A simple and rapid method was developed for the determination of five common adulterants found in herbal medicines (HM) and food supplements (FS) including caffeine, hydrochlorothiazide, chlorpheniramine, diazepam and gliclazide using high performance liquid chromatography (HPLC) coupled to diode array detector (DAD). Initially, three columns were evaluated, hydrophilic interaction liquid chromatography (HILIC), monolithic (MC18) and porous graphitic carbon (PGC). Results showed that PGC and MC18 column gave good separation. HPLC-DAD method was developed for the qualitative and quantitative analysis of the five adulterants. The identification was based on the retention time of the five adulterants in MC18 and PGC columns. Additionally UV spectrum and peak purity test were also used for qualitative analysis. The quantitative analysis was carried out using UV absorbance at 254 nm of the five adulterants. The developed method was then fully validated in terms of accuracy, linearity, precision, limit of detection (LOD) and limit of quantification (LOQ). The LOD varied from 0.01 to 0.06 mg L" for both PGC and MC18 columns. The calibration curves were linear over a wide concentration range of 0.05-50 mg L and analytical recoveries were between 87.2 and 106 % for PGC column. On the other hand, the concentration range was 0.08-50 mg 1" and analytical recoveries were between 87.9 and 102.9 % for MC18 column. The developed method is accurate and precise, as well as having advantages such as simplicity and short duration of analysis. Finally, 25 samples of labelled as "natural" products were analyzed. Samples were supplied by the Public Authority of Costumer Protection (PACP), Ministry of Health (MOH) and some were purchased directly from the local market. Caffeine was detected in 20 % of the samples. Fortunately, concentration of caffeine in these 5 samples was within the allowable limit.