Method for evaluating uncertainty of polycarbonate molecular weight distribution measured by GPC (Gel Permeation Chromatography)

Abstract

The invention provides an uncertainty evaluation method for determining polycarbonate molecular weight distribution by GPC (Gel Permeation Chromatography), and relates to the technical field of chemical detection. The uncertainty of the polycarbonate molecular weight distribution comprises a standard uncertainty component urel (Msample) introduced in a sample detection process and a standard uncertainty component urel (L) introduced by an operation error of a gel permeation chromatograph. Wherein the urel (M sample) comprises uncertainty u1 introduced by using sample repeated detection, uncertainty u2 introduced by using a weighing apparatus, uncertainty u3 introduced by using a container and uncertainty u4 introduced by a dissolution process. According to the method, the blank of the uncertainty evaluation method for the molecular weight distribution of the high-rigidity polycarbonate at present is filled, and the problem of unclear result expression in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical detection, and in particular to an uncertainty evaluation method for measuring molecular weight distribution of polycarbonate by GPC. Background Art

[0002] In the measurement process, the determination of uncertainty is crucial. Uncertainty is a parameter that cannot be accurately estimated for the measurement result, which reflects the possible error range of the measured value. This error may come from many factors, such as the accuracy limitation of the measuring equipment, the influence of the measuring environment, the operating skills of the measuring personnel, etc. Determining uncertainty helps to evaluate the reliability of the measurement. A measurement result with high uncertainty means that its true value may fluctuate within a large range, which is unreliable for decision-making and judgment. On the contrary, a measurement result with low uncertainty is closer to the true value and is therefore more reliable.

[0003] Polycarbonate is widely used in the field of optical lenses. Its molecular weight distribution will greatly affect the physical properties of the material. It is very important to evaluate the uncertainty of polycarbonate molecular weight distribution measured by GPC (gel permeation chromatography), but there are few related methods disclosed. Therefore, it is urgent to evaluate the uncertainty of the measurement system to reflect the authenticity and accuracy of the test results, and at the same time provide an accurate scientific basis for judging the rationality of the test results. Summary of the invention

[0004] The purpose of the present invention is to provide a method for evaluating the uncertainty of polycarbonate molecular weight distribution determined by GPC, so as to fill the gap in evaluating the uncertainty of polycarbonate molecular weight distribution determined by gel permeation chromatography.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for evaluating the uncertainty of polycarbonate molecular weight distribution by GPC, wherein the uncertainty of the polycarbonate molecular weight distribution includes a standard uncertainty component u introduced in the sample detection process. rel (M 样 ) and the standard uncertainty component u introduced by the operating error of the gel permeation chromatograph rel (L);

[0007] The uncertainty of the molecular weight distribution of polycarbonate is u Crel The calculation formula of (M) is:

[0008]

[0009] Preferably, the standard uncertainty component u introduced in the sample detection process is rel (M样 ) is calculated as:

[0010]

[0011] Among them, u1 is the uncertainty introduced by repeated sample testing, u2 is the uncertainty introduced by using a scale, u3 is the uncertainty introduced by using a container, and u4 is the uncertainty introduced by the dissolution process.

[0012] Preferably, the calculation method of the uncertainty u1 introduced by repeated sample testing is:

[0013] Repeat the test on the same sample several times to test its weight average molecular weight M W , the standard deviation Sd between the test results is evaluated as Class A and its inclusion factor K1 is determined;

[0014] According to the formula u1 = Sd / (K1×M w ) Calculate the uncertainty u1 introduced by repeated sample testing.

[0015] Preferably, the calculation formula of the uncertainty u2 introduced by the weighing instrument is:

[0016] u2=u (测) / (K2×m 样 )

[0017] Among them, u (测) is the measurement uncertainty recorded in the weighing instrument manual, K2 is the coverage factor, m 样 is the mass of the sample weighed each time.

[0018] Preferably, the calculation method of the uncertainty u3 introduced by using the container is:

[0019] 1) Determine the type of uncertainty introduced by the container;

[0020] 2) If it is a type A uncertainty, the calculation formula is u3 = E / K3, where E is the error value recorded in the container manual and K3 is the coverage factor;

[0021] If it is Type B uncertainty, the calculation formula is u3=S / √n, where S is the standard deviation between multiple measurement results and n is the number of measurements.

