CN112986218A - N-methyl pyrrolidone element content detection method - Google Patents

N-methyl pyrrolidone element content detection method Download PDF

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CN112986218A
CN112986218A CN202110179536.4A CN202110179536A CN112986218A CN 112986218 A CN112986218 A CN 112986218A CN 202110179536 A CN202110179536 A CN 202110179536A CN 112986218 A CN112986218 A CN 112986218A
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methylpyrrolidone
content
nmp
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李岩
李智
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Tianjin Aike Kaisheng Graphene Technology Co ltd
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    • G01—MEASURING; TESTING
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    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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    • G01N21/73—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited using plasma burners or torches
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
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    • G01N1/40—Concentrating samples
    • G01N1/4044—Concentrating samples by chemical techniques; Digestion; Chemical decomposition
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/44—Sample treatment involving radiation, e.g. heat

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Abstract

The invention provides a method for detecting the content of N-methylpyrrolidone elements, which is characterized by comprising the following steps: s1: weighing N-methylpyrrolidone, and placing the N-methylpyrrolidone in a drying beaker; s2: heating and concentrating, heating and concentrating on an electric hot plate, cooling to room temperature, weighing, adding purified water to wash the wall of a beaker, shaking uniformly, and weighing to obtain concentrated N-methylpyrrolidone; s3: microwave digestion, namely placing the concentrated N-methyl pyrrolidone in a digestion tank for digestion treatment; s4: preparing a measuring solution, transferring the liquid in the digestion tank into a volumetric flask, and fixing the volume to obtain the measuring solution; s5: testing element content, namely measuring the element content of the measured liquid by adopting an inductively coupled plasma atomic emission spectrometer; s6: and (6) data processing. According to the NMP pretreatment method provided by the invention, the NMP is concentrated, so that elements in the NMP with very low content are enriched, the test accuracy is improved, and the test error is reduced.

Description

N-methyl pyrrolidone element content detection method
Technical Field
The invention relates to a method for detecting the content of N-methylpyrrolidone element, belonging to the technical field of element detection methods.
Background
N-methylpyrrolidone of formula C5H9NO, an organic compound, a colorless transparent oily liquid, has a slight amine odor. Low volatility, good thermal stability and chemical stability, and capability of steaming with waterThe gas is volatilized. It is easily soluble in water, ethanol, diethyl ether, acetone, ethyl acetate, chloroform and benzene, and can dissolve most organic and inorganic compounds, polar gas, natural and synthetic high molecular compounds. N-methyl pyrrolidone is widely applied to the industries of lithium batteries, medicines, pesticides, pigments, cleaning agents, insulating materials and the like.
N-methyl pyrrolidone (NMP) is used as a dispersing agent in the production of oily graphene conductive slurry, and the content of key elements (iron, chromium, copper, nickel, zinc, cobalt, aluminum, calcium and manganese) needs to be controlled in the graphene conductive slurry, so the element content of the raw material NMP also needs to be controlled, but the national standard GB/T27563-2011 industrial N-methyl-2-pyrrolidone (NMP) does not have a method for testing the element content, and therefore a method suitable for detecting the element content of NMP is urgently needed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for detecting the content of N-methylpyrrolidone.
In order to achieve the purpose, the invention is realized by the following technical scheme: a method for detecting the content of N-methylpyrrolidone elements is characterized by comprising the following steps:
s1: weighing sample
Weighing N-methylpyrrolidone and placing the N-methylpyrrolidone in a drying beaker;
s2: concentrating by heating
Heating and concentrating on an electric hot plate, cooling to room temperature, weighing, adding purified water to wash the wall of the beaker, shaking uniformly, and weighing to obtain concentrated N-methylpyrrolidone;
s3: microwave digestion
Placing the concentrated N-methyl pyrrolidone in a digestion tank for digestion treatment;
s4: preparation of assay solution
Transferring the liquid in the digestion tank to a volumetric flask, and carrying out constant volume to obtain a measured liquid;
s5: element content test
Measuring the element content of the measured liquid by using an inductively coupled plasma atomic emission spectrometer;
s6: and (6) data processing.
