Purification

First, gather the necessary materials for the chromatography column.

mobile phase

The photo shows a graduated cylinder filled with a clear liquid up to the 10 mL marking. Next to the graduated cylinder is a large brown glass reagent bottle labeled “hexane:ethyl acetate; 1:1 mixture; TLC developing solvent.”

stationary phase

The photo shows a small glass Erlenmeyer flask sitting on a laboratory scale. Inside the glass is a moderate quantity of white powder. The screen on the scale reads “0.6489 g.” Next to the scale is a small brown glass reagent bottle labeled “silica gel.”

column set-up

The photo shows a small glass chromatography column held vertically in midair by a metal clamp attached to a ring stand. We can see a small quantity of off-white gel-like substance in the bottom of the column, extending up to approximately one third the overall height of the column. The stopcock valve at the bottom of the column is in the horizontal position, and the column is topped with a small plastic funnel.

Then, make observations in your lab notebook based on the column preparation video below.

The video shows a small glass chromatography column held in midair by a metal clamp attached to a ring stand. The stopcock valve at the bottom of the column is in the horizontal position and there is a small plastic funnel affixed to the top of the column. Below the nozzle of the column is a small glass beaker. Next to the column set up is a graduated cylinder filled with approximately 10 mL of clear liquid. Next to that is an Erlenmeyer flask containing with a small quantity of fine white powder. Next to that is a glass one dram vial containing a small quantity of clumpy off white solids. A gloved hand appears and pipettes approximately 2 mL of the clear liquid from the graduated cylinder into the Erlenmeyer flask. The flask is swirled and poured into the funnel at the top of the column while another gloved hand taps the side of the column gently. Another 1 mL of clear liquid is pipetted into the Erlenmeyer flask, and this mixture is also poured into the funnel at the top of the column while tapping the side of the column gently. The Erlenmeyer flask is rinsed one more time with another 1 mL of clear liquid and the rinse is also added to the funnel. The gloved hand points at the place where the column meets the metal clamp, highlighting that the mixture inside the column has begun to settle and separate into a foggier white substance at the bottom with a clear liquid floating on top. The column is tapped one more time and the stopcock turned into the vertical position. Clear liquid begins to drip out of the nozzle into the beaker below. Next the screen goes black except for a caption reading “Allow solvent to drain…” When the video reappears, we see a close up view of the bottom half of the column, showing clear liquid continuing to drip out of the nozzle. The screen goes black against except for a caption reading “~10 minutes later…” When the video reappears, we see a close up view of the top of the foggy white portion of the column, revealing that the clear liquid has drained down such that its meniscus is just above the top of the foggy white mixture. The view zooms back to show that the stopcock has been returned to the horizontal position. A gloved hand holds up the one dram vial with chunky off white solids and twirls the contents with a metal spatula before scraping them into the funnel at the top of the column. These chunks land at the top of the foggy white stationary phase in the column. The one dram vial is rinsed twice with 0.5 mL portions of the clear liquid from the graduated cylinder and each rinse is added to the funnel as well. After each rinse, the stopcock is opened to allow the added solvent to drain until the meniscus is just above the top of the chunky solids from the one dram vial. Finally, the remainder of the clear liquid from the graduated cylinder is pipetted into the column, rinsing down the sides of the funnel in the process.

Onward to fraction collection!

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