title: Gold nanoparticles bridging infra-red spectroscopy and laser desorption/ionization mass spectrometry for direct analysis of over-the-counter drug and botanical medicines.
abstract: With a coating of gold nanoparticles (AuNPs), over-the-counter (OTC) drugs and Chinese herbal medicine granules in KBr pellets could be analyzed by Fourier Transform Infra-red (FT-IR) spectroscopy and Surface-assisted Laser Desorption/Ionization mass spectrometry (SALDI-MS). FT-IR spectroscopy allows fast detection of major active ingredient (e.g., acetaminophen) in OTC drugs in KBr pellets. Upon coating a thin layer of AuNPs on the KBr pellet, minor active ingredients (e.g., noscapine and loratadine) in OTC drugs, which were not revealed by FT-IR, could be detected unambiguously using AuNPs-assisted LDI-MS. Moreover, phytochemical markers of Coptidis Rhizoma (i.e. berberine, palmatine and coptisine) could be quantified in the concentrated Chinese medicine (CCM) granules by the SALDI-MS using standard addition method. The quantitative results matched with those determined by high-performance liquid chromatography with ultraviolet detection. Being strongly absorbing in UV yet transparent to IR, AuNPs successfully bridged FT-IR and SALDI-MS for direct analysis of active ingredients in the same solid sample. FT-IR allowed the fast analysis of major active ingredient in drugs, while SALDI-MS allowed the detection of minor active ingredient in the presence of excipient, and also quantitation of phytochemicals in herbal granules.
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China.
authors.forename: Siu-Leung
authors.initials: SL
authors.lastname: Chau
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China.
authors.forename: Ho-Wai
authors.initials: HW
authors.lastname: Tang
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China. Electronic address: kwanmng@hku.hk.
authors.forename: Kwan-Ming
authors.initials: KM
authors.lastname: Ng
mesh_terms: D004365:Drugs, Chinese Herbal / Q000032:analysis*; D006046:Gold / Q000737:chemistry*; D008516:Medicine, Chinese Traditional; D053768:Metal Nanoparticles / Q000737:chemistry*; D015394:Molecular Structure; D004366:Nonprescription Drugs / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D004365:Drugs, Chinese Herbal; D004366:Nonprescription Drugs; D006046:Gold
keywords: Botanical medicines; Drug; Gold nanoparticles; Infra-red spectroscopy; Laser desorption/ionization; Mass spectrometry