Using the monolithic column, gradient elution and UV-absorbance detection, the four major analytes – morphine, oripavine, codeine and thebaine – were separated in 15 min with unnecessarily high resolution.
Consequently, the gradi-ent and flow rates were manipulated to provide more rapid separation that was complete within 2 min.
When post-column chemiluminescence detection was employed, the flow rate through the column was set at 3 mL/min, which gave a total flow rate that matched the optimum conditions estab-lished with flow injection analysis.
Higher flow rates resulted in only minor reductions in run time and no increase in chemiluminescence response.
The chromatographic and detec-tion conditions used in this study have been summarised in Table 1 .