; otherwise, the L-PFOS enters the separation stage and the concentration and drying stage again, and the steps are repeated until the conditions are met, so that the accuracy of the preparation process can be improved, and the success of the experiment is ensured; the method has the advantages of shortening the experiment period, improving the experiment efficiency, meeting the requirement of accurate detection and having important research significance and use value.
In order to improve the efficiency and accuracy, in a specific embodiment of the invention, the L-PFOS collection in the second step is isocratic elution, the L-PFOS is collected for multiple times, collected liquid is merged and then subjected to the third step, and the third step is to perform concentration and drying treatment on the L-PFOS collected liquid collected for multiple times to obtain the L-PFOS.
In the embodiment of the invention, the collection condition of the L-PFOS collection in the second step is to characterize the chromatographic peak of the L-PFOS by using retention time, collect when the monitor shows a peak signal, stop collecting after the chromatographic peak completely appears, specifically as shown in fig. 5 and 6 in the embodiment of the invention, fig. 5 semi-preparative liquid chromatography-evaporative light scattering method separates single collection of the L-PFOS; FIG. 6 semi-preparative liquid chromatography-evaporative light scattering separation for multiple L-PFOS collection.
In a specific embodiment of the invention, the chromatographic conditions are: fluoroSep-RP Octyl (5 μm,250 mm. Times.10 mm,
ES Industries), 65% by volume A (phase A is methanol, phase B is acetic acid in water pH 3.5), isocratic elution, flow rate 5mL/min; sample introduction amount: 150 mul,
drift tube temperature 40 deg.C, pressure 385kPa, signal amplification 6 times, and high purity nitrogen as carrier gas. Collecting conditions are as follows: determining the chromatographic peak of the L-PFOS by using retention time, and starting to collect the target object when a peak signal appears on a monitor; collection was stopped after the chromatographic peak was completely present.
In the qualitative and quantitative analysis of anions of the L-PFOS solution by the liquid chromatography-mass spectrometry, the model of a liquid chromatography separation column is FluoroSep-RP Octyl, which specifically refers to: the reversed phase liquid chromatography separation column is formed by bonding the fluorooctyl groups and is called a chromatographic column for short. The grain diameter of the chromatographic column packing is 3 mu m; the length of the chromatographic column is 150mm, and the inner diameter of the chromatographic column is 2.1mm; the pore diameter of the filler is
The mobile phase is formed by mixing A phase and B phase in a ratio of 7: 3, wherein the A phase is methanol, and the B phase is a mixed solution of 60mmol/L ammonia water and 20mmol/L formic acid aqueous solution.
The invention also provides high-purity L-PFOS which is prepared according to the preparation method of the high-purity L-PFOS. The accuracy is high, the efficiency of obtaining the high-purity L-PFOS is high, the requirement of accurate detection is met, and the method has important research significance and use value.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.