Preferably, step S1 specifically includes: 45-55g of N-methylpyrrolidone is weighed and placed in a dry beaker.
Preferably, in step S2, the dry beaker containing N-methylpyrrolidone is placed on an electric heating plate and heated and concentrated until the mass of N-methylpyrrolidone is 5-10mL, the dry beaker is cooled to room temperature and weighed, purified water is added to wash the wall of the beaker, the beaker is shaken up and weighed, and the concentrated N-methylpyrrolidone is obtained.
Preferably, the temperature of the electric heating plate is 200-.
Preferably, the content of the N-methyl pyrrolidone in the concentrated N-methyl pyrrolidone is less than or equal to 1 g.
Preferably, step S3 specifically includes: weighing 2g of concentrated N-methylpyrrolidone into a digestion tank, adding 6mL of concentrated nitric acid, and sequentially digesting according to the first condition, the second condition and the third condition.
Preferably, the first condition is that the temperature is increased to 120 ℃ for 6min, the temperature is kept for 8min, and the power is 1600W; the second condition is that the temperature is increased to 160 ℃ within 5min, the temperature is kept for 8min, and the power is 1600W; and the third condition is that the temperature is increased to 180 ℃ within 5min, the temperature is kept for 8min, and the power is 1600W.
Preferably, step S5 specifically includes: nine metal elements of Fe, Cr, Cu, Ni, Zn, Co, Al, Ca, Mn and nonmetal S are selected, the concentrations of the nine metal element mixed standard solution and the nonmetal S standard solution are 0, 0.5, 1, 2 and 5ppm in sequence, a metal mark line and a sulfur mark line are respectively established for the nine metal element mixed standard solution and the sulfur standard solution, and the content of the elements is measured by ICP (inductively coupled plasma) of the prepared measuring solution.
By adopting the technical scheme, the first five spectral lines with the maximum intensity are selected for each element, the ICP instrument can perform element content measurement according to a plurality of spectral lines of each element, preferably the five spectral lines with the maximum intensity, and thus calculated data are more accurate.
Preferably, the ICP test parameters are specifically: auxiliary gas flow 0.5L/min, atomizer flow 0.5L/min, radio frequency power 1150W, rinsing pump speed 50rpm, analysis pump speed 50rpm, pump stabilization time 5s, test time 30s, test times 3 times.
Preferably, step S6 specifically includes: after the standard liquid spectral line and the test spectral line are adjusted, the average concentration under the spectral line is the concentration of the test liquid, and the calculation formula is as follows:
the element content (ppm) in NMP is (test solution concentration-blank average concentration) × 50 × NMP solution mass after concentration and water addition/(NMP sample amount before concentration × NMP sample amount in digestion tank).
By adopting the technical scheme, one or more of the nine metal elements and the nonmetal sulfur element can also exist in the blank group, and the content of the element in the blank group is further removed by using the concentration of the test solution-the blank average concentration, so that the result is more accurate.
The invention has the beneficial effects that:
(1) according to the NMP pretreatment method provided by the invention, the NMP is concentrated, so that elements in the NMP with very low content are enriched, the test accuracy is improved, and the test error is reduced.
(2) The NMP microwave digestion method provided by the invention adopts sealed microwave heating and pressurization, is different from the traditional open type heating which can not pressurize, and has the advantages of simple and convenient operation, high digestion speed, less required samples and solvents, almost no loss of elements and high digestion efficiency.
(3) The NMP microwave digestion method provided by the invention utilizes the oxidability and acidity of nitric acid to fully digest elements in NMP, and does not adopt acid with high risk such as perchloric acid, thereby ensuring the digestion safety.
(4) The NMP microwave digestion method provided by the invention utilizes closed pressurization to completely digest organic matters in NMP, thereby eliminating the interference of the organic matters during ICP test and improving the test accuracy.
