Technical Abstract: Conventional HPLC provides ready detection of the major phenolic compounds in methanol extracts of orange leaves, yet conventional HPLC also shows the presence of many more compounds, to an extent where extensive peak overlap prevents distinct peak detection and reliable quantitation. A more complete chromatographic analysis of the complex compound profiles of orange (Citrus sinensis) leaves was made possible with separations by Fast Centrifugal Partition Chromatography prior to HPLC analysis. Separations by Fast Centrifugal Partition Chromatography were achieved using the biphasic system of ethanol/butanol/water (20/80/100, v/v/v). Early eluted fractions contained numerous polar and mid-polar hydroxycinnamates. Later eluting fractions contained various profiles of polar and mid-polar flavonoids, many of which significantly overlapped in the HPLC of the original orange leaf extract. Analysis of the Fast Centrifugal Partition Chromatography fractions by HPLC-time-of-flight mass spectrometry provided detection of many more compounds compared to other conventional methods of detection used with HPLC.