📚 Mastering Chromatography for IB and CIE Chemistry | IB CIE 化学：色谱 考点精讲
Chromatography is one of the most powerful separation techniques in chemistry, and it features prominently in both IB and CIE examinations. From paper and thin‑layer chromatography to gas chromatography, understanding the underlying principles, practical procedures, and data analysis methods is essential. This article unpacks every key concept you need to master chromatography, always linking theory to the exam questions you are likely to face.
色谱法是化学中最强大的分离技术之一，在 IB 和 CIE 考试中都占有重要地位。从纸色谱、薄层色谱到气相色谱，理解分离原理、实验步骤和数据分析方法至关重要。本文将逐一解析你需要掌握的核心概念，并将理论与考试常见题型紧密联系。
1. What is Chromatography? | 什么是色谱法？
Chromatography is a physical separation technique used to separate components of a mixture based on their differential distribution between two phases: a stationary phase and a mobile phase. The mobile phase carries the sample through the stationary phase, and components that interact more strongly with the stationary phase move more slowly, leading to separation.
色谱法是一种物理分离技术，根据混合物中各组分在两相——固定相和流动相——之间的分配差异进行分离。流动相携带样品通过固定相，与固定相作用更强的组分移动更慢，从而实现分离。
In all chromatographic methods, the separation depends on the relative affinity of each component for the stationary and mobile phases. A component that adsorbs strongly onto the stationary phase will have a longer retention time or a lower Rf value.
在所有色谱方法中，分离取决于每种组分对固定相和流动相的相对亲和力。对固定相吸附强烈的组分会有更长的保留时间或更小的 Rf 值。
The term chromatography comes from the Greek words chroma (colour) and graphein (to write), as the technique was originally developed to separate coloured plant pigments. Today it is widely used for colourless substances by using locating agents or detectors.
“色谱法”一词源自希腊语 chroma（颜色）和 graphein（书写），因为该技术最初是为分离有色植物色素而开发的。如今通过使用显色剂或检测器，它已广泛用于无色物质。
2. Key Principles of Separation | 分离的关键原理
Separation is achieved because different substances undergo adsorption (or partitioning) to varying extents on the stationary phase while being carried along by the mobile phase. The balance between adsorption and solubility determines how far a substance travels in a given time.
分离的实现是因为不同物质在固定相上发生不同程度的吸附（或分配），同时被流动相携带前进。吸附和溶解度之间的平衡决定了物质在给定时间内移动的距离。
In adsorption chromatography, such as TLC and paper chromatography, the stationary phase is a solid on which components adsorb. The mobile phase can be a liquid (solvent). In partition chromatography, such as gas‑liquid chromatography, the stationary phase is a liquid bonded to a solid support, and components partition between the liquid stationary phase and a gaseous mobile phase.
在薄层色谱和纸色谱等吸附色谱中，固定相是一种固体，组分在其表面吸附。流动相可以是液体（溶剂）。在气液色谱等分配色谱中，固定相是附着在固体载体上的液体，组分在液体固定相和气态流动相之间进行分配。
The efficiency of separation depends on the choice of stationary phase, the nature and polarity of the mobile phase, and temperature (especially in gas chromatography). A more polar stationary phase will retain polar solutes more strongly.
分离效率取决于固定相的选择、流动相的性质和极性以及温度（尤其在气相色谱中）。极性更强的固定相对极性溶质的保留更强。
3. Paper Chromatography: Setup and Procedure | 纸色谱：装置与步骤
In paper chromatography, the stationary phase is water molecules bound to cellulose fibres of the chromatography paper, and the mobile phase is a liquid solvent or solvent mixture. A small spot of the mixture is placed near the bottom of the paper (the baseline), and the paper is placed upright in a sealed container with the solvent level below the baseline.
在纸色谱中，固定相是结合在色谱纸纤维素纤维上的水分子，流动相是液体溶剂或混合溶剂。将一小点混合物点在纸张底部附近（基线处），然后将纸张垂直放入密闭容器中，溶剂液面低于基线。
The solvent rises up the paper by capillary action, carrying the components with it. When the solvent front nears the top, the paper is removed, and the positions of the separated spots are marked. If the substances are colourless, a locating agent (e.g. ninhydrin for amino acids or iodine vapour) is used to visualise the spots.
溶剂通过毛细作用沿纸上升，携带组分移动。当溶剂前沿接近顶部时，取出纸，标记分离斑点的位置。如果物质无色，则使用显色剂（例如氨基酸用茚三酮或碘蒸气）显色。
Paper chromatography is simple and inexpensive, making it ideal for separating small amounts of polar substances such as amino acids, sugars, and plant pigments. However, it has relatively low resolution and is not suitable for quantitative analysis.
