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Wu Q. A review on quantitation-related factors and quantitation strategies in mass spectrometry imaging of small biomolecules. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2022; 14:3932-3943. [PMID: 36164961 DOI: 10.1039/d2ay01257j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Accurate quantitative information of the analytes in mass spectrometry imaging (MSI) is fundamental for determining the accurate spatial distribution, which can provide additional insight into the living processes, disease progression or the pharmacokinetic-pharmacodynamic mechanisms. However, performing a quantitative analysis in MSI is still challenging. This review focuses on the quantitation-related factors and recent advances in the strategies of quantitative MSI (q-MSI) of small molecules. The main quantitation-related factors are discussed according to the new investigations in recent years, including the regionally varied extraction efficiencies and ionization efficiencies, signal-concentration regression functions, and the repeatability of surface sampling/ionization methods. Newly developed quantitation strategies in MSI based on aforementioned factors are introduced, including new techniques in standard curve calibration with normalization to an internal standard, kinetic calibration, and chemometric methods. Different strategies for validating q-MSI methods are discussed. Finally, the future perspectives to q-MSI are proposed.
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Affiliation(s)
- Qian Wu
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, P. R. China.
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Abstract
Mass spectrometry imaging (MSI) could provide chemical spatial distribution within a diverse range of samples, but absolute quantitation with those techniques is still challenging. Recent years, ambient liquid extraction-based MSI techniques, such as liquid microjunction surface sampling (LMJSS), have been largely developed and were found to be favorable to quantitation by directly doping standards in the extraction solvent. Here, we describe the detailed experimental protocols and the data processing methods for quantitative MSI with LMJSS. The new methods could have absolute quantitative MSI of both endogenous lipids and small metabolites from tissue samples.
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Affiliation(s)
- Qian Wu
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, P. R. China
| | - Hongmei Lu
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, P. R. China.
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Luo S, Wu Q, Li Y, Lu H. Per-pixel absolute quantitation for mass spectrometry imaging of endogenous lipidomes by model prediction of mass transfer kinetics in single-probe-based ambient liquid extraction. Talanta 2021; 234:122654. [PMID: 34364463 DOI: 10.1016/j.talanta.2021.122654] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 06/21/2021] [Accepted: 06/22/2021] [Indexed: 10/21/2022]
Abstract
With the development of mass spectrometry imaging (MSI), techniques providing quantitative information on the spatial distribution have attracted more attentions recent years. However, for MSI of endogenous compounds in bio-samples, the uncertainty of locally varied sampling efficiencies always hinders accurate absolute quantitation. Here single-probe was used for ambient liquid extraction MSI in rat cerebellum, and standards of phosphatidylcholines (PCs) and cerebrosides (CBs) were doped in extraction solvent. The extraction kinetic curves of endogenous lipids in the ambient liquid extraction during probe parking in single pixel of tissue were investigated. From the results, the extraction kinetic curves were varied between different lipid species in different brain regions, resulting in variations of extraction efficiencies between imaging pixels, and calibration with standards deposited in tissue could not compensate for the variations. In our approach, the theoretical kinetic model of ambient liquid extraction was established, and original concentrations of endogenous lipids in each pixel of tissue were predicted by fitting the experimental extraction kinetic curve in each imaging pixel to the model. The experimental data was demonstrated to be well fitted to the kinetic model with R2 > 0.86, and only with 18-s extraction in each pixel, the original lipid concentrations were predicted accurately with relative errors <23%. With the new method, totally 157 lipids and small metabolites were imaged, and per-pixel quantitation was achieved for 19 PCs and 4 CBs. Compared with conventional quantitative MSI (q-MSI) method, the new q-MSI method had better reproducibility and wider linear range, and produced better contrast in the quantitative images of lipids in brain tissue with less hot spots and noises. The absolute quantitation results by the new method were verified by quantitative LC-MS method with Pearson'r > 0.9 and the slope of the linear fitting line of the correlation plot near 1.
