Chemicals—Determination of the low molecular weight content of a polymer using Gel permeation chromatography (GPC)
Some standard content:
ICSJ3.300
National Standard of the People's Republic of China
GB/T27843—2011
Chemicals
Determination of the low molecular weight content of polymer using Gel permeation chromatography (GPC)
Chemicals-Determination of the low molecular weight content of polymer using Gel permeation chromatography (GPC) Issued on 2011-12-30
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Standardization Administration of China
Implementation on 2012-08-01
This standard was drafted according to the rules given in GB/T 1,1-2009. GB/T 27843—2011
The technical content of this standard is the same as that of the Organization for Economic Cooperation and Development (OECD) Chemical Test Method No. 119 (1996) Gel Permeation Chromatography (GPC) for the Determination of the Content of Low Molecular Weight Components in Compounds\ (English version). The following editorial changes have been made to this standard:
The scope section has been added;
The page numbers have been rearranged:
The original text has been renumbered.
This standard was proposed and managed by the National Technical Committee for the Management of Hazardous Chemicals (SAC/TC251). The drafting units of this standard are: China Institute of Inspection and Quarantine, China Chemical Economic and Technological Development Center, Jiangsu Coal Chemical Engineering Design and Research Institute Co., Ltd., and Sinochem Chemical Standardization Research Institute. The main drafters of this standard are: Mi Naining, Chen Huiming, Wang Xiaobing, Yang Yao, and Guo Xinyu. 1
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GE/ 27843—201t
The original proposal for this method was contained in the European Commission (EC) working document on methods for polymer characterization. The case was presented at the OECD Expert Committee held in Gambon in April 1993 and was recommended as the basis for the development of the OECD test method. In 1994, the Secretariat formatted the proposal as an EC text in the format of the OECD test method and circulated it to the member states. Subsequently, the proposal for the test method was discussed and revised at the 1994 OECD/EC Joint Expert Meeting. The revised proposal was circulated to the member states for further discussion. After two rounds of discussion, the draft test method was completed in a pre-international form. This method is based on DIV55672-1:2007. The specific determination method and data processing methods are described in the DIV standard. When the actual determination conditions need to be changed, corresponding adjustments can be made. Other complete reference methods can also be used if available. This method describes the use of polystyrene samples with known polydispersity as the calibration curve. This method can be modified to suit specific polymers, such as water-soluble polymers and long-chain branched polymers.
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1 Scope
Chemicals Polymers Determination of low molecular weight components GPC
GB/T27843--2011
This standard specifies the use of gel permeation chromatography (GPC)
This standard is applicable to the determination of the content of low molecular weight components in compounds. Due to the diverse properties of compound materials and the different low molecular weight substances contained, some compounds are not suitable for the determination of low molecular weight content by gel chromatography due to their special complex structure. Other methods can be used for determination. When determining, the corresponding instrument should be selected according to the detailed information of the compound materials. 2 Normative references
The following documents are indispensable for the application of this document. For all dated references, only the dated version applies to this document. For undated references, the latest version (including all amendments) applies to this document. DIN55672-1:2007 Gel permeation chromatography (GPC) - Part 1 + Tetrehydrofuran (THF) as elution solvent (Gelpcr-meation chromatography (GpC) - Part I: Tetrehydrofuran (THF) as elution solvent., )3 Terms and Definitions
The following terms and definitions apply to this document. 3.1
The number-average molecular weight (M.) and the weight-average molecular weight (M) of the conjugate:
H. is the height from the baseline with an elution volume of V. to the detection signal; M is the molecular weight of the conjugate with an elution volume of V; n
is the number of data obtained.
