Determination scheme of industrial ethylene glycol ultraviolet transmittance

Introduction: Ethylene glycol, also known as glycol. Chemical formula: HOCH2—CH2OH. A simple binary alcohol. It is colorless, odorless, with sweet liquid, which can be mixed with water in any proportion. It is used for solvent, antifreeze and synthetic polyester resin. Ethylene glycol is toxic to animals, the human lethal dose was estimated at 1.6 g / kg, but  it may already cause death if adults take 30ml of it.

Axiom: Place the sample in an absorption of 50mm or 10mm, take water as the reference, to detect its absorption at 220nm, 275nn and 350 nm, the UV transmittance of the sample at 10mm was calculated. If necessary, the dissolved oxygen in the sample can be removed by hydrogen, and then the UV transmittance can be measured.

Instruments and reagents and materials

US Analysis of the UV-1800PC Dual Beam UV Visible Spectrophotometer

Double beam, measured from 200 n m to 400 n m.At 220 nm, the bandwidth was not greater than 2.0 nm, the wavelength accuracy was ± 0.5 nm, and the wavelength repeatability was ± 0.3 nm. When the light transmittance is greater than 50%, the light transmittance accuracy is ± 0.5%. The stray light was no greater than 0.1% at 220 nm. Equipped with paired quartz absorption pools respectively with an optical diameter of 50 mm ± 0. 1 mm or 10 mm ± 0.01 mm, .

Nitrogen stripping device: fix the oil-free pressure relief valve to the nitrogen cylinder,and connected to the flow control valve through a suitable material line (e. g., polyethylene pipe) and the closed glass tube inserted into a 25mL volumetric bottle. All parts need be clean and pollution-free.Samples should avoid contacting with plastic products that contains plasticizer.

Reagent bottle: the capacity of it at least 500 m L, equipped with good sealing Mill bottle cap.

Naphthalene solution (1 mg/L):

After calibration,Titanium oxide standard solution (4% mass fraction) iron oxide wavelength calibrated filter .

After calibration, A standard solution (0.6% mass fraction) standard absorbance filter.

Sodium iodide (or potassium iodide) solution (10 g / L)

Optic light filter of stray light .

Nitrogen: volume fraction> 99.99%, oil-free.

Take sample

Take the sample at a gentle flow rate as per GB / T 6680- -2003, When the distance between the liquid level and the bottle mouth is less than 10 mm, the sampling is stopped, and the storage sample is covered immediately. Samples should avoid shocking violently and be analyzed as soon as possible.

Preparation of instruments

UV-1800PC Double Beam UV Visible Spectrophotometer of Macy Lab

According to the following steps, check the function of the spectrophotometer as specified in JJG682-1990. Wavelength accuracy; recommend using naphthalene solution to test the wavelength accuracy of the spectrophotometer at 220 nm. Using the spectral pure isooctane as the reference,the maximum absorption wavelength of naphthalene was determined by using the 10 mm absorption pool, and the measurement value should be within 220.6 nm 士0. 3 nm, otherwise, the absorbance of the ethylene glycol sample should be measured at a wavelength below 0.6 nm.

Using holmium oxide standard solutions or holmium oxide calibration filters to test the wavelength accuracy, too.

Note: The absorbance of ethylene glycol varies greatly around 220 nm, so the wavelength accuracy at 220 nm should be ensured.

Transmittance accuracy: test the accuracy of spectrometer transmittance with standard solution or standard absorbance filter, should meet the requirements.

Stray light:Measurement of the transmittance of the spectrometer at 220 nm with sodium or potassium iodide solution or stray light filter （That is Stray Light）， shall meet the requirements.

Glassware：Use hydrochloric acid-water-methanol solution (1:3:4, volume ratio) or chromic acid lotion，clean the absorption pool thoroughly and other glassware.

Nitrogen stripping device: thoroughly sweep the pipe with nitrogen.A sample of 20 mL of ethylene glycol was added to a volumetric flask of 25 ml and fed into nitrogen to observe whether the absorbance of the sample at 220 nm decreased with the removal of dissolved oxygen in the ethylene glycol until remain unchanged,to check the purity of the nitrogen gas.

Sample Pretreatment

Usually, the absorbance of the collected sample can be measured directly. If the determination is suspicious, or the sample light transmittance at 220 nm is below the specified critical value (e. g., the product index), samples will be pre-processd.

A sample of 20 mL of ethylene glycol was added to 25ml of a volumetric flask,use a clean closing glass tube to pass the nitrogen to the bottom of the sample for 15 min, keep it with plug.

Note: ethylene glycol has an absorption peak at 180 nm in the far UV zone. When dissolved oxygen (air) in the sample, Loxygen oxygen associate with ethylene glycol, it causes the absorption peak of ethylene glycol to transfer in the long-wave direction, and reduce the light transmittance of ethylene glycol at 220 nm. So the injection of nitrogen into the sample can exclude the effect of rocky oxygen on the light transmittance of ethylene glycol at 220 nm. Nitrogen transfer treatment of fresh samples (storage time within three days), Nitrogen flow rate shall be greater than 50 mL / min, At the same time, the solution is not spattered when bubbling.

Analytical procedure

Adjust the spectrometer to the optimal setting, the bandwidth of 2.0 nm is generally used, because the bandwidth is too small, the baseline noise will increase.

