Phosphorescence Properties of p-Aminobenzoic Acid Immobilized on a Nylon Membrane

The properties of nylon as a new material for obtaining room-temperature phosphorescence from p-aminobenzoic acid (PABA) have been investigated. Although PABA shows native phosphorescence when adsorbed on a nylon membrane, a significant improvement in both sensitivity and limit of detection is achieved in the presence of α-cyclodextrin and heavy atoms. An additional enhancement of the phosphorescence signal is attained when the measurements are carried out under a nitrogen atmosphere. The analytical figures of merit obtained under the best experimental conditions are: linear calibration range from 0.6 to 6 ng/spot (the lowest value corresponds to the quantitation limit); correlation coefficient, 0.998 for 18 data points; relative standard deviation, 2.2% ( n = 5) at a level of 2.4 ng/spot; and limit of detection, 0.2 ng/spot (calculated according to Clayton's definition).