Sometimes it feels as if organic chemistry and chromatography are a mixture of art and science. Maybe its because of the necessary creativity needed to address the variety of challenges that we face almost daily. Frankly, its what I find most interesting about this world. One of the bigger challenges facing chemists is the ability to detect and collect compounds … Continue reading Detecting the undetectable in flash column chromatography using wavelength focusing
In my role as senior technical specialist at Biotage I am often asked about compound detection options. For most flash chromatography methods, UV is the default detection tool since a majority of compounds do absorb some UV light. Diode array UV detectors provide chemists choices in wavelength selection, providing the ability to widen or narrow … Continue reading So, which detector should I use for flash column chromatography?
Usually, a 2-solvent or binary gradient will separate your desired compound from the by-products and impurities. Sometimes though, you can encounter a mixture in which some compounds co-elute and are not separable with any binary gradient you try. I encountered this situation recently while trying to purify a lavender essential oil and have dedicated this post … Continue reading What do I do if a 2-solvent gradient will not separate my sample?
Organic and medicinal chemists frequently utilize flash chromatography to purify their reaction mixtures. Normal-phase flash chromatography is most often used but may not the best methodology, especially when the compounds are quite polar and/or ionizable. For these molecules, reversed-phase flash chromatography is preferred but often is not used due to an uncertainty regarding the best solvent choices … Continue reading How does mobile phase organic solvent choice impact reversed-phase flash column chromatography?
A baseline that rises or drops when using flash chromatography with a UV detector can be a problem, especially if you are trying to collect compounds with poor detectability or that exist in low quantities. In this post I will talk about the causes and solutions for a rising (or even dropping) baseline.
Mass spectrometers today are typically available with either Electrospray Ionization (ESI) or APCI (Atmospheric Pressure Chemical Ionization) sources. That’s really nice but, how do you know which source will work best when purifying your sample? In this post I attempt to provide some guidance to selecting the ionization source best suited to your sample types.
Compound detection challenges are, for many chemists, a part of life. In a previous post I discussed how wavelength focusing can help your flash system detect and fractionate compounds with poor chromophores. However, compounds naked to UV-Vis light, such as carbohydrates, are impossible to detect by UV when separating by liquid chromatography. There are some alternatives, however, … Continue reading Detecting the undetectable in flash column chromatography, part 2
For most organic and medicinal chemists, normal-phase flash chromatography is used to purify and isolate many types of organic compounds, most with some polar functional groups which help them retain on silica. However, some compound mixtures are water insoluble such as lipids, carotenoids, terpenes, tocopherols, polyaromatic and other hydrocarbons with minimal polar functionality. These lipophilic compounds do not retain well … Continue reading Non-aqueous (or nearly so) reversed-phase flash column chromatography – a nice alternative for purifying lipophilic compounds
It is hard for me to believe but the flash purification blog is a year old. This started as an idea within the technical group here at Biotage to share knowledge of flash column chromatography that we have learned over 30-plus years. Though I was reticent at first, now after only a year its hard to … Continue reading Celebrating 1 year of the flash purification blog
The UV absorption spectrum of some solvents overlaps with the product they dissolve, meaning that fraction collection processes cannot distinguish between solvent and product. The phenomenon, especially when applied to mobile phase gradients, can also result in drifting baselines and, in a worst case, swamp the sample out completely. Luckily, there is technology that solves this … Continue reading Overcoming UV-Absorbing Mobile Phases