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Static head-space gas chromatography  

2009-02-10 13:56:21|  分类: 分析方法 |  标签: |举报 |字号 订阅

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Static head-space gas chromatography

静态顶空气相色谱法

 

Static head-space gas chromatography is a technique particularly suitable for separating and determining volatile compounds present in solid or liquid samples. The method is based on the analysis of the vapour phase in equilibrium with the solid or liquid phase.

静态顶空气相色谱法是一种尤其适用于分离和确定固体或液体样品中的挥发性组分。方法是基于挥发相和固相或挥发相和液相的平衡实现分析的。

 

APPARATUS

装置

 

The apparatus consists of a gas chromatograph provided with a device for introducing the sample that may be connected to a module that automatically controls the pressure and the temperature. If necessary, a device for eliminating solvents can be added.

装置包含一个装有引入样品设备的气相色谱仪,引入样品的设备和自动控制压力和温度的组件相连,若必要的话,可以加上去除溶剂的设备。

 

The sample to be analyzed is introduced into a container fitted with a suitable stopper and a valve-system which permits the passage of the carrier gas. The container is placed in a thermostatically controlled chamber at a temperature set according to the substance to be examined.

待分析样品住入到配有合适制动器和允许载气通过阀门系统的容器中。容器置于温度控制的箱中,根据待测物质的性质,设置温度。

 

The sample is held at this temperature long enough to allow equilibrium to be established between the solid or liquid phase and the vapour phase.

样品在此温度下保存足够长的时间,以建立固体相和气相或液相和气相的平衡。

 

The carrier gas is introduced into the container and, after the prescribed time, a suitable valve is opened so that the gas expands towards the chromatographic column taking the volatilized compounds with it.

在指定的时间后,载气被注入容器中,开启适当的阀门,载气带着挥发性的物质在色谱柱中扩散。

 

Instead of using a chromatograph specifically equipped for the introduction of samples, it is also possible to use airtight syringes and a conventional chromatograph. Equilibration is then carried out in a separate chamber and the vapour phase is carried onto the column, taking the precautions necessary to avoid any changes in the equilibrium.

取代使用装有特定的样品注入的色谱仪,也可以使用密闭的进样器和常用的色谱仪。在隔离箱中实现平衡,气相被携带进入色谱柱,必要的注意,避免平衡发生变化。

 

METHOD

方法

Using the reference preparations, determine suitable instrument settings to produce an adequate response.

使用标准品,确定合适的仪器设置,产生准确的响应。

 

DIRECT CALIBRATION

直接校正

 

Separately introduce into identical containers the preparation to be examined and each of the reference preparations, as prescribed in the monograph, avoiding contact between the sampling device and the samples.

按各论中的指定的方法,在相同的容器中分别注入待测样品和每一个标准品,避免取样装置和样品的接触。

 

Close the containers hermetically and place in the thermostatically controlled chamber set to the temperature and pressure prescribed in the monograph; after equilibration, carry out the chromatography under the prescribed conditions.

密闭容器,放于各论中指定的温度和压力的恒温控制箱中,在平衡后,在指定的条件下,进行色谱分析。

 

STANDARD ADDITIONS

标准加入

 

Add to a set of identical suitable containers equal volumes of the preparation to be examined. Add to all but one of the containers, suitable quantities of a reference preparation containing a known concentration of the substance to be determined so as to produce a series of preparations containing steadily increasing concentrations of the substance.

在一组相同的容器中加入等量的待测样品。一个容器除外的所有的容器中,在已知浓度的待测物质中,加入适当的标准品,以得到包含有规则增加浓度的物质的待测品。

 

Close the containers hermetically and place in the thermostatically controlled chamber set to the temperature and pressure prescribed in the monograph; after equilibration, carry out the chromatography under the prescribed conditions.

密闭容器,放于恒温控制的箱中,温度和压力根据各论来设定;平衡后,在指定的条件下,进行色谱分析。

 

Calculate the linear equation of the graph using a least-squares fit, and derive from it the concentration of the substance to be determined in the preparation to be examined.

使用最小二乘法拟合计算图谱的线性方程,根据线性方程,得到待检验样品中待测物质的浓度。

 

Alternatively, plot on a graph the mean of readings against the added quantity of the substance to be determined. Extrapolate the line joining the points on the graph until it meets the concentration axis. The distance between this point and the intersection the axes represents the concentration of the substance to be determined in the preparation to be examined.

替代地,根据待测物质添加的量,读书的平均值绘制图谱。连接图谱上的点,直至其符合浓度轴,外推线性方法。点和轴交点的距离代表了待检验样品中测定样品的浓度。

 

SUCCESSIVE WITHDRAWALS (MULTIPLE HEAD-SPACE EXTRACTION)

连续地撤消

 

If prescribed, the successive withdrawal method is fully described in the monograph.

若指定,连续的撤消方法在各论中完全叙述。

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