Experimental purpose
1、Further understand and be familiar with the principle and structure of UV-spectrophotometer, and learn the operation of ultraviolet spectrophotometer with UV-1700PC as an example.
2、Master the use of ultraviolet spectrophotometry to determine the absorption spectra of benzoic acid and sorbate.
3、Master the standard curve method to determine the content of benzoic acid and sorbate and sodium salt and potassium salt in the sample.
2、Master the use of ultraviolet spectrophotometry to determine the absorption spectra of benzoic acid and sorbate.
3、Master the standard curve method to determine the content of benzoic acid and sorbate and sodium salt and potassium salt in the sample.
Experimental principle
In order to prevent corrosion and deterioration of food during storage and transportation, a small amount of preservatives are often added to food. Benzoic acid has an aromatic structure with K absorption bands and B absorption bands at wavelengths 225nm and 272nm. According to the maximum absorption of benzoic acid (sodium) at 225nm, its absorbance can be measured and the content of benzoic acid in the sample can be obtained by standard curve method. Sorbic acids have α, β-unsaturated carbonyl structure and K absorption band of π-π * transition at wavelength 255nm, so they can be qualitatively identified and quantitatively determined according to their UV absorption spectra.
Experimental instruments and reagents
1.Ultraviolet visible spectrophotometer UV-1700PC（Macylab Instruments Inc.）,25pxquartz cuvette,50mL volumetric flask.
2.HCl solution（1:1）,NaOH solution（40g/L）,NaCl solution（5%）.
3.Preparation of sodium benzoate standard solution
（1）Sodium benzoate standard storage solution（1.000g/L）：Accurately weigh 1.000g of dried sodium benzoate (dried at 105℃ for 2h) in a 1000mL volumetric bottle, dissolve with appropriate amount of distilled water and set the volume. The reserve liquid can be stored in the refrigerator for a period of time.
（2）Sodium benzoate standard solution (32mg/L) : Accurately remove 32.00mL of sodium benzoate reserve solution into 1000mL volumetric bottle, and add distilled water to dilute the constant volume.
（3）Preparation of a series of standard solutions: accurately remove 0.50mL, 1.00mL, 1.50mL, 2.00mL and 2.50mL of sodium benzoate standard solutions into 5 10mL volumetric bottles, and dilute the volume with NaOH solution. The standard solutions of sodium benzoate with concentrations of 1.6mg/L, 3.2mg/L, 4.8mg/L, 6.4mg/L and 8.0mg/L were obtained.
4.Preparation of potassium sorbate standard solution
（1）Potassium sorbate standard storage solution (1.000g/L) : accurately weigh 1.000g dried sodium sorbate (drying at 105℃ for 2h) in a 1000mL volumetric bottle, dissolve with appropriate amount of distilled water and set the volume. The reserve liquid can be stored in the refrigerator for a period of time.
（2）Potassium sorbate standard solution (16mg/L) : Accurately remove 16.00mL potassium sorbate reserve solution into 1000mL volumetric bottle, and add distilled water to dilute the constant volume.
（3）Preparation of a series of standard solutions: 0.50mL, 1.00mL, 1.50mL, 2.00mL and 2.50mL of potassium sorbate standard solutions were accurately removed into 5 10mL volumetric bottles and diluted with NaOH solution. The standard solutions of potassium sorbate with concentrations of 0.8mg/L, 1.6mg/L, 2.4mg/L, 3.2mg/L and 4.0mg/L were obtained.
2.HCl solution（1:1）,NaOH solution（40g/L）,NaCl solution（5%）.
3.Preparation of sodium benzoate standard solution
（1）Sodium benzoate standard storage solution（1.000g/L）：Accurately weigh 1.000g of dried sodium benzoate (dried at 105℃ for 2h) in a 1000mL volumetric bottle, dissolve with appropriate amount of distilled water and set the volume. The reserve liquid can be stored in the refrigerator for a period of time.
（2）Sodium benzoate standard solution (32mg/L) : Accurately remove 32.00mL of sodium benzoate reserve solution into 1000mL volumetric bottle, and add distilled water to dilute the constant volume.
（3）Preparation of a series of standard solutions: accurately remove 0.50mL, 1.00mL, 1.50mL, 2.00mL and 2.50mL of sodium benzoate standard solutions into 5 10mL volumetric bottles, and dilute the volume with NaOH solution. The standard solutions of sodium benzoate with concentrations of 1.6mg/L, 3.2mg/L, 4.8mg/L, 6.4mg/L and 8.0mg/L were obtained.
4.Preparation of potassium sorbate standard solution
（1）Potassium sorbate standard storage solution (1.000g/L) : accurately weigh 1.000g dried sodium sorbate (drying at 105℃ for 2h) in a 1000mL volumetric bottle, dissolve with appropriate amount of distilled water and set the volume. The reserve liquid can be stored in the refrigerator for a period of time.
（2）Potassium sorbate standard solution (16mg/L) : Accurately remove 16.00mL potassium sorbate reserve solution into 1000mL volumetric bottle, and add distilled water to dilute the constant volume.