(5) The ICP testing method for elements in NMP provided by the invention can be used for simultaneously testing various elements, the testing efficiency is improved, the using amount of the testing liquid is reduced, and the operation is simple and convenient.
Drawings
FIG. 1 is a standard curve of Fe element;
FIG. 2 is a standard curve of Cr element;
FIG. 3 is a standard curve of Cu element;
FIG. 4 is a standard curve of Ni element;
FIG. 5 is a standard curve of Zn element;
FIG. 6 is a standard curve of Co element;
FIG. 7 is a standard curve of Al element;
FIG. 8 is a standard curve of Ca element;
FIG. 9 is a standard curve of Mn element;
fig. 10 is a standard curve of the S element.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.
Example 1
(1) Weighing: a dry beaker was weighed and NMP 50.08g was added.
(2) Heating and concentrating: heating and concentrating on an electric hot plate at 220 ℃ until the mass of NMP is 5g, cooling to room temperature, weighing, adding purified water to wash the wall of the beaker for 3-5 times, wherein the total amount of the purified water is 10mL, shaking up, and weighing again to obtain the concentrated NMP, wherein the mass of the concentrated NMP is 14.89 g;
if the consumption of the purified water is too much, the concentration of NMP is too low, and the subsequent test result is influenced; if the consumption of the purified water is too low, the concentration of NMP in the solution is too high, and the reaction is too violent in the microwave digestion process.
(3) Microwave digestion: respectively taking 1.967g, 2.045g and 2.106g of concentrated NMP in three digestion tanks, simultaneously taking the three clean digestion tanks as blanks, adding 6ml of concentrated nitric acid to completely bring the samples into the bottom, covering the digestion tank cover, installing an outer sleeve, screwing, taking the tank with the largest sample weighing amount as a main control tank, putting the tank into a microwave digestion instrument, and digesting according to the following method parameters;
the first step is as follows: heating to 120 ℃ for 6min, keeping for 8min, and keeping the power at 1600W;
the second step is that: heating to 160 ℃ for 5min, keeping for 8min, and keeping the power at 1600W;
the third step: the temperature is increased to 180 ℃ for 5min, the temperature is kept for 8min, and the power is 1600W.
(4) Preparation of a determination solution: after digestion is completed, the temperature in the digestion tank is reduced to be lower than 80 ℃, the digestion tank is taken out and placed into a fume hood, a jacket is unscrewed and taken down, a series of clean 50ml volumetric flasks are taken out, a funnel is arranged, liquid in the digestion tank is transferred into the volumetric flasks through the funnel, the digestion tank is washed by purified water for 3-5 times, filtrate is transferred into the volumetric flasks, after the liquid in the funnel completely flows into the volumetric flasks, the funnel is washed, and after the process is repeated for 3-5 times, the constant volume is adjusted to 50 ml.
(5) ICP test: selecting nine metal elements of Fe, Cr, Cu, Ni, Zn, Co, Al, Ca, Mn and nonmetal S elements, selecting five spectral lines with the maximum intensity for each element, sequentially setting the concentrations of all the element standard solutions to be 0, 0.5, 1, 2 and 5ppm, preparing a mixed standard solution of the nine metal elements and a sulfur standard solution to respectively establish a metal standard line and a sulfur standard line, and measuring the element content of the prepared measuring solution by using ICP (inductively coupled plasma atomic emission spectrometer);
step six: data processing: keeping an element spectral line with a correlation coefficient of the marked line being more than 0.999, selecting an optimal spectral line of each element after adjusting peak types of the standard liquid spectral line and the test liquid spectral line, wherein the average concentration under the spectral line is the concentration of the test liquid, and the calculation formula is as follows:
the element content (ppm) in NMP (test solution concentration-blank average concentration) 50 is the mass of NMP solution after concentration and water addition/(NMP sampling amount before concentration) in digestion tank is formula (1)
The above-mentioned optimum spectral line determination criteria are:
(1) according to the spectral line of which the adjusted peak type is closest to normal distribution;
(2) the spectral line with the highest accuracy;
(3) the spectral line with the best repeatability;
(4) the spectral line with the highest correlation coefficient of the standard curve.
