Liquid chromatography (LC) is a method of chromatographic separation based on the difference in the distribution of species between two non-miscible phases, in which the mobile phase is a liquid which percolates through a stationary phase contained in a column.
液相色谱是基于两个互不相溶相中不同品种差异实现分离的色谱分离方法。两相中移动相是液相，流经柱中的固定相。
LC is mainly based on mechanisms of adsorption, mass distribution, ion exchange, size exclusion or stereochemical interaction.
液相色谱主要是基于吸附，质量分配，离心交换，尺寸排阻或立体化学相互作用。
APPARATUS
装置
The apparatus consists of a pumping system, an injector, a chromatographic column (a column temperature controller may be used), a detector and a data acquisition system (or an integrator or a chart recorder). The mobile phase is supplied from one or several reservoirs and flows through the column, usually at a constant rate, and then through the detector.
装置包括泵系统，进样器，色谱柱（可能会使用柱温控制器），检测器和数据采集系统（或积分仪或图表记录器）。移动相由一个或多个容器提供，通常以常速流经色谱柱，然后流经检测器。
PUMPING SYSTEMS
泵系统
LC pumping systems are required to deliver the mobile phase at a constant flow rate. Pressure fluctuations are to be minimized, e.g. by passing the pressurized solvent through a pulse-dampening device. Tubing and connections are capable of withstanding the pressures developed by the pumping system. LC pumps may be fitted with a facility for “bleeding” the system of entrapped air bubbles.
要使用泵系统常速传输移动相。减少压力波动，如经脉冲-缓冲装置传输常压溶剂。管道和连接可以经受住泵系统产生的压力。LC泵可能会装有放出系统残留空气的装置。
Microprocessor controlled systems are capable of accurately delivering a mobile phase of either constant (isocratic elution) or varying composition (gradient elution), according to a defined programme. In the case of gradient elution, pumping systems which deliver solvent(s) from several reservoirs are available and solvent mixing can be achieved on either the low or high-pressure side of the pump(s).
微处理器控制系统可以根据确定的程序准确地传输恒定的移动相（恒溶剂洗脱法）或变化组分的移动相（梯度洗脱法）。梯度洗脱的情况，传输几个容器中的溶剂的泵系统是可行的，并且溶剂混合可以低压或高压的泵来实现。
INJECTORS
进样器
The sample solution is introduced into the flowing mobile phase at or near the head of the column using an injection system which can operate at high pressure. Fixed-loop and variable volume devices operated manually or by an auto-sampler are used. Manual partial filling of loops may lead to poorer injection volume precision.
使用进样系统（可以在高压下操作），在色谱柱的顶端或旁边将样品溶液引入流动相中。使用固定环，手动的可变容积装置，或自动取样器。环的部分填补可能会导致较差的进样溶剂精密度。
STATIONARY PHASES
固定相
There are many types of stationary phases employed in LC, including:
液相色谱使用的固定相有很多类型，包括：
- silica, alumina or porous graphite, used in normal-phase chromatography, where the separation is based on differences in adsorption and/or mass distribution,
- 正相色谱法中使用的硅土，氧化铝或多孔石墨，分离是基于吸附和/或质量分配的差异，
- resins or polymers with acid or basic groups, used in ion-exchange chromatography, where separation is based on competition between the ions to be separated and those in the mobile phase,
- 离子交换色谱法中使用的带有酸性或碱性基团树脂或聚合物，分离是基于待分离离子和移动相中离子的竞争，
- porous silica or polymers, used in size-exclusion chromatography, where separation is based on differences between the volumes of the molecules, corresponding to steric exclusion,
- 尺寸排阻色谱法中使用的多孔硅土或聚合物，分离是基于分子大小的差异，对应于空间排阻，
- a variety of chemically modified supports prepared form polymers, silica or porous graphite, used in reversed-phase LC, where the separation is based principally on partition of the molecules between the mobile phase and the stationary phase,
- 反相LC中使用的由多聚物，硅土或多孔石墨制成的多种化学修饰载体，分离主要是基于分子在移动相和固定相中的分配。，
- special chemically modified stationary phased, e.g. cellulose or amylase derivatives, proteins or peptides, cyclodextrins etc., for the separation of enantiomers (chiral chromatography).
