Oxidized carbon nanotubes are tested as a matrix for analysis of small molecules by matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). Compared with nonoxidized carbon nanotubes, oxidized carbon nanotubes facilitate sample preparation because of their higher solubility in water. The matrix layer of oxidized carbon nanotubes is much more homogeneous and compact than that of nonoxidized carbon nanotubes. The efficiency of desorption/ionization for analytes and the reproducibility of peak intensities within and between sample spots are greatly enhanced on the surface of oxidized carbon nanotubes. The advantage of the oxidized carbon nanotubes in comparison with ␣-cyano-4-hydroxycinnamic acid (CCA) and carbon nanotubes is demonstrated by MALDI-TOF-MS analysis of an amino acid mixture. The matrix is successfully used for analysis of synthetic hydroxypropyl ␤-cyclodextrin, suggesting a great potential for monitoring reactions and for product quality control. Reliable quantitative analysis of jatrorrhizine and palmatine with a wide linear range (1-100 ng/mL) and good reproducibility of relative peak areas (RSD less than 10%) is achieved using this matrix. Concentrations of jatrorrhizine (8.65 mg/mL) and palmatine (10.4 mg/mL) in an extract of Coptis chinensis Franch are determined simultaneously using the matrix and a standard addition method. [27] developed a method for quantitative analysis of small molecules with desorption/ionization on porous silicon using electrospray deposition of analytes, and a quite good quantitative result with linear calibrations R 2 Ͼ 0.99 and values of RSD Ͻ 7% was achieved. It is believed that MALDI could be a powerful technique to provide both qualitative and quantitative determination of small compounds.Carbon nanotubes have been attracting wide interest [28,29] of scientists since they were initially discovered by Iijima et al. [30,31]. Recently, Carbon nanotubes have been developed as the matrix for MALDI-TOF-MS for analysis of small molecules [25], in which carbon nanotubes function both as the energy receptacle for laser radiation and as the energy transporter for desorption/ionization of analytes with the minimization of interference signals caused by matrix ion. The effectiveness of the method as matrix has been demonstrated by several compounds with low molecular weight. However, the low solubility of carbon nanotubes in water or organic solvent makes it hard to deposit carbon nanotubes onto the sample target and to form a homogeneous layer of matrix, leading to the relatively poor reproducibility and resolution of peaks for analytes.

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