- Determination of 2-hydroxyphenylacetic acid (2HPAA) in urine after oral and parenteral administration of coumarin by gas-liquid chromatography with flame-ionization detection. Meineke, I., Desel, H., Kahl, R., Kahl, G.F., Gundert-Remy, U. Journal of pharmaceutical and biomedical analysis. (1998)