- 专用化学修饰的固定相， 如纤维素或淀粉衍生物，蛋白质或肽，环糊精等，用于分离异构体（手性色谱柱）。
Most separations are based upon partition mechanisms utilizing chemically modified silica as the stationary phase and polar solvents as the mobile phase. The surface of the support, e.g. the silanol groups of silica, is reacted with various silane reagents to produce covalently bound silyl derivatives covering a varying number of active sites on the surface of the support. The nature of the bonded phase is an important parameter for determining the separation properties of the chromatographic system.
绝大多数分离是基于分配的机理，使用化学修饰的硅胶为固定相，溶剂为移动相。担体的表面，如，硅胶的硅烷醇基团，和不同的甲硅烷试剂反应制备共价键甲硅烷基衍生物，此衍生物在担体表面覆盖了许多不同的活性点。键合相性质是确定色谱系统分离性质的重要的参数。
Commonly used bonded phases are shown below:
常使用的键合相如下：
Unless otherwise stated by the manufacturer, silica based reversed-phase columns are considered to be stable in mobile phases having an apparent Ph in the range 2.0 to 8.0. columns containing porous graphite or particles of polymeric materials such as styrene-divinylbenzene copolymer are stable over a wider Ph range.
除非制造商有特殊的说明，基于反相色谱柱的硅胶被认为在2.0—8.0pH范围的移动相中稳定。多孔石墨或如苯乙烯-二乙烯基苯共聚物的颗粒在更宽的pH范围内稳定。
Analysis using normal-phase chromatography with unmodified silica, porous graphite or polar chemically modified silica, e.g., cyanopropyl or diol, as the stationary phase with a non-polar mobile phase is applicable in certain cases.
用未修饰的硅胶，多孔石墨或极性化学修饰硅胶的正相，如氰基丙基或二醇，用非极性移动相为固定相在某些情况下是可行的。
For analytical separations, the particle size of the most commonly used stationary phases varies between 3 um and 10 um. The particles may be spherical or irregular, of varying porosity and specific surface area. These parameters contribute to the chromatographic behaviour of a particular stationary phase. In the case of reversed phases, the nature of the stationary phase, the extent of bonding, e.g., expressed as the carbon loading, and whether the stationary phase is end-capped (i.e. residual silanol groups are silylated) are additional determining factors. Tailing of peaks, particularly of basic substances, can occur when residual silanol groups are present.
对于分析分离，常使用的固定相的颗粒大小有变化，在3到10微米之间。颗粒可以是球型的，也可以是不规则形状的，多孔性和比表面积有所不同。这些参数导致了特定固定相的分离行为。在反相的情况下，固定相的性质，键合程度，如以碳装载来表示，以及是否固定相末端加盖的（如残留硅烷醇是硅烷化的）是多加的测定因素。尤其是，在残留的硅烷醇存在下，峰的拖尾可能会发生。
Columns, made of stainless steel unless otherwise prescribed in the monograph, of varying length and internal diameter (Ø) are used for analytical chromatography. Columns with internal diameters of less than 2 mm are often referred to as microbore columns. The temperature of the mobile phase and the column must be kept constant during an analysis. Most separations are performed at room temperature, but columns may be heated to give higher efficiency. It is recommended that columns not be heated above 60°C because of the potential for stationary phase degradation or changes occurring to the composition of the mobile phase.
由不锈钢制成的（或者其它各论中指明的）色谱柱，长度和内径有变化，被用于分析色谱。低于2毫米内径的柱子通常被认为是微孔柱/在分析中移动相和色谱柱的温度应保持恒定。绝大部分的分离是在常温下进行的，可以加热色谱柱以得到较高的效率。建议柱子不要加热到60度以上，因为固定相的降解或变化对移动相的组成有潜在的影响。
MOBILE PHASES
移动相
For normal-phase chromatography, less polar solvents are employed. The presence of water in the mobile phase is to be strictly controlled to obtain reproducible results. In reversed-phase LC, aqueous mobile phases, with or without organic modifiers, are employed.
