para-Aminobenzoic acid (PABA) is a precursor of folate in certain bacteria and is commonly used in sun-blocking creams because of its UV-absorbing property. It has mild anti-inflammatory activity and protects against photocarcinogenesis in hairless mice. However, there have been very few reports on the quantitative determination of PABA in foods, plants and animal tissues. In this study we utilized the fluorescent property of PABA in neutral solution (excitation at 280 nm, emission at 340 nm) to quantify PABA in multivitamin preparations, cereals, rat liver and blood, and compared with a colorimetric method and a HPLC/uv method. In addition to the assessment of PABA, we compared the precision (standard deviation, S.D., coefficient variation, C.V.) and recovery (as a criterion of accuracy) between the three methods. Intercomparison of the methods in multi-vitamin products showed that the colorimetric method was superior in reproducibility (i.e., within-run C.V., 0.2-0.7 %; run-to-run C.V., 2.6-6.1 %) compared to the other methods. The recovery (78.5 %) was also higher for the colorimetric method compared to the other methods. For cereals, the fluorimetric method was not applicable because of interferences and colorimetric method was found superior to HPLC/uv in both precision (2.2- 12.8 vs. 10.8-19.4 %) and recovery (96.1-100.8 vs. 53.4-69.9 %). In rat blood, PABA was detected exclusively by the colorimetric method (1.52 ± 0.22 μg / ml of blood), although each method produced nearly 100 % recovery . For rat liver, PABA was detected by colorimetric (5.92 ± 0.10μg / g liver) and HPLC/uv (1.23 ± 0.09 μg / g liver) while the fluorimetric method was not useful due to interferences. This research demonstrates the comparative applicability, quality and problems of the three methods assessing 3 varieties of samples. In general, the colorimetric method is simple and economical with satisfactory precision and accuracy. In addtion, the detection limit (0.3μM) was comparable to that of fluorimetric method (0.2μM) and HPLC/uv (0.2μM). However, in animal tissues, the HPLC/uv method is superior due to avoidance of interferences, and may be readily improved to apply to other types of samples.
Chen, L.-C. and Hu, M.-L.
"Comparison of methods for determination of para-aminobenzoic acid (PABA),"
Journal of Food and Drug Analysis: Vol. 4
, Article 7.
Available at: https://doi.org/10.38212/2224-6614.3002