Views: 0 Author: Site Editor Publish Time: 2022-05-04 Origin: Site
There are many organic solvents used in liquid phase test, acetonitrile and methanol are two common solvents, but because of the difficulty of separation in some tests, tetrahydrofuran has an irreplaceable role. It will be noted that THF comes in two different products, one containing stabilizers and one without. What's the difference between these two products?
First to introduce tetrahydrofuran: tetrahydrofuran (THF) is a colorless, miscible with water, at room temperature and pressure with a small viscosity of organic liquid. Because of its long liquid range, it is a commonly used medium polar aprotic solvent, and it is often used as a precursor of polymer.
Tetrahydrofuran is unstable in nature and has a common characteristic with many other ether solvents. When it is exposed to oxygen or air for a long time, a small amount of peroxide will be generated, and the peroxide in the solvent will have a certain impact on the experimental test. If the peroxide content exceeds 1%, tetrahydrofuran can no longer be used. Adding stabilizers to tetrahydrofuran can slow down the production of peroxide. Common stabilizers to inhibit the formation of peroxide include hydrohydroquinone, 3, 5-di-tert-butyl-p-methylphenol (BHT) and butyl-hydroxyanisole (BHA). BHT of 0.01 to 0.04% is generally added to tetrahydrofuran as a stabilizer. Because tetrahydrofuran is unstable, the shelf life of tetrahydrofuran without adding stabilizer is relatively short, but adding stabilizer can effectively prolong the shelf life of tetrahydrofuran. So what are the effects of adding stabilizers on the use of TETRAhydrofuran in testing?
As we know, commonly used HPLC detectors are ULTRAVIOLET detector and photodiode array detector. Generally, UV absorption data will be indicated on the label or COA of HPLC solvent, as shown in the figure below:
Tetrahydrofuran COA without stabilizer (part)
Containing stabilizer tetrahydrofuran COA (part)
Comparing the two figures, it can be found that there is no UV data for TETRAhydrofuran containing stabilizer, which is also suitable for HPLC. Why is this? To this end, we tested the uv transmittance of two tetrahydrofurans by uv spectrum, and the spectra are as follows:
Uv spectrum of tetrahydrofuran without stabilizer
Ultraviolet spectrum of tetrahydrofuran containing stabilizer
It can be seen from the spectra of the two that the tetrahydrofuran with the stabilizer has obvious absorption at 260 ~ 290 nm, which will affect the signal of the target compound at 260 ~ 290 nm. Therefore, tetrahydrofuran with the stabilizer is not suitable for the detection of ultraviolet detector and photodiode array detector in some bands. The detection and analysis methods that do not involve uv absorption, such as GPC, can be used for tetrahydrofuran containing stabilizers.
It can be seen that THF without stabilizer has a wider application scope, and the specific selection principle can be selected according to test requirements and use frequency. In addition, TETRAhydrofuran can cause certain damage to the liquid chromatography pipeline materials, so the proportion of tetrahydrofuran should be controlled and the instrument should be well maintained.