CN117368369A - Method for measuring moisture content in cleaning agent - Google Patents
Method for measuring moisture content in cleaning agent Download PDFInfo
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- CN117368369A CN117368369A CN202311470420.1A CN202311470420A CN117368369A CN 117368369 A CN117368369 A CN 117368369A CN 202311470420 A CN202311470420 A CN 202311470420A CN 117368369 A CN117368369 A CN 117368369A
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- 239000012459 cleaning agent Substances 0.000 title claims abstract description 104
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- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 58
- 238000000605 extraction Methods 0.000 claims description 47
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 44
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- 238000004364 calculation method Methods 0.000 claims description 5
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- 230000001988 toxicity Effects 0.000 abstract description 2
- 238000004817 gas chromatography Methods 0.000 description 13
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 12
- 230000000694 effects Effects 0.000 description 10
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- 206010010071 Coma Diseases 0.000 description 2
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- XVMSFILGAMDHEY-UHFFFAOYSA-N 6-(4-aminophenyl)sulfonylpyridin-3-amine Chemical compound C1=CC(N)=CC=C1S(=O)(=O)C1=CC=C(N)C=N1 XVMSFILGAMDHEY-UHFFFAOYSA-N 0.000 description 1
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- 150000001298 alcohols Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- VEFXTGTZJOWDOF-UHFFFAOYSA-N benzene;hydrate Chemical compound O.C1=CC=CC=C1 VEFXTGTZJOWDOF-UHFFFAOYSA-N 0.000 description 1
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- DZVVLBSDPBGJEM-UHFFFAOYSA-N heptane;hydrate Chemical compound O.CCCCCCC DZVVLBSDPBGJEM-UHFFFAOYSA-N 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
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- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/28—Control of physical parameters of the fluid carrier
- G01N30/30—Control of physical parameters of the fluid carrier of temperature
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/28—Control of physical parameters of the fluid carrier
- G01N30/32—Control of physical parameters of the fluid carrier of pressure or speed
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/62—Detectors specially adapted therefor
- G01N30/64—Electrical detectors
- G01N30/66—Thermal conductivity detectors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/86—Signal analysis
- G01N30/8675—Evaluation, i.e. decoding of the signal into analytical information
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N2030/062—Preparation extracting sample from raw material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/28—Control of physical parameters of the fluid carrier
- G01N30/30—Control of physical parameters of the fluid carrier of temperature
- G01N2030/3007—Control of physical parameters of the fluid carrier of temperature same temperature for whole column
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/28—Control of physical parameters of the fluid carrier
- G01N30/32—Control of physical parameters of the fluid carrier of pressure or speed
- G01N2030/324—Control of physical parameters of the fluid carrier of pressure or speed speed, flow rate
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- Physics & Mathematics (AREA)
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- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
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Abstract
The invention discloses a method for determining the moisture content in a cleaning agent, and relates to the technical field of analysis and test. The method for measuring the moisture content in the cleaning agent has the advantages of simple steps, high sensitivity, good repeatability, short analysis time and accurate and reliable data; compared with a Karl Fischer method, the method for measuring the moisture content in the cleaning agent has the advantages that the toxicity of the used reagent is low, the using amount is low, the damage to human bodies is small, the environmental pollution is reduced, the batch test can be performed, and the test efficiency is improved; compared with an external standard method and an internal standard method, the method for measuring the moisture content in the cleaning agent has the advantages that the dosage of the reagent is small, a working curve is not required to be prepared, the uncertainty introduced in the preparation process is reduced, and the data are accurate; the invention adopts GC-TCD for measurement, has proper sensitivity and wide moisture test range, responds to various substances capable of doing chromatography, and has lower cost and easier equipment maintenance.
Description
Technical Field
The invention relates to the technical field of analysis and test, in particular to a method for measuring the moisture content in a cleaning agent.
