ROOM-TEMPERATURE PHOSPHORIMETRY OF METHYLXANTHINE STIMULANTS ON ZEOLITE-MODIFIED FILTER-PAPER SUBSTRATES

The phosphorescence characteristics at room temperature of methylxanth ine stimulants (caffeine, theophylline and theobromine) on several fil ter paper substrates (Whatman # 1, Whatman DE-81 and Albet) modified w ith a cation-exchange zeolite have been studied. The zeolite was incor porated into the paper matrix by immersion and stirring of the filter paper in a zeolite aqueous suspension. The effect of zeolite on the ph osphorescence decay of the drugs has been studied. Compared to the unt reated filter papers, the zeolite-modified paper substrate shows lower background signal and enhanced analyte phosphorescence. As a result, improved limits of detection are found under optimum experimental cond itions.