[0022] Preferably, the uncertainty u4 introduced by the dissolution process includes the uncertainty u introduced by dilution q , the uncertainty u introduced by the container g And the uncertainty u introduced by the temperature difference h , the calculation formula is:

[0023]

[0024] The u q The calculation formula is: q =S q / (K q ×V q ), where S q is the indication error of the pipetting tool, K q is the inclusion factor, V q is the volume of liquid removed;

[0025] The u g The calculation formula is: g =S g / (K g ×V g ), where S g is the indication error of the volumetric flask, K g is the inclusion factor, V g is the volume of the volumetric flask;

[0026] The u h The calculation formula is: h =V g ×(α1-α2) / K h , where V g is the volume of the volumetric flask, α1 is the thermal expansion coefficient of tetrahydrofuran, α2 is the thermal expansion coefficient of the volumetric flask material, K h is the inclusion factor.

[0027] Preferably, the standard uncertainty component u introduced by the gel permeation chromatograph operating error is rel The calculation formula of (L) is:

[0028] u rel (L) = S L / K L , where S L is the error range given in the manual of the gel permeation chromatograph, K L is the inclusion factor.

[0029] The present invention has at least the following beneficial effects:

[0030] 1. Improve measurement accuracy and reliability

[0031] In the field of polycarbonate material research, accurate molecular weight determination is particularly important for understanding the performance of the material. Publishing uncertainty methods allows other researchers to clearly identify the source and magnitude of errors in the measurement process and provide a basis for accurately evaluating measurement results.

[0032] 2. Promote standardization and regularization of methods

[0033] It provides a standard uncertainty assessment process for the determination of molecular weight distribution in the industry. It helps different laboratories to adopt a unified uncertainty assessment method when measuring polycarbonate molecular weight, making the data between laboratories comparable.

[0034] 3. Promote scientific research progress

[0035] For researchers engaged in the synthesis and modification of polycarbonates, understanding the uncertainty of molecular weight determination can optimize experimental plans. When developing new polycarbonate synthesis methods, the reaction conditions can be controlled more accurately to obtain products with target molecular weights. Moreover, this also provides more accurate data support for theoretical research. In the process of combining theoretical models of key properties of polycarbonate, accurate experimental data and their uncertainty can make the model more in line with actual conditions.

[0036] 4. Assist in quality control and product development

[0037] In the production process of polycarbonate products, the quality control department can use the uncertainty method to set a reasonable molecular weight tolerance range. This helps to ensure the stability of product quality. At the same time, during the product development process, it can better understand the impact of molecular weight changes on product performance and develop polycarbonate products with better performance. DETAILED DESCRIPTION

[0038] The invention provides a method for evaluating the uncertainty of polycarbonate molecular weight distribution measured by GPC, which fills the blank of evaluating the uncertainty of polycarbonate molecular weight distribution measured by gel permeation chromatography.

[0039] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0040] The present invention provides a method for evaluating the uncertainty of polycarbonate molecular weight distribution by GPC, wherein the uncertainty of the polycarbonate molecular weight distribution includes a standard uncertainty component u introduced in the sample detection process. rel (M 样 ) and the standard uncertainty component u introduced by the operating error of the gel permeation chromatograph rel (L);

[0041] The uncertainty of the molecular weight distribution of polycarbonate is u Crel The calculation formula of (M) is:

[0042]

[0043] In the present invention, the molecular weight of the polycarbonate is 5×10 -3 ~1×10 -6 .

[0044] In the present invention, the standard uncertainty component u introduced in the sample detection process is rel (M 样 ) is calculated as:

[0045]

[0046] Among them, u1 is the uncertainty introduced by repeated sample testing, u2 is the uncertainty introduced by using a scale, u3 is the uncertainty introduced by using a container, and u4 is the uncertainty introduced by the dissolution process.

[0047] In the present invention, the calculation method of the uncertainty u1 introduced by repeated sample testing is:

[0048] Repeat the test on the same sample several times to test its weight average molecular weight M W , the standard deviation Sd between the test results is evaluated as Class A and its inclusion factor K1 is determined; the test is repeated 6 to 15 times.

[0049] When calculating measurement uncertainty, the Bessel formula is used to calculate the sample standard deviation to characterize the uncertainty introduced by repeatability. The standard deviation calculated by the Bessel formula is an estimate of the population standard deviation. From a statistical point of view, when the number of measurements is small, the deviation of this estimate is large; as the number of measurements increases, the estimate will be closer to the true population standard deviation. When the number of measurements reaches 10 times or more, the accuracy of the estimate will be significantly improved, so the number of tests is between 6 and 15 times.

[0050] According to the formula u1 = Sd / (K1×M w ) Calculate the uncertainty u1 introduced by repeated sample testing.

