Application of a simple column-switching ion chromatography technique for removal of matrix interferences and sensitive fluorescence determination of acidic compounds (pharmaceutical drugs) in complex samples.

This work illustrates the introduction of a simple, rugged and flexible column-switching ion chromatography (IC) technique for an automated on-line QuEChERS extracted samples extracts washing followed by sensitive fluorescence (FLD) determination of five acidic pharmaceutical drugs namely; clofibric acid (CLO), ibuprofen (IBU), aspirin (ASP), naproxen (NAP) and flurobrofen (FLU) in three complex samples (spinach, apple and hospital sewage sludge). An old anion exchange column IonPac AS11-HC was utilized as a pre-treatment column for on-line washing of inorganic and organic interferences followed by isocratic separation of five acidic drugs with another anion exchange IonPac AS12A analytical column by exploiting the column-switching technique. This novel method exhibited good linearity with correlation coefficients (r) for all drugs were in the range 0.976-0.996. The limit of detection and quantification of all five acidic drugs were in the range 0.024μg/kg to 8.70μg/kg and 0.082μg/kg to 0.029mg/kg, respectively, and better recoveries in the range 81.17-112.5% with percentage relative standard deviations (RSDs) less than 17.8% were obtained. This on-line sample pre-treatment method showed minimum matrix effect in the range of 0.87-1.25 except for aspirin. This simple rugged and flexible column-switching system required only 28min for maximum elimination of matrices and interferences in three complex samples extracts, isocratic separation of five acidic drugs and for the continuous regeneration of pre-treatment column prior to every subsequent analysis. Finally, this simple automated IC system was appeared so rugged and flexible, which can eliminate and wash out most of interference, impurities and matrices in complex samples, simply by adjusting the NaOH and acetonitrile concentration in washing mobile phase with maximum recoveries of acidic analytes of interest.