Abstract: A sequential injection extraction is presented based on the different flow velocities of aqueous and organic segments through a PTFE extraction coil (6 m x 0.8 mm i.d.) due to the hydrophobic interaction between the extraction coil and the organic segment. An air segment of 5 cm was inserted into the extraction coil followed by the organic segment and the aqueous segment. Air was then pumped into the coil to propel the aqueous segment through the organic segment which formed a coating on the inner walls of the coil. The flow direction was reversed and the aqueous segment was removed from the coil. The procedure was repeated with a second aqueous segment buffered at an optimal pH for back extraction. The technique was tested by extracting mixtures of barbiturates (as acid/neutral drugs) or serotonin re-uptake inhibitors (as basic drugs) from 500 µL urine using 50 µL butyl chloride/octanol (4:1) as the organic segment. The drugs were back extracted into 100 µL 0.45 M NaOH (for acidic/neutral drugs) or 0.18 M H3PO4 (for basic drugs) for analysis by HPLC. The absolute recoveries were 11-30% for urine samples spiked at the 50 µg/ml level. The sample throughput was 20/h.

Abstract: A review is presented, with 248 references, which covers derivatization - HPLC analysis of, e.g., alkaloids, amines, antibiotics, barbiturates and steroids. Application to biological materials is included.