[0051] In the present invention, the calculation formula of the uncertainty u2 introduced by the scale is:

[0052] u2=u (测) / (K2×m 样 )

[0053] Among them, u (测) is the measurement uncertainty recorded in the weighing instrument manual, K2 is the coverage factor, m 样 is the mass of the sample weighed each time.

[0054] In the present invention, the calculation method of the uncertainty u3 introduced by the container is:

[0055] 1) Determine the type of uncertainty introduced by the container. When the data is obtained by measuring the relevant value through the container multiple times (such as measuring the container volume multiple times), it is specified as a Type A uncertainty type; when the uncertainty is based on non-statistical information such as the container volume error range provided by the developer or manufacturer, the indication of the calibration certificate, and the material properties of the container, it is specified as a Type B uncertainty;

[0056] 2) If it is a type A uncertainty, the calculation formula is u3 = E / K3, where E is the error value recorded in the container manual and K3 is the coverage factor;

[0057] If it is Type B uncertainty, the calculation formula is u3=S / √n, where S is the standard deviation between multiple measurement results and n is the number of measurements.

[0058] In the present invention, the uncertainty u4 introduced by the dissolution process includes the uncertainty u q , the uncertainty u introduced by the container g And the uncertainty u introduced by the temperature difference h , the calculation formula is:

[0059] In the present invention, the u q The calculation formula is: q =S q / (K q ×V q ), where S q is the indication error of the pipetting tool, K q is the inclusion factor, V q is the volume of liquid removed.

[0060] In the present invention, the u g The calculation formula is: g =S g / (K g ×V g ), where S g is the indication error of the volumetric flask, K g is the inclusion factor, V g is the volume of the volumetric flask.

[0061] In the present invention, the u h The calculation formula is: h =V g ×(α1-α2) / K h , where V g is the volume of the volumetric flask, α1 is the thermal expansion coefficient of tetrahydrofuran, α2 is the thermal expansion coefficient of the volumetric flask material, K h is the inclusion factor.

[0062] In the present invention, the standard uncertainty component u introduced by the operation error of the gel permeation chromatograph is rel The calculation formula of (L) is:

[0063] u rel (L) = S L / K L , where S L is the error range given in the manual of the gel permeation chromatograph, K L is the inclusion factor.

[0064] In the present invention, the method for determining the molecular weight distribution of polycarbonate by GPC comprises the following steps:

[0065] 1) Take 0.015g of polycarbonate sample in a glass cup, add 2g of tetrahydrofuran and dissolve it completely at room temperature, then add 1g of tetrahydrofuran and seal it for later use;

[0066] 2) Preparation of standard curve

[0067] The gel permeation chromatograph was calibrated and zeroed with tetrahydrofuran, and then 20uL of a mixed standard sample with a mass fraction of 5‰ was accurately transferred using a pipette and introduced into the instrument injection port to obtain the weight average molecular weight Mw and polydispersity PDI of polystyrene.

[0068] The standard sample used in establishing the standard curve by gel chromatography external standard method is generally polystyrene, because it has the advantages of narrow molecular weight distribution, good stability, easy synthesis and purification, and rich related research and data, and can be used in various solvents such as tetrahydrofuran. If a polycarbonate standard sample is used as a standard sample, although it is most similar to the chemical structure and properties of the polycarbonate sample to be measured, it can minimize the measurement error caused by the difference between the sample and the standard sample, but the acquisition of the standard sample is difficult and costly, so the present invention uses polystyrene to prepare the standard curve.

[0069] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0070] Example 1

[0071] The complete procedure for determining the molecular weight of polycarbonate by GPC is as follows:

[0072] 1. Sample Preparation

[0073] With tetrahydrofuran as the mobile phase, accurately weigh an appropriate amount of polycarbonate sample, place it in a clean container, add an appropriate amount of solvent, and completely dissolve it under appropriate temperature and stirring conditions to prepare a 0.05% solution, and then use a 0.2μm ultrafiltration membrane to filter out solid impurities.

[0074] 2. Instrument Preparation

[0075] According to the mobile phase selection and molecular weight range, select a suitable chromatographic column. The chromatographic column used in this experiment is an oil-soluble polymer chromatographic column. Debug the flow rate, temperature and other parameters of the GPC instrument. The flow rate is set to 1mL / min and the temperature is set to 25℃. Before installing the chromatographic column, use a two-way pipe to connect the pipeline, replace the system with the mobile phase tetrahydrofuran, and then replace the GPC column. Then flush the detector flow path with the mobile phase for about 20 minutes, then switch the flow path several times to drive the bubbles out of the detection pool and wait for the baseline to stabilize.

