Solidification of floating dispersed organic droplets and ionic liquid microextraction methods for the determination of non-steroidal anti-inflammatory drugs in human urine

Abstract

Dispersive liquid-liquid microextraction based on solidification of floating organic droplets (DLLME-SFO) and ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) methods coupled with high performance liquid chromatography-ultraviolet detector (HPLC-UV) were developed for the determination of non-steroidal anti-inflammatory drugs (NSAIDs) in human urine samples. Three NSAIDs namely ketoprofen, diclofenac sodium, and mefenamic acid were investigated. In the optimized DLLME-SFO method, a mixture of 1-undecanol (20 µL) as extraction solvent and acetonitrile (100 µL) as disperser solvent was rapidly injected into 5 mL sample solution (pH 2) containing 1% (w/v) NaCl. After 4 min of centrifugation at 5000 rpm, the mixture was separated into two phases with the fine droplets of 1-undecanol floated at the top of sample solution. Then, the test tube was placed in an ice bath for cooling and solidification. The solidified extract was transferred into a small vial where it melts and injected into HPLC-UV system. The DLLME-SFO method gave good linearity over the concentration range from 0.01–10 µg/mL with coefficient of estimation (r2) ranging from 0.9949 – 0.9994. The method also provide low limit of detections (LODs) in the range of 0.0034 – 0.0052 µg/mL. Diclofenac sodium was detected in human urine samples at concentration levels of 1.204 and 0.340 µg/mL after two and four hours of administration. In ILDLLME method, the optimum IL-DLLME parameters was a mixture of 1-butyl-3- methylimidazolium hexafluorophosphate, [BMIM][PF6] (20 µL) as extractionsolvent and acetone (80 µL) as disperser solvent was injected into a 5 mL of sample solution (pH 2), containing 1% (w/v) of NaCl. Then, the sample solution was centrifuged for 4 min at 5000 rpm to settle the extractant. The settled phase was then withdrawn, and diluted with 1:1 ratio of dispersive solvent before injected into the HPLC-UV system. The developed method shows good linearity for the analytes in the range of 0.01 – 10 µg/mL, with coefficient of estimation (r2) in the range of 0.9955 – 0.9974, and low LODs for the analytes in the range of 0.0057 – 0.0088 µg/mL. This method was successfully applied to the determination of diclofenac sodium in human urine samples. The analyte was detected in human urine samples at concentration levels of 1.196 and 0.223 µg/mL after two and four hours of administration. Both methods were applied for intra- and inter-day precision of the target analytes in urine sample at spiking levels of 0.05 and 1.0 µg/mL. The results showed excellent relative recoveries and acceptable RSD were achieved for both DLLME-SFO (95.73 – 115.64%, <9.80%) and IL-DLLME (84.92 – 99.99%, <8.82%), respectively. Based on the results obtained, it could be concluded that the DLLME-SFO method was more efficient and sensitive than IL-DLLME.