*Chemicals and Reagents*

For HPLC analysis, chromatographic-grade methanol was used (VWR, Vienna, Austria). A Millipore purifier (Millipore, USA) was used to obtain water for HPLC. Potassium dihydrogen phosphate, potassium chloride, ascorbic acid, ibuprofen, ketoprofen, dipotassium hydrogen phosphate, sodium chloride, hydrogen peroxide, trypsin, Tris-HCl buffer, and perchloric acid were purchased from Sigma-Aldrich, Taufkirchen, Germany. Human albumin 20%—BB, 200 g/L was ordered from BB-NCIPD Ltd., Sofia, Bulgaria. Chromatographic plates, Kieselgel 60 F254, were purchased from Merck (Darmstadt, Germany).
