CN101858896B - Combination method of polymer carbon nanotube chromatographic column and ion chromatography single pump column switching technology - Google Patents

Abstract

A method for combining polymer carbon nanotube chromatographic column and ion chromatographic column switching technology, carried out in the ion chromatography single-pump column switching system, characterized in that the polymer carbon nanotube chromatographic column is used for online pretreatment of samples, and ion The combination of chromatography single-pump column switching technology, the analysis steps include baseline mapping, sample loading to the quantitative loop, matrix elimination and target ion enrichment, separation and analysis of target ions; compared with the traditional column switching system, the system requires The equipment is more simplified, the amount of reagents is reduced, the analysis time is shortened, no redundant sample pretreatment steps are required, the range of applicable samples is increased, and it is suitable for online high-throughput analysis. The invention has low cost, simple manufacturing process and excellent performance, and can be effectively used for the separation and analysis of various organic compounds, including organic solvents, organic acids and organic acid salts.

Description

Method for combining polymer carbon nanotube chromatographic column with ion chromatography single-pump column switching technology

technical field

The invention relates to an ion chromatography single-pump column switching technology combined with a polymer carbon nanotube chromatographic column, in particular to a simplified ion chromatographic column switching using a polymer carbon nanotube chromatographic column as a sample online pretreatment technology. the

Background technique

As a classic sample pretreatment technology, column switching technology is widely used in online elimination of complex matrix, enrichment of samples, and multidimensional chromatographic separation. In the field of ion chromatography, column switching technology is often used to eliminate high-concentration matrix interferences when analyzing trace ions. Because too high matrix concentration often contaminates the ion chromatography column, and the matrix peak easily covers the target ion peak; in addition, because the target ion concentration is too low, the target peak cannot be separated from the impurity peak by dilution. In addition, column switching technology is also used in ion chromatography systems that simultaneously separate anions and cations, using switching technology to simultaneously use anion columns and cation columns to separate. However, in all these ion chromatography column switching systems, two flow path systems are often used, one flow path is used for matrix elimination, and the other flow path is used for target ion separation. This will cause the entire analysis system to be too complicated, requiring multiple chromatographic pumps and numerous pipelines, which is undoubtedly a burden for ordinary laboratories. Therefore, it is necessary to further simplify the equipment flow path of the ion chromatography column switching system, thereby saving reagents and more in line with the purpose of green chemistry. In addition, the pretreatment columns generally used for ion chromatography column switching are usually ion-pair chromatography and ion-exclusion chromatography. General purpose, shorter retention time pretreatment columns make up for this deficiency. the

Contents of the invention

The invention provides a method for combining polymer carbon nanotube chromatographic column and ion chromatographic column switching technology. The ion chromatography column switching system is simplified, the use of reagents is saved, the retention time is reduced, and the sample analysis range is broadened. the

The invention provides a method for combining a polymer carbon nanotube chromatographic column and an ion chromatographic column switching technology, which is carried out in an ion chromatography single-pump column switching system, and is characterized in that the polymer carbon nanotube chromatographic column is used for online pretreatment of samples , combined with ion chromatography single-pump column switching technology, the analysis steps include baseline mapping, sample loading into the quantitative loop, matrix elimination and target ion enrichment, separation and analysis of target ions, and pretreatment column regeneration; the specific steps are:

(1) Connect the various components in the ion chromatography single-pump column switching system to form the ion chromatography single-pump column switching system. The nitrogen gas is turned on, the detector is turned on, and the baseline signal is recorded. the

(2) The sample is injected into the ten-way valve through manual injection, and the quantitative loop controls the sample capacity. After the sample is loaded, switch the six-way valve and the ten-way valve to the opposite position, and the eluent flows through the quantitative loop to inject the sample, and the pretreatment column Connected with the enrichment column, the pretreatment column does not retain the target ions, but retains the matrix compound, so the target ions directly flow out of the pretreatment column and are enriched on the enrichment column. the

(3) After 4.8 minutes, after the target ions on the pretreatment column are completely eluted, switch the six-way valve and the ten-way valve to the original position together, and the eluent generated by the eluent generator will elute rich The target ions on the collection column are separated and analyzed by the analytical column, and detected by the conductivity detector; after passing through the suppressor, the eluent becomes pure water, which is used to clean the pretreatment column and remove residual matrix substances. the

(4) A detector is added after the pretreatment column to monitor the eluent flowing into the waste liquid bottle, and all target ions will flow through the pretreatment column after passing through the first detector, and finally enter the waste liquid Therefore, there are small peaks of the target ion after the matrix peak on the baseline recorded by the post-added detector; wait until all the small peaks are out, indicating that the pretreatment column has been regenerated, stop the detection, and start the next injection. the

