Determination of p-aminobenzoic acid in the presence of bovine serum albumin by room-temperature phosphorimetry on a poly(vinyl alcohol) substrate Original Research Article

Solid substrate room-temperature phosphorimetry on a poly(vinyl alcohol) (PVA) substrate was applied to the analysis of p-aminobenzoic acid (PABA) in the presence of bovine serum albumin (BSA). The buffer solution containing PABA and BSA was spotted on the PVA substrate and after sufficient drying, room-temperature phosphorescence (RTP) measurements were performed on both the front and the back side of the substrate. The BSA was separated on the front surface of the substrate and it emitted a negligibly weak RTP signal. Therefore, the RTP measurement of PABA on the reverse of the sample spotted side was not interfered by BSA, whereas, impurities in the BSA permeated into the PVA and emitted a weak RTP signal on the back side of the substrate. However, the RTP intensities of the impurities were weak enough as compared to that of PABA under the experimental conditions, so that their interference could be neglected. To improve the RTP intensity and reproducibility of PABA in the presence of BSA, a new substrate that consisted of Millipore-VS and PVA layer was prepared. The analytical figures of merit of this substrate obtained under the best experimental condition for maximum phosphorescence emission are a relative standard deviation of 6.0% (n=5) at a level of 2 nmol/spot and a linear calibration curve from 0.5 to 20 nmol/spot with a correlation coefficient of 0.996 for 25 data points.