Load reference water in two paired 50 mm or 10 mm quartz absorption pools.Place the absorption pool into the pool holder of the spectrometer, note the orientation of the absorption pool,and the absorbance was measured at 220 nm, 275 nm and 350 nm or at other wavelengths as specified in the relevant product specifications were determined.The absorption pool with high absorbance values was used as the sample pool,the other serves as a reference pool,absorbance values were recorded as a correction value for the absorption pool at different wavelengths.

Note: For a paired absorption pool, its absorption pool correction value should not be greater than 0.01 AU.

Pour out the water from the sample pool and use nitrogen to dryness.Install the pending test sample in the sample pool,take water as the reference,the absorbance values of the samples at each wavelength were measured and recorded.Note that the direction of the absorption pool in the tank frame should be similar to the one-cause in the tank frame.The water in the reference pool shall be replaced for each set of measurements.

Note: You should be very careful when transferring the samples to avoid producing air bubbles and affect the results of the test test.

Empty the absorption pool and rinse with water. Clean the absorption tank according to 7.2 and store it full with water.

Results are calculated

When using a 50 mm absorption pool, the net absorbance at each wavelength at a 10 mm light diameter is calculated as formula1: A:

.........in the formula 1

As —— -Absorbance of samples determined at relevant wavelengths; Ae —— is at the absorbance correction value of the absorption pool at the relevant wavelength.

If a 10 mm absorption pool is used, the net absorbance A at each wavelength under a 10 mm light diameter is calculated by formula: (2),

...........2

10.2 Calculate the light transmittance T at each wavelength at 10 mm light diameter according to formula (3), and the value is expressed as a percentage.

.........3

Reatability limit (after nitrogen stripping)

In the same laboratory,using the same equipment by the same operator , according to the same test method,and the absolute value of the two independent results obtained by testing the same subject independently in a short time,the repetitive limit listed in Table 1 (r),assuming that the repetitive limit (r) does not exceed 5%.

Table 1 The repeatability limit of the UV transmittance of ethylene glycol(after nitrogen stripping) 

Instrument Parameter

UV-1800PC Dual-beam UV-visible spectrophotometer

Instrument Characteristics

*The UV-1800 series uses a dual-beam optical system，a perfect combination of high precision and high reliability measurement, can meet the requirements of various applications,it can be used in biological research, biological industry, drug analysis, pharmaceutical products, teaching and research, environmental protection, food hygiene, clinical testing, health and epidemic prevention and other fields.

Introduction

●UV-1800 successful implementation of the stringent requirements of high accuracy and reliability measurement to meet the requirements of various applications that can be used in biological research, bio-industry , pharmaceutical analysis , pharmaceutical, teaching and research, environmental protection , food hygiene, clinical examination , health and epidemic prevention , and other fields.

●A wide wavelength range, the wavelength range to meet the various requirements of the field.

●Automatic design to achieve the most simple means of measurement.

●LSI design greatly improves the stability and reliability of the system.

●Improved optimization of the optical design , import source and receiver system created a high performance and high reliability.

●Rich measurement methods , with a wavelength scan , time scan , multi-wavelength determination , multi-order derivative determination (optional ) , dual-wavelength , three-wavelength (optional ) DNA protein measurements (optional ) , and other measurement methods to meet different measurement requirements , and can be displayed directly on a 6- inch screen.

●Based on user requirements optional hole rack , manual four with stand , manual Eighth rack , automatic Eighth frame, glass stand , test tube rack , 1cm colorimetric frame , 5cm colorimetric frame , 10cm colorimetric racks.

●Measurement data can be output through the printer with USB interface.

●Can be powered down to save the measurement parameters and data , user-friendly.

●Can achieve more accurate and flexible measurement via PC control , which can meet the needs of different users.

Optical Specifications

About us

Introduction of Shanghai Macy Lab

Shanghai Macy Lab Instrument Co.Ltd (The following shorter form Macy Lab), it is a high-tech enterprise with independent intellectual property rights, the entrepreneurial ideas of Macy Lab “ science and technology -- change because of you”, and with it as the enterprise tenet, .Continuous exploration, determination and innovation. Especially in the field of analytical and testing instruments, developing constantly advanced products and make Macy Lab become a supplier of High-quality instrument resources.

The main spectrometer visible spectrophotometer, ultraviolet visible spectrophotometer, atomic absorption spectrometer, ultra trace spectrophotometer, atomic fluoruminometer, ICP inductively coupled plasma emission spectrometer, ICP inductively coupled plasma mass spectrometer. 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, using the rich experience accumulated in product mechanical structure, optical design, electrical application and software development, combined with the latest actual demand of the market, a batch of new analytical instruments will be launched in the near future.

The headquarters and production base in Macy Lab which is located in Shanghai,The marketing center is located in Beijing. And research and development bases were built in Jiangsu, Shanghai, Shandong. To make full use of the intellectual resources around the country. Macy Lab has conducted deep scientific research cooperation with some scientific research institutions at home and abroad,constantly transform scientific research achievements into productive forces. For a better service to the majority of customers, Macy lab has 12 business offices in China, customize the application solutions that meet your needs, increase the added value of products. While constantly serving domestic users, it has also established deep strategic partnerships with distribution agencies in more than 20 countries.

                                       Macy Lab is not only a high-tech certification enterprise, but also has passed the CE certification, FCC certification, RoHS certification and a number of domestic qualification examination and certification, and has a number of self-developed spectral patent copyright, etc.)