Question

In a colour spot test, why do you typically add a reagent (e.g. marquis) to a spot plate prior to adding the drug specimen to be tested?

1) Neither a nor b. To ensure any colour change observed is due to the drug specimen added.
2) Both a and b.
3) To ensure the spot plate is not contaminated.

Answer 1

In a colour spot test, reagents are added first to ensure any colour change is due to the drug specimen, verifying that the results are accurate.

Step-by-step explanation:

In a colour spot test, a reagent such as marquis is added to a spot plate prior to the addition of the drug specimen to ascertain that any observed colour change is specifically due to the drug specimen and not from any other source. This is to maintain the integrity of the test and ensure that results are accurate. When conducting a test for the presence of barium sulphate in products, a white precipitate should form if barium sulphate is present. This confirms the reaction between barium ions and sulphate ions, indicating the compound's presence.