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The modern headspace analysis method has formed a relatively complete analysis system, which can be divided into three categories. Static headspace analysis 2. Dynamic headspace analysis or purging and trapping 3. Headspace-solid phase microextraction.1.5ml crimp headspace analysis vials
Static headspace analysis is the earliest form in the development of headspace analysis; static headspace analysis can be divided into three categories in instrument mode: head air direct injection mode, balanced pressure sampling mode and pressurization Sample sampling mode.
The headspace direct injection system is equipped with a gas tight gas sampling needle, usually with a temperature control device on the outside of the gas sampling needle. This static headspace analysis mode has wide applicability and easy cleaning. It is suitable for samples with high volatile content such as flavor, flavor and tobacco. When the pressure of the head air is too high under heating conditions, the loss of volatile components will occur at the moment when the syringe is pulled out of the headspace bottle, 1.5ml crimp headspace analysis vials so there is a certain deficiency in quantitative analysis. To reduce condensation of volatile materials in the syringe, the syringe should be heated to the appropriate temperature and the injector cleaned with gas before each injection to minimize the memory effect of the system.
The balanced pressurized sampling mode system consists of a pressure control valve and a gas injection needle. When the volatile matter in the sample reaches the equilibrium of distribution, a certain air pressure is applied to the headspace bottle to directly press the head air body into the carrier gas flow. This sampling mode relies on a time program to control the analysis process, so it is difficult to calculate the specific injection volume. However, the system with balanced pressurized sampling mode has a small dead volume and good reproducibility. Also to reduce condensation of volatile materials in the tube wall and syringe, the tube wall and syringe should be heated to the appropriate temperature and the syringe should be purged with gas before each injection.
The pressurized constant volume sampling injection mode consists of a gas loop, a pressure control valve and a gas transfer line. The system presses the top air into the loop of the six-way valve by applying a certain pressure to the headspace bottle. Then use the carrier gas to enter the headspace component of the loop of the six-way valve into the column. The advantage of this method is that it is very reproducible and is very suitable for quantitative analysis of headspace. However, because the longer volatiles in the system tubing tend to adsorb on the tube wall, the tubing and syringe are typically heated to a higher temperature.
The main disadvantage of the static headspace analysis method is that large-volume gas injection is sometimes necessary, so that the initial broadening of the peak of the volatile material will affect the separation efficiency of the chromatogram. 1.5ml crimp headspace analysis vials Static methods are still a very simple and effective method of analysis if the amount of components to be analyzed in the sample is not very low and less gas injection can meet the needs of the analysis.
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