Extraction of dyes contained in glow sticks using liquid CO₂

Separation of glow stick dyes adhered to a cotton swab using liquid CO₂ provides an engaging demonstration of several chemical concepts including polarity, kinetics, chemiluminescence, and the importance of CO₂ a green solvent. The simple protocol allows access to a broad range of students. Differential polarities of the glow stick dyes allow certain dyes to be preferentially dissolved in liquid CO₂, leaving other dyes adhered onto cotton. Both TCPO (bis(2,4,6-trichlorophenyl)oxalate) and H₂O₂, which together provide the necessary reaction for chemiluminescence, are present in both the extracted liquid and cotton upon dissipation of CO₂. Thus, it is possible to compare the emission spectrum of the extracted fluid to that of the original glow stick and the residue left on the cotton swab. Emission peaks resulting from the presence of polar dyes in the original glow stick and on the cotton are routinely observed to be missing in the extracts.