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天道酬勤--药品注册质量管理

 
 
 

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GAS CHROMATOGRAPHY ---20090206  

2009-02-06 15:32:18|  分类: 分析方法 |  标签: |举报 |字号 订阅

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Gas chromatography (GC) is a chromatographic separation technique based on the difference in the distribution of species between two non-miscible phases in which the mobile phase is a carrier gas moving through or passing the stationary phase contained in a column. It is applicable to substances or their derivatives which are volatilized under the temperatures employed.

气相色谱法是一种基于样品在两种不相溶相中分配差别的一种色谱分离技术。移动相是载气在固定相上流过。气相色谱法适用于在运用温度下挥发的物质或其衍生物。

 

GC is based on mechanisms of adsorption, mass distribution or size exclusion.

气相色谱法基于吸附,质量分配或尺寸排阻的机理。

 

APPARATUS

装置

 

The apparatus consists of an injector, a chromatographic column contained in an oven, a detector and a data acquisition system (or an integrator or a chart recorder). The carrier gas flows through the column at a controlled rate or pressure and then through the detector.

装置包括进样器,恒温箱中装有的色谱柱, 检测器, 数据采集系统(或为积分仪或图表记录器), 载气在控制的流速,或压力下流过色谱柱,然后流到检测器。

 

The chromatography is carried out either at a constant temperature or according to a given temperature programme.

气相色谱法可以在常温下进行,也可以根据给定的温控程序进行。

 

INJECTORS

进样器

 

Direct injections of solutions are the usual mode of injection, unless otherwise prescribed in the monograph. Injection may be carried out either directly at the head of the column using a syringe or an injection valve, or into a vaporization chamber which may be equipped with a stream splitter.

溶液的直接进样是进样的常用方式, 除非在各论中指明。可以用注射器或进样阀在柱顶直接进样,也可以在气化箱中进样,汽化箱可能会装有分流器。

 

Injections of vapour phase may be effected by static or dynamic head-space injection systems.

气相进样可能会受静态或动态顶空进样系统的影响。

 

Dynamic head-space (purge and trap) injection systems include a sparging device by which volatile substances in solution are swept into an absorbent column maintained at a low temperature. Retained substances are then desorbed into the mobile phase by rapid heating of the absorbent column.

动态顶空(吹脱和补集)进样系统包含鼓泡装置,通过这个鼓泡装置,溶液中的挥发性物质进入维持低温的吸附柱中。通过快速加热吸附柱,残留的物质被解附到移动相。

 

Static head-space injection systems include a thermostatically controlled sample heating chamber in which closed vials containing solid or liquid samples are placed for a fixed period of time to allow the volatile components of the sample to reach equilibrium between the on-gaseous phase and the vapour phase. After equilibrium has been established, a predetermined amount of the head-space of the vial is flushed into the gas chromatograph.

静态顶空进样系统包括恒温控制的样品加热箱,装有固体或液体样品的样品瓶放置于此加热箱中一定的时间以使样品中的挥发组分在非气相和挥发相中达到平衡。在平衡建立以后,顶空瓶中预定量的样品进入气相色谱仪。

 

STATIONARY PHASES

固定相

 

Stationary phases are contained in columns which may be:

固定相装载色谱柱中,柱子可以是:

-          a capillary column of fused-silica whose wall is coated with the stationary phase,

-          熔融二氧化硅毛细管柱,壁上涂有固定相,

-          a column packed with inert particles impregnated with the stationary phase,

-          用惰性粒子填充的色谱柱,惰性粒子浸泡过固定相

-          a column packed with solid stationary phase.

-          固态固定相填充的色谱柱。

 

Capillary columns are 0.1mm to 0.53 mm in internal diameter (Ø) and 5 m to 60 m in length. The liquid or stationary phase, which may be chemically bonded to the inner surface, is a film 0.1 um to 5.0 um thick.

毛细管柱内径0.1毫米至0.53毫米,长度5米至60米。液体或称为固定相键合于内表面,是0.1微米至5.0微米厚的薄膜。

 

Packed columns, made of glass or metal, are usually 1 m to 3 m in length with an internal diameter (Ø) of 2 mm to 4 mm. Stationary phases usually consist of porous polymers or solid supports impregnated with liquid phase.

填充柱,由玻璃或金属制成,通常1米至3米长,内径2毫米到4毫米。固定相通常由多孔聚合体或浸渍过液相的固体担体构成。

 

Supports for analysis of polar compounds on columns packed with low-capacity, low-polarity stationary phase must be inert to avoid peak tailing. The reactivity of support materials can be reduced by silanising prior to coating with liquid phase. Acid-washed, flux-calcinated diatomaceous earth is often used. Materials are available in various particle sizes, the most commonly used particles are in the ranges of 150 um to 180 um and 125 um to 150 um.

用于分析极性化合物,用低容量,低极性填充的色谱柱的担体必须是惰性的,以避免峰拖尾。担体材料的活性在涂液相前可以通过硅烷化实现降低。通常使用酸洗的,通量煅烧硅藻土。各种不同粒径的材料可以使用。最常使用的是150微米至180微米,以及125到150微米的范围的粒径。

 

MOBILE PHASES

移动相

Retention time and peak efficiency depend on the carrier gas flow rate; retention time is directly proportional to column length and resolution is proportional to the square root of the column length. For packed columns, the carrier gas flow rate is usually expressed in milliliters per minute at atmospheric pressure and room temperature. Flow rate is measured at the detector outlet, either with a calibrated mechanical device or with a bubble tube, while the column is at operating temperature. The linear velocity of the carrier gas through a packed column is inversely proportional to the square root of the internal diameter of the column for a given flow volume. Flow rates of 60ml/min in a 2 mm internal diameter column, give identical linear velocities and thus similar retention times.

保留时间和峰效取决于载气流速,保留时间正比于柱长,分离度正比于柱长的平方根。对于填充柱,载气流速通常以常压室温下毫升/分钟表示。当在运行的温度下,流速在检测器出口,用标刻度的机械装置或用气泡法测量。对给定的流量,流经填充柱的载气的线速度反比于柱子内部直径的平方根。4毫米内径,60毫升/分的流速和2毫米内径,15毫升/分的流速,可以得到相同的线速度,因此有相同的保留时间。

 

Helium or nitrogen are usually employed as the carrier gas for packed columns, whereas commonly used carrier gases for capillary columns are nitrogen, helium and hydrogen.

填充柱的载气通常使用氦气或氮气,而毛细管柱的载气通常使用氮气,氦气和氢气。

 

DETECTORS

检测器

 

Flame-ionisation detectors are usually employed but additional detectors which may be used include: electron-capture, nitrogen-phosphorus, mass spectrometric, thermal conductivity, Fourier transform infrared spectrophotometric, and others, depending on the purpose of the analysis.

通常使用火焰-离子检测器,根据检验的目的,其它的检测器也可以使用,包括:电子俘获检测器,氮磷检测器,质谱检测器,热导检测器,傅立叶转化红外光度计。

 

METHOD

方法

 

Equilibrate the column, the injector and the detector at the temperatures and the gas flow rates specified in the monograph until a stable baseline is achieved. Prepare the test solution(s) and the reference solution(s) as prescribed. The solutions must be free from solid particles.

按照各论中指出的温度和载气流速平衡色谱柱,进样器和检测器,直至获得稳定的基线。按指定的方法配置供试溶液和标准溶液。溶液中必须无固体颗粒。

 

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.

评价系统适应性的标准在色谱分离技术章节中(2.2.46)有叙述。色谱系统参数调整的什么程度以满足系统适应性的标准也在这一章节中给出叙述。

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