Lm. Cabalin et al., ROOM-TEMPERATURE PHOSPHORIMETRY OF METHYLXANTHINE STIMULANTS ON ZEOLITE-MODIFIED FILTER-PAPER SUBSTRATES, Fresenius' journal of analytical chemistry, 346(10-11), 1993, pp. 1003-1007
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.