The essential oil contents of many plants have been investigated using gas chromatography and gas chromatography-mass spectrometry techniques. The plants studied were Cinnamomum sp., Curcuma sp., Citrus sp., Zingiber sp., Cymbopogon sp., Gastrochilus pandurata and Melaleuca leucadendron, as well as come traditional herbal products consisting of essential oil-containing plants. Iron content of raw materials and products containg L. pumila was also determined using atomic absorption spectroscopic technique. High-performance liquid chromatographic technique had been used to profile phytochemical contents of Andrographis paniculata and L. pumila var. alata. chemometric analysis of spectroscopic and chromatographic fingerprints of A. paniculata and L. pumila var. alata was performed to classif herbal materials and to establish standard quality control protocols for raw materials and extracts.