[0076] 3. Standard curve drawing

[0077] A group of polystyrene standard samples with known molecular weight and narrow molecular weight distribution were selected and dissolved in tetrahydrofuran as solvent to prepare standard solutions of different concentrations. The standard solutions were added to the GPC instrument through the injector in sequence, and the retention time of each standard sample was recorded. The logarithm of the molecular weight of the standard sample (lgM) was used as the ordinate and the retention time was used as the abscissa to draw a standard curve, and the lgM-t relationship curve could be obtained.

[0078] 4. Sample determination

[0079] Take an appropriate amount of filtered polycarbonate sample solution and inject it into the injection port of the GPC instrument. The injection volume is between 50μL. The sample solution enters the chromatographic column with the mobile phase and is separated according to the molecular weight in the column. The molecules with larger molecular weight are eluted first, and the molecules with smaller molecular weight are eluted later. At the outlet of the column, the response signal of the solution is measured by the detector to obtain the chromatogram of the sample.

[0080] 5. Data Processing

[0081] According to the sample's chromatogram, determine its retention time, substitute it into the standard curve equation, and calculate the corresponding molecular weight value. Through data processing software, the number average molecular weight, weight average molecular weight, molecular weight distribution width and other parameters of polycarbonate can be further calculated.

[0082] Instruments: American Waters Breeze2 GPC gel permeation chromatograph, DLAB pipette;

[0083] Reagents: tetrahydrofuran (chromatographic grade); polystyrene mixed standard: 5‰, Zhenzhun Biotechnology.

[0084] Instruments: American Waters Breeze2 GPC gel permeation chromatograph, DLAB pipette;

[0085] Reagents: tetrahydrofuran (chromatographic grade); polystyrene mixed standard: 5‰, Zhenzhun Biotechnology.

[0086] (1) Calculate the uncertainty u introduced during sample testing rel (M 样 ):

[0087] u rel (M 样 ) includes the uncertainty u1 introduced by repeated sample testing, the uncertainty u2 introduced by the use of a weighing instrument, the uncertainty u3 introduced by the use of a container, and the uncertainty u4 introduced by the dissolution process.

[0088] The same sample was tested 8 times to test its corresponding weight average molecular weight Mw and dispersion PDI. The test results are shown in Table 1:

[0089] Table 1 Summary of standard sample reproducibility data

[0090]

[0091] Calculate the standard deviation of the test results Sd = 606.62, and make a Class A assessment of the standard deviation Sd between the test results, which includes factors Its uncertainty u1=u (样) / Mw=350.24 / 37718=0.0093.

[0092] An electronic balance is used to weigh the sample during the measurement process, so the uncertainty u2 introduced by the scale mainly comes from the indication error of the balance. The measurement uncertainty u2 given in the manual of the balance (Sartorius BSA224S) is (测) ±0.00005g, obeys rectangular distribution, and contains factor The mass of the sample weighed each time is m 样 is 0.005g, so

[0094] Table 2 Summary of sample quality test data

[0095]

[0096] In the measurement process, a Class A volumetric flask with a capacity of 10 mL is used, the error E is ±0.03 mL, and it obeys the normal distribution, including the factor so

[0097] The uncertainty u4 introduced by the dissolution process includes the uncertainty u introduced by dilution q , the uncertainty u introduced by the container g And the uncertainty u introduced by the temperature difference h .

[0098] Uncertainty u introduced by dilution q :Mainly due to the pipetting process, using a pipette with a range of 20 to 200uL, the indication error S q is ±0.1%, and the coverage factor Kp is The volume of liquid V that is pipetted each time during the dilution process q is 0.5mL, so

[0099] Uncertainty of container volume u g :This embodiment uses a 10mLA grade volumetric flask, and the maximum allowable error S of the A grade container g ±0.02mL, including factor K g for The volume of the volumetric flask V g is 10mL, so

[0100] Uncertainty u introduced by temperature difference h :In the test process of this embodiment, the ambient temperature changes by ±1°C, and the thermal expansion coefficient α1 of the diluent tetrahydrofuran is 2.0×10 -4 ℃ -1 The thermal expansion coefficient of a glass volumetric bottle is α2, which is 2.5×10 -5 ℃ -1 , including factor K h for So u h =V g ×(α1-α2) / K h =3.2×10 -5 .

[0101] According to the formula Calculated u4 = 1.95 × 10 -3 .

