On-chip ion pair-based dispersive liquid-liquid extraction for quantitative determination of histamine H2 receptor antagonist drugs in human urine.

In the present work, an ion-pair based dispersive liquid-liquid microextraction was performed on a centrifugal chip for the first time. The entire DLLME procedure, including flow direction, desperation, and sedimentation of the extracting phase, can be fulfilled automatically on a solitary chip. The chip was made of Poly(methyl methacrylate) (PMMA) and was of two units for two parallel extractions, each consisting of three chambers (for the sample solution, extracting solvents, and sedimentation). As the chip rotated, fluids flowed within the chip, and the dispersion, mixing, extraction, and sedimentation of the final phase were performed on the chip by simply adjusting the spin speed. Determination of two histamine H2 receptor antagonist drugs, cimetidine and ranitidine, as the model analytes from the urine samples was done using the developed on-chip ion-pair based DLLME method followed by an HPLC-UV. The effective parameters on the extraction efficiency of the model analytes were investigated and optimized using the one variable at a time method. Under optimized conditions, the calibration curve was linear in the range of 15-2000 μg L-1 with a coefficient of determination (R2) more than 0.9987. The relative standard deviations (RSD %) for extraction and determination of the analytes were less than 3.7% based on five replicated measurements. LODs less than 10.0 μg L-1 and preconcentration factors higher than 39-fold were obtained for both of the model analytes. The proposed chip enjoys the advantages of both the DLLME method and miniaturization on a centrifugal chip.