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Double beam UV spectrophotometry for the determination of N, N-dimethylacetamide
Date: 2021-04-09Read: 13
Shanghai Spectral AnalysisTU-1901plus
Dual beam ultraviolet spectrophotometry
N,N-Determination of Dimethylacetamide
A UV spectrophotometric method for determining the content of N, N-dimethylacetamide (DMAC) was established based on its strong absorption in the 190-230nm range in the UV absorption spectrum. At 196nm, DMAC conforms to Beer's law within the range of 0-0.8% (volume fraction of 1000 fold dilution of chromatographically pure DMAC), with an R2 of 0.9998. The average recovery rate of actual sample determination is 93.6% to 103.5%, and the relative standard deviation is less than 2.38%. This method has good linear correlation, simple and fast operation, and is suitable for daily detection of N, N-dimethylacetamide in industries such as chemical fiber.
A UV spectrophotometric method for determining the content of N, N-dimethylacetamide (DMAC) was established based on its strong absorption in the 190-230nm range in the UV absorption spectrum. At 196nm, DMAC conforms to Beer's law within the range of 0-0.8% (volume fraction of 1000 fold dilution of chromatographically pure DMAC), with an R2 of 0.9998. The average recovery rate of actual sample determination is 93.6% to 103.5%, and the relative standard deviation is less than 2.38%. This method has good linear correlation, simple and fast operation, and is suitable for daily detection of N, N-dimethylacetamide in industries such as chemical fiber.
N. N-Dimethylacetamide [DMAC, CH3CON (CH3) 2] is an excellent polar solvent and important chemical raw material, with polar and non-polar groups. It can be miscible with organic solvents such as water, alcohols, ethers, esters, etc. It is mainly used as a solvent in the production of synthetic fibers such as spandex and acrylic fibers and some synthetic resins. It can also be used as an additive in the production of pharmaceuticals, coatings, and catalysts, and as a raw material for the synthesis of antibiotics and insecticides. DMAC is widely used as a solvent in the production of spandex and acrylic fibers, and its quality requirements are relatively high. At present, the domestic demand for DMAC products still mainly relies on imports. In addition, DMAC is toxic to the human body and harmful to the environment. Therefore, whether from the perspective of improving economic efficiency or protecting personnel health and ecological environment, it is particularly important to achieve rapid and accurate detection of its content. The DMAC determination method reported is mainly gas chromatography, which is used for monitoring workshop air, water, and wastewater. However, the instruments used in this method are expensive, the measurement time is long, and the operating costs are also high. This article establishes a UV spectrophotometry method based on the molecular characteristics of DMAC through experiments, and investigates the accuracy and precision of the method. The results show that this method is easy to operate, fast, and accurate, and is suitable for daily detection of DMAC in industries such as spandex and acrylic fiber.
1 Experimental section
1.1 Main instruments and reagents:ultravioletVisible spectrophotometerUltra pure water purifier. DMAC standard solution: Accurately transfer 100 μ L of chromatographically pure DMAC to a 100mL volumetric flask, dilute to the mark with ultrapure water, shake well, and the solution is equivalent to diluting chromatographically pure DMAC 1000 times. The DMAC reagent used in this experiment was provided by a certain spandex company, with chromatographic purity and a mass fraction of 99.9%; The experimental water is ultrapure water, self-made.
1.2 Experimental Method: Accurately add a certain amount of DMAC standard solution to a 50.0mL volumetric flask and dilute to volume with ultrapure water. Using a 1cm quartz cuvette and ultrapure water as a reference, measure the absorbance at 196nm and perform quantitative analysis using UV spectrophotometry.
2 Results and Discussion
2.1 Accurate selection of measurement wavelength: Take 50 μ L and 400 μ L of DMAC standard solution, place them in 50.0mL volumetric flasks, and prepare standard solutions with DMAC standard solution volume fractions of 0.1% and 0.8%, respectively, according to the experimental method. Then, using ultrapure water as a reference, spectral scans (medium speed, 2nm spectral bandwidth) were performed on the above standard solutions in the wavelength range of 190-400nm, and absorption curves were plotted. The results indicate that the maximum absorption wavelength of the measured substances is located at 196nm, and the absorbance values are linearly correlated with the concentration of DMAC. So, the measurement wavelength was chosen to be 196nm. Figure 1 shows the absorption spectrum 0.8% standard solution; 2. 0.1% standard solution
2.2 Accurate Drawing of Standard Curve: Transfer 0 μ L, 50 μ L, 100 μ L, 200 μ L, 300 μ L, and 400 μ L of DMAC standard solution into a 50.0mL volumetric flask, dilute with ultrapure water, and prepare standard series of DMAC standard solution with volume fractions of 0, 0.1%, 0.2%, 0.4%, 0.6%, and 0.8%. Measure the absorbance at a wavelength of 196nm at 1 × 104L · mol-1 · cm-1. The linear regression equation obtained by the least squares method is Y=0.00206X+0.00839 (Y is the absorbance); X is the transfer amount of DMAC standard solution, μL），R2=0.9998。 The results indicate that the volume fraction of DMAC standard solution conforms to Beer's law within the range of 0-0.8% (i.e., the transfer amount of DMAC standard solution in a 50.0mL volumetric flask is 0-400 μ L).