纸色谱简单、成本低，非常适合分离少量极性物质，如氨基酸、糖类和植物色素。但它的分辨率相对较低，不适合定量分析。
4. Thin‑Layer Chromatography (TLC) | 薄层色谱法
TLC uses a glass, plastic, or aluminium plate coated with a thin layer of a solid adsorbent, typically silica gel (SiO₂) or alumina (Al₂O₃). The stationary phase is this solid adsorbent, which is usually polar. The mobile phase is a solvent or mixture of solvents that travels up the plate by capillary action.
薄层色谱法使用涂有一层薄薄固体吸附剂（通常是硅胶 SiO₂ 或氧化铝 Al₂O₃）的玻璃、塑料或铝板。固定相就是这种通常为极性的固体吸附剂。流动相是溶剂或混合溶剂，通过毛细作用沿板上升。
The sample is spotted near the bottom, and the plate is developed in a closed chamber. Because silica gel and alumina are highly polar, polar compounds adsorb more strongly and move more slowly, while non‑polar compounds travel further. TLC provides better separation and faster development than paper chromatography.
样品点在板的底部附近，然后在密闭展开缸中展开。由于硅胶和氧化铝是强极性的，极性化合物吸附更强、移动更慢，而非极性化合物移动更远。与纸色谱相比，TLC 分离效果更好且展开更快。
TLC is widely used in organic chemistry to monitor the progress of a reaction, check the purity of a product, and identify compounds by comparing Rf values with known standards.
TLC 在有机化学中广泛用于监测反应进程、检验产品纯度以及通过与已知标准品比较 Rf 值来鉴定化合物。
5. Calculating and Interpreting Rf Values | Rf 值的计算与解读
The Rf (retention factor) is a dimensionless number defined as the ratio of the distance travelled by the component to the distance travelled by the solvent front, both measured from the baseline: Rf = distance moved by substance ÷ distance moved by solvent front.
Rf（比移值）是一个无量纲数，定义为组分移动的距离与溶剂前沿移动的距离之比，两者均从基线测量：Rf = 物质移动距离 ÷ 溶剂前沿移动距离。
e that stays at the baseline has Rf = 0; one that moves with the solvent front has Rf = 1.
在固定相和流动相一定的条件下，特定物质的 Rf 值在受控条件下是常数，可通过与已知值比较用于鉴定。Rf 值总是在 0 与 1 之间。停留在基线上的物质 Rf = 0；随溶剂前沿移动的物质 Rf = 1。
Exam questions often ask you to calculate Rf or to compare Rf values to deduce which spot corresponds to which substance. Always measure to the centre of the spot and express the answer to two or three significant figures.
考试题常常要求计算 Rf 值或比较 Rf 值以推断哪个斑点对应哪种物质。务必测量到斑点中心，并将答案表示为两到三位有效数字。
Factors that affect Rf include temperature, the composition of the mobile phase, the thickness of the stationary phase, and the humidity. Slight variations are common, which is why a known standard is often run on the same plate for comparison.
影响 Rf 的因素包括温度、流动相的组成、固定相的厚度和湿度。轻微变化很常见，因此常常在同一块板上点加已知标准品进行比较。
6. Gas Chromatography (GC): Instrumentation | 气相色谱法：仪器装置
Gas chromatography, often called gas‑liquid chromatography (GLC), is used to separate and analyse volatile organic compounds. The mobile phase is an inert carrier gas, typically helium or nitrogen, and the stationary phase is a high‑boiling liquid coated on the inner wall of a narrow capillary column or packed in a column.
气相色谱法，常被称为气液色谱法，用于分离和分析挥发性有机化合物。流动相是惰性载气，通常是氦气或氮气，固定相是涂覆在细毛细管柱内壁或填充在色谱柱中的高沸点液体。
The sample is injected into a heated injection port where it vaporises and is swept into the column by the carrier gas. The column is housed in a temperature‑controlled oven. As components travel through the column, they partition between the liquid stationary phase and the carrier gas, separating based on their boiling points and solubility.
样品注入加热的气化室，汽化后被载气带入色谱柱。色谱柱置于温控烘箱中。组分通过色谱柱时，在液体固定相和载气之间进行分配，根据其沸点和溶解度的差异实现分离。
A detector measures the components as they elute from the column. Common detectors include the flame ionisation detector (FID) and the thermal conductivity detector (TCD). The signal is recorded as a chromatogram, a graph of detector response against time.
检测器在组分从色谱柱洗脱时对其进行测量。常用的检测器包括火焰离子化检测器（FID）和热导检测器（TCD）。信号被记录为色谱图，即检测器响应随时间变化的曲线图。
7. Retention Time and Peak Area | 保留时间与峰面积
Retention time (tR) is the time taken for a particular component to travel from the injection point to the detector. For a given set of conditions (column, temperature, carrier gas flow rate), each compound has a characteristic retention time, which can be used for qualitative identification.
