SINGLE StEP Column FAQs

Why do SINGLE StEP Columns work better?

• SINGLE StEP Columns (patented) are a direct injection Flash column. Like any chromatography method, flash chromatography is done best when the compound of interest is placed on to the silica bed head directly.
• SINGLE StEP Columns have a simple screw top design, which allows for easy sample introduction and even distribution over the top of the accessible silica column bed.
• This lowers any dilution factor and allows for even flowing bands throughout the column, versus uneven dispersion from a small injection port. Even spreading of the compounds on the top frit is key to giving the best possible separation.
• SINGLE StEP Columns are tightly packed which provides a good silica bed.
• SINGLE StEP Columns are tightly packed and as a result, can take more pressure to push the liquid loading through the top of the column. Some people may use a vacuum to suction this evenly on, or use a syringe (attached to the cap) to press the liquid past the top frit.
• SINGLE StEP Columns use E. Merck and Standard High quality silica, which have a narrow particle range. These attributes make Thomsons' SINGLE StEP Columns preferred around the world.

Loading capacity of SINGLE StEP Silica Columns?

• The ratio of silica should be 1 gram of compound to every 20 grams of silica with a ∆ RF=.2. Please check out the General Methods paper (PDF), it shows SINGLE StEP Columns can stretch that down to ∆ RF=.1.

General loading methods:

• Dry loading is the best method but not always as time efficient upfront.
• Liquid loading can be accomplished best by minimizing the amount of solvent you load your compound in. This helps peak shape and reduces broad banding. Check 3-4 solvent systems for the best method of separation.

Which method is the best: Dry Loading or Wet Loading?

• Dry loading gives you the most capabilities because you start with the polarity of 0. When liquid loading it's not clear where you are starting at (DCM polarity is around .5, 50% Hexane/Ethyl Acetate is around .25).
• We will give a simple technique below on how to liquid load with dry absorption for those who don't have time to rotovap down.

What is the best way to Liquid load on a SINGLE StEP Columns (patented)?

• We will explain our best way to "Liquid-dry loading" which will result in better separations.
  
  • Liquid-dry loading can be done by pouring silica and celite (50%/50% mixture) on top of the SINGLE StEP column top frit.
  • Pour the compound in liquid evenly on the top of the silica and celite mixture. This mixture absorbs catalyst or other impurities that take away from silica separation power. We recommend at least one inch of this mixture for each column size.
  • Other brands that have a sealed top columns like the Isco® style use a second column, or Biotage® users use Samplets® Isco® style cartridges use a 2nd cartridge. The price of silica and celite is much less and direct injection is important as highlighted above.
  • Have you ever tried to put 100mLs in a syringe and push it through some tiny 1/8" port? It sometimes leads to the Volcano effect. That is why people prefer SINGLE StEP Columns. Open the top and pour the contents of your round bottom flask or vial in and seal it yourself.

Do I need to pre-equilibrate the flash column?

• There is no need to equilibrate your flash columns if you are going to 50%-100% Hexane/Ethyl Acetate or dry loading.
• Simply, pour your compound right in and then at 5-10% Ethyl Acetate do 2 column volumes (a column volume is defined as 1g of silica = 2mLs of solvent, example 25g=50mLs) for a wash and then go to 50% within the run.
• If you have something extremely non-polar do equilibrate your compound which will elute in less than 15% Ethyl Acetate. Again preferred method for really non-polar products application to silica columns is dry loading.

DCM/Methanol 10%

• Please do equilibrate your flash column with DCM/Methanol 10% for 2 Column volumes (1g of silica= 2mLs of solvent).
• The reason for this is that the silica is extremely polar and contains 5-7% water content; the methanol wash will allow everything extremely polar to come off.
• Then run 2 column volumes of 100% DCM through the column.

Head Space Myths??

• Please read: Column Void Study (PDF)
• The real truth is that headspace does not affect Flash Chromatography as long as you have a pump going at 15 PSI and you are not doing a 4 minute ballistic HPLC Gradient. The best story we have heard was, "The column gave great separation but I was scared of the headspace". Stop the fear, do Chemistry!!

What do I do with Head Space if it leaves me with have extra solvent?

• If you don't like it because you prefer to equilibrate your column, no worries, we have Teflon Reusable Gap Plugs for people who need to have them. Some people put glass beads, or sand in the top.

Patent 7,138,061, 7,381,327, 7,410,571, 8,070,957 and 8,066,875. U.K. Patent 2413972.