Effervescent tablet-assisted demulsified dispersive liquid-liquid microextraction based on solidification of floating organic droplet for determination of methadone in water and biological samples prior to GC-flame ionization and GC-MS.

A novel effervescent tablet-assisted demulsified dispersive liquid-liquid microextraction based on the solidification of floating organic droplet was developed to determine methadone prior to gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. In this method, a tablet composed of citric acid, sodium carbonate, and 1-undecanol was utilized. The resulting effervescent tablet generated carbon dioxide in situ to disperse 1-undecanol in the sample. Thus, the dispersive and extraction processes were performed in one synchronous step. An aliquot of acetonitrile as the demulsifier solvent was used for the separation of two phases instead of centrifugation. Under optimal conditions, the developed method was linear up to 50 000 µg/L with correlation coefficients higher than 0.99. Moreover, limits of detection and limits of the quantification were in the range of 3-10  and 7-30 µg/L in water and biological samples, respectively. Intra- and interday precisions (n = 6) of the spiked methadone at a concentration level of 50 µg/L were over ranges of 5.1-6.8% and 5.7-7.1%, respectively. The preconcentration factors and recovery values were obtained in the range of 140-145 and 98.1 to 101.6% in real samples, respectively.