（3）Preparation of a series of standard solutions: 0.50mL, 1.00mL, 1.50mL, 2.00mL and 2.50mL of potassium sorbate standard solutions were accurately removed into 5 10mL volumetric bottles and diluted with NaOH solution. The standard solutions of potassium sorbate with concentrations of 0.8mg/L, 1.6mg/L, 2.4mg/L, 3.2mg/L and 4.0mg/L were obtained.
Sample pretreatment
Liquid samples: 5mL of soy sauce and vinegar, 10mL of beverage were taken into a 125mL separation funnel, 2mL of hydrochloric acid solution was added for acidification, and then extracted with anhydrous ether three times, 30mL each time, and shaken for 1min each time. The combined ether layer was washed in a 250mL separation funnel with NaCl solution twice, 5-10mL each time. Then the ether was recovered with Soxhlet extractor, dissolved with NaOH solution, and the volume was fixed to 100mL for use.
If the carbonated beverage such as Sprite is used, 1.5ml of the beverage can be directly removed into a 50mL volumetric bottle, and the carbon dioxide can be expelled by ultrasonic degassing for 5min, and then the volume can be diluted with NaOH,
If the carbonated beverage such as Sprite is used, 1.5ml of the beverage can be directly removed into a 50mL volumetric bottle, and the carbon dioxide can be expelled by ultrasonic degassing for 5min, and then the volume can be diluted with NaOH,
Instrument parameters
UV-1700PC ultraviolet and visible spectrophotometer
Characterisitics
UV－1700 has successfully achieved the strict requirements of high precision and high reliability measurement, and can meet the requirements of various applications, which can be used in biological research, biological industry, drug analysis, pharmaceutical, teaching research, environmental protection, food hygiene, clinical testing, health and epidemic prevention and other fields.
Wide wavelength range, can meet the requirements of various fields of wavelength range
The design of large-scale integrated circuits greatly improves the scalability and reliability of the system
Improved and optimized optical path design, imported light sources and receivers result in high system performance and reliability
Rich measurement methods, with wavelength scanning, time scanning, multi-wavelength measurement, multi-order derivative measurement (optional), dual wavelength, three-wavelength (optional) DNA protein measurement (optional) and other measurement methods, can meet the requirements of different measurements, and can be directly displayed on the 6-inch screen
According to the requirements of users, it can choose single hole frame, manual four frame, manual eight frame, automatic eight frame, glass bracket, test tube bracket, 1cm cuvette holder, 5cm cuvette holder, 10cm cuvette holder, etc
*The measurement data can be output through the printer,With USB interface
Power off to save measurement parameters and data, easy to use
More precise and flexible measurement requirements such as spectral scanning can be achieved through PC software control
Technical indicators and basic parameters
Wavelength Range：190～1100nm
spectral bandwidth：1.8nm
wavelength accuracy：±0.3nm
Wavelength repeatability：≤0.1nm
photometric accuracy: ±0.3% τ（0-100%τ）±0.002A(0～0.5A) ±0.003A(0.5A～1A)
photometric repeatability：±0.15% τ（0-100%τ）±0.001A(0～0.5A) ±0.0015A(0.5A～1A)
stray light：≤0.03% τ (220nm NaI，340nm NaNO2)
stability：0.0005A/h（500nmAfter preheating）
photometric Mode: transmittance, absorbance, concentration, energy
Wavelength adjustment: Automatic adjustment
Photometric display range：-4～4A
Display mode: 6-inch high brightness LCD screen
Detector: imported silicon photodiode
Light source: imported deuterium lamp, imported tungsten lamp
power supply：AC 220V/50Hz or 110V/60Hz
power：120W
Instrument dimensions ：560×450×230mm
Wide wavelength range, can meet the requirements of various fields of wavelength range
The design of large-scale integrated circuits greatly improves the scalability and reliability of the system
Improved and optimized optical path design, imported light sources and receivers result in high system performance and reliability
Rich measurement methods, with wavelength scanning, time scanning, multi-wavelength measurement, multi-order derivative measurement (optional), dual wavelength, three-wavelength (optional) DNA protein measurement (optional) and other measurement methods, can meet the requirements of different measurements, and can be directly displayed on the 6-inch screen
According to the requirements of users, it can choose single hole frame, manual four frame, manual eight frame, automatic eight frame, glass bracket, test tube bracket, 1cm cuvette holder, 5cm cuvette holder, 10cm cuvette holder, etc
*The measurement data can be output through the printer,With USB interface
Power off to save measurement parameters and data, easy to use
More precise and flexible measurement requirements such as spectral scanning can be achieved through PC software control
Technical indicators and basic parameters
Wavelength Range：190～1100nm
spectral bandwidth：1.8nm
wavelength accuracy：±0.3nm
Wavelength repeatability：≤0.1nm
photometric accuracy: ±0.3% τ（0-100%τ）±0.002A(0～0.5A) ±0.003A(0.5A～1A)
photometric repeatability：±0.15% τ（0-100%τ）±0.001A(0～0.5A) ±0.0015A(0.5A～1A)
stray light：≤0.03% τ (220nm NaI，340nm NaNO2)
stability：0.0005A/h（500nmAfter preheating）
photometric Mode: transmittance, absorbance, concentration, energy
Wavelength adjustment: Automatic adjustment
Photometric display range：-4～4A
Display mode: 6-inch high brightness LCD screen
Detector: imported silicon photodiode
Light source: imported deuterium lamp, imported tungsten lamp
power supply：AC 220V/50Hz or 110V/60Hz
power：120W
Instrument dimensions ：560×450×230mm
About Us
Macylab Instruments Inc., (hereinafter referred to as Macy), is a high-tech enterprise with independent intellectual property rights, Macy’s entrepreneurial philosophy “science and technology – because you change”, and take this as the enterprise purpose, continuous exploration, bold innovation. Especially in the field of analytical testing instruments, we have continuously developed advanced products, making us a supplier of high-quality instrument resources.