The breadth of molecular weight distribution is a measure of the dispersion of conjugate molecules, expressed by the ratio of the weight-average molecular weight to the number-average molecular weight, M,/M. 3.3
Low molecular weight
Molecular weight is a molecular weight less than 1 000 Da (1 Da=1 u=1, 660 54X10- kg), 4 sets of reference materialsbzxz.net
GP wide determination of the average molecular weight of the compound is a relative method, which needs to be calibrated with a calibration curve: generally, linear polystyrene with a narrow molecular weight distribution and a known number average molecular weight 1
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GB/T27843-2011
M. and a weight average molecular weight M are used as standard materials for calibration. The obtained calibration curve is only applicable to the determination of unknown samples under the same experimental conditions as the standard material. Because the conversion relationship between elution volume and molecular weight only exists under specific experimental conditions. These experimental conditions include: temperature, solvent (or mixed solvent), chromatographic system conditions and separation column or chromatographic column system, etc.: The molecular weight of the compound sample determined by this method is a relative value, called "polystyrene equivalent molecular weight (polystyrene equivalent molecular weight)". Due to the differences in the structure and chemical composition of the sample and the standard material, the measured relative molecular weight value is more or less different from the absolute value. If other standard substances are used, such as ethylene glycol, polyoxyethylene, polymethyl methacrylate and acrylic acid, the reasons for their use must be provided. 5 Principle of the method
5.1 GPC can determine the number average molecular weight M, weight average molecular weight M, and molecular weight distribution of polymers. GPC is a special type of liquid chromatography, in which sample separation is based on the hydrodynamic volume of individual components. When the sample passes through a separation column filled with a porous material (the passband is an organic gel), small molecules can enter the pores, while large molecules are excluded from the pores, so the path of large molecules is shorter than that of small molecules and they are eluted first. Medium-sized molecules enter some pores and elute later; the smallest molecules can enter all pores and elute last because their average hydrodynamic radius is smaller than the pore size of the gel. 5.2 The separation of the chromatographic column is completely determined by the matching of the gel pore size and its distribution with the sample size, but in practice it is difficult to avoid the influence of adsorption effects on the results. In addition, the unevenness of the gel filling in the column and the dead volume will also have an adverse effect on the separation! . 5.3 The detector is affected by the refractive index or ultraviolet absorption and presents a simple distribution curve. The curve represents the actual molecular weight. The chromatographic column needs to be calibrated by a known molecular compound. Ideally, a polymer with a similar structure is selected for calibration within a wide molecular weight range. The GPC curve of the sample being tested is generally a typical Gaussian distribution curve, but some are asymmetric due to the tailing of the small molecule part. The vertical coordinate represents the mass, and components of different molecular weights are eluted. The horizontal coordinate represents the molecular weight of 1g. The low molecular weight component is obtained from the curve. If the composition and structure of the low molecular weight component are exactly the same as the polymer, the content of the low molecular weight component can be accurately calculated. 6 Quality Standard
The repeatability of the elution volume (relative standard deviation RSD) should be less than 0.3%. If the evaluation of the chromatographic system is time-dependent and does not meet DIN55672-1:2007. Internal standard calibration is used to ensure compliance with the reproducibility requirements of the analysis. Dispersibility depends on the molecular weight of the standard. The requirements for the commonly used styrene standard samples are: M, 2 000
2000M.≤10
M,> 105
where M is the peak molecular weight of the standard sample. Method description
7.1 Preparation of standard polystyrene solution
M./M,<1.20
M./M ≤ 1. 05
M./M, 1, 20
7.1.1 Dissolve the polystyrene standard sample in the eluent and prepare the standard sample solution concentration according to the instructions of the standard sample manufacturer.
7.1.2 The concentration of the standard sample solution depends on various factors, such as injection volume, solution viscosity, and detector sensitivity. The maximum injection volume should be adapted to the length of the chromatographic column, and the injection plate should be used to prevent the column from being overloaded. When using GPC analysis using a 30cm×7.8mtm column, the usual injection volume is 40μL~100μL, and the maximum should not exceed 250μL. The ratio of the injection volume to the dissolved concentration should be determined before the column is calibrated.
