Kelvin Sze-Yin Leung

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An HPLC-DAD method has been developed to quantitatively analyze for the content of zeaxanthin dipalmitate, a major carotenoid in Fructus Lycii, in different species of the genus Lycium. Determination was performed using an Alltima C18 column with the mobile phase consisting of acetonitrile and dichloromethane (42:58). The total contents of carotenoids in(More)
An HPLC-PAD-MS method has been developed for the qualitative and quantitative analysis of the major chemical constituents in Polygonum multiflorum Thunb. Chromatographic separation was conducted on an Alltima C18 column using water:acetonitrile:acetic acid as the mobile phase. Altogether nine compounds of various classes, including stilbene glucosides,(More)
Patchoulic oil, the volatile oil of Pogostemon cablin (Blanco) Benth. and the Chinese crude drug Herba Pogostemonis, is widely used in the cosmetic and oral hygiene industries. Patchoulic alcohol is commonly used as an indicator for the quality assessment of dried P. cablin. However, the complexity of the herbal constituents makes it difficult for using(More)
An HPLC-DAD-MS method was developed for the qualitative and quantitative analysis of the major constituents in Chuanxiong (the dried rhizome of Ligusticum chuanxiong Hort). Twenty compounds including phenolic constituents, alkylphthalides and phthalide dimers were identified using online ESI-MS and comparisons with literature data and standard compounds,(More)
A high-performance liquid chromatographic method using diode-array detection (HPLC-DAD) has been developed for the simultaneous quantification of eight naphthoquinone derivatives namely shikonin, acetylshikonin, deoxyshikonin, beta-acetoxyisovalerylshikonin, isobutylshikonin, beta,beta-dimethylacrylshikonin, 2-methyl-n-butyrylshikonin and isovalerylshikonin(More)
Herba Asari (Xixin, Manchurian Wildginger, Asarum spp.) is a traditional Chinese medicinal herb commonly used as a crude drug and an ingredient in patent medicines. The herb contains aristolochic acid I (AA-I), which has recently caused several incidents of poisoning in Hong Kong. Therefore, the safe use of Asarum is questionable. The present study was(More)
The article describes a simple sample pretreatment procedure for the analysis of ten organophosphorus pesticides using dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography-mass spectrometry (GC-MS) in three distinctively different types of matrices: fresh fruits, fresh vegetables and dried herbs. The method was carefully(More)
This paper describes an improved quality assessment method for Rhizoma et Radix Notopterygii (the rhizome and root of Notopterygium incisum Ting ex H.T. Chang or Notopterygium forbesii Boiss). The method was established by using fingerprinting and quantitation of marker compounds (isoimperatorin, notopterol and bergapten) in this herbal medicine. The(More)
Determination of urinary free cortisol is one of the first lines in screening for the diagnosis of Cushing's syndrome where its measurement is mostly done by immunoassay. Although easy to perform, immunoassays suffer from the problem of assay interferences and are unable to measure cortisone levels. To enhance such techniques for clinical diagnosis, an(More)
A high-performance liquid chromatographic (HPLC) fingerprint of Chinese Angelica (CA) was developed basing on the consistent chromatograms of 40 CA samples (Angelica sinensis (Oliv.) Diels). The unique properties of this HPLC fingerprints were validated by analyzing 13 related herbs including 4 Japanese Angelicae Root samples (JA, A. acutiloba Kitagawa and(More)