Background
Cleaning agents (including liquid chemicals or formulations) are often used in industrial production and service activities to remove equipment, products, equipment, and surface soils using related principles of chemical dissolution, complexation, emulsification, permeation, dispersion, stripping, etc. of cleaning agents. The main components of the cleaning agent comprise water, surfactants, alcohols, organic hydrocarbons, halogenated hydrocarbons and other organic substances, and the organic substances become main factors of environmental pollution and have great influence on human health. The moisture is used as a main solvent or a dispersion medium of the cleaning agent, and the content of the moisture has an important influence on the detection result of the volatile organic compounds. The test method for the moisture content of the cleaning agent specified in the standard of the limit value of the content of the volatile organic compounds of the cleaning agent is a Karl Fischer method, and the method is an internationally recognized moisture quantification method. However, there are many problems in using the karl fischer method to measure the moisture of cleaning agents, such as 1) the sample weighing requirements are more stringent: in order to achieve the best titration effect, when a 5mL burette is used, the volume of the Karl Fischer reagent needs to be ensured to be 1.3-2.5 mL, namely 26-50% of the volume of the burette. Therefore, the sample weighing amount needs to be adjusted according to the moisture content in the sample, so that a better test result is achieved. 2) The influence of the ambient humidity on the test result is large, and the requirement on the test environment is high: air humidity is the most significant cause of errors in karl fischer titration, and moisture can enter the sample, titrant and titration bench. 3) The volume of the titration cup is only 120mL, and the reagent needs to be replaced frequently when the sample is more, so that the test efficiency is affected. 4) The electrode is easily contaminated, and when the sample is relatively viscous, the sample may wrap around the electrode, resulting in an inability to titrate to the endpoint. 5) The components of the sample are complex and various, and the Karl Fischer reagent used for the samples with different components is different. The specification of the karl fischer reagent varies according to the moisture content in the sample. 6) The karl fischer reagent is more toxic: a solution consisting essentially of iodine, sulfur dioxide, pyridine and methanol. Sulfur dioxide and pyridine in the composition have great harm to human bodies, and the inhalation of high-concentration steam can produce symptoms such as dizziness, numbness, spasm, inappetence, coma and the like. Vapor and liquid seriously damage the eye. Mistaking damages central nerves, especially optic nerves, and severe blindness; damage to kidneys, liver and heart, severe cases can cause coma and death. 7) The karl fischer method can not be used for batch testing, needs artificial sample injection and has lower testing efficiency.
In the prior art, various moisture content measurement standards and methods are disclosed, such as GB/T2366-2008 gas chromatography for measuring water content in chemical products, but the standard defines the application range of 0.003-1.0% of water content (mass fraction), and the application range is narrow; the standard experiment process is complex and tedious in operation, and the normal heptane-water saturated solution standard sample or the benzene-water saturated solution standard sample needs to be prepared, so that the uncertainty and the danger are high. GB/T41953-2022 gas chromatography for determining moisture content in paints and varnishes the standard recommended method uses hydrogen carrier gas, which has the characteristics of inflammability, explosiveness and higher risk; the standard adopts split sample injection, the split ratio is 5:1, the peak shape of the chromatogram is wide and fat, the response value is large, the response is easy to saturate when a sample with large moisture content is tested, and the test is inaccurate; the carrier gas flow is 6.5L/min, the flow speed is too high, the column effect of the chromatographic column is easy to be reduced, the peak-out time of the target compound is too high, and the peak-shaped trailing is obvious; the quantitative method in the standard judges the sample weighing quality according to the range of the expected water content, ensures the water content in the final test solution to be about 0.4g, and when the water content in the sample is low, the sample consumption is large, the extraction effect is affected, and the data is unreliable. The prior literature provides for the determination of moisture content using a gas chromatograph-mass spectrometer analysis method, but suffers from the following disadvantages: 1) Water and isopropanol are strong polar compounds, and are analyzed by using a nonpolar chromatographic column in the literature, so that chromatographic peak tailing is serious and separation effect is poor. 2) The curve preparation process is relatively complex, and has more interference factors, so that the result is unstable. The curve range has a certain limitation, the water content range of the cleaning agent is 0% -95% or even higher, and the curve range needs to be adjusted according to the water content of the sample in the test process. 3) Moisture can affect the sensitivity of the mass spectrometer and thus the accuracy of the detection results. The long-term use has larger damage to instruments and higher laboratory cost.
Compared with various problems in the use process of the Karl Fei Xiuyi, the gas chromatography technology has the advantages of rapidness, good reproducibility, high precision, batch test and the like, which are obvious compared with other methods, consumable materials and reagents used in the experimental process are safer than Karl Fischer reagents, and are commonly applied to the measurement of the moisture content in the paint, but the moisture content of the cleaning agent is not related to the gas chromatography method in the current standards and documents.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for measuring the moisture content in a cleaning agent.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a method of determining the moisture content of a cleaning agent comprising the steps of:
(1) Carrying out water removal treatment on the internal standard solution and the extraction solvent;
(2) Primary screening of moisture content in samples: weighing a sample, uniformly mixing an internal standard solution and an extraction solvent, extracting supernatant, and testing by adopting a gas chromatography-thermal conductivity detector to obtain peak areas of moisture and the internal standard solution in the sample, and roughly measuring the moisture content of the sample according to the ratio of the moisture to the internal standard solution in the sample;
(3) Calculation of the relative correction factor R: weighing an internal standard solution and ultrapure water which have the same mass as the water content of the sample in the step (2), adding an extraction solvent, uniformly mixing, extracting supernatant, and testing by adopting a gas chromatography-thermal conductivity detector to obtain peak areas of the internal standard solution and the ultrapure water, and calculating a relative correction factor R=m according to the following formula Internal standard: (A water and its preparation method -A Blank space )/m Water and its preparation method /A Internal standard Wherein: r is the relative response factor of water, m internal standard is the mass of an internal standard, A water is the peak area of water, A blank is the peak area of water in a blank sample, m water is the mass of water, and A internal standard is the peak area of an internal standard;
(4) Determination of moisture content in sample: weighing the sample with the same mass as the sample in the step (2) and an internal standard solution with the same mass as the moisture content of the sample in the step (2), adding an extraction solvent, uniformly mixing, extracting supernatant, testing by adopting a gas chromatography-thermal conductivity detector, and calculating the moisture content in the sample according to the following formula: w (W) Water and its preparation method ＝(A Water and its preparation method -A Blank space )*m Internal standard /A Internal standard /R/m Sample of *100%, wherein m is the moisture content of the sample, R is the relative response factor of water, m internal standard is the mass of the internal standard, A water is the peak area of water, A blank is the peak area of water in the blank, A internal standard is the peak area of the internal standard, W water is the moisture content (%) of the sample, and m sample is the mass of the sample.