Example 2
(1) Weighing: a dry beaker was weighed and NMP 51.88g was added.
(2) Heating and concentrating: heating and concentrating on an electric hot plate at 220 ℃ until the mass of NMP is 8g, cooling to room temperature, weighing, adding purified water to wash the wall of the beaker for 3-5 times, wherein the total amount of the purified water is 10mL, shaking up, and weighing again to obtain the concentrated NMP, wherein the mass of the concentrated NMP is 19.09 g;
if the consumption of the purified water is too much, the concentration of NMP is too low, and the subsequent test result is influenced; if the consumption of the purified water is too low, the concentration of NMP in the solution is too high, and the reaction is too violent in the microwave digestion process.
(3) Microwave digestion: respectively taking the concentrated NMP in three digestion tanks, simultaneously taking three clean digestion tanks as blanks, adding 6ml of concentrated nitric acid to completely bring the sample into the bottom, covering the digestion tank cover, installing an outer sleeve, screwing down, taking the tank with the largest sample weighing amount as a main control tank, putting the tank into a microwave digestion instrument, and digesting according to the following method parameters;
the first step is as follows: heating to 120 ℃ for 6min, keeping for 8min, and keeping the power at 1600W;
the second step is that: heating to 160 ℃ for 5min, keeping for 8min, and keeping the power at 1600W;
the third step: the temperature is increased to 180 ℃ for 5min, the temperature is kept for 8min, and the power is 1600W.
(4) Preparation of a determination solution: after digestion is completed, the temperature in the digestion tank is reduced to be lower than 80 ℃, the digestion tank is taken out and placed into a fume hood, a jacket is unscrewed and taken down, a series of clean 50ml volumetric flasks are taken out, a funnel is arranged, liquid in the digestion tank is transferred into the volumetric flasks through the funnel, the digestion tank is washed by purified water for 3-5 times, filtrate is transferred into the volumetric flasks, after the liquid in the funnel completely flows into the volumetric flasks, the funnel is washed, and after the process is repeated for 3-5 times, the constant volume is adjusted to 50 ml.
(5) ICP test: selecting nine metal elements of Fe, Cr, Cu, Ni, Zn, Co, Al, Ca, Mn and nonmetal S elements, selecting five spectral lines with the maximum intensity for each element, sequentially setting the concentrations of all the element standard solutions to be 0, 0.5, 1, 2 and 5ppm, preparing a mixed standard solution of the nine metal elements and a sulfur standard solution to respectively establish a metal standard line and a sulfur standard line, and measuring the element content of the prepared measuring solution by using ICP (inductively coupled plasma atomic emission spectrometer);
step six: data processing: keeping an element spectral line with a correlation coefficient of the marked line being more than 0.999, selecting an optimal spectral line of each element after adjusting peak types of the standard liquid spectral line and the test liquid spectral line, wherein the average concentration under the spectral line is the concentration of the test liquid, and the calculation formula is as follows:
the element content (ppm) in NMP (test solution concentration-blank average concentration) 50 is the mass of NMP solution after concentration and water addition/(NMP sampling amount before concentration) in digestion tank is formula (1)
The above-mentioned optimum spectral line determination criteria are:
(1) according to the spectral line of which the adjusted peak type is closest to normal distribution;
(2) the spectral line with the highest accuracy;
(3) the spectral line with the best repeatability;
(4) the spectral line with the highest correlation coefficient of the standard curve.
Example 3
(1) Weighing: a dry beaker was weighed and 51.33g of NMP was added.
(2) Heating and concentrating: heating and concentrating on an electric hot plate at 220 ℃ until the mass of NMP is 10g, cooling to room temperature, weighing, adding purified water to wash the wall of the beaker for 3-5 times, wherein the total amount of purified water is 10mL, shaking up, and weighing again to obtain 21.02g of concentrated NMP;
if the consumption of the purified water is too much, the concentration of NMP is too low, and the subsequent test result is influenced; if the consumption of the purified water is too low, the concentration of NMP in the solution is too high, and the reaction is too violent in the microwave digestion process.
