Re-open the 2 liter container and insert the test strip of a spot test cassette into the liquid. Wait and read the result. A clear positive should be recorded. A clear positive is a single clear line at ‘C’ on the cassette, with no line forming at the ‘T’ level (see Fig 18.3).
Use a 3ml syringe attached to a 2ml micro-pipette to take exactly 2ml of liquid from this 2 liter container and add this to the second 2 liter distilled water container - label this bottle #2.
Reseal and again invert to mix thoroughly. Finally, use a new cassette to test bottle #2. Another positive should be recorded, although a faint line may now be noticed at ‘T’. A clear ‘C’ confirms that the test sample has a purity of better than 70%.
Note: To test veterinary Nembutal liquid, use a syringe with a 25G needle. Remove exactly 3ml of the sample and add this directly into the first distilled water bottle - proceed as above.