WO2015139462A1

WO2015139462A1 - On-line solid-phase extraction column with mono-dispersion and high specific surface area and preparation method therefor

Info

Publication number: WO2015139462A1
Application number: PCT/CN2014/090304
Authority: WO
Inventors: 李爱民; 唐松林; 钟声; 周庆; 张满成
Original assignee: 南京大学; 江苏省环境监测中心
Priority date: 2014-03-20
Filing date: 2014-11-05
Publication date: 2015-09-24
Also published as: CN103881000A

Abstract

Disclosed are an on-line solid-phase extraction column with mono-dispersion and a high specific surface area, and a preparation method therefor, belonging to the field of solid-phase extractions. A membrane emulsification-suspension polymerization method is used to prepare a mono-dispersed styrene-divinylbenzene copolymer microsphere, which then undergoes a Friedel-Crafts reaction to prepare a hypercrosslinked microsphere, and finally the hypercrosslinked microspheres are packed into an on-line SPE microcolumn by an equidensity homogenation method. The membrane emulsification-suspension polymerization method is used in the present invention. The obtained microsphere has a homogeneous particle size and it is convenient to adjust the particle size, crosslinking degree, etc. It is convenient to adjust the specific surface area and surface polarity such that a microsphere having a high specific surface area and a certain polarity can be obtained. The equidensity homogenation method is used to fill the on-line SPE microcolumn, and the obtained microcolumn has an easily adjustable polarity and structure, a small sample amount and a good enrichment and separation effect, can be applied to the liquid-phase chromatographic analysis field, and greatly improves the automation degree of the analysis. The on-line SPE column obtained in the present invention can be applied in the fields of analytical chemistry etc.

Description

Monodisperse high specific surface area online solid phase extraction column and preparation method thereof

Technical field:

The invention relates to a solid phase extraction column and a preparation method thereof, and more particularly to a monodisperse high specific surface area online solid phase extraction column and a preparation method thereof.

Background technique:

The enrichment and separation of samples is a key part of the analysis work. It accounts for a large proportion of the entire analytical work in terms of workload and operating costs. The choice of enrichment methods will also affect the sensitivity and accuracy of the entire test procedure. Sex. Compared with other enrichment and separation technologies, solid phase extraction (SPE) has the following advantages: it can be carried out in batches; saves time; reduces solvent use and waste generation; can select various bonded stationary phases; can be enriched and separated by trace analysis Object; can eliminate emulsification; easy to achieve automation; high recovery rate, good reproducibility. The SPE method has gradually become the main method of sample pretreatment. Solid phase extraction technology can be approximated as a simple chromatographic process ^[3] . According to different methods of operation, it can be divided into On-Line SPE and Off-Line SPE. Online solid phase extraction technology, also known as online purification and enrichment technology, is mainly used for high performance liquid chromatography (HPLC) analysis. Extraction and chromatographic analysis are often completed simultaneously. SPE processing samples and analysis are unified in one system through valve switching. As an automated sample processing technology, the online SPE method enables on-line enrichment and matrix elimination of samples, avoids cumbersome manual sample preparation, saves sample usage and time, has high reproducibility, and has good recovery rates. The development of SPE cartridges will have a wider range of applications in the future. The SPG film is an abbreviation of Shirasu Porous Glass membrane and is a porous glass film.

Due to its excellent chemical stability and easy modification and modification, its development has been a hot spot in the field of SPE fillers. At present, polymer fillers have been widely used in the trace contaminants in offline SPE enrichment analysis environment, but the application in the online SPE analysis neighborhood is still relatively rare. One of the major problems in the application of polymer fillers in online SPE for many years is that the particle size is not uniform and the specific surface area is not high enough. Therefore, how to increase the monodispersity and specific surface area of the polymer filler to obtain a higher enrichment separation effect is People have long been concerned about the issue.