2.3 Sample Determination and Precision Experiment This experiment measured the DMAC content of actual water samples 1 # and 2 # provided by a certain spandex company, and examined the precision of the method. Dilute the two samples 1000 times with ultrapure water, and measure the absorbance according to the experimental method. Obtain the transfer amount (μ L) of DMAC standard solution from the standard curve, convert it to the dilution factor of chromatographically pure DMAC, and calculate the DMAC content in the sample based on the mass fraction of chromatographically pure DMAC being 99.9%. The final result is expressed in mass fraction. Parallel operation 6 times. Table 1 Determination Results of Samples (n=6) Item 1 # 2 # Determination Values/μ L259.5666136.6930254.8862137.826262260.1086140.6525272.6226141.3242259.51741
33.2443265.9714136.0525 average value/μ L262.1121137.6321 mass fraction/% 0.520.27RSD/% 2.382.19 According to Table 1, the relative standard deviation is less than 2.38%, indicating good repeatability of the method.
2.4 Accuracy Experiment
2.4.1 Determination of Relative Error Accurately transfer 40 μ L, 80 μ L, 150 μ L, 250 μ L, 350 μ L, and 450 μ L of DMAC standard solution into a 50.0mL volumetric flask, dilute with ultrapure water, and prepare a standard series of DMAC standard solution with volume fractions of 0.08%, 0.16%, 0.30%, 0.50%, 0.70%, and 0.90%. Use this method for determination. Take 3 parallel samples at each concentration level.
According to Table 2, the relative error is within ± 2.91%, indicating that the accuracy of this method is good.
2.4.2 Determination of Recovery Rate: Add a certain amount of DMAC standard solution to samples 1 # and 2 # respectively for recovery rate determination, and perform parallel operations three times. The average recovery rates of the two samples were 93.6% and 103.5%, respectively, indicating good accuracy of the method. Table 2 Relative Error Determination of Experiment (n=3) Actual Sampling Quantity/μ L Determination Result/μ L Average Determination Result/μ L Relative Error/% 1234036.35870.0037 40.149538.8373-2.918077.570879.2718 80.486779.1098-1.5461 148.9629 155.1836 151.2309 0.. 8867 251.9931 251.5557 254.8118 1.. 4269 346.4212 345.7894 347.8792-0.7447 440.6063 446.7298 443.3603-1.472.5
Precautions
To ensure the accuracy and precision of experimental results, the following points should be noted when using this method to determine DMAC content: (1) Due to the measurement wavelength of 196nm being located at the low end of the ultraviolet region, and DMAC having strong absorption in the range of 190-230nm, theUV visible spectrophotometerThe indicators such as stray light, noise, and wavelength accuracy should be good in order to minimize the systematic errors caused by the instrument to the greatest extent possible; (2) A pipette or pipette with good accuracy and repeatability should be selected to ensure the accuracy of the pipetting operation; (3) The purity of experimental water should be high, and the volumetric flasks, quartz colorimetric dishes, etc. used should be kept clean to minimize errors caused by trace impurities.
3 Conclusion
A new method for determining the content of N, N-dimethylacetamide (DMAC) by UV spectrophotometry was established through experiments. The operation process of this method is simple, fast, with good accuracy and precision, suitable for daily detection of DMAC in industries such as spandex and acrylic fiber.
Shanghai Spectral Analysis Instrument Co., Ltd. is a professional manufacturerDual beam UV visible spectrophotometerThe research and development, production, sales, and service of spectral analysis instruments and laboratory instruments such as UV spectrophotometers, visible spectrophotometers, UV visible spectrophotometers, ultra trace spectrophotometers, etcProfessional manufacturing enterprisesGuided by the development strategy of high starting point in research and development, modern management, and marketization, we have combined our more than ten years of rich product design and manufacturing experience with the advantages of multiple spectrophotometer models and brand products, enabling us to quickly establish ourselves in the domestic market and gradually develop towards the market.