保留时间 (tR) 是特定组分从进样点到检测器所需的时间。在给定的一组条件（色谱柱、温度、载气流速）下，每种化合物都有其特征保留时间，可用于定性鉴定。
The area under a peak in the chromatogram is proportional to the amount of that component in the sample. By measuring peak areas and comparing them with calibration standards, quantitative analysis can be performed. Exam questions often present a chromatogram and ask you to calculate the percentage composition of a mixture.
色谱图中峰下的面积与该组分在样品中的含量成正比。通过测量峰面积并与校准标准品比较，可以进行定量分析。考试题常常给出色谱图，要求计算混合物的百分组成。
Modern GC instruments use software to integrate peak areas automatically, but in exam scenarios, you may be given peak areas or asked to estimate them from a diagram. Always check that all peaks are accounted for and that the total area equals 100% when calculating relative abundance.
现代气相色谱仪使用软件自动积分峰面积，但在考试中，可能会给出峰面积或要求从图表中估算。计算相对含量时，务必确保所有峰都已计入，且总面积等于 100%。
8. Interpreting Chromatograms: TLC vs GC | 解读色谱图：TLC 与 GC 对比
In planar chromatography (paper or TLC), the chromatogram is a visual display of separated spots. You can immediately see how many components are present (if one spot, the sample may be pure) and calculate Rf values for identification. The relative size or intensity of spots gives a rough indication of relative amounts.
在平面色谱（纸色谱或 TLC）中，色谱图是分离斑点的直观展示。可以立即看出存在多少种组分（如果只有一个斑点，样品可能是纯品），并计算 Rf 值进行鉴定。斑点的相对大小或深浅可以粗略指示相对含量。
In gas chromatography, the chromatogram is a series of peaks. The number of peaks indicates the number of components (assuming they are resolved). The retention time identifies the component, and the peak area gives the quantity. Peak shapes also provide information: broader peaks suggest slower equilibration, while very sharp peaks indicate efficient separation.
在气相色谱中，色谱图是一系列峰。峰的数量表示组分的数量（假设它们已被分离）。保留时间用于鉴定组分，峰面积确定其含量。峰形也能提供信息：宽峰表明平衡速度慢，而非常尖锐的峰则表明分离效率高。
Exam questions may ask you to deduce which component is most abundant, which has the highest boiling point (longer retention time on a non‑polar column), or which has the strongest affinity for the stationary phase. Understanding both types of chromatogram is essential.
考试题可能要求推断哪种组分含量最丰富、哪种沸点最高（在非极性柱上保留时间更长），或者哪种组分对固定相的亲和力最强。理解这两种色谱图都至关重要。
9. Factors Affecting Separation Quality | 影响分离质量的因素
Temperature is critical in gas chromatography. Higher oven temperatures reduce retention times because compounds spend more time in the gas phase, but resolution may decrease if peaks overlap. A temperature programme (gradual increase) often improves separation of mixtures with a wide range of boiling points.
温度在气相色谱中至关重要。烘箱温度越高，保留时间越短，因为化合物在气相中的时间更长，但如果峰重叠，分辨率可能会降低。程序升温（逐步升高）通常能改善沸点范围宽的混合物的分离效果。
In TLC and paper chromatography, the polarity of the mobile phase is the main variable. A more polar solvent will compete more effectively for adsorption sites, causing polar solutes to travel further. Mixing solvents allows fine‑tuning of polarity. The chamber must be saturated with solvent vapour to prevent the plate from drying out.
在 TLC 和纸色谱中，流动相的极性是主要变量。极性更强的溶剂会更有效地竞争吸附位点，使极性溶质移动得更远。混合溶剂可以微调极性。展开缸必须用溶剂蒸气饱和，以免板干涸。
Other factors include the thickness and uniformity of the stationary phase, the size of the starting spot (keep it small and concentrated), and the distance the solvent travels (longer development often improves resolution but causes spot diffusion).
其他因素包括固定相的厚度和均匀性、起始点的大小（保持小而浓）、以及溶剂的展开距离（更长的展开距离常能提高分辨率，但会导致斑点扩散）。
10. Practical Applications and Real‑World Uses | 实际应用与现实用途
Chromatography is indispensable in forensic science for analysing drugs, poisons, and ink dyes. It is used in food chemistry to detect additives, pesticides, and contaminants. In environmental monitoring, GC is used to measure volatile organic pollutants in air and water.
