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The headspace is a sampler for the gas chromatograph hplc vials manufacturer in china headspace sampler. The common gas chromatograph is injection with a syringe. The injection volume is at the ul level and the sample is a liquid. The headspace injection volume is in the ml. Level, the gas entering the gas chromatograph; the volatile impurities in the general test substance are better tested by headspace, such as measuring residual solvents, such as detecting organic pollutants in the air, which may require large volume injection or need to enter Gas samples were analyzed and headspace injections well met these requirements.
(1) Dispersion system of high polymer
Headspace sampler top air phase chromatography can be used to separate and analyze dispersions of plastics, copolymers, and polymers. For example: for the detection of polyethylene group degradation products such as ethane, propane, n-butane and butene-1. When polyethylene is used as a packaging material for milk, these components cause the milk to produce an unpleasant odor.
Hachenberg has given examples of top air phase chromatography for the determination of solid polymer and polymer dispersions. He found that using this technique to detect residual monomers is much more sensitive than the conventional method of dissolving the polymer and then reprecipitating it.
Figures 2-40 illustrate the determination of styrene in polystyrene by conventional gas chromatography hplc vials manufacturer in china. First, the polystyrene was dissolved in dichloromethane (CH 2 Cl 2 ), and then precipitated by adding methanol (CH 3 OH), and then the sample solution was taken with a syringe and sent to a chromatography column for separation analysis. In this analysis, except for the styrene peak, * only the internal standard peak was observed, and the solvent (CH2Cl2) and the precipitant (CH3OH) flowed together, while the other impurities were not separated and were hidden in the mixed peak of CH2Cl2 and CH3OH. in. The figure shows that only two components with a higher content in the sample can be detected, so the sensitivity of the conventional method for determining styrene is very low.
The headspace gas chromatography analysis does not take time to prepare the sample (dissolution and precipitation), and the volatile gaseous sample is directly subjected to gas chromatography separation analysis to obtain a chromatogram as shown in Fig. 2-41. As can be seen from the figure, the headspace gas chromatography analysis can detect more components and achieve lower detection limits. Therefore, this method is fast and sensitive.
The petroleum ether remaining in the polymer was also analyzed by headspace gas chromatography; α-methylstyrene and other types of polymers, copolymers, and polymer dispersions were analyzed.
(2) Food volatile components
Headspace gas chromatography analysis was first applied to the food industry. In the past, people only used the smell and taste to identify the quality of food. Now, this method can be used to help identify. In many cases, the peak of the component representing the characteristic flavor of the food can be found on the chromatogram. Therefore, the headspace gas chromatography The law is called "gas chromatograph nose".
Mackay et al. have performed headspace gas chromatography analysis of volatile components of banana, peppermint oil, roasted coffee, brandy, whisky, and the like. Even without precise qualitative and quantitative analysis, the true smell of taste or taste can be understood from the chromatogram; Figure 2-39 shows the analysis of fresh banana and banana flavor.
Brown and others, Romani and Ku (Ku) and others have done the analysis of apple and pear volatiles. Drauttle et al. performed a liquid-liquid extraction method using pentane-dichloromethane (2:1) as a solvent and top air phase chromatography to analyze apple flavor. The two methods were different. result. They believe that headspace gas chromatography analysis is very useful for the qualitative analysis of odorant components, but the accuracy of its quantitative analysis needs to be improved hplc vials manufacturer in china.
Weurman used top air phase chromatography to study the composition of volatile enzymes in mature raspberries. In addition, he also made measurements of NO, N2O, N2, O2, CO2, CO and H2 in packaged foods; comparative analysis of the quality of fresh vegetables, frozen vegetables and wrapped vegetables.
Miethke analyzed the composition of various alcoholic beverages by headspace gas chromatography. For example: pear wine, eggnog, brandy, cherry brandy, French brandy, etc., the content of alcohol, component name and dopants are determined.
Jentzsch et al. used top air phase chromatography to distinguish chamomile tea from mint tea.
(3) Volatile components in water
Gottauf uses top air phase chromatography to quantify volatile organic impurity components in water. Before performing gas chromatography analysis, the components in the water gas are purged and concentrated by an enrichment tube filled with an adsorbent, and then the enriched gaseous components are carried into the gas chromatography column by appropriate heating. Separation analysis was performed in the middle.
Ozeris et al. used top air phase chromatography to quantitatively analyze trace organic components (such as alcohols, ketones, aldehydes, esters, and sulfides) in water, and established trace organic components in water. The relationship between the concentration and the peak height is shown in Figure 2-44.
As seen in Figure 2-44, there is a linear relationship between the peak height and the concentration of the corresponding component in this concentration range (0.01 to 10 ppm), and the slope of the line is related to the type of the compound. It can also be seen from Figure 2-44 that most of the compounds can detect 0.01 ppm, while alcohols are not detected at 0.1 ppm, and methanol or even 1 ppm cannot be detected because in the headspace gas chromatography. The reason why the hydrogen flame detector has low sensitivity to methanol.
(4) Stability of the polymer
Headspace gas chromatography is also a fast and easy way to test the chemical stability of polymers. By taking gas from the vessel for gas chromatography analysis, the properties of the container material against water vapor, anti-HCl gas, etc. at various temperatures can be known hplc vials manufacturer in china.
For example: Figure 2-42 shows headspace analysis of polyacetal before exposure to HCl gas; Figure 2-43 shows headspace analysis of this material after exposure to HCl gas for 0.5 to 1 h. Comparing the two figures, it can be seen that after the polyacetal was exposed to HCl gas, the gaseous component increased significantly, indicating that the polyacetal was destroyed.
This is the end of the introduction of Headspace gas chromatograph analysis of headspace sampler. I hope it can help you.