Dual beam ultraviolet spectrophotometry
N,N-Determination of Dimethylacetamide
A UV spectrophotometric method for determining the content of N, N-dimethylacetamide (DMAC) was established based on its strong absorption in the 190-230nm range in the UV absorption spectrum. At 196nm, DMAC conforms to Beer's law within the range of 0-0.8% (volume fraction of 1000 fold dilution of chromatographically pure DMAC), with an R2 of 0.9998. The average recovery rate of actual sample determination is 93.6% to 103.5%, and the relative standard deviation is less than 2.38%. This method has good linear correlation, simple and fast operation, and is suitable for daily detection of N, N-dimethylacetamide in industries such as chemical fiber.
A UV spectrophotometric method for determining the content of N, N-dimethylacetamide (DMAC) was established based on its strong absorption in the 190-230nm range in the UV absorption spectrum. At 196nm, DMAC conforms to Beer's law within the range of 0-0.8% (volume fraction of 1000 fold dilution of chromatographically pure DMAC), with an R2 of 0.9998. The average recovery rate of actual sample determination is 93.6% to 103.5%, and the relative standard deviation is less than 2.38%. This method has good linear correlation, simple and fast operation, and is suitable for daily detection of N, N-dimethylacetamide in industries such as chemical fiber.
N. N-Dimethylacetamide [DMAC, CH3CON (CH3) 2] is an excellent polar solvent and important chemical raw material, with polar and non-polar groups. It can be miscible with organic solvents such as water, alcohols, ethers, esters, etc. It is mainly used as a solvent in the production of synthetic fibers such as spandex and acrylic fibers and some synthetic resins. It can also be used as an additive in the production of pharmaceuticals, coatings, and catalysts, and as a raw material for the synthesis of antibiotics and insecticides. DMAC is widely used as a solvent in the production of spandex and acrylic fibers, and its quality requirements are relatively high. At present, the domestic demand for DMAC products still mainly relies on imports. In addition, DMAC is toxic to the human body and harmful to the environment. Therefore, whether from the perspective of improving economic efficiency or protecting personnel health and ecological environment, it is particularly important to achieve rapid and accurate detection of its content. The DMAC determination method reported is mainly gas chromatography, which is used for monitoring workshop air, water, and wastewater. However, the instruments used in this method are expensive, the measurement time is long, and the operating costs are also high. This article establishes a UV spectrophotometry method based on the molecular characteristics of DMAC through experiments, and investigates the accuracy and precision of the method. The results show that this method is easy to operate, fast, and accurate, and is suitable for daily detection of DMAC in industries such as spandex and acrylic fiber.
1 Experimental section
1.1 Main instruments and reagents:ultravioletVisible spectrophotometerUltra pure water purifier. DMAC standard solution: Accurately transfer 100 μ L of chromatographically pure DMAC to a 100mL volumetric flask, dilute to the mark with ultrapure water, shake well, and the solution is equivalent to diluting chromatographically pure DMAC 1000 times. The DMAC reagent used in this experiment was provided by a certain spandex company, with chromatographic purity and a mass fraction of 99.9%; The experimental water is ultrapure water, self-made.
1.2 Experimental Method: Accurately add a certain amount of DMAC standard solution to a 50.0mL volumetric flask and dilute to volume with ultrapure water. Using a 1cm quartz cuvette and ultrapure water as a reference, measure the absorbance at 196nm and perform quantitative analysis using UV spectrophotometry.
2 Results and Discussion
2.1 Accurate selection of measurement wavelength: Take 50 μ L and 400 μ L of DMAC standard solution, place them in 50.0mL volumetric flasks, and prepare standard solutions with DMAC standard solution volume fractions of 0.1% and 0.8%, respectively, according to the experimental method. Then, using ultrapure water as a reference, spectral scans (medium speed, 2nm spectral bandwidth) were performed on the above standard solutions in the wavelength range of 190-400nm, and absorption curves were plotted. The results indicate that the maximum absorption wavelength of the measured substances is located at 196nm, and the absorbance values are linearly correlated with the concentration of DMAC. So, the measurement wavelength was chosen to be 196nm. Figure 1 shows the absorption spectrum 0.8% standard solution; 2. 0.1% standard solution
2.2 Accurate Drawing of Standard Curve: Transfer 0 μ L, 50 μ L, 100 μ L, 200 μ L, 300 μ L, and 400 μ L of DMAC standard solution into a 50.0mL volumetric flask, dilute with ultrapure water, and prepare standard series of DMAC standard solution with volume fractions of 0, 0.1%, 0.2%, 0.4%, 0.6%, and 0.8%. Measure the absorbance at a wavelength of 196nm at 1 × 104L · mol-1 · cm-1. The linear regression equation obtained by the least squares method is Y=0.00206X+0.00839 (Y is the absorbance); X is the transfer amount of DMAC standard solution, μL），R2=0.9998。 The results indicate that the volume fraction of DMAC standard solution conforms to Beer's law within the range of 0-0.8% (i.e., the transfer amount of DMAC standard solution in a 50.0mL volumetric flask is 0-400 μ L).