色谱法在法医学中对于分析药物、毒物和墨水染料不可或缺。在食品化学中用于检测添加剂、杀虫剂和污染物。在环境监测中，气相色谱用于测量空气和水中的挥发性有机污染物。
In the pharmaceutical industry, chromatography ensures the purity of drug compounds and quantifies active ingredients. Biochemists use chromatography to separate and purify proteins, nucleic acids, and metabolites. Even space missions carry miniature GC instruments to analyse the atmosphere of other planets.
在制药工业中，色谱法可确保药物化合物的纯度并定量活性成分。生物化学家使用色谱法分离和纯化蛋白质、核酸和代谢产物。甚至太空任务也搭载微型气相色谱仪来分析其他行星的大气。
Linking these applications to exam contexts helps you understand why a particular technique is chosen and what information the chromatogram provides. For example, a question might describe the detection of alcohol in a blood sample by GC, asking you to identify ethanol by its retention time and quantify it by peak area.
将这些应用与考试情境联系起来有助于理解为什么选择特定技术以及色谱图提供了哪些信息。例如，题目可能描述通过气相色谱检测血液样本中的酒精，要求你根据保留时间鉴定乙醇并根据峰面积定量。
11. Common Exam Pitfalls and How to Avoid Them | 常见考试错误与避坑指南
he substance moved with the solvent front, so it is the fastest. In GC, longer retention time means slower elution.
一个常见错误是混淆 Rf 值与保留时间，或认为 Rf 值越大的物质移动越慢。记住：Rf = 1 表示物质随溶剂前沿移动，所以它是最快的。在气相色谱中，保留时间越长，表示洗脱越慢。
Another error is measuring the distance to the wrong edge of a spot. Always measure from the baseline to the centre of the spot. When calculating peak areas, students sometimes forget to account for all peaks or incorrectly sum the areas.
另一个错误是测量时误量斑点的边缘。务必从基线测量到斑点中心。在计算峰面积时，学生有时忘记计入所有峰，或错误地求总面积。
In TLC, students may draw the baseline in ink (which would run in the solvent) instead of pencil. They may also allow the solvent level to submerge the spots, dissolving the sample into the solvent reservoir. Always state that the baseline is drawn in pencil and the solvent level is below the spots.
在 TLC 中，学生可能用墨水笔画基线（墨水会在溶剂中扩散）而不是铅笔。还可能让溶剂液面淹没斑点，使样品溶入溶剂中。务必说明基线用铅笔画，溶剂液面低于斑点。
For gas chromatography, forgetting that the detector response is proportional to concentration, not directly to mass unless calibrated, can lead to misinterpretation. Also, always clarify whether peak areas are given and how to convert them to percentage composition.
对于气相色谱，忘记检测器响应与浓度成正比（除非经过校准，否则不直接与质量成正比）可能会导致误解。此外，务必澄清是否给出了峰面积以及如何将其转换为百分组成。
12. Exam Tips and Revision Strategies | 应试技巧与复习策略
Create a summary table comparing paper chromatography, TLC, and gas chromatography across categories: stationary phase, mobile phase, principle of separation, typical application, and how to obtain qualitative and quantitative data. This helps you answer comparison questions quickly.
制作一张总结表，比较纸色谱、TLC 和气相色谱的各个类别：固定相、流动相、分离原理、典型应用以及如何获得定性和定量数据。这有助于你快速回答比较类题目。
Practice interpreting chromatograms by drawing spots on a TLC plate and calculating Rf values from given measurements. For gas chromatography, work through problems that provide retention times and peak areas, and ask you to calculate the mole percentage or mass percentage of a mixture.
练习解读色谱图：在 TLC 板上画斑点并根据给出的测量值计算 Rf 值。对于气相色谱，练习提供保留时间和峰面积的题目，要求计算混合物的摩尔百分比或质量百分比。
Be ready to explain why a solvent mixture is used in TLC (to fine‑tune polarity for optimal separation), why the chamber is covered (to prevent evaporation and maintain a saturated atmosphere), and why helium is used as a carrier gas in GC (it is inert and gives good peak shapes).
做好解释以下问题的准备：为什么 TLC 中使用混合溶剂（微调极性以达到最佳分离），为什么要盖住展开缸（防止蒸发并保持饱和气体环境），以及为什么气相色谱中使用氦气作为载气（惰性且能提供良好峰形）。
Finally, always look for clues in the question: if a sample is a mixture of volatile liquids, GC is likely the technique. If it is a small amount of coloured or UV‑active organic compound, TLC may be indicated. Link the technique to the physical properties described.
最后，始终在题目中寻找线索：如果样品是挥发性液体混合物，则很可能使用气相色谱。如果是少量有色或紫外活性的有机化合物，则可能指 TLC。将技术与其描述的物理性质联系起来。
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