At present, the main methods for synthesizing a uniform particle size polymer filler are a precipitation polymerization method, a dispersion polymerization method, a seed polymerization method, and the like. The main problem of these methods is that the production process uses more organic raw materials, pollutes the environment, and the technology is complicated and difficult to control. The seed polymerization method is also prone to generate broken particles during the swelling process, forming a so-called polymer porogen effect. . Although the suspension polymerization method does not have the above disadvantages, the microspheres prepared by the conventional high-speed stirring method have a wide particle size distribution, and need to be classified into a narrow distribution to be effectively used, and the yield is low and the effect is poor. The membrane emulsification method is a highly efficient emulsification method, which can obtain a uniform particle size by passing an oil phase through a membrane having a uniform pore size, and then obtaining a microsphere having a uniform particle size by suspension polymerization.

A typical porous polymer can increase the degree of crosslinking by increasing the amount of crosslinking agent to increase the specific surface area, but after reaching a certain level, the increase in specific surface area will not be apparent. The PS-DVB polymer can further increase the degree of crosslinking by the Friedel-Crafts reaction to obtain an ultrahighly crosslinked resin having a specific surface area of up to 1000 m ² /g or more. The adsorption mechanism of the ultra-highly crosslinked resin is mainly hydrophobic. Due to the large amount of benzene ring in the skeleton, it also undergoes π-π interaction with the conjugated structure; in addition, the Friedel-Crafts reaction introduces a part of the oxygen-containing group. This makes it a certain enrichment ability for some polar organics.

Summary of the invention:

1. The technical problem to be solved by the invention

The present invention provides a monodisperse high specific surface area online solid phase extraction column and a preparation method thereof for preparing a monodisperse high specific surface area on-line solid phase extraction column according to the prior art, and the preparation method can be obtained online by the preparation method. The SPE small column realizes simple process, easy operation, high yield and low production cost.

2. Technical solutions

The principle of the present invention is to prepare a monodisperse ultra-high crosslinked styrene-divinylbenzene copolymer pellet by a membrane emulsification-suspension polymerization method, and then fill it into an online SPE cartridge by an equal density homogenization method.

A method for preparing a monodisperse high specific surface area online solid phase extraction column comprises the following steps:

(1) Preparing an oil phase containing styrene monomer, divinylbenzene crosslinker, initiator and porogen as a dispersed phase, and formulating water, emulsifier, inorganic salt, stabilizer and deoxidation according to the requirements of SPG membrane pore size The aqueous phase of the agent, then, under nitrogen pressure, the initial emulsion slowly passes through the SPG membrane and enters the outer aqueous phase to form an O/W emulsion;

(2) The O/W emulsion emulsified in the step (1) is heated under stirring, and the monodisperse porous styrene-divinylbenzene white sphere is obtained by suspension polymerization;

(3) adding the white ball obtained in the step (2) to the chloromethyl ether to swell, and then adding the zinc chloride to the chloromethylation in batches to obtain a chlorine ball;

(4) swelling the chlorine sphere prepared in the step (3) in a swelling agent, and performing Friedel-Crafts reaction under the catalyst condition to obtain ultra-high crosslinked resin microspheres;

(5) The microspheres prepared in (4) were ultrasonically dispersed in dichloromethane/ethanol and adjusted to an equal density. The microspheres were filled into a 2×4.6 cm stainless steel column at a pressure of 20 MPa to obtain a monodisperse height ratio. Surface area online solid phase extraction column.

The step (1) membrane emulsification method for preparing the aqueous phase and the formulation used in the monodisperse emulsion requires specific embodiments.

Step (2) Suspension polymerization method for preparing monodisperse microspheres, transferring the emulsion emulsified in step (1) into a three-necked flask, removing oxygen by nitrogen, and gradually raising the temperature to above 78 ° C and maintaining for more than 6 hours under stirring conditions. . The product was suction filtered with a sand core funnel and washed with a large amount of hot water. The synthesized microspheres were then charged into a cable extractor and extracted with ethanol, acetone and tetrahydrofuran for 24 hours. on. The extracted microspheres were washed with absolute ethanol and acetone and dried under vacuum for more than 3 hours. A microsphere-dispersed porous microsphere white ball can be obtained.

