串联质谱（MS/MS）是如何实现复杂样品中目标物定量的？
How does tandem mass spectrometry (MS/MS) enable quantification of targets in complex samples?
MS/MS 先在第一级质量分析器中选定母离子，经碰撞诱导解离（CID）碎裂为子离子，再在第二级中检测特征子离子，即选择-碎裂-选择的三重筛选。这种母子离子组合（MRM/SRM）极大抑制背景干扰，使复杂基质中痕量目标物也能高灵敏度、高特异性定量。
In MS/MS, a precursor ion is selected in the first analyzer, fragmented by collision-induced dissociation (CID) into product ions, and a characteristic product ion is detected in the second analyzer—a select–fragment–select triple filter. This precursor–product pairing (MRM/SRM) strongly suppresses background, allowing highly sensitive and specific quantification of trace targets in complex matrices.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
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出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
《分析化学》(武汉大学, 第五版) 质谱章；Nature Protocols 质谱定量方法
Nature Protocols, targeted MS/MS quantification; Analytical Chemistry (ACS), MRM methods
#串联质谱 #碰撞诱导解离 #MRM #定量
核磁共振中化学位移是怎么产生的？它为什么能反映分子结构？
How does chemical shift arise in NMR, and why does it reflect molecular structure?
原子核外电子在磁场中感生环流，产生屏蔽局部磁场，使不同化学环境的核共振频率发生偏移，以相对于四甲基硅烷（TMS）的 ppm 值表示即化学位移。屏蔽程度取决于核周围电子云密度与化学键的各向异性，因此 δ 值直接反映官能团类型与邻接环境。结合耦合裂分可解析完整连接关系。
Electrons around a nucleus circulate in a magnetic field and generate a local shielding field, shifting the resonance frequency of nuclei in different chemical environments; expressed in ppm relative to tetramethylsilane (TMS), this is the chemical shift. The shielding depends on electron density and bond anisotropy, so δ reflects functional groups and neighboring environments. Combined with coupling splittings, it reveals full connectivity.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
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《有机波谱学》(宁永成) 核磁共振章；IUPAC（核磁共振术语，2001）
IUPAC Recommendations for NMR Terminology (2001); Claridge, High-Resolution NMR Techniques in Organic Chemistry
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL16817875W：High-resolution NMR te
#核磁共振 #化学位移 #屏蔽 #TMS
荧光检测的高灵敏度来自何处？荧光量子产率受哪些因素影响？
Where does the high sensitivity of fluorescence detection come from, and what factors affect fluorescence quantum yield?
荧光是发射光与激发光波长不同，可在全暗背景下测量极弱信号，故检测限远低于吸收法。荧光量子产率取决于辐射跃迁速率与非辐射过程（内转换、系间窜越、能量转移、猝灭）的竞争。重原子、顺磁性物质、碰撞猝灭剂及分子内旋转都会降低产率。
Fluorescence emits at a different wavelength from excitation, so it can be measured against a dark background, giving detection limits far below absorption methods. Quantum yield depends on the competition between radiative decay and nonradiative processes (internal conversion, intersystem crossing, energy transfer, quenching). Heavy atoms, paramagnetic species, collisional quenchers, and intramolecular rotation all lower the yield.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
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《分析化学》(武汉大学, 第五版) 分子发光章；IUPAC（光化学术语，2006）
IUPAC (Photochemistry Terminology, 2006); Lakowicz, Principles of Fluorescence Spectroscopy
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL8055938W：Principles of Fluoresce
#荧光 #量子产率 #猝灭 #非辐射
电化学分析中电位法（如 pH 计）的依据是什么？
On what principle does potentiometry in electroanalysis (such as a pH meter) rely?
电位法测量工作电极与参比电极间在无净电流下的电动势，该电位由能斯特方程与待测离子活度相关。pH 计用玻璃电极响应氢离子活度，电势随 pH 每改变 1 单位约变化 59 mV（25 ℃）。由于不扰动体系，电位法适合原位、连续监测。
Potentiometry measures the electromotive force between a working and a reference electrode at zero net current, a potential linked to analyte activity by the Nernst equation. A pH meter's glass electrode responds to hydrogen-ion activity, with potential changing about 59 mV per pH unit at 25 ℃. Because it does not perturb the system, potentiometry suits in situ and continuous monitoring.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
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《分析化学》(武汉大学, 第五版) 电化学分析章；IUPAC（电化学术语，1985）
IUPAC (Electrochemical Terminology, 1985); Bard & Faulkner, Electrochemical Methods
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL17203337W：Electrochemical Method
#电位法 #能斯特方程 #pH计 #参比电极
拉曼光谱与红外光谱有什么联系与区别？
What are the connections and differences between Raman and infrared spectroscopy?