Based on the problems of the existing method for measuring the moisture content in the cleaning agent, such as the fact that the measurement result is easy to be interfered by environmental conditions, the Karl Fischer method has complex operation steps, poor parallelism and poor repeatability of the measurement result, the method for measuring the moisture content in the cleaning agent is simple and feasible and is easy to operate, the method for measuring the moisture content in the cleaning agent is low in using amount of reagents, does not need to prepare a working curve, reduces uncertainty introduced in the preparation process, and is accurate in data; the method of the invention utilizes the relative correction factors which are equal to the moisture content in the sample and are brought into the formula to calculate the mass fraction of the moisture, and the test result data is stable, accurate and reliable.
As a preferred embodiment of the method for measuring the moisture content in a cleaning agent according to the present invention, the sample sampling amount in the step (2) is 0.6g. The present inventors have found through a large number of experiments that, when the sampling amount of the sample is 0.6g, the extraction effect of the sample is the best and the sample amount is representative.
As a preferred embodiment of the method for determining the moisture content in a cleaning agent according to the present invention, the internal standard solution is isopropyl alcohol.
As a preferred embodiment of the method for determining the moisture content in a cleaning agent according to the present invention, the extraction solvent includes N, N-dimethylformamide. Acetonitrile, methanol, ethyl acetate and N, N-dimethylformamide are common extraction solutions, and the inventor of the application researches and discovers that when N, N-dimethylformamide is selected as an extraction solvent, the measurement result of the moisture content in the cleaning agent is closest to the true value of the moisture.
As a preferred embodiment of the method for determining the moisture content in a cleaning agent according to the present invention, the temperature-raising program of the gas chromatography-thermal conductivity detector is kept for 3min at an initial temperature of 100 ℃; heating to 180 ℃ at a speed of 10 ℃/min and keeping for 2min; heating to 260 deg.C and holding for 4min.
As a preferred implementation mode of the method for determining the moisture content in the cleaning agent, the temperature of the sample inlet of the gas chromatography-thermal conductivity detector is 250 ℃, the carrier gas is helium, and split sample injection is adopted, wherein the split ratio is 50-250: 1.
as a preferred embodiment of the method for determining the moisture content in a cleaning agent according to the present invention, when the moisture content of a sample is less than 70%, the split ratio is 100:1, a step of; when the moisture content of the sample is greater than 70%, the split ratio is 250:1. the inventor of the application researches find that the split ratio has an influence on the accuracy of a measurement result of the moisture content in the cleaning agent, when a sample with the moisture content below 70% is measured, the split ratio is set to be 100:1, and the deviation between the measurement result and a true value is minimum; when the moisture content of the sample is measured to be more than 70%, the split ratio is set to be 250:1, and the deviation between the test result and the true value is minimum.
As a preferred embodiment of the method for measuring the moisture content in a cleaning agent according to the present invention, the gas chromatography-thermal conductivity detector uses a column of HP-PLOT/Q, the column having a length of 30m, a film thickness of 20 μm and an inner diameter of 0.32mm.
As a preferred embodiment of the method for determining the moisture content in a cleaning agent according to the present invention, the column flow rate of the gas chromatography-thermal conductivity detector is 1.5mL/min.
As a preferred embodiment of the method for determining the moisture content in a cleaning agent according to the present invention, the water removal treatment in the step (1) specifically includes: the internal standard solution and the extraction solvent were added with a 3A molecular sieve and allowed to stand for half an hour.
As a preferred embodiment of the method for measuring the moisture content in a cleaning agent according to the present invention, the extraction in the method for measuring the moisture content in a cleaning agent according to the present invention employs vortex oscillation extraction. The inventors of the present application have found that the use of vortex-oscillation extraction allows the final measured moisture content value to be closer to the moisture true value than ultrasonic extraction. More preferably, the vortex oscillation extraction is specifically vortex oscillation until uniform mixing.
The invention also provides application of the method for measuring the moisture content in the cleaning agent in measuring the moisture content of the cleaning agent.
