将样品与溶剂混合并注入气相色谱仪中。通常样本量很小 – 在微升范围内。尽管样品以液体形式开始,但它会蒸发成气相。惰性载气也流过色谱仪。该气体不应与混合物的任何组分反应。此时,您可能想知道为什么混合物的组分在沿管推动时会分开。管的内部涂有薄层液体(固定相)。管内部的气体或蒸汽(气相)比与液相相互作用的分子更快地移动。与气相相互作用更好的化合物往往具有较低的沸点(挥发性)和较低的分子量,而较喜欢​​固定相的化合物往往具有较高的沸点或较重。影响化合物向下进行速率的其他因素(称为洗脱时间)包括极性和色谱柱的温度。因为温度非常重要,所以通常将温度控制在十分之一度,并根据混合物的沸点进行选择。常见的载气包括氩气,氦气,有时还包括氢气。将样品和载气加热并进入长管,该长管通常盘绕以保持色谱仪的尺寸可控。管可以是开放的(称为管状或毛细管)或填充有分开的惰性载体材料(填充柱)。管长,以便更好地分离组件。在管的末端是检测器,其记录击中它的样品量。在某些情况下,样品也可以在色谱柱末端回收。来自检测器的信号用于生成图表,色谱图显示在y轴上到达检测器的样品量以及通常在x轴上到达检测器的速度(取决于检测器检测到的内容) )。色谱图显示一系列峰。峰的大小与每种组分的量成正比,尽管它不能用于量化样品中的分子数。通常,第一个峰来自惰性载气,下一个峰是用于制备样品的溶剂。随后的峰代表混合物中的化合物。为了识别气相色谱图上的峰,需要将图表与标准(已知)混合物的色谱图进行比较,以查看峰出现的位置。

英国曼彻斯特大学化学Assignment代写:气相色谱

The sample is mixed with a solvent and is injected into the gas chromatograph. Typically the sample size is small — in the microliters range. Although the sample starts out as a liquid, it is vaporized into the gas phase. An inert carrier gas is also flowing through the chromatograph. This gas shouldn’t react with any components of the mixture. At this point, you may be wondering why the components of the mixture separate while they are pushed along the tube. The inside of the tube is coated with a thin layer of liquid (the stationary phase). Gas or vapor in the interior of the tube (the vapor phase) moves along more quickly than molecules that interact with the liquid phase. Compounds that interact better with the gas phase tend to have lower boiling points (are volatile) and low molecular weights, while compounds that prefer the stationary phase tend to have higher boiling points or are heavier. Other factors that affect the rate at which a compound progresses down the column (called the elution time) include polarity and the temperature of the column. Because temperature is so important, it is usually controlled within tenths of a degree and is selected based on the boiling point of the mixture. Common carrier gases include argon, helium, and sometimes hydrogen. The sample and carrier gas are heated and enter a long tube, which is typically coiled to keep the size of the chromatograph manageable. The tube may be open (called tubular or capillary) or filled with a divided inert support material (a packed column). The tube is long to allow for a better separation of components. At the end of the tube is the detector, which records the amount of sample hitting it. In some cases, the sample may be recovered at the end of the column, too. The signals from the detector are used to produce a graph, the chromatogram, which shows the amount of sample reaching the detector on the y-axis and generally how quickly it reached the detector on the x-axis (depending on what exactly the detector detects). The chromatogram shows a series of peaks. The size of the peaks is directly proportional to the amount of each component, although it can’t be used to quantify the number of molecules in a sample. Usually, the first peak is from the inert carrier gas and the next peak is the solvent used to make the sample. Subsequent peaks represent compounds in a mixture. In order to identify the peaks on a gas chromatogram, the graph needs to be compared a chromatogram from a standard (known) mixture, to see where the peaks occur.

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