The combined use of the polymer carbon nanotube chromatographic column and the ion chromatographic column cut-off technology provided by the invention includes online elimination of sample matrix, pre-enrichment of target ions and chromatographic separation and analysis of target ions. the

The ion chromatography single-pump column switching system of the present invention includes: a pump, an eluent generator, a six-way valve, a ten-way valve, a quantitative loop, a suppressor, a detector, and a manual injection needle , a concentration column, a waste liquid bottle, a pretreatment column, a guard column, an analysis column, and a nitrogen cylinder; the connection relationship of each component is: the pump is connected with the eluent generator, and then the eluent is washed The liquid passes through the six-way valve, connects the guard column and the analysis column, enters the detector after passing through the suppressor, and then connects with the pretreatment column through the ten-way valve, and finally enters the waste liquid bottle; the ten-way valve is connected with a quantitative loop. The six-way valve is connected to concentrate, and the whole system of the column is protected by nitrogen gas bottle. the

The polymer carbon nanotube chromatographic column provided by the present invention uses styrene-divinylbenzene as the polymer matrix and multi-walled carbon nanotubes as the doping phase, and adopts a dispersion polymerization method to prepare monodisperse linear polystyrene microcolumns. Ball seeds, after the seeds are activated, use the single-step seed swelling method to synthesize polymer carbon nanotube composite microspheres, extract and remove the pore-forming agent, and use the homogenate method to pack the obtained chromatographic packing. The preparation steps are:

a. Synthesis of monodisperse linear polystyrene microsphere seeds by dispersion polymerization

Using styrene as a monomer, polyvinylpyrrolidone as a stabilizer, and azobisisobutyronitrile as an initiator, monodisperse linear polystyrene microsphere seeds are generated by free radical polymerization in a mixed reaction medium of ethanol and water. The particle size is about 1.8μm, the particle size is uniform, and no classification is required;

b. Synthesis of polymer carbon nanotube composite microspheres by single-step seed swelling method

Add dibutyl phthalate to the synthesized monodisperse linear polystyrene microspheres to activate the seeds, then add monomer styrene, crosslinking agent divinylbenzene, additive multi-walled carbon nanotubes, emulsifier ten Sodium dialkyl sulfate, polyvinyl alcohol as a stabilizer, benzoyl peroxide as an initiator, and toluene as a porogen are used to swell; then, the reaction is initiated by heating to polymerize the monomers, and monodisperse polymer carbon nanotube composite microspheres are prepared. The diameter is about 5 μm, without sieving and grading. The prepared pellets need to be extracted with toluene to remove porogens to obtain polymer carbon nanotube composite chromatographic fillers. Wash with methanol and water, and pack the column by homogenization method. the

The multi-walled carbon nanotubes used in the present invention are pre-oxidized by mixed strong acids, using 3:1 (v/v) concentrated sulfuric acid/concentrated nitric acid as an oxidant, and the multi-walled carbon nanotubes are placed in a mixed strong acid at 35 ° C. Sonicate, stop after 6 hours, wash with deionized water until neutral and dry. the

Advantages of the present invention:

The polymer carbon nanotube chromatographic column provided by the present invention can be used as an online sample pretreatment column for various organic compounds, including organic solvents, organic acids and corresponding organic acid salts, expanding the sample range of the column cutting system , It also simplifies the configuration of the chromatographic column and reduces the analysis cost. the

The column switching technology provided by the present invention uses the anion suppressor to electrolyze the KOH mobile phase into pure water through the action of the cation exchange membrane. Therefore, the mobile phase before the suppressor is completely different from that after the suppressor, and the same flow path can provide two One kind of mobile phase, which greatly facilitates the simplification of experimental equipment. Only one chromatographic pump is needed to provide power, and the two mobile phases can be used for matrix elimination and ion analysis respectively. the

The present invention utilizes a ten-way valve and a six-way valve to realize the whole column switching process, and at the same time, the elimination of the sample matrix and the analysis and detection are carried out simultaneously, thereby accelerating the analysis speed. Compared with the traditional ion chromatography column switching system, it saves the amount of switching valves and also saves analysis time. At the same time, using this switching technology, there is no need for sample pretreatment at all, and all pretreatment processes are carried out online, which is conducive to high-throughput analysis and saves the amount of reagents in the pretreatment process, which meets the requirements of green chemistry. the

The invention provides an ion chromatography single-pump column switching technology that is simple in equipment, fast in analysis, does not require sample pretreatment, and is suitable for high-throughput sample testing. the