The invention has the beneficial effects that: the method for measuring the moisture content in the cleaning agent is simple in steps, high in sensitivity, good in repeatability, short in analysis time and accurate and reliable in data; compared with a Karl Fischer method, the method for measuring the moisture content in the cleaning agent has the advantages that the toxicity of the used reagent is low, the using amount is low, the damage to human bodies is small, the environmental pollution is reduced, the batch test can be performed, and the test efficiency is improved; compared with an external standard method and an internal standard method, the method for measuring the moisture content in the cleaning agent has the advantages that the dosage of the reagent is small, a working curve is not required to be prepared, the uncertainty introduced in the preparation process is reduced, and the data are accurate; the invention adopts GC-TCD for measurement, has proper sensitivity and wide moisture test range, responds to various substances capable of doing chromatography, and has lower cost and easier equipment maintenance.
Drawings
FIG. 1 is a gas chromatogram of the method for measuring the moisture content in a cleaning agent of example 1.
FIG. 2 is a gas chromatogram of the method of determining the moisture content in a cleaning agent of example 2.
FIG. 3 is a graph showing analysis results of the measurement of the water content of the same cleaning agent in example 1 and comparative examples 1 and 2.
FIG. 4 shows the deviation comparison of the results of the gas chromatography and gas chromatography mass spectrometry measurements of example 1, GB/T41953-2022 determination of moisture content in paints and varnishes.
FIG. 5 is a mass spectrum of a method for measuring moisture content in a cleaning agent of example 1.
FIG. 6 is a mass spectrum of GB/T41953-2022 gas chromatography for determination of moisture content in paints and varnishes.
Fig. 7 is a mass spectrum of a gas chromatography mass spectrometry.
Detailed Description
The above-described aspects of the present invention will be described in further detail below with reference to specific embodiments in the form of examples. It should not be understood that the scope of the above subject matter of the present invention is limited to the following examples only. All techniques implemented based on the above description of the invention are within the scope of the invention.
Laboratory instrument and reagent
Gas chromatograph (equipped with thermal conductivity detector): agilent 7890B, agilent corporation, USA;
precision electronic analytical balance: the precision is 0.1mg,METTLER TOLEDO;
ultrasonic cleaner: KQ-300DE, suzhou Jiang Dong precision instruments Co., ltd
Reagent: methanol, acetonitrile, N-dimethylformamide, ethyl acetate, HPLC grade.
Example 1
The embodiment provides a method for determining the moisture content in a cleaning agent, which comprises the following steps:
(1) Adding a 3A molecular sieve into N, N-dimethylformamide and isopropanol in advance, and standing for half an hour for use;
(2) Primary screening of moisture content in samples: accurately weighing 0.6g in a sample bottle, adding 0.2g isopropanol, adding 5mL N, N-dimethylformamide, covering the cover, shaking thoroughly by vortex oscillation, standing for 1Filtering the supernatant with 0.45 μm organic phase needle filter into 2mL chromatographic vial for 0min, compacting the cap, and testing with gas chromatography-thermal conductivity detector; analyzing to obtain the peak area of water and isopropanol, and determining the mass m of the internal standard substance to be added by roughly measuring the water content in the sample according to the ratio of the peak area to the internal standard peak area 0 ；
(3) Calculation of the relative correction factor R: accurately weigh distilled water m 0 g and isopropanol m 0 g, adding 5mL of N, N-dimethylformamide, covering a cover, shaking thoroughly by vortex oscillation, standing for 10min, filtering the supernatant into 2mL chromatographic vials by using a 0.45 μm organic phase needle filter, compacting the vial cover, testing by using a gas chromatograph-thermal conductivity detector to obtain peak areas of an internal standard solution and ultrapure water, and calculating a relative correction factor R=m according to the following formula Internal standard: (A water and its preparation method -A Blank space )/m Water and its preparation method /A Internal standard ，
Wherein: r is the relative response factor of water, m internal standard is the mass of an internal standard, A water is the peak area of water, A blank is the peak area of water in a blank sample, m water is the mass of water, and A internal standard is the peak area of an internal standard;
(4) Determination of moisture content in sample: accurately weighing 0.6g into a sample bottle, adding m 0 g isopropyl alcohol (internal standard), adding 5mL N, N-dimethylformamide, covering a cover, shaking by vortex shaking fully, standing for 10min, filtering the supernatant by a 0.45 μm organic phase needle filter into a 2mL chromatographic vial, compacting the cover, testing by a gas chromatography-thermal conductivity detector, and calculating to obtain the moisture content in the sample according to the following formula: w (W) Water and its preparation method ＝(A Water and its preparation method -A Blank space )*m Internal standard /A Internal standard /R/m Sample of *100％，
Wherein m is the water content in the sample, R is the relative response factor of water, m internal standard is the mass of the internal standard, A water is the peak area of water, A blank is the peak area of water in the blank sample, A internal standard is the peak area of the internal standard, W water is the water content (%) in the sample, and m sample is the mass of the sample.
