Introduction: Multiple TLC Spotting Device

Columns suck. Every chemist knows this. Having to collect all the fractions and then spot every other one can be torturous. So to help ease some of the pain, here is a device that can spot a whole row of fractions in one go. It is designed to take a sample from 6 different test tubes at one time, collapse into a space perfect for a TLC plate, and then spot.

Step 1: What You Will Need

You will need the following:

  • 3D printer
  • 3D printing filament
  • Super glue or a high temp glue gun
  • Black foam (the kind that is like the foam found on foam paint brushes)
  • A thin stick to poke with (like an unfolded paper clip)
  • Spotters
  • Test tube rack
  • test tubes
  • TLC plate

Step 2: Download Basic Components

  1. Go to:
  2. Select "Download This Thing!" (blue button on the right)
  3. Select "Download All Files (blue button on the right)

Step 3: Decide on Measurements

Since test tube racks vary in size, you will probably need to edit the dimensions

  1. Measure the length of the test tube rack (labeled X). This will be the length of the base.
  2. Measure the distance between the 3rd and 5th test tube (labeled y). This will be the length of the separator.

Step 4: Print Base

There are two components to the base. One component has an open and closed end and the other component has two open ends.

  1. Print the file titled "JI-2-RIGHTSIZE.stl" this is the component with the one closed end.
  2. Subtract the length of this piece from the overall length of your test tube rack (x)
  3. Print enough of the objects from"JI-2-finalNoEnd.stl" so that the overall length of those objects and the object printed from "JI-2-RIGHTSIZE.stl" equals x.

X = base length = n(length of "JI-2-finalNoEnd.stl") + (length of "JI-2-RIGHTSIZE.stl")

Use super glue or a glue gun to glue all the pieces together. Be sure that they line up together as well as possible.

Step 5: Print and Prepare T-shaped Pieces

The t-shaped pieces are designed to spot 6 fractions in one average sized TLC plate, however it is possible to spot 7 or even 8 fractions in one TLC plate.

  1. Print half as many t-shaped piece as there are test tubes in one row of your test tube rack
  2. Use your pointing object to force a small amount of the black foam into the t-shaped piece.
  3. Gently, poke your TLC spotter into the foam so that it points straight up.

Step 6: Edit and Print Separating Piece

The piece above is responsible for ensuring that each spotter is placed into the right test tube.

  1. Edit the file titled "JI-3-pointedright_size.skp" in SketchUp so that the length of the piece is equal to measurement y from step 3.
  2. Print as many separators as there are t-shaped pieces.

Step 7: How to Use

After ensuring that all of the spotters point out of the t-shaped pieces straight up and that they are all the same length, you are ready to spot!

  1. Slide the t-shaped piece into the base and pop in the separator so that the t-shaped piece is inside the separator.
  2. Slide the separator down to the end and repeat step 1 until all the pieces are in.
  3. Turn the base upside down and place over the test tubes until a small sample from each test tube is sucked up into each spotter.
  4. While keeping the base upside down, remove the separators and slide all of the t-shaped pieces down to the end of the base.
  5. Spot onto TLC plate.