OPTIMIZATION OF MODIFIED QuEChERS METHOD FOR EXTRACTION OF SELECTED PHARMACEUTICALS FROM VEGETABLE SAMPLES USING HPLC

Optimized QuEChERS (quick, easy, cheap, effective, rugged and safe) method of sample preparation was employed for five selected pharmaceutical compounds on its advantage of simplicity, less extraction solvent and extraction time. Different parameters affecting the extraction efficiency of the target analyte was optimized. Since QuEChERS was developed for pesticides, uses of the method for pharmaceuticals need modification and evaluation of different parameters. Clean-up sorbents were evaluated for their matrix effect removal after extraction and a combination of d-SPE sorbent, MgSO4, PSA, C18 and diatomaceous earth found to be selective clean-up sorbent for the targeted compounds. The addition and amount of diatomaceous earth and EDTA during the clean-up and extraction steps, respectively, were also examined and the amount was optimized. Solvent type and composition, salt type and extraction time were also optimized and methanol, MgSO4 with NaCl salt and 5 min extraction time was obtained. The method was successfully applied to different vegetable samples collected from Addis Ababa, Ethiopia and Johannesburg, South Africa (carrot, cabbage and lettuce) and none of the target analytes were found in the sample investigated. The matrix effect study on vegetable samples collected was found very high that suppresses the signal during analysis.