(3) Microwave digestion: respectively taking the concentrated NMP in three digestion tanks, simultaneously taking three clean digestion tanks as blanks, adding 6ml of concentrated nitric acid to completely bring the sample into the bottom, covering the digestion tank cover, installing an outer sleeve, screwing down, taking the tank with the largest sample weighing amount as a main control tank, putting the tank into a microwave digestion instrument, and digesting according to the following method parameters;
the first step is as follows: heating to 120 ℃ for 6min, keeping for 8min, and keeping the power at 1600W;
the second step is that: heating to 160 ℃ for 5min, keeping for 8min, and keeping the power at 1600W;
the third step: the temperature is increased to 180 ℃ for 5min, the temperature is kept for 8min, and the power is 1600W.
(4) Preparation of a determination solution: after digestion is completed, the temperature in the digestion tank is reduced to be lower than 80 ℃, the digestion tank is taken out and placed into a fume hood, a jacket is unscrewed and taken down, a series of clean 50ml volumetric flasks are taken out, a funnel is arranged, liquid in the digestion tank is transferred into the volumetric flasks through the funnel, the digestion tank is washed by purified water for 3-5 times, filtrate is transferred into the volumetric flasks, after the liquid in the funnel completely flows into the volumetric flasks, the funnel is washed, and after the process is repeated for 3-5 times, the constant volume is adjusted to 50 ml.
(5) ICP test: selecting nine metal elements of Fe, Cr, Cu, Ni, Zn, Co, Al, Ca, Mn and nonmetal S elements, selecting five spectral lines with the maximum intensity for each element, sequentially setting the concentrations of all the element standard solutions to be 0, 0.5, 1, 2 and 5ppm, preparing a mixed standard solution of the nine metal elements and a sulfur standard solution to respectively establish a metal standard line and a sulfur standard line, and measuring the element content of the prepared measuring solution by using ICP (inductively coupled plasma atomic emission spectrometer);
step six: data processing: keeping an element spectral line with a correlation coefficient of the marked line being more than 0.999, selecting an optimal spectral line of each element after adjusting peak types of the standard liquid spectral line and the test liquid spectral line, wherein the average concentration under the spectral line is the concentration of the test liquid, and the calculation formula is as follows:
the element content (ppm) in NMP (test solution concentration-blank average concentration) 50 is the mass of NMP solution after concentration and water addition/(NMP sampling amount before concentration) in digestion tank is formula (1)
The above-mentioned optimum spectral line determination criteria are:
(1) according to the spectral line of which the adjusted peak type is closest to normal distribution;
(2) the spectral line with the highest accuracy;
(3) the spectral line with the best repeatability;
(4) the spectral line with the highest correlation coefficient of the standard curve.
Example 4
(1) Weighing: a dry beaker was weighed and NMP 50.98g was added.
(2) Heating and concentrating: heating and concentrating on an electric hot plate at 220 ℃ until the mass of NMP is 7g, cooling to room temperature, weighing, adding purified water to wash the wall of the beaker for 3-5 times, wherein the total amount of purified water is 9mL, shaking up, and weighing again to obtain the concentrated NMP, wherein the mass of the concentrated NMP is 17.65 g;
if the consumption of the purified water is too much, the concentration of NMP is too low, and the subsequent test result is influenced; if the consumption of the purified water is too low, the concentration of NMP in the solution is too high, and the reaction is too violent in the microwave digestion process.
(3) Microwave digestion: respectively taking the concentrated NMP in three digestion tanks, simultaneously taking three clean digestion tanks as blanks, adding 6ml of concentrated nitric acid to completely bring the sample into the bottom, covering the digestion tank cover, installing an outer sleeve, screwing down, taking the tank with the largest sample weighing amount as a main control tank, putting the tank into a microwave digestion instrument, and digesting according to the following method parameters;
the first step is as follows: heating to 120 ℃ for 6min, keeping for 8min, and keeping the power at 1600W;
the second step is that: heating to 160 ℃ for 5min, keeping for 8min, and keeping the power at 1600W;
the third step: the temperature is increased to 180 ℃ for 5min, the temperature is kept for 8min, and the power is 1600W.