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7.2 Preparation of sample solution
GB/T 27843—2011
In principle, the preparation requirements are the same as those of the standard sample solution. The sample is dissolved in a suitable solvent, such as tetrahydrofuran (THF), and shaken carefully to fully dissolve. Ultrasonic dissolution cannot be used under any circumstances. In order to prevent large particles or micro-condensation cavities in the sample solution from clogging the chromatographic column, the sample solution should first be filtered through a membrane with a pore size of 0.2μm~2um. In the final experimental report, it should be stated whether there are undissolved particles, which may be the high molecular weight part of the sample. An appropriate method should be used to determine the percentage of the dissolved part in the sample. The prepared solution must be used within 24 hours. 7.3 Calibration of impurities and additives
It is necessary to calibrate the non-polymer components (such as impurities and/or additives) with a molecular weight lower than 1000 in the sample. Calibration is not required only when the content of these components is lower than 1%. The analysis of non-polymer components with a molecular weight lower than 1000 can be obtained by directly analyzing the sample liquid, or by analyzing the GPC eluent fraction. If the concentration of low-molecular-weight components in the column eluent fraction is too low and further analysis is required, it needs to be concentrated. The method is to evaporate the eluent and then redissolve it. However, it is necessary to ensure that the eluent composition does not change during the evaporation process. The concentration treatment method of the GPC eluent fraction depends on the quantitative analysis method used in the next step. 8 Equipment
8.1 Components of Gel Permeation Chromatography
Gel permeation chromatography generally consists of the following components: solvent reservoir:
Solvent degassing filter device,
---pressure buffer:
Injection system;
Chromatographic column,
·Detector,
---flow meter (if necessary);
--data acquisition and processing system;
Waste liquid.
It should be ensured that the GPC system equipment materials are insensitive to the mobile phase solvent used (for example, stainless steel capillaries should be used when THF is used as the mobile phase).
8.2 Injection and droplet delivery system
A certain amount of sample droplet is delivered to the chromatographic column through an automatic injector or manual injection to form a sharp strip. When injecting manually, rapid aspiration of the syringe may cause significant changes in the molecular distribution. The liquid delivery system should be kept as pulsation-free as possible, and a pulsation damper should be installed under ideal conditions. The flow rate is 1.0 mL/min. 8.3 Chromatographic column
Select a single chromatographic column or a combination of multiple chromatographic columns according to the characteristics of the polymer sample. Commercial chromatographic column packings have different specifications (such as pore size, exclusion limit and other properties). The choice of gel type and chromatographic column length is determined by the sample properties (such as hydrodynamic volume, molecular weight distribution) and specific separation conditions such as solvent, temperature and flow rate, see DIN55672-1:2007. TTTKAONYKACA
GB/T 27843—2011
8.4 Theoretical plate number
The separation capacity of a chromatographic column or a combination of chromatographic columns shall be expressed in terms of theoretical plates. The method for determining the theoretical plate number of a chromatographic column is to use a solvent (such as THF) as the mobile phase, and inject a certain amount of ethylbenzene or other non-polar solvent into a chromatographic column of known length. The theoretical plate number is expressed by formula (1):
Theoretical plate number:
N = 5.4(W)
4() or N = 16()
The elution volume of the largest peak,
The baseline width at the bottom of the peak,
Wx the half-peak width.
8.5 Separation efficiency
8.5.1 In addition to the theoretical plate number, the separation efficiency is also related to the bandwidth, and the separation efficiency depends on the width of the calibration curve. The separation efficiency of the chromatographic column is obtained from formula (2):
Where:
Vom. -Vanom2 ≥ 6. 0
The elution volume of polystyrene with molecular weight M, -10 times the elution volume of polystyrene fraction, column cross section,
8.5.2 The resolution of the system is generally obtained by formula (3): Ya-Yex-
Rt.=2×w.+W.