[0102] According to the formula Calculate u(M 样 )=0.0205.

[0103] (2) Calculate the standard uncertainty component u introduced by the operating error of the gel permeation chromatograph rel (L):

[0104] The signal intensity indication is directly collected by the data collection system during the gel permeation chromatography measurement process. The uncertainty of the instrument operation error is mainly due to the flow error. The flow setting error is classified as Class B assessment. The error range S given in the instrument manual is L is 1.0%, including factor K L =2, therefore, the uncertainty component of instrument operation error u(L) = S L / K L=1.0% / 2=0.005.

[0105] (3) According to the formula The total uncertainty u of the detection method is calculated Crel (M) = 0.0087012.

[0106] The combined uncertainty of the weight average molecular weight is:

[0107] u(Mw)=u Crel (M)×37718=459.76328.15;

[0108] The combined uncertainty of polydispersity is:

[0109] u(P)=u rel (PDI)×1.87=0.01.

[0110] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for evaluating the uncertainty of polycarbonate molecular weight distribution by GPC, characterized in that: The uncertainty of the polycarbonate molecular weight distribution includes the standard uncertainty component u introduced in the sample detection process. rel (M 样 ) and the standard uncertainty component u introduced by the operating error of the gel permeation chromatograph rel (L); The uncertainty of the molecular weight distribution of polycarbonate is u Crel The calculation formula of (M) is:

2. The uncertainty evaluation method for determining the molecular weight distribution of polycarbonate by GPC according to claim 1, characterized in that the standard uncertainty component introduced in the sample detection process is u rel (M 样 ) is calculated as: in, u1 is the uncertainty introduced by repeated sample testing, u2 is the uncertainty introduced by using a scale, u3 is the uncertainty introduced by using a container, and u4 is the uncertainty introduced by the dissolution process.

3. The uncertainty evaluation method for determining the molecular weight distribution of polycarbonate by GPC according to claim 2, characterized in that: The calculation method of the uncertainty u1 introduced by repeated sample testing is: Repeat the test on the same sample several times to test its weight average molecular weight M W , the standard deviation Sd between the test results is evaluated as Class A and its inclusion factor K1 is determined; According to the formula u1 = Sd / (K1×M w ) Calculate the uncertainty u1 introduced by repeated sample testing.

4. The uncertainty evaluation method for determining the molecular weight distribution of polycarbonate by GPC according to claim 2 or 3, characterized in that: The calculation formula for the uncertainty u2 introduced by the weighing instrument is: u2=u (测) / (K2×m 样 ) Among them, u (测) is the measurement uncertainty recorded in the weighing instrument manual, K2 is the coverage factor, m 样 is the mass of the sample weighed each time.

5. The uncertainty evaluation method for determining the molecular weight distribution of polycarbonate by GPC according to claim 4, characterized in that: The calculation method of the uncertainty u3 introduced by the use of the container is: 1) Determine the type of uncertainty introduced by the container; 2) If it is a type A uncertainty, the calculation formula is u3 = E / K3, where E is the error value recorded in the container manual and K3 is the coverage factor; If it is Type B uncertainty, the calculation formula is u3=S / √n, where S is the standard deviation between multiple measurement results and n is the number of measurements.

6. The uncertainty evaluation method for determining the molecular weight distribution of polycarbonate by GPC according to claim 5, characterized in that: The uncertainty u4 introduced by the dissolution process includes the uncertainty u introduced by dilution q , the uncertainty u introduced by the container g And the uncertainty u introduced by the temperature difference h , the calculation formula is: The u q The calculation formula is: q =S q / (K q ×V q ), where S q is the indication error of the pipetting tool, K q is the inclusion factor, V q is the volume of liquid removed; The u g The calculation formula is: g =S g / (K g ×V g ), where S g is the indication error of the volumetric flask, K g is the inclusion factor, V g is the volume of the volumetric flask; The u h The calculation formula is: h =V g ×(α1-α2) / K h , where V g is the volume of the volumetric flask, α1 is the thermal expansion coefficient of tetrahydrofuran, α2 is the thermal expansion coefficient of the volumetric flask material, K h is the inclusion factor.

7. The uncertainty evaluation method for determining the molecular weight distribution of polycarbonate by GPC according to claim 1, characterized in that: The standard uncertainty component u introduced by the operating error of the gel permeation chromatograph rel The calculation formula of (L) is: u rel (L) = S L / K L , where S L is the error range given in the manual of the gel permeation chromatograph, K L is the inclusion factor.

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