Our Main spectral instruments: visible spectrophotometer, UV-visible spectrophotometer, atomic absorption spectrometer, atomic fluorescence photometer, ICP-AES, ICP-MS, life science instruments: Micro-Volume spectrophotometer, automatic nucleic acid extraction instrument, at present, our products have been widely used in organic chemistry, inorganic chemistry, biochemistry, medicine, environmental protection, metallurgy, petroleum, agriculture and other fields.At the same time, with the rich experience accumulated in product mechanical structure, optical design, electrical application and software development, combined with the latest practical needs of the market, the company will launch a number of new analytical instruments in the near future.
Macy attaches great importance to the introduction and training of talents, the human factor is a core factor for the sustainable development of an enterprise, so Macy fully respects every employee, and truly “build a platform and realize yourself”. To this end, the company has established a strong training team to provide comprehensive training for in-service employees and help employees develop career plans, in order to develop the company and employees together. At the same time, Macylab inspires employees with the professional ethics of “family, dedication and learning”, and every Macylab people are full of enthusiasm and professional skills, and the United States presents every instrument and serves every customer.The importance and respect for talents make all aspects of the company full of rigor and passion, the new design concept, the demanding requirements of high precision and high parameters, the continuous extension of the scope of application, all of which are perfectly presented in the advanced nature of our products；From the strict acceptance of raw materials, to the standard assembly line operation of each process, and then to the strict factory inspection of the quality inspection department,The harsh requirements of the company on all aspects of production make the company establish a complete process quality control system, and the quality of the instrument has been strongly reflected. Therefore, our products are well received by domestic and foreign users.The headquarters and production base of Macy are located in Shanghai, the marketing center is located in Beijing, and the R & D base is set up in Shanghai, Beijing and Jiangsu.In order to make full use of the intellectual resources around the country, Macy has also carried out in-depth scientific research cooperation with some scientific research institutions at home and abroad, and constantly transform scientific research achievements into productive forces.In order to better serve our customers, Macy has 12 offices in China to customize application solutions that meet your needs and improve the added value of products. In the continuous service of domestic users at the same time, Macylab has also established a deep strategic cooperation relationship with more than 20 countries.
With the acceleration of Macy’s pace among the ranks of global brand instruments, Macy’s requirements for itself continue to improve, and we also hope to get care and support from all walks of life, let us work together to look forward. Technology will change because of you and me.
Macy attaches great importance to the introduction and training of talents, the human factor is a core factor for the sustainable development of an enterprise, so Macy fully respects every employee, and truly “build a platform and realize yourself”. To this end, the company has established a strong training team to provide comprehensive training for in-service employees and help employees develop career plans, in order to develop the company and employees together. At the same time, Macylab inspires employees with the professional ethics of “family, dedication and learning”, and every Macylab people are full of enthusiasm and professional skills, and the United States presents every instrument and serves every customer.The importance and respect for talents make all aspects of the company full of rigor and passion, the new design concept, the demanding requirements of high precision and high parameters, the continuous extension of the scope of application, all of which are perfectly presented in the advanced nature of our products；From the strict acceptance of raw materials, to the standard assembly line operation of each process, and then to the strict factory inspection of the quality inspection department,The harsh requirements of the company on all aspects of production make the company establish a complete process quality control system, and the quality of the instrument has been strongly reflected. Therefore, our products are well received by domestic and foreign users.The headquarters and production base of Macy are located in Shanghai, the marketing center is located in Beijing, and the R & D base is set up in Shanghai, Beijing and Jiangsu.In order to make full use of the intellectual resources around the country, Macy has also carried out in-depth scientific research cooperation with some scientific research institutions at home and abroad, and constantly transform scientific research achievements into productive forces.In order to better serve our customers, Macy has 12 offices in China to customize application solutions that meet your needs and improve the added value of products. In the continuous service of domestic users at the same time, Macylab has also established a deep strategic cooperation relationship with more than 20 countries.
With the acceleration of Macy’s pace among the ranks of global brand instruments, Macy’s requirements for itself continue to improve, and we also hope to get care and support from all walks of life, let us work together to look forward. Technology will change because of you and me.
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