Where:
Wi,We-
The elution volume of the two polystyrene standard peaks: the baseline peak width of the two polystyrene standard peaks; 1
The peak positions of the two polystyrene standard peaks are divided in half (there should be a 10-fold difference). 8.5.3 The R value of the chromatographic column system should be greater than 1.7.8.6 Solvent
All solvents should be high purity solvents (THF purity greater than 99.5%). The solvent reservoir [under inert gas if necessary] should have sufficient capacity to complete column calibration and sample analysis. The solvent should be degassed before being pumped to the column. 8.7 Temperature Control
The critical temperature of the main components of the instrument (injection tube, chromatographic column, detector and pipeline) should be constant and consistent with the selected solvent. 8.8 Detector
The purpose of the detector is to quantitatively record the concentration of the sample eluted from the chromatographic column. In order to avoid unnecessary peak broadening effects, the volume of the detection chamber should be reduced as much as possible. Except for light scattering and viscosity detectors, it should not exceed 10 uL, differential refractometer is usually used for detection. If the sample characteristics or elution solvent have special requirements, other types of detectors can also be used, such as UV/visible, differential refractive index, viscosity detector, etc. 4
9 Data and Report
9.1 Data
9.1.1 Requirements for data acquisition and data processing and related evaluation standards D1N55672-1:2007. 9.1.2 Each sample to be tested should be tested twice and analyzed separately. 9.1.3 It is necessary to clearly indicate that the measured value is a relative value equivalent to the molecular weight of the standard sample. 9.1.4 Ensure that a blank sample is measured and the blank sample is processed in the same way as the sample being tested. GB/T 27843—2011
9,1.5 After determining the elution volume or retention time (possibly using an internal standard correction), plot ·· of the above values with 1gM. value (M. is the peak position molecular weight of the standard sample). At least two calibration points are required for every 10-fold difference in molecular weight. At least five calibration points are required for the entire calibration curve, covering the expected sample molecular weight range. The low molecular weight endpoint of the calibration curve is defined by n-hexylene or other suitable non-polar solutes. When the corresponding portion of the curve with a molecular weight below 1000 is used for the determination of impurities and additives, it is necessary to calibrate. 9.1.6 If there are insoluble affinity compounds (molecular weight is generally greater than the soluble part) retained in the chromatographic column, if this is not taken into account: it will lead to an overestimation of the low molecular weight component. The content of the low molecular weight portion needs to be corrected for insoluble polymers, see Appendix A. 9.1. The distribution curve should be in tabular form or in a graph (differentials, percentages, sums, etc.). When plotting the graph, a 10-fold molecular weight difference should usually be 4 cm wide and the maximum peak height should be 8 cm. For the integral distribution curve, the difference on the ordinate should be approximately 10 cm from 0% to 100%.
9.2 Test report
9.2.1 Test sample
9.2.1.1 Relevant information on the test sample (characteristics, additives, impurities); 9.2.1.2 Sample processing method, observed phenomena and existing problems. 9.2.2 Instrument
9.2.2. 1 Eluent container, gas, eluent composition 9.2.2.2 Pump, pulse damper, injection system 9.2.2.3 Column (manufacturer, all information about the characteristics of the column, such as pore size, type of separation material, etc. 1 Label, length and column connection sequence),
9.2.2.4 Theoretical plate number of chromatographic column (or combined column); separation efficiency (system resolution); peak symmetry information:
9. 2.2. 5
9.2.2.6 Column, temperature control type:
9.2.2.7 Detector (measurement principle, model, detection chamber volume); 9.2.2, 8 Flowmeter, if used (manufacturer, measurement principle) 9.2.2.9 Data acquisition and processing system (hardware and software). 9.2.3 Calibration of the system
9.2.3.1 A detailed description of the calibration curve method; 9.2.3.2 Quality criteria for using this method (e.g., correlation coefficient, sum of variances, etc.); 9.2.3.3 All extrapolation methods, assumptions and approximations used in the test process and in the data calculation and processing; 9.2.3.4 List the relevant information of the calibration curve in a table. Including: - Name of the standard sample;
Manufacturer of the standard sample,
GB/T27843-2011
- Characteristic parameters of the standard sample provided by the manufacturer or measured later and calculated by the definition method M, M, Mp.M,/M. - Concentration and injection volume of the standard sample;
- M, value of the standard sample used in the calibration,
- Elution volume or retention time of the maximum value of the measured standard sample peak; - Molecular mass M, calculated based on the maximum value,
-IM, and the percentage error of the calibration value.