(4) Preparation of a determination solution: after digestion is completed, the temperature in the digestion tank is reduced to be lower than 80 ℃, the digestion tank is taken out and placed into a fume hood, a jacket is unscrewed and taken down, a series of clean 50ml volumetric flasks are taken out, a funnel is arranged, liquid in the digestion tank is transferred into the volumetric flasks through the funnel, the digestion tank is washed by purified water for 3-5 times, filtrate is transferred into the volumetric flasks, after the liquid in the funnel completely flows into the volumetric flasks, the funnel is washed, and after the process is repeated for 3-5 times, the constant volume is adjusted to 50 ml.
(5) ICP test: selecting nine metal elements of Fe, Cr, Cu, Ni, Zn, Co, Al, Ca, Mn and nonmetal S elements, selecting five spectral lines with the maximum intensity for each element, sequentially setting the concentrations of all the element standard solutions to be 0, 0.5, 1, 2 and 5ppm, preparing a mixed standard solution of the nine metal elements and a sulfur standard solution to respectively establish a metal standard line and a sulfur standard line, and measuring the element content of the prepared measuring solution by using ICP (inductively coupled plasma atomic emission spectrometer);
step six: data processing: keeping an element spectral line with a correlation coefficient of the marked line being more than 0.999, selecting an optimal spectral line of each element after adjusting peak types of the standard liquid spectral line and the test liquid spectral line, wherein the average concentration under the spectral line is the concentration of the test liquid, and the calculation formula is as follows:
the element content (ppm) in NMP (test solution concentration-blank average concentration) 50 is the mass of NMP solution after concentration and water addition/(NMP sampling amount before concentration) in digestion tank is formula (1)
The above-mentioned optimum spectral line determination criteria are:
(1) according to the spectral line of which the adjusted peak type is closest to normal distribution;
(2) the spectral line with the highest accuracy;
(3) the spectral line with the best repeatability;
(4) the spectral line with the highest correlation coefficient of the standard curve.
Test example 1 content of relevant elements in test example 1
The standard curves are shown in FIGS. 1-10 (where the x-axis is concentration and the y-axis is test intensity).
As shown in fig. 1, the standard curve of Fe element is 7373x +24.39, correlation coefficient 0.999744; as shown in fig. 2, the standard curve of Cr element is y 14425x +72.74, and the correlation coefficient 0.999762; as shown in fig. 3, the standard curve of Cu element is y — 3250x +0.7318, correlation coefficient 0.999775; as shown in fig. 4, the standard curve of Ni element is y 1192x-1.723, and the correlation coefficient is 0.999431; as shown in fig. 5, the standard curve of Zn element is y 7246x +0.1402, correlation coefficient 0.999763; as shown in fig. 6, the standard curve of Co element is y ═ 6223x +9.492, correlation coefficient 0.999819; as shown in fig. 7, the standard curve of Al element is y 11803x-23.63, and the correlation coefficient is 0.999736; as shown in fig. 8, the standard curve of Ca element is y-29590 x +122.0, correlation coefficient 0.999439; as shown in fig. 9, the standard curve of Mn element is y 67589x +192.1, correlation coefficient 0.999796; as shown in fig. 10, the standard curve of S element is y ═ 51.75x +1.751, correlation coefficient 0.999931.
The contents of the respective elements in example 1 obtained according to the formula (1) are shown in table 1.
TABLE 1 NMP content of each element
Figure RE-GDA0003030963920000101
Test example 2 recovery rate by adding standard
The 10 elements in the sample were spiked to 20ug, and the spiked recovery rates are shown in Table 2.
The recovery rate of the added standard of the spectrum analysis is generally between 90 and 110 percent, and the recovery rate of the added standard of the sample conforms to the range.