The invention uses the polymer carbon nanotube composite chromatographic column as a pretreatment column, and can analyze various sample matrices, including organic solvents, organic acids and their salts. the

The invention provides a simplified ion chromatography single-pump column switching technology combined with polymer carbon nanotube composite chromatography. Compared with the traditional column switching system, the equipment required by this system is more simplified, the amount of reagents is reduced, the analysis time is shortened, no redundant sample pretreatment steps are required, the applicable sample range is increased, and it is suitable for online high-throughput analysis, which is in line with green chemistry Require. the

The analysis method of the present invention analyzes seven common anions, the linear range is 5-2000 μg/L, the linear correlation coefficient is above 0.9990, the detection limit is less than 3.17 μg/L, and the relative standard deviation of retention time and peak area is less than 3.36%. the

Description of drawings

Figure 1 Schematic diagram of sample loading into the quantitative loop (before 0 minutes) and chromatographic analysis (after 4.8 minutes)

Figure 2 Schematic diagram of matrix elimination and target ion enrichment (0-4.8 minutes)

In Figure 1 and Figure 2, 1 is the pump, 2 is the eluent generator, 3 is the six-way valve, 4 is the ten-way valve, 5 is the 200μL quantitative loop, 6 is the electrochemical self-regeneration suppressor, and 7 is the conductivity detector , 8 is a manual injection needle, 8 is a concentration column, 10 is a waste liquid bottle, 11 is a pretreatment column, 12 is a guard column, 13 is an analytical column, 14 is a nitrogen bottle, and 15 is a deionized water eluent. the

Figure 3 Schematic diagram of switching time and target ions entering the pretreatment column for the second time

In Figure 3, 1-target ion mixed ion peak, 2-matrix sample peak, 3-target ion separation and enter the pretreatment column for the second time to exit the peak

Figure 4 Standard chromatograms of 7 common anions

Figure 5 Chromatogram of trace anions in ethylene glycol phenyl ether

Chromatogram of trace anions in Fig. 6 sodium octanoate

Detailed ways

Embodiment 1: the making process of polymer carbon nanotube composite chromatographic filler is as follows, and its steps are:

(1) Synthesize 1.8 μm monodisperse polystyrene seed by dispersion polymerization method earlier, monomer concentration is 20%, stabilizer concentration is 3%, initiator consumption is 4% of monomer, and reaction medium is 95% ethanol aqueous solution, The reaction temperature was 70°C, the stirring speed was 250 rpm, and the reaction time was 24 hours. the

(2) 50 mg of multi-walled carbon nanotubes were oxidized with 200 mL of concentrated sulfuric acid/concentrated nitric acid=3:1 (v/v) mixed acid solution, ultrasonicated at 35° C. for 6 hours, washed until neutral and then dried. Then, monodisperse polystyrene-divinylbenzene-carbon nanotube composite microspheres with a crosslinking degree of 55% were prepared by seed swelling method. The concentration of the monomer is 10%, the content of carbon nanotubes accounts for 1% of the monomer, the amount of emulsifier is 1%, the amount of stabilizer is 3%, the amount of initiator is 2% of the monomer, and the amount of porogen is 50% , the swelling ratio is 50, the emulsification temperature is 25°C, the reaction temperature is 75°C, the stirring speed is 300 rpm, and the reaction time is 48 hours. the

(3) Extract the copolymerized microspheres with toluene to remove the porogen, and then wash them with water and ethanol to obtain the required filler. The prepared filler is loaded into the column by the homogenization method. It is used as the pretreatment column in the column switching system. the

Embodiment 2: The specific detection steps of polymer carbon nanotube composite chromatography and ion chromatography single-pump column switching are as follows:

1) Connect the system according to Figure 1: the pump 1 is connected to the eluent generator 2, then the eluent passes through the six-way valve 3, connects the guard column 12 and the analysis column 13, and enters the detector 7 after passing through the suppressor 6 Detect, then connect with the pretreatment column 11 through the ten-way valve 4, and finally enter the waste liquid bottle 10. A 200 μL quantitative loop 5 is connected to the ten-way valve 4 , and the entire system is protected by nitrogen gas, 14 is a nitrogen cylinder, and a concentration column 8 is connected to the six-way valve 3 . After pump 1 was filled with mobile phase, it was turned on at a flow rate of 0.5 mL/min. The nitrogen gas 14 for protection is opened to a pressure of about 5 psi. Detector 7 is turned on and the baseline signal is recorded. the