2.3 Sample Determination and Precision Experiment This experiment measured the DMAC content of actual water samples 1 # and 2 # provided by a certain spandex company, and examined the precision of the method. Dilute the two samples 1000 times with ultrapure water, and measure the absorbance according to the experimental method. Obtain the transfer amount (μ L) of DMAC standard solution from the standard curve, convert it to the dilution factor of chromatographically pure DMAC, and calculate the DMAC content in the sample based on the mass fraction of chromatographically pure DMAC being 99.9%. The final result is expressed in mass fraction. Parallel operation 6 times. Table 1 Determination Results of Samples (n=6) Item 1 # 2 # Determination Values/μ L259.5666136.6930254.8862137.826262260.1086140.6525272.6226141.3242259.51741
33.2443265.9714136.0525 average value/μ L262.1121137.6321 mass fraction/% 0.520.27RSD/% 2.382.19 According to Table 1, the relative standard deviation is less than 2.38%, indicating good repeatability of the method.
2.4 Accuracy Experiment
2.4.1 Determination of Relative Error Accurately transfer 40 μ L, 80 μ L, 150 μ L, 250 μ L, 350 μ L, and 450 μ L of DMAC standard solution into a 50.0mL volumetric flask, dilute with ultrapure water, and prepare a standard series of DMAC standard solution with volume fractions of 0.08%, 0.16%, 0.30%, 0.50%, 0.70%, and 0.90%. Use this method for determination. Take 3 parallel samples at each concentration level.
According to Table 2, the relative error is within ± 2.91%, indicating that the accuracy of this method is good.
2.4.2 Determination of Recovery Rate: Add a certain amount of DMAC standard solution to samples 1 # and 2 # respectively for recovery rate determination, and perform parallel operations three times. The average recovery rates of the two samples were 93.6% and 103.5%, respectively, indicating good accuracy of the method. Table 2 Relative Error Determination of Experiment (n=3) Actual Sampling Quantity/μ L Determination Result/μ L Average Determination Result/μ L Relative Error/% 1234036.35870.0037 40.149538.8373-2.918077.570879.2718 80.486779.1098-1.5461 148.9629 155.1836 151.2309 0.. 8867 251.9931 251.5557 254.8118 1.. 4269 346.4212 345.7894 347.8792-0.7447 440.6063 446.7298 443.3603-1.472.5
Precautions
To ensure the accuracy and precision of experimental results, the following points should be noted when using this method to determine DMAC content: (1) Due to the measurement wavelength of 196nm being located at the low end of the ultraviolet region, and DMAC having strong absorption in the range of 190-230nm, theUV visible spectrophotometerThe indicators such as stray light, noise, and wavelength accuracy should be good in order to minimize the systematic errors caused by the instrument to the greatest extent possible; (2) A pipette or pipette with good accuracy and repeatability should be selected to ensure the accuracy of the pipetting operation; (3) The purity of experimental water should be high, and the volumetric flasks, quartz colorimetric dishes, etc. used should be kept clean to minimize errors caused by trace impurities.
3 Conclusion
A new method for determining the content of N, N-dimethylacetamide (DMAC) by UV spectrophotometry was established through experiments. The operation process of this method is simple, fast, with good accuracy and precision, suitable for daily detection of DMAC in industries such as spandex and acrylic fiber.
Shanghai Spectral Analysis Instrument Co., Ltd. is a professional manufacturerDual beam UV visible spectrophotometerThe research and development, production, sales, and service of spectral analysis instruments and laboratory instruments such as UV spectrophotometers, visible spectrophotometers, UV visible spectrophotometers, ultra trace spectrophotometers, etcProfessional manufacturing enterprisesGuided by the development strategy of high starting point in research and development, modern management, and marketization, we have combined our more than ten years of rich product design and manufacturing experience with the advantages of multiple spectrophotometer models and brand products, enabling us to quickly establish ourselves in the domestic market and gradually develop towards the market.