两者都基于分子振动提供结构信息，但机理不同：红外源于偶极矩变化，拉曼源于极化率变化（光的非弹性散射）。因此红外活跃而拉曼沉默的对称振动（如同核双键）在拉曼中可见，二者互补。拉曼可用可见光激发，适合水溶液与玻璃容器样品。
Both probe molecular vibrations for structural information but by different mechanisms: IR arises from a change in dipole moment, Raman from a change in polarizability (inelastic light scattering). Symmetric vibrations silent in IR (e.g., homonuclear bonds) appear in Raman, so the two are complementary. Raman uses visible light and suits aqueous and glass-contained samples.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
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《有机波谱学》(宁永成) 拉曼章；IUPAC（分子光谱术语）
IUPAC (Nomenclature of IR and Raman spectroscopy); Ferraro, Introductory Raman Spectroscopy
独立核验依据 · Independent verification: 核验依据 1 CROSSREF 标识 10.1016/c2009-0-21238-4：Introductory Raman S
#拉曼光谱 #红外光谱 #极化率 #互补
质谱仪的基本工作原理是什么？它主要提供什么信息？
What is the basic working principle of a mass spectrometer, and what information does it mainly provide?
质谱仪先将样品分子电离成带电离子，再在电磁场中按质荷比（m/z）分离并检测。它可提供分子的相对分子质量、元素组成（由精确质量与同位素峰）以及结构碎片信息。现代串联质谱还能进行复杂混合物中痕量化合物的定性与定量。
A mass spectrometer first ionizes sample molecules into charged ions, then separates them by mass-to-charge ratio (m/z) in electric or magnetic fields and detects them. It provides relative molecular mass, elemental composition (from exact mass and isotope patterns), and structural fragments. Modern tandem MS also enables qualitative and quantitative analysis of trace compounds in complex mixtures.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
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《分析化学》(武汉大学, 第五版) 质谱章；美国化学会(ACS)分析化学
Harris, Quantitative Chemical Analysis, mass spectrometry chapter; Analytical Chemistry (ACS)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL2747424W：Quantitative chemical a
#质谱 #质荷比 #电离 #分子离子
红外光谱为什么能用来鉴定分子中的官能团？
Why can infrared spectroscopy be used to identify functional groups in a molecule?
红外光被分子吸收后会激发特定化学键的振动（伸缩、弯曲），不同键的力常数与折合质量决定其特征吸收频率。含氧、氮、氢等官能团在 4000–400 cm⁻¹ 范围内有可指认的特征吸收带，因此红外光谱是官能团鉴定的快速手段。
Infrared light excites specific bond vibrations (stretching, bending), and each bond's force constant and reduced mass set its characteristic absorption frequency. Functional groups containing O, N, or H show identifiable bands across 4000–400 cm⁻¹, making IR a rapid tool for functional-group identification.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
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《有机波谱学》(宁永成) 红外章；IUPAC（分子光谱术语）
IUPAC (Nomenclature of IR and Raman spectroscopy); Silverstein, Spectrometric Identification of Organic Compounds
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL2679187W：Spectrometric identific
#红外光谱 #官能团 #分子振动 #特征吸收
色谱法分离混合物的基本原理是什么？
What is the basic principle by which chromatography separates mixtures?
色谱利用混合物中各组分在固定相与流动相之间分配（吸附、溶解或亲和作用）的差异实现分离。分配系数大的组分在固定相停留更久、迁移更慢，因而在不同时间流出。常见形式包括气相色谱、液相色谱和薄层色谱。
Chromatography separates mixtures based on differences in how components partition between a stationary phase and a mobile phase (by adsorption, solubility, or affinity). Components with larger partition coefficients spend more time in the stationary phase and migrate slower, eluting at different times. Common formats include GC, HPLC, and TLC.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
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《分析化学》(武汉大学, 第五版) 色谱章；美国化学会(ACS)分析化学
Harris, Quantitative Chemical Analysis, chromatography chapter; Analytical Chemistry (ACS)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL2747424W：Quantitative chemical a
#色谱 #固定相 #流动相 #分配系数