RESUMEN
Liquid-liquid microextraction without phase segmentation was implemented in a multicommuted flow system for determination of the anti-hypertensive diltiazem. The procedure was based on ion pair formation between the drug and the dye bromothymol blue at pH 3.5. The detection was performed without phase separation in a glass tube coupled to a fiber-optics spectrophotometer. The total volume of chloroform was reduced to 50 µL in comparison with 10 mL consumed in batch. A linear response was observed between 9 and 120 µmol L(-1), with a detection limit of 0.9 µmol L(-1) (99.7% confidence level). The coefficient of variation (n=10), sampling rate and extraction efficiency were estimated as 0.6%, 78 determinations per hour and 61%, respectively. About 30 µg of bromothymol blue was consumed and the waste volume was 380 µL per determination. The results for pharmaceutical samples agreed with those obtained by the reference procedure at the 95% confidence level.