All that stuff about whether or not you can use THF for liquid chromatography

All that stuff about whether or not you can use THF for liquid chromatography

Some time ago, there was a sudden discussion in a social group about whether tetrahydrofuran (THF) could be used in liquid chromatography. The answer is yes, of course, but there may be more to pay attention to than other solvents.
Before we begin today's topic, let's briefly introduce the concentrated solvents commonly used in reverse phase chromatography. In reversed-phase chromatography, in addition to water, acetonitrile, methanol, tetrahydrofuran are most commonly used. That's right. Tetrahydrofuran is also a common reagent.
Let's first look at the absorption-wavelength curves of commonly used inverting solvents:

In recent years, the research requirements of drug impurity spectrum are becoming higher and higher, leading to the impurity spectrum usually has many components. In order to take account of different components at the same time, from the perspective of UV absorption, and acetonitrile has lower column back pressure than methanol and tetrahydrofuran, acetonitrile has become one of our favorite solvents. In a long time of subtle influence, methanol can also occupy part of the home field because of the advantages of low price and toxicity, while TETRAhydrofuran, due to the use of problems, including price and toxicity, gradually used less. Of course, technology and stationary phase updates are also contributing to this. And, of course, it's important to note that even though they're used less often, and even though people like to start with acetonitrile, there's no denying that methanol and TETRAhydrofuran have a unique selectivity that makes acetonitrile irreplaceable.

Firstly, it can be seen from the absorption wavelength curve above that although the cutoff wavelength of THF (212nm) is 7nm more than that of MeOH (205nm), the absorption difference between the two is obvious. THF still absorbs at a higher wavelength. Therefore, when selecting THF as part of the additive, please pay attention to the wavelength selection and sensitivity of the method.

Secondly, because of the obvious chemical instability of TETRAhydrofuran, it is easy to oxidize into peroxide. As we know, the stability of the solvent is the first key point. If there are certain peroxides with higher activity, it is likely to be destroyed in the process of sample analysis, thus showing false impurity spectrum and affecting our judgment of results. Of course, in order to control the peroxide content in THF, a chemical stabilizer is usually added to the THF. This chemical stabilizer is BHT (2, 5-di-tert-butyl-4-methylphenol). Therefore, we usually buy two kinds of THF, one is added with the stabilizer BHT, the other is not added with BHT. At this point, please pay attention to the reagent label in the actual work process, because these information will definitely be reflected on the label. As we can see from the name of BHT, it has benzene ring. Therefore, BHT with treatment is easy to bring into the uv absorption material, which affects the test results with the UV detector.

Finally, there is the impact of THF on hardware systems. Before we get to that, let's take a look at peek materials.

Polyetheretherketone (PEEK) -- Polyetheretherketone (PEEK) -- polyetheretherketone (PEEK) Peek tube and PEEK joint are highly versatile chromatographic accessories in our daily work. Peek offers more flexibility and matching than stainless steel, and a better price than titanium. Peek material has excellent chemical stability and biological compatibility. This chemical stability allows us to use a mobile phase with a partial addition of tetrahydrofuran. Why a partial addition? This is because peek material has excellent chemical stability, but it still has small swelling in a high concentration of THF environment. This swelling may not necessarily affect the robustness of our method, but in the long run, peek tube in the system will become brittle and aging. Therefore, controlling the ratio of THF and always paying attention to the hardware performance of the instrument is also an important concern in the use of THF. In addition, there are also claims that the sealing pad of the pump is also corrosive. Although xiaobian think ptfe gasket is not so easy to break, but, pay attention to the instrument itself, good use and maintenance of it, is also very important! Sophisticated instruments, good performance of the system can provide us with a more solid guarantee.