Step (3) preparing a chlorine ball for chloromethylation: adding a white ball prepared by the step (2) to a three-necked flask equipped with a mechanical stirring, a reflux condenser, and a calcium chloride drying tube on the condenser. Add chloromethyl ether to swell for more than 12 h at 25 °C. Zinc chloride was added in three batches (interval time was half an hour). After the addition, the temperature was further increased to 39 ° C by stirring for 1 hour, and the reaction was kept for 12 hours or more. After the reaction is completed, the chlorinated mother liquor is extracted by cooling, and methanol is added in two batches to soak and stir, the resin is washed, filtered, and air-dried to obtain chloromethylated microspheres.

In the step (4), the chlorine sphere obtained in the step (3) is prepared into the ultrahigh crosslinked microspheres according to the following two methods.

a) Swell the prepared chlorine spheres in dichloroethane. Anhydrous ferric chloride was added under stirring, and the reaction was carried out at 90 ° C for 12 hours or more. The mixture was cooled, filtered, and transferred to an acetone solution containing hydrochloric acid having a concentration of 1% by weight. After filtration, it was extracted with acetone and dried to obtain an ultrahigh crosslinked resin microsphere a having a specific surface area.

b) Swelling the prepared chlorine spheres into nitrobenzene. Anhydrous zinc chloride was added under stirring, and the reaction was carried out at 80 ° C for 12 hours or more. The mixture was cooled, filtered, and transferred to an acetone solution containing hydrochloric acid having a concentration of 1% by weight. After filtration, it was extracted with acetone and dried (in the same manner as in a) to obtain ultrahigh crosslinked resin microspheres b having a specific surface area.

Filling the online SPE cartridge in step (5)

The microspheres prepared in (4) were filled into the online SPE cartridge by an equal density homogenization method. The microspheres were ultrasonically dispersed in dichloromethane/ethanol and adjusted to an equal density, and the microspheres were filled into the SPE column under high pressure conditions. Use ethanol as the displacement fluid, stop the pressurization after flowing out a certain volume, and take it off after the pressure is equilibrated. After filling, it was washed with formic acid aqueous solution, ammonia water, and methanol.

3. Beneficial effects

The invention discloses a monodisperse high specific surface area online solid phase extraction column and a preparation method thereof, and the invention has the following remarkable effects:

(1) Using membrane emulsification-suspension polymerization method, the obtained microspheres have uniform particle size, and the particle size and crosslinking degree are conveniently adjusted;

(2) using styrene-divinylbenzene structure, easy to modify various groups on the surface and post-crosslinking, convenient adjustment of specific surface area and surface polarity, and obtaining microspheres with high specific surface area and certain polarity;

(3) Filling the online SPE cartridge with equal density homogenization method, the polarity and structure of the obtained column are easy to adjust, the sample amount is small, the enrichment and separation effect is good, and it can be applied to the field of liquid chromatography analysis, greatly improving the automation degree of analysis. .

The microspheres prepared by the invention have a particle diameter of 3-40 μm, a dispersion degree of 10% to 33%, and a specific surface area of 900 m ² /g or more; and the obtained SPE cartridge is enriched for the brominated flame retardant. The multiple can be more than 1000 times, and the recovery rate is 85% to 115%.