对于正相色谱，采用低极性的溶剂。严格控制移动相中水分，以可以重现结果。在反相液相色谱中，采用含水的移动相，含有或不含有有机修饰剂。
Components of the mobile phase are usually filtered to remove particles greater than 0.45 um. Multicomponent mobile phases are prepared by measuring the required volumes (unless masses are specified) of the individual components, followed by mixing. Alternatively, the solvents may be delivered by individual pumps controlled by proportioning valves by which mixing is performed according to the desired proportion. Solvents are normally degassed before pumping by sparging with helium, sonication or using on-line membrane/vacuum modules to avoid the creation of gas bubbles in the detector cell.
通常过滤移动相的组分以除去大于0.45微米的颗粒。多组分的移动相的制备通常测量单个组分的量，然后混合。其他的，根据需要的比例，溶剂可以通过又比例阀门控制的单个泵来传输，通过此阀门溶剂得到混合。溶剂被抽之前，通常用氦气鼓泡，超声波或使用再线膜/真空组件来去除气体，以避免检测池中气泡的产生。
Solvents for the preparation of the mobile phase are normally free of stabilizers and are transparent at the wavelength of detection, if an ultraviolet detector is employed. Solvents and other components employed are to be of appropriate quality. Adjustment of the Ph, if necessary, is effected using only the aqueous component of the mobile phase and not the mixture. If buffer solutions are used, adequate rinsing of the system is carried out with a mixture of water and the organic modifier of the mobile phase ( 5 per cent V/V) to prevent crystallization of salts after completion of the chromatography.
如果使用紫外检测器，用于制备移动相的溶剂通常应无稳定剂，并且在检测波长下是透明的。采用的溶剂和其它组分应有合适的质量。若必要，仅使用含水组分的，并不是混合成分的移动相，调整pH是有效果的。如果使用缓冲溶液，在色谱完成后，用水和移动相中有机修饰剂（5% V/V）对系统进行充分的冲洗，以避免盐结晶。
Mobile phases may contain other components, e.g. a counter-ion for ion-pair chromatography or a chiral selector for chromatography using an achiral stationary phase.
移动相可能包含其它的组分，如离子对色谱中的平衡离子，或者使用手性固定相色谱的手性选择器。
DETECTORS
检测器
Ultravioles/visible (UV/Vis) spectrophotometers, including diode array detectors, are the most commonly employed detectors. Fluorescence spectrophotometers, differential refractometers, electrochemical detectors, mass spectrometers, light scattering detectors, radioactivity detectors or other special detectors may also be used.
紫外/可见光度计，包括二极管阵列检测器是较为常用的检测器。荧光分光光度计，差示折射仪，电化检测器，质谱光度计，光扫描检测器，放射强度检测器或其它专门的仪器也可以使用。
METHOD
方法
Equilibrate the column with the prescribed mobile phase and flow rate, at room temperature or at the temperature specified in the monograph, until a stable baseline is achieved. Prepare the solution(s) of the substance to be examined and the reference solution(s) required. The solutions must be free from solid particles.
在室温或专论中指定的温度，用指定的流动相和流速平衡色谱柱，直至获得稳定的基线。制备待测物质的溶液，及需要的对照品溶液。溶液必须无固体颗粒。
Criteria for assessing the suitability of the system are described in the chapter on chromatographic separation techniques (2.2.46). the extent to which adjustments of parameters of the chromatographic system can be made to satisfy the criteria of system suitability are also given in this chapter.
评估系统适用性的标准在色谱分离技术章节（2.2.46）中叙述。色谱系统参数调整到什么程度，以满足系统适应性的标准，也在这一章节中给出。
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