The gas chromatography conditions of this example are specifically: chromatographic column: HP-PLOT/Q (length 30m, film thickness 20 μm, inner diameter 0.32 mm); sample inlet temperature: 250 ℃; carrier gas: helium (99.999% purity); sample injection mode: split, split ratio: 100:1; chromatographic column flow rate: 1.5mL/min; heating program: the initial temperature is 100 ℃, kept for 3min, and the temperature is raised to 180 ℃ at the speed of 10 ℃/min, and kept for 2min; heating to 260 deg.C and holding for 4min.
Example 2
The present embodiment provides a method for measuring the moisture content in a cleaning agent, and the method for measuring the moisture content in the cleaning agent in the present embodiment is different from that in embodiment 1 only in the temperature increasing program of gas chromatography, and specifically the temperature increasing program of gas chromatography in the present embodiment is as follows: the initial temperature is 100 ℃, kept for 3min, and the temperature is raised to 180 ℃ at the speed of 5 ℃/min, and kept for 4min; heating to 260 deg.C and holding for 4min.
Example 3
The present example provides a method for measuring the moisture content in a cleaning agent, and the method for measuring the moisture content in a cleaning agent of the present example is different from example 1 only in the column flow rate, and the column flow rate of the gas chromatograph of the present example is 1.0mL/min.
Example 4
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in a cleaning agent in this embodiment is different from that in embodiment 1 only in the split ratio, and the split ratio in this embodiment is 50:1.
example 5
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in a cleaning agent in this embodiment is different from that in embodiment 1 only in terms of the split ratio, and the split ratio in this embodiment is 200:1.
example 6
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in a cleaning agent in this embodiment is different from that in embodiment 1 only in the split ratio, and the split ratio in this embodiment is 250:1.
example 7
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in a cleaning agent in this embodiment is different from that in embodiment 1 only in the split ratio, and the split ratio in this embodiment is 300:1.
example 8
The present embodiment provides a method for measuring the moisture content in a cleaning agent, and the method for measuring the moisture content in a cleaning agent of the present embodiment is different from that of embodiment 1 in that only the extraction solvent is acetonitrile.
Example 9
The present embodiment provides a method for measuring the moisture content in a cleaning agent, and the method for measuring the moisture content in a cleaning agent of the present embodiment is different from that of embodiment 1 in that only the extraction solvent is methanol.
Example 10
The present embodiment provides a method for measuring the moisture content in a cleaning agent, and the method for measuring the moisture content in a cleaning agent of the present embodiment is different from that of embodiment 1 only in that the extraction solvent is ethyl acetate.
Example 11
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in the cleaning agent in this embodiment is different from that in embodiment 1 only in terms of extraction, and the extraction in this embodiment specifically includes: the ultrasonic power is 100% and the extraction time is 5min.
Example 12
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in the cleaning agent in this embodiment is different from that in embodiment 1 only in terms of extraction, and the extraction in this embodiment specifically includes: the ultrasonic power is 100%, and the extraction time is 10min.
Example 13
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in the cleaning agent in this embodiment is different from that in embodiment 1 only in terms of extraction, and the extraction in this embodiment specifically includes: the ultrasonic power is 100%, and the extraction time is 15min.
Example 14
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in the cleaning agent in this embodiment is different from that in embodiment 1 only in terms of extraction, and the extraction in this embodiment specifically includes: the ultrasonic power is 100%, and the extraction time is 20min.
Example 15
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in the cleaning agent in this embodiment is different from that in embodiment 1 only in terms of extraction, and the extraction in this embodiment specifically includes: the ultrasonic power is 100%, and the extraction time is 30min.
Example 16
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in the cleaning agent in this embodiment is different from that in embodiment 1 only in terms of extraction, and the extraction in this embodiment specifically includes: the ultrasonic power is 100%, and the extraction time is 40min.
Example 17
The present embodiment provides a method for determining the moisture content in a cleaning agent, and the method for determining the moisture content in the cleaning agent in this embodiment is different from that in embodiment 1 only in terms of extraction, and the extraction in this embodiment specifically includes: the ultrasonic power is 100% and the extraction time is 50min.