DRAWINGS

Figure 1 is a graph showing the changes before and after the synthesis of the emulsion prepared by using a 1.4 μm film, where a is the emulsion before synthesis, and b is The 6% cross-linked white ball obtained by preliminary polymerization, c is the microsphere obtained by cross-linking using dichloroethane as a swelling agent, and the ultra-high cross-linked microsphere obtained by using nitrobenzene as a swelling agent. It can be seen from the figure that the obtained microspheres have a uniform particle size distribution and no major changes during the synthesis;

Figure 2 is an on-line SPE chromatogram of the bromine flame retardant prepared by the on-line SPE extraction column. According to the peak time, it is: tetrabromobisphenol A, α, β, γ hexabromododecane. It can be seen from the figure that the brominated flame retardant is separated by baseline, the extraction recovery rate is good, and the separation effect is good.

detailed description

The technical solutions of the present invention together with the specific embodiments below constitute the implementation of the present invention. The formula of the aqueous phase in the step (1) is shown in Table 1, and the formulation of the oil phase is shown in Table 2.

Table 1 Water phase formulation of emulsions of different particle sizes (in 450mL)

Note: The emulsifier is sodium lauryl sulfate, the stabilizer is polyvinyl alcohol 1788, and the salt is sodium sulfate.

Table 2 Oil phase formulation for different cross-linking emulsions (in 50mL)

Example 1

Step 1: 23 g of styrene, 2 g of divinylbenzene, 0.75 g of benzoyl peroxide, 25 mL of n-heptane were combined into an oil phase, 450 mL of water, 0.5 g of sodium lauryl sulfate, 0.1 g of sodium sulfate, 5 g of poly Vinyl alcohol 1788 and 0.2 g of methylene blue were mixed into an aqueous phase, and a 1.4 μm SPG film was selected to prepare a monodisperse emulsion, and then an O/W emulsion was prepared under a nitrogen pressure of 0.06 MPa.

Step 2: The emulsion was transferred to a three-necked flask under nitrogen for 20 minutes at a stirring speed of 120 rpm, at 78 ° C for 4 hours, at 85 ° C for 2 hours, at 90 ° C for 2 hours, and at 95-98 ° C for 6 hours. The product was suction filtered with a sand core funnel and washed with a large amount of hot water. The synthesized microspheres were then placed in a cable extractor and extracted with ethanol, acetone and tetrahydrofuran for 48 h. The extracted microspheres were washed with absolute ethanol and acetone, and dried at a vacuum of 0.06 MPa at a temperature of 60 ° C for 3 hours. A white ball of 6% cross-linking degree was produced.

Step 3: In a 100 ml three-necked flask equipped with a mechanical stirring, reflux condenser and a calcium chloride drying tube on a condenser, 10 g of dried white balls were added, and 50 mL of methyl chloride was added thereto to swell for 12 hours at 25 °C. Further, 10 g of zinc chloride was added in three portions (interval time was half an hour). After the addition, the mixture was further stirred for 1 hour and heated to 39 ° C, and the reaction was kept for 12 hours. After the reaction, After cooling, the chlorinated mother liquor was withdrawn, and 60 ml of methanol was added and soaked in two batches for 1 hour, the resin was washed, filtered, and air-dried to obtain a chlorine pellet.

Step 4: The prepared chlorine spheres were swollen in 50 mL of nitrobenzene. 2 g of anhydrous zinc chloride was added thereto with stirring, and the mixture was reacted at 80 ° C for 18 hours. The mixture was cooled, filtered, and transferred to an acetone solution containing 1% hydrochloric acid, filtered, extracted with acetone, and dried to obtain ultrahigh crosslinked resin microspheres having a specific surface area. The particle size was 5.6 ± 0.7 μm and the dispersion was 16.6%. The average pore diameter of the microspheres was 3.17 nm and the BET specific surface area was 1056 m ² /g.

Step 5: The prepared ultra-highly crosslinked microspheres were filled into an online SPE cartridge by an equal density homogenization method. The microspheres were ultrasonically dispersed in dichloromethane/ethanol and adjusted to an equal density. The microspheres were filled into a 2 x 4.6 cm stainless steel column at a pressure of 20 MPa. Ethanol was used as the displacement liquid, and the pressure was stopped until the flow of 120 ml was stopped. After the pressure was equilibrated, it was taken out for use. After filling, it was washed once with 10 mL of 2% formic acid aqueous solution, 10 mL of 5% ammonia water, and 10 mL of methanol.