TABLE 2 recovery by spiking in spectral analysis
Figure RE-GDA0003030963920000102
As can be seen from Table 2, the accuracy of the detection method of the present invention meets the relevant requirements.
While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (10)

1. A method for detecting the content of N-methylpyrrolidone elements is characterized by comprising the following steps:
s1: weighing sample
Weighing N-methylpyrrolidone and placing the N-methylpyrrolidone in a drying beaker;
s2: concentrating by heating
Heating and concentrating on an electric hot plate, cooling to room temperature, weighing, adding purified water to wash the wall of the beaker, shaking uniformly, and weighing to obtain concentrated N-methylpyrrolidone;
s3: microwave digestion
Placing the concentrated N-methyl pyrrolidone in a digestion tank for digestion treatment;
s4: preparation of assay solution
Transferring the liquid in the digestion tank to a volumetric flask, and carrying out constant volume to obtain a measured liquid;
s5: element content test
Measuring the element content of the measured liquid by using an inductively coupled plasma atomic emission spectrometer;
s6: and (6) data processing.
2. The method for detecting the content of N-methylpyrrolidone elements according to claim 1, wherein step S1 specifically comprises: 45-55g of N-methylpyrrolidone is weighed and placed in a dry beaker.
3. The method for detecting the content of N-methylpyrrolidone elements according to claim 1, wherein in step S2, a dry beaker containing N-methylpyrrolidone is placed on an electric heating plate and heated and concentrated until the mass of N-methylpyrrolidone is 5-10g, the dry beaker is cooled to room temperature, 8-10mL of purified water is added to wash the wall of the beaker, the beaker is shaken well and weighed, and the concentrated N-methylpyrrolidone is obtained.
4. The method as claimed in claim 3, wherein the temperature of the electric heating plate is 200 ℃ to 230 ℃.
5. The method for detecting the content of N-methylpyrrolidone elements according to claim 3 or 4, wherein the content of N-methylpyrrolidone in the concentrated N-methylpyrrolidone is less than or equal to 50%.
6. The method for detecting the content of N-methylpyrrolidone elements according to claim 1, wherein step S3 specifically comprises: weighing 2g of concentrated N-methylpyrrolidone into a digestion tank, adding 6mL of concentrated nitric acid, and sequentially digesting according to the first condition, the second condition and the third condition.
7. The method for detecting the content of N-methylpyrrolidone elements in claim 6, wherein the first condition is that the temperature is increased to 120 ℃ for 6min, the temperature is kept for 8min, and the power is 1600W; the second condition is that the temperature is increased to 160 ℃ within 5min, the temperature is kept for 8min, and the power is 1600W; and the third condition is that the temperature is increased to 180 ℃ within 5min, the temperature is kept for 8min, and the power is 1600W.
8. The method for detecting the content of N-methylpyrrolidone elements according to claim 1, wherein step S5 specifically comprises: preparing a metal element standard solution and a sulfur element standard solution, respectively establishing a metal marking and a sulfur marking, and measuring the element content of the prepared measuring solution by using ICP (inductively coupled plasma).
9. The method for detecting the content of the N-methylpyrrolidone element according to claim 8, wherein the ICP test parameters are specifically as follows: auxiliary gas flow 0.5L/min, atomizer flow 0.5L/min, radio frequency power 1150W, rinsing pump speed 50rpm, analysis pump speed 50rpm, pump stabilization time 5s, test time 30s, test times 3 times.
10. The method for detecting the content of N-methylpyrrolidone elements according to claim 1, wherein step S6 specifically comprises: after the standard liquid spectral line and the test spectral line are adjusted, the average concentration under the spectral line is the concentration of the test liquid, and the calculation formula is as follows:
the element content (ppm) in NMP is (test solution concentration-blank average concentration) × 50 × NMP solution mass after concentration and water addition/(NMP sample amount before concentration × NMP sample amount in digestion tank).
CN202110179536.4A 2021-02-07 2021-02-07 N-methyl pyrrolidone element content detection method Pending CN112986218A (en)

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