Comparative example 1
The comparative example provides a method for determining the moisture content in a cleaning agent, comprising the steps of:
(1) Adding a 3A molecular sieve into N, N-dimethylformamide and isopropanol in advance, and standing for half an hour for use;
(2) Primary screening of moisture content in samples: accurately weighing 0.6g in a sample bottle, adding 0.2g isopropyl alcohol, adding 5mL N, N-dimethylformamide, covering a cover, shaking uniformly by vortex oscillation, standing for 10min, filtering the supernatant by a 0.45 μm organic phase needle filter into a 2mL chromatographic vial, compacting the cover, and testing by a gas chromatography-thermal conductivity detector; analysis to obtain water content and different contentThe water content in the sample is roughly measured according to the ratio of the peak area of the propanol to the peak area of the internal standard, so as to determine the mass m of the internal standard to be added 0 ；
(3) Calculation of the relative correction factor R: accurately weighing distilled water 1/3m 0 g and isopropanol 1/3m 0 g, adding 5mL of N, N-dimethylformamide, covering a cover, shaking thoroughly by vortex oscillation, standing for 10min, filtering the supernatant into 2mL chromatographic vials by using a 0.45 μm organic phase needle filter, compacting the vial cover, testing by using a gas chromatograph-thermal conductivity detector to obtain peak areas of an internal standard solution and ultrapure water, and calculating a relative correction factor R=m according to the following formula Internal standard: (A water and its preparation method -A Blank space )/m Water and its preparation method /A Internal standard ，
Wherein: r is the relative response factor of water, m internal standard is the mass of an internal standard, A water is the peak area of water, A blank is the peak area of water in a blank sample, m water is the mass of water, and A internal standard is the peak area of an internal standard;
(4) Determination of moisture content in sample: accurately weighing 0.6g into a sample bottle, adding 1/3m 0 g isopropyl alcohol (internal standard), adding 5mL N, N-dimethylformamide, covering a cover, shaking by vortex shaking fully, standing for 10min, filtering the supernatant by a 0.45 μm organic phase needle filter into a 2mL chromatographic vial, compacting the cover, testing by a gas chromatography-thermal conductivity detector, and calculating to obtain the moisture content in the sample according to the following formula: w (W) Water and its preparation method ＝(A Water and its preparation method -A Blank space )*m Internal standard /A Internal standard /R/m Sample of *100％，
Wherein m is the water content in the sample, R is the relative response factor of water, m internal standard is the mass of the internal standard, A water is the peak area of water, A blank is the peak area of water in the blank sample, A internal standard is the peak area of the internal standard, W water is the water content (%) in the sample, and m sample is the mass of the sample.
The gas chromatography conditions of this comparative example are specifically: chromatographic column: HP-PLOT/Q (length 30m, film thickness 20 μm, inner diameter 0.32 mm); sample inlet temperature: 250 ℃; carrier gas: helium (99.999% purity); sample injection mode: split, split ratio: 100:1; chromatographic column flow rate: 1.5mL/min; heating program: the initial temperature is 100 ℃, kept for 3min, and the temperature is raised to 180 ℃ at the speed of 10 ℃/min, and kept for 2min; heating to 260 deg.C and holding for 4min.
Comparative example 2
The comparative example provides a method for determining the moisture content in a cleaning agent, comprising the steps of:
(1) Adding a 3A molecular sieve into N, N-dimethylformamide and isopropanol in advance, and standing for half an hour for use;
(2) Primary screening of moisture content in samples: accurately weighing 0.6g in a sample bottle, adding 0.2g isopropyl alcohol, adding 5mL N, N-dimethylformamide, covering a cover, shaking uniformly by vortex oscillation, standing for 10min, filtering the supernatant by a 0.45 μm organic phase needle filter into a 2mL chromatographic vial, compacting the cover, and testing by a gas chromatography-thermal conductivity detector; analyzing to obtain the peak area of water and isopropanol, and determining the mass m of the internal standard substance to be added by roughly measuring the water content in the sample according to the ratio of the peak area to the internal standard peak area 0 ；
(3) Calculation of the relative correction factor R: accurately weighing distilled water 2/3m 0 g and isopropanol 2/3m 0 g, adding 5mL of N, N-dimethylformamide, covering a cover, shaking thoroughly by vortex oscillation, standing for 10min, filtering the supernatant into 2mL chromatographic vials by using a 0.45 μm organic phase needle filter, compacting the vial cover, testing by using a gas chromatograph-thermal conductivity detector to obtain peak areas of an internal standard solution and ultrapure water, and calculating a relative correction factor R=m according to the following formula Internal standard: (A water and its preparation method -A Blank space )/m Water and its preparation method /A Internal standard ，
Wherein: r is the relative response factor of water, m internal standard is the mass of an internal standard, A water is the peak area of water, A blank is the peak area of water in a blank sample, m water is the mass of water, and A internal standard is the peak area of an internal standard;
(4) Determination of moisture content in sample: accurately weighing 0.6g into a sample bottle, adding 2/3m 0 g isopropyl alcohol (internal standard), adding 5mL N, N-dimethylformamide, covering the cover, shaking thoroughly by vortex, standing for 10min, collecting supernatant, and passing through 0.45 μm organic solventThe phase needle filter was filtered into a 2mL chromatographic vial, the vial cap was compressed, and tested using a gas chromatograph-thermal conductivity detector, and the moisture content of the sample was calculated according to the following formula: w (W) Water and its preparation method ＝(A Water and its preparation method -A Blank space )*m Internal standard /A Internal standard /R/m Sample of *100％，
Wherein m is the water content in the sample, R is the relative response factor of water, m internal standard is the mass of the internal standard, A water is the peak area of water, A blank is the peak area of water in the blank sample, A internal standard is the peak area of the internal standard, W water is the water content (%) in the sample, and m sample is the mass of the sample.