2) The sample is injected into the ten-way valve 4 through the manual injection 8, and the sample capacity of the quantitative loop 5 is 200 microliters. After the sample is loaded, the six-way valve 3 and the ten-way valve 4 are switched to the opposite position, and the eluent flows through the quantitative loop for sample injection. The pretreatment column is connected with the enrichment column, and the pretreatment column does not retain the target ions, but retains the matrix compound, so the target ions directly flow out of the pretreatment column and are enriched on the enrichment column (Figure 2). the

3) After 4.8 minutes, after the target ions on the pretreatment column are completely eluted, switch the six-way valve 3 and the ten-way valve 4 to the original position together, and the KOH eluent generated by the eluent generator 2 The target ions on the enrichment column are eluted, separated and analyzed by the analytical column, and detected by a conductivity detector (Figure 1). However, the pretreatment column is still flushed with the eluent transformed by the suppressor 6 to wash away the residual matrix substances. the

4) Add a pump after the pretreatment column, it will be found that all the target ions will pass through the pretreatment column after the detector, and then enter the waste liquid bottle, so there are small peaks of the target ions after the matrix peak on the baseline ( As shown in Figure 3). Wait until all the small peaks have been released before the detection can be stopped and the next sample injection can be started. the

See Figure 3 for a schematic diagram of switching time and target ions entering the pretreatment column for the second time

1- target anion mixed peak, 2- sample matrix peak, 3- secondary elution target ion separation peak, switching time: 4.8 minutes. the

Embodiment 3: This embodiment is to analyze seven kinds of common inorganic anion mixed standard samples with column switching technology

Instruments used: ion chromatograph; chromatographic pump; conductivity detector; chromatographic workstation; one six-way valve; one ten-way valve; high-purity nitrogen cylinder; analytical column; guard column; enrichment column; 200 μL injection volume; electrochemical Self-regenerating suppressor. the

Pretreatment column: use the polymer carbon nanotube composite filler in Example 1 to fill in a 4.6×150mm stainless steel column. the

Eluent: H ₂ O, KOH eluent generator concentration: 18mM, suppressor current: 90mA, flow rate 0.65mL/min.

Analysis steps:

(1) Baseline surveying and mapping

The eluent is pumped into the chromatographic separation column to achieve equilibrium, and the eluent output from the chromatographic separation column is converted into an electrical signal by the conductivity detector when it flows through the conductivity flow cell, thereby forming a baseline and being mapped. the

(2) Switching time optimization

A conductivity detector is connected behind the polymer carbon nanotube composite chromatographic column, and the time required for the complete separation of conventional anions to be eluted from the matrix is observed through the spectrum, which is used as the switching time. The switching time determined in this experiment is 4.8 minutes. (Attachment 3)

(3) Standard sample analysis

After determining the switching time, operate according to the analysis steps described in Example 2. Spectrum of conventional inorganic anion mixed standard in 7 (Figure 4). the

Analysis results: the linear range of various inorganic anions in the standard sample is 5-2000μg/L, the linear correlation coefficient is above 0.9990, the detection limit is 3.17μg/L, and the relative standard deviation of retention time and peak area is less than 3.36%. the

See the chromatograms of 7 common inorganic anions in accompanying drawing 4

1-F ^- (1ppm), 2-BrO ₃ ^- (1ppm), 3-Cl ^- (1ppm), 4-NO ₂ ^- (1ppm), 5-Br ^- (1ppm), 6-NO ₃ ^- (1ppm) , 7-SO ₄ ^2- (1ppm)

Embodiment 4: This embodiment is the analysis of trace inorganic anions in the ethylene glycol phenyl ether sample

Apparatus used: same as Example 3. the

Pretreatment column: same as embodiment 3

Eluent: same as Example 3. the

The analysis steps are the same as in Example 3. The plotted spectrum is shown in Figure 5. the

The analysis results are: the fluoride ion concentration in ethylene glycol phenyl ether is 1.53mg/Kg, the chloride ion concentration is 4.90mg/Kg, the nitrate ion concentration is 5.63mg/Kg, and the sulfate ion concentration is 41.27mg/Kg. Other ions were not detected. The recoveries of seven kinds of inorganic anions ranged from 85.4% to 119.0%. the

See the chromatogram of trace inorganic anion in accompanying drawing 5 benzyl alcohol

1-F ^- , 2-Cl ^- , 3-NO ₃ ^- , 4-SO ₄ ^2-

Embodiment 5: This embodiment is the analysis of trace inorganic anion in sodium octanoate sample

Apparatus used: same as Example 3. the

Pretreatment column: same as embodiment 3

Eluent: same as Example 3. the

The analysis steps are the same as in Example 3. The plotted spectrum is shown in Figure 6. the

The analysis results are: the concentration of fluoride ion in sodium octanoate is 16.54mg/Kg, the concentration of chloride ion is 26.18mg/Kg, the concentration of nitrite ion is 2.12mg/Kg, the concentration of nitrate ion is 2.77mg/Kg, the concentration of sulfate ion It is 21.06mg/Kg. Other ions were not detected. The recoveries of seven kinds of inorganic anions ranged from 88.3% to 119.5%. the

See the chromatogram of trace inorganic anion in accompanying drawing 6 benzoic acid

1-F ^- , 2-Cl ^- , 3-NO ₂ ^- , 4-NO ₃ ^- , 5-SO4 ₂ ^- .