9.2.4 Data on low molecular weight polymer content 9.2.4.1 Description of the sample processing process and the analytical method used: 9.2.4.2 Mass fraction of low molecular weight components in the entire sample: 9.2.4.3 Mass fraction of impurities, additives and other non-compound components in the entire sample. 9.2.5 Calculations
When making calculations, the following should be noted: 一Calculations based on time, all methods used should achieve the required repeatability (marking calibration methods, internal standards, etc.); 一Factors affecting calculations based on elution volume or retention time: 一If the peaks are not completely separated, list the calculation range; 一If the curve is smoothed, list the smoothing method used; 一Sample pretreatment and droplet preparation methods and steps; 一Whether there are insoluble particles in the sample; 一Sample concentration (mg/mL) and sample injection volume (μL); 一Observed factors that lead to deviations from the ideal GPC graph! 一Detailed description of all corrections made during the test; 一State the error range;
一Any reports and data related to the test results. 6
Appendix A
(Normative Appendix)
Correction Guidelines for Calculating Low Molecular Weight When Insoluble Polymers Exist in Polymer Solutions GB/T27843—2011
A.1 When the sample to be tested contains insoluble polymers, mass loss will occur after GPC analysis. This is because the insoluble polymer will be retained in the chromatographic column or on the filter, and only the dissolved part will pass through the chromatographic column. In this case, the mass loss caused by the polymer solution flowing through the chromatographic column can be calculated by measuring or calculating the refractive index increase (dn/dc) of the concentration of the polymer solution. This can be done by using an external calibration method with an external standard substance of known concentration and d/ to calibrate the response value of the thermal refractometer. The following example uses methyl methacrylate (PMMA) as the standard substance for calibration.
A,2 Use external standard to calibrate an acrylic acid compound. The standard substance PMMA can be used to prepare a THF solution of known concentration for GPC analysis. The measured data can be used to obtain the differential refractometer constant K according to formula (A.1): R
K=(CxV× an/de)
Wherein:
Differential refractometer constant, in microvolt seconds per milliliter (μV·s/mL): - Response value of standard sample PMMA, in microvolt seconds (μV·s): - Solution concentration of standard sample PMMA, in milligrams per milliliter (mg/mL); - Calibration volume, in liters (L);
dn/dc Refractive index increment of THF solution of standard sample PMMA, in milliliters per milligram (mL/rg). A.3 The following data are typical data of standard material PMMA: R=293 789
C-1.07 mg/mL;
V=0.1 mL;
dn/dc=9×10-5mL/mg.
A.4 If 10% of the injected compound flows out of the detector, the K value calculated according to the theoretical response value of this detector is 3.05×10ll. GB/T 27843—2011
Art Examination Literature
[1] Yau, WW ,Kitkland,JJ ,and Bly,DD Modcrn Sizc Exelusion Liquid Chromatography.J, Witey and Sans,197905×10ll. GB/T 27843—2011
Art Examination Literature
[1] Yau, WW ,Kitkland,JJ ,and Bly,DD Modcrn Sizc Exelusion Liquid Chromatography.J, Witey and Sans,197905×10ll. GB/T 27843—2011
Art Examination Literature
[1] Yau, WW ,Kitkland,JJ ,and Bly,DD Modcrn Sizc Exelusion Liquid Chromatography.J, Witey and Sans,1979
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