The gas chromatography conditions of this comparative example are specifically: chromatographic column: HP-PLOT/Q (length 30m, film thickness 20 μm, inner diameter 0.32 mm); sample inlet temperature: 250 ℃; carrier gas: helium (99.999% purity); sample injection mode: split, split ratio: 100:1; chromatographic column flow rate: 1.5mL/min; heating program: the initial temperature is 100 ℃, kept for 3min, and the temperature is raised to 180 ℃ at the speed of 10 ℃/min, and kept for 2min; heating to 260 deg.C and holding for 4min.
Effect example
1. The same cleaning agent was subjected to moisture content measurement by the method of measuring moisture content in the cleaning agent of examples 1 and 2, and the gas chromatograms thereof were analyzed, and the results are shown in fig. 1 and 2. As can be seen from fig. 1 and 2, the gas chromatograph of example 1 has better symmetry of peak shape, no interference of impurity peak around the retention time, and shorter analysis time.
2. The cleaning agents having different moisture contents were measured by the method for measuring moisture contents in the cleaning agents of examples 1 and 4 to 7, and the results are shown in tables 1 to 2.
Table 1 split ratio 50:1 at moisture content < 70%; 100:1;200:1; comparison of cases 250:1 and 300:1
| Sample numbering | Example 4 | Example 1 | Example 5 | Example 6 | Example 7 |
| Deviation of the test average value from the theoretical value of 1% moisture content% | 23.00 | 8.07 | -9.33 | -9.52 | -14.17 |
| Deviation of the test average value from the theoretical value of 5% moisture content% | 5.75 | 1.08 | -3.42 | -4.83 | -4.57 |
| Deviation of the test average value from the 10% moisture content theory value% | 4.21 | 3.16 | 4.26 | -4.91 | 5.07 |
| Deviation of the test average value from the theoretical value of 36% moisture content% | 2.11 | 1.17 | 1.73 | 2.01 | 2.97 |
| Deviation of the test average value from the theoretical value of 50% moisture content% | 4.66 | 1.19 | -2.04 | -1.72 | -2.71 |
| Deviation of the test average value from the 62% moisture content theory value% | -2.64 | -0.65 | 1.21 | 1.03 | -1.07 |
Table 2 split ratio 50:1 at > 70% moisture content; 100:1;200:1; comparison of cases 250:1 and 300:1
As can be seen from tables 1 to 2, when the sample with the moisture content below 70% is measured when the split ratio is set to 100:1, the deviation between the test result and the true value is found to be minimum, and the numerical stability and accuracy are higher; when the split ratio is 100:1, the test result and the true value are found to have larger deviation when the sample with higher moisture content is measured; and when the split ratio is set to be 250:1, the deviation between the test result and the true value is smaller and is closer to the true value when the sample with the water content of more than 70% is measured.
3. The same cleaning agents were subjected to measurement of the moisture content by the method of measuring the moisture content in the cleaning agents of examples 1 and 8 to 10, and the results are shown in table 3.
TABLE 3 Table 3
As shown in Table 3, the test results are closest to the true values when the extraction solvent is acetonitrile and N, N-dimethylformamide, and N, N-dimethylformamide has a high dissolving power and can be mixed with water and most organic solvents at will, so N, N-dimethylformamide is preferable as the extraction reagent.
4. The same cleaning agents were subjected to measurement of the moisture content by the method of measuring the moisture content in the cleaning agents of examples 1 and 11 to 17, and the results are shown in table 4.
TABLE 4 Table 4
As can be seen from table 4, the different extraction modes have an effect on the accuracy of the determination of the moisture content in the cleaning agent, and the deviation of the sample results from the true values is minimal when the sample is subjected to vortex oscillation.
5. The same cleaning agent was measured for the water content value by the method of example 1 and comparative examples 1 and 2. The results are shown in FIG. 3.
As can be seen from fig. 3, when the moisture content in the sample is approximately equal to the peak area of the isopropyl alcohol, the test result is closer to the true value, and when the moisture content is measured, the quality of the internal standard close to the moisture content in the sample is weighed for testing, so that the obtained result is more accurate and has higher reliability.
6. The method for measuring the moisture content in the cleaning agent of example 1 was used for measuring the recovery rate and the precision, and the specific method is as follows: recovery was performed by a blank matrix labelling experiment, using a sample without water as the blank matrix, setting 6 different labelling concentration levels (5%, 15%, 30%, 50%, 80% and 100% moisture content). Each labeled level was tested in parallel 6 times (n=6) and precision experiments were performed.
Under 6 standard adding levels, the standard adding recovery rate of water is 98.8% -99.3%, and the relative standard deviation of the recovery rate is not more than 2%, which indicates that the accuracy of the test method is higher, and the test requirement can be met.
TABLE 5
7. Samples of cleaning agents of different moisture content were tested using the karl fischer method provided in example 1 and the related cleaning agent standard, respectively, and the results are shown in table 6.
TABLE 6
As can be seen from table 6, the accuracy of the method for determining the moisture content in the cleaning agent according to example 1 can meet the karl-fischer test requirements among the standard requirements, even smaller deviation from the true value than the karl-fischer method, and more stable data results.