Claims (3)

1. the method for a polymer carbon nano tube chromatographic column and Column-switch ion chromatography coupling, in ion chromatography single-pump column switching system, carry out, it is characterized in that adopting the polymer carbon nano tube chromatographic column to carry out the online pre-treatment of sample, with the coupling of ion chromatography single-pump column handoff technique, analytical procedure comprises that successively baseline mapping, sample are loaded into quantitative ring, matrix elimination and object ion enrichment, compartment analysis object ion, pre-treatment column regeneration; Concrete steps are:

(1) each parts of ion chromatography single-pump column switching system are connected, consist of ion chromatography single-pump column switching system, the pre-treatment post is the polymer carbon nano tube chromatographic column; Pump is opened after filling leacheate, and the nitrogen of protection usefulness is opened, and detecting device is opened, and begins to record background signal;

(2) sample injects ten-way valve by hand sampling, quantitatively encircle the Quality control capacity, after the sample loading is complete, six-way valve and ten-way valve are switched to opposite location, leacheate flows through quantitative ring sample introduction, and the pre-treatment post is communicated with evaporating column, and the pre-treatment post to object ion without reserve, and matrix compounds is withed a hook at the end, so object ion directly flows out the pre-treatment post and is enriched on the evaporating column;

After (3) 4.8 minutes, by the time behind the complete wash-out of the quilt of the object ion on the pre-treatment post, six-way valve and ten-way valve are switched to original position more together, the object ion on the leacheate wash-out evaporating column that the leacheate generator produces, carry out compartment analysis by analytical column, electric conductivity detector detects; Behind rejector, leacheate becomes pure water, is used for cleaning the pre-treatment post, and the base matter that flush away is residual is with the pre-treatment column regeneration;

(4) adding a detecting device behind the pre-treatment post monitors the leacheate that flows into before the waste liquid bottle again, all object ions are through the pre-treatment post of can flowing through again behind first detecting device, enter at last waste liquid bottle, therefore after the matrix peak, also have the small peak of object ion on the baseline of rear detector recording of adding; By the time all small peaks have all gone out, and show that the pre-treatment post regenerated completely, stop to detect, and begin next time sample introduction;

Comprise in the described ion chromatography single-pump column switching system: a pump, a leacheate generator, a six-way valve, a ten-way valve, one is quantitatively encircled a rejector, a detecting device, a hand sampling pin, an evaporating column, a waste liquid bottle, a pre-treatment post, a guard column, an analytical column, a nitrogen cylinder; The annexation of each parts is: chromatogram pump links to each other with the leacheate generator, and then leacheate connects guard column and analytical column through six-way valve, detects through entering detecting device behind the rejector, then links to each other with the pre-treatment post by ten-way valve, enters at last waste liquid bottle; Be connected with quantitative ring on the ten-way valve, be connected with evaporating column at six-way valve, whole system is provided the protection of nitrogen by nitrogen cylinder;

In the ion chromatography single-pump column switching system, utilizing anion suppressor to pass through the effect of cation-exchange membrane, is pure water with the electrolysis of KOH leacheate, before the rejector from rejector after leacheate fully different, two kinds of leacheates can be provided in same stream.

2. the method for polymer carbon nano tube chromatographic column according to claim 1 and Column-switch ion chromatography coupling, it is characterized in that described polymer carbon nano tube chromatographic column, as polymer substrate take styrene-divinylbenzene, multi-walled carbon nano-tubes is as the doping phase, adopt dispersion copolymerization method to prepare monodispersed linear polystyrene microballoon seed, behind seed activation, adopt single step seed swelling method, synthetic polymer carbon nano-tube complex microsphere, perforating agent is removed in extracting, the chromatograph packing material that obtains, chromatograph packing material fills post with the homogenate method.

3. the method for polymer carbon nano tube chromatographic column according to claim 1 and Column-switch ion chromatography coupling, it is characterized in that polymer carbon nano tube chromatographic column on-line sample preparation post, processing comprises organic solvent, organic acid and corresponding organic acid salt material.

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