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Affiliation(s)
- Shifen Luo
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China
| | - Qian Wu
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China.
| | - Youmei Li
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China
| | - Hongmei Lu
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China
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Zhou S, Wu Q, Wang Z, Liang Q, Lu H. Photocatalytic reduction-based liquid microjunction surface sampling-mass spectrometry for rapid in situ analysis of aromatic amines originating from azo dyes in packaging papers. Anal Bioanal Chem 2021; 413:6649-6660. [PMID: 34495385 DOI: 10.1007/s00216-021-03631-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 11/25/2022]
Abstract
A rapid in situ analytical method was developed for the detection of generated carcinogenic aromatic amines from banned azo dyes utilizing a photocatalytic reduction-based liquid microjunction surface sampling (LMJSS)-mass spectrometry (MS) system. We utilized photocatalytic reduction under UV irradiation with TiO2 as catalyst to have rapid and mild reduction of azo dyes. The reaction conditions were optimized to have complete photocatalytic reduction within 2-5 min in pure methanol at room temperature. TiO2 was immobilized in the inner wall of the capillaries in the LMJSS system to achieve in situ sampling-online rapid reduction-MS detection for aromatic amines originating from azo dyes in packaging surface. The yields of in-tube photocatalytic reduction were near 100% by delivering the azo dye extracts through the capillary at 1 μL/min under UV irradiation. With this design, in situ analysis was completed within 2 min via direct MS detection and 7 min via liquid chromatography (LC)-MS detection. The detection limits for five aromatic amines originating from four different azo dyes were in the range of 1-17 mg/kg with relative standard deviations (RSDs) < 8.5%. In the application of the new method, four carcinogenic aromatic amines were detected and identified in three commercial packaging materials, and the quantitation results were comparable with those obtained by the conventional chemical reduction-LC-MS method (relative recovery, 81-121%). Moreover, due to the spatial resolution of the present method with a flow probe, MS imaging was achieved demonstrating clear azo dye patterns of a lab-made sample.
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Affiliation(s)
- Shiwen Zhou
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, People's Republic of China
| | - Qian Wu
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, People's Republic of China.
| | - Zhiguo Wang
- Technology Center of China Tobacco Hunan Industrial Co. Ltd., Changsha, 410007, Hunan, China
| | - Qiuju Liang
- Technology Center of China Tobacco Hunan Industrial Co. Ltd., Changsha, 410007, Hunan, China
| | - Hongmei Lu
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, People's Republic of China
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Xiao Y, Deng J, Fang L, Tu L, Luan T. Mapping the distribution of perfluoroalkyl substances in zebrafishes by liquid extraction surface analysis mass spectrometry. Talanta 2021; 231:122377. [PMID: 33965041 DOI: 10.1016/j.talanta.2021.122377] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 03/24/2021] [Accepted: 03/27/2021] [Indexed: 10/21/2022]
Abstract
Investigation on the distribution of persistent organic pollutants (POPs) in aquatic organisms is of great importance for exploring the biological toxicity and health risks of environmental pollutants. In this study, a liquid extraction surface analysis mass spectrometry (LESA-MS) method was developed for rapid and in situ analysis of the spatial distribution of perfluoroalkyl substances (PFASs) in zebrafish. By combining the high-precision automated moving platform of LESA device and the high-resolution MS, quantitative analysis of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in zebrafish tissue section were easily achieved. A tissue-specific ionization efficiency factor (TSF) strategy was also proposed to correct the matrix effect in different parts of zebrafish tissue. By using the developed method, high sensitive and efficient imaging of PFOA and PFOS in zebrafish tissue was achieved, and the distributions of PFOA and PFOS in descending order were gills, organs, roes, pelvic fin, muscle, and brain. The experimental results demonstrated that the coupling of LESA-MS method with TFS strategy is an efficient and reliable approach for monitoring the content distribution of environmental pollutants in biological tissues.
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Affiliation(s)
- Yipo Xiao
- State Key Laboratory of Biocontrol, South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, School of Life Sciences, Sun Yat-Sen University, 135 Xingangxi Road, Guangzhou, 510275, China
| | - Jiewei Deng
- School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, 100 Waihuanxi Road, Guangzhou, 510006, China.
| | - Ling Fang
- State Key Laboratory of Biocontrol, South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, School of Life Sciences, Sun Yat-Sen University, 135 Xingangxi Road, Guangzhou, 510275, China
| | - Lanyin Tu
- State Key Laboratory of Biocontrol, South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, School of Life Sciences, Sun Yat-Sen University, 135 Xingangxi Road, Guangzhou, 510275, China
| | - Tiangang Luan
- State Key Laboratory of Biocontrol, South China Sea Bio-Resource Exploitation and Utilization Collaborative Innovation Center, School of Life Sciences, Sun Yat-Sen University, 135 Xingangxi Road, Guangzhou, 510275, China; Institute of Environmental and Ecological Engineering, Guangdong University of Technology, 100 Waihuanxi Road, Guangzhou, 510006, China.
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