8. The cleaning agent samples with different moisture contents are respectively detected by adopting a gas chromatography method for measuring moisture content in colored paint and varnish paint of example 1 and GB/T41953-2022 and a gas chromatography mass spectrometry method (cited from patent CN111060630A, a method for measuring moisture content in GC-MS-based water paint), stability of analysis result data and chromatographic peak type and separation degree of spectrograms of each measuring method are compared.
The results are shown in FIGS. 4 to 7. As can be seen from FIG. 4, the method of example 1 has a more stable test result data for the cleaning agent sample and a wider application range, while the other methods have a larger fluctuation degree of data. As is clear from FIG. 5, the method of example 1 has good chromatographic peak separation effect and normal peak shape. Even at higher moisture levels, the peak response is at a preferred level and does not cause detector overload. As is clear from FIGS. 6 and 7, GB/T41953-2022, "gas chromatography for measuring moisture content in paint and varnish", gas chromatography mass spectrometry, shows that there are cases where peak tailing and separation effect are poor.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.
Claims (10)
1. A method for determining the moisture content of a cleaning agent comprising the steps of:
(1) Carrying out water removal treatment on the internal standard solution and the extraction solvent;
(2) Primary screening of moisture content in samples: weighing a sample, uniformly mixing an internal standard solution and an extraction solvent, extracting supernatant, and testing by adopting a gas chromatography-thermal conductivity detector to obtain peak areas of moisture and the internal standard solution in the sample, and roughly measuring the moisture content of the sample according to the ratio of the moisture to the internal standard solution in the sample;
(3) Calculation of the relative correction factor R: weighing an internal standard solution and ultrapure water which have the same mass as the water content of the sample in the step (2), adding an extraction solvent, uniformly mixing, extracting supernatant, and testing by adopting a gas chromatography-thermal conductivity detector to obtain peak areas of the internal standard solution and the ultrapure water, and calculating a relative correction factor R=m according to the following formula Internal standard *(A Water and its preparation method -A Blank space )/m Water and its preparation method /A Internal standard Wherein: r is the relative response factor of water, m Internal standard For the mass of the internal standard substance, A Water and its preparation method Peak area of water, A Blank space Water in blank samplePeak area, m Water and its preparation method For the mass of water, A Internal standard Is the peak area of the internal standard substance;
(4) Determination of moisture content in sample: weighing the sample with the same mass as the sample in the step (2) and an internal standard solution with the same mass as the moisture content of the sample in the step (2), adding an extraction solvent, uniformly mixing, extracting supernatant, testing by adopting a gas chromatography-thermal conductivity detector, and calculating the moisture content in the sample according to the following formula: w (W) Water and its preparation method ＝(A Water and its preparation method -A Blank space )*m Internal standard /A Internal standard /R/m Sample of *100%, where m is the moisture content of the sample, R is the relative response factor of water, m Internal standard For the mass of the internal standard substance, A Water and its preparation method Peak area of water, A Blank space Peak area of water in blank sample, A Internal standard Peak area of internal standard, W Water and its preparation method For the moisture content (%), m in the sample Sample of Is the mass of the sample.
2. The method for determining the moisture content in a cleaning agent according to claim 1, wherein the internal standard solution is isopropyl alcohol.
3. The method of determining the moisture content in a cleaning agent according to claim 1, wherein the extraction solvent comprises N, N-dimethylformamide.
4. The method for determining the moisture content in a cleaning agent according to claim 1, wherein the temperature-raising program of the gas chromatography-thermal conductivity detector is kept for 3 minutes at an initial temperature of 100 ℃; heating to 180 ℃ at a speed of 10 ℃/min and keeping for 2min; heating to 260 deg.C and holding for 4min.
5. The method for determining the moisture content in a cleaning agent according to claim 1, wherein the gas chromatograph-thermal conductivity detector has a sample inlet temperature of 250 ℃, the carrier gas is helium, and split sample injection is adopted, and the split ratio is 50-250: 1.
6. the method for measuring the moisture content in a cleaning agent according to claim 5, wherein when the moisture content of the sample is less than 70%, the split ratio is 100:1, a step of; when the moisture content of the sample is greater than 70%, the split ratio is 250:1.
7. the method for measuring the moisture content in a cleaning agent according to claim 1, wherein the column for the gas chromatography-thermal conductivity detector is HP-PLOT/Q, the column has a length of 30m, a film thickness of 20 μm, and an inner diameter of 0.32mm.
8. The method according to claim 4, wherein the column flow rate of the gas chromatography-thermal conductivity detector is 1.5mL/min.
9. The method for determining the moisture content in a cleaning agent according to claim 1, wherein the water removal treatment in step (1) is specifically: the internal standard solution and the extraction solvent were added with a 3A molecular sieve and allowed to stand for half an hour.
10. Use of the method for determining the moisture content of a cleaning agent according to any one of claims 1 to 9 in the determination of the moisture content of a cleaning agent.
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