I am not really a chemistry expert but I will try my best to answer your question.
First, identify the effects each pure element has on the paper. For example, does the paper absorb the element easily and what is the rate of absorption.
Secondly, use paper chromatography to analyze the combination of elements and see if the ending result is similar to the pure elements tested above.
If you don't know, paper chromatography usually works by hanging a paper with ink from a pen on a toothpick above a beaker. The paper should slightly touch the water (preferably with food colouring) below. The paper will then slowly absorb the water and when the water reaches the dot made by the pen, it will spread out in a specific way that experts can easily identify the substance.
Hope that helps!