The performance was evaluated using an online SPE-Ultra Performance Liquid Chromatography Triple Quadrupole Mass Spectrometer (SPE-UPLC-XEVO-TQMS) from Waters, Inc., using four brominated flame retardants (tetrabromobisphenol A). , α, β, γ hexabromododecane), the loading concentration is 1ppb, the chromatographic conditions are shown in Table 3, the analysis conditions of the online SPE are shown in Table 4, and the chromatogram is shown in Figure 2. The results showed that the enrichment factor was 1000 times and the recovery rate was 90% to 105%.

Table 3 Liquid phase conditions of brominated flame retardants

Table 4 Online SPE conditions

Example 2

The basic conditions are the same as in Example 1, except that the water phase and the fuel tank components and their ratios are adjusted according to Tables and Table 2. The prepared online SPE extraction column was basically the same as in Example 1.

Example 2

The basic conditions are the same as those in the first embodiment, except that in step 3: "Additional zinc chloride (interval time is half an hour) is added in three batches. After the addition is completed, the temperature is further increased to 39 ° C by stirring for 1 hour, and the heat retention reaction is carried out for more than 12 hours". Further, zinc chloride was added in two batches (interval time was half an hour). After the addition, the temperature was further increased to 45 ° C by stirring for 1 hour, and the reaction was kept for 12 hours or more. The result was inferior to that of Example 1.

Claims

A method for preparing a monodisperse high specific surface area online solid phase extraction column comprises the following steps:

(1) Preparing an oil phase containing styrene monomer, divinylbenzene crosslinker, initiator and porogen as a dispersed phase, and formulating water, emulsifier, inorganic salt, stabilizer and deoxidation according to the requirements of SPG membrane pore size The aqueous phase of the agent, then, under nitrogen pressure, the initial emulsion slowly passes through the SPG membrane and enters the outer aqueous phase to form an O/W emulsion;

(2) The O/W emulsion emulsified in the step (1) is heated under stirring, and the monodisperse porous styrene-divinylbenzene white sphere is obtained by suspension polymerization;

(3) adding the white ball obtained in the step (2) to the chloromethyl ether to swell, and then adding the zinc chloride to the chloromethylation in batches to obtain a chlorine ball;

(4) swelling the chlorine sphere prepared in the step (3) in a swelling agent, and performing Friedel-Crafts reaction under the catalyst condition to obtain ultra-high crosslinked resin microspheres;

(5) The microspheres prepared in (4) were ultrasonically dispersed in dichloromethane/ethanol and adjusted to an equal density. The microspheres were filled into a 2×4.6 cm stainless steel column at a pressure of 20 MPa to obtain a monodisperse height ratio. Surface area online solid phase extraction column.
The preparation method according to claim 1, wherein the SPG film having a uniform pore diameter is used in the step (1), and the particle diameter of the O/W emulsion prepared by the membrane emulsification method is uniform and adjustable.
The preparation method according to claim 1 or 2, wherein the styrene-divinylbenzene copolymer obtained in the steps (2), (3), and (4) has a crosslinking degree of 2 to 10%. Ultrahigh crosslinked resin microspheres having a high specific surface area and polarity can be obtained by chloromethylation and by Friedel-Crafts reaction.
The preparation method according to claim 1 or 2, wherein the filling method of the microspheres filled with the 2 x 4.6 cm stainless steel column at a pressure of 20 MPa in the step (5) is an equal density homogenization method.
The monodisperse high specific surface area on-line solid phase extraction column prepared by the preparation method according to claim 1, wherein the prepared microspheres have a particle diameter of 3 to 40 μm and a dispersion degree of 10% to 33%. The specific surface area is above 900 m 2 /g.