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The size and distribution of matrix crystals deposited on the surface of a tissue section play a key role in the performance of MALDI mass spectrometry imaging (MALDI-MSI). In this study, uniform distribution and a restricted size of matrix crystals were achieved via a homemade matrix sublimation device with controllable crystallization temperature. The crystallization temperature was stably controlled at a subzero temperature, and homogeneous matrix crystals with diameters <0.2 μm were generated on the sample surface. Typical MALDI-MSI experiments of endogenous and exogenous components in the tissues of strawberries, kidneys, and mussels were conducted to examine the performance of the sublimator. Good reproducibility of MALDI-MSI was achieved, and the quality of ion images was significantly improved. These results demonstrate that the developed sublimator should have potential in matrix deposition for further high resolution MALDI-MSI application.

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Rationale:A thorough understanding of the content and distribution of active ingredients in pharmaceuticals is essential for drug efficacy and safety.Technological advancements in mass spectrometry imaging present an opportunity for methodological innovation by providing qualification and quantification analysis, as well as spatial information, in the same assay, which has great potential for applications in the rapid analysis and quality control of drugs.Methods: Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was employed to directly analyze oxytetracycline tablets in order to map the distribution of the active constituent within the whole tablet. Quantitative analysis was capable of differentiating tablets containing various doses of the active pharmaceutical ingredient. Results:To establish the methodology, detailed factors that influence matrix spraying and spatial resolution during sample preparation and the data acquisition process were optimized systematically. Quantitative analysis could differentiate the tablets containing various doses of the active compound. The proposed method was successfully applied to analyze real commercial tablets. Conclusions:The developed method could successfully achieve the spatial location of oxytetracycline in actual tablet samples. These results could contribute to pharmaceutical tracing technology, especially the formulation process of tablets, which is helpful for monitoring the quality of pharmaceutical products and guaranteeing drug security.

Medicine food homologous (MFH) plants provide therapeutic and health care effects through diet. Thus, a risk assessment system for hazardous ingredient residues is urgently required to ensure their safe use. In this study, the pesticide contamination of six root and rhizome Chinese herbs, Ginseng Radix et Rhizoma, Panacis Quinquefolii Radix, Pseudostellariae Radix, Salviae Miltiorrhizae Radix et Rhizoma, Codonopsis Radix, and Glehniae Radix, and the risks associated with their intake were investigated. A total of 420 MFH plant samples collected from 22 provinces in China were tested, and 61 pesticides were detected in 413 samples. Multiple pesticide residues were detected in each MFH sample, with contents ranging from 0.0002 to 3.010 mg/kg dry weight. Carbendazim (≥47.14%) and propham (≥40%) were the most frequently detected pesticides. Risk assessment determined by hazard quotients indicated that the risks were acceptable, with no short-or long-term adverse health effects. However, considering the high incidence of residues and the detection of unregistered or even prohibited pesticides, strict supervision of soil quality and pesticide application (particularly cadusafos) in MFH plant cultivation are recommended to aid in monitoring MFH plant quality and ensuring diet and drug safety.