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The headspace-gas chromatography vials are required to be accurate in volume, capable of withstanding a certain pressure, good sealing performance, and no adsorption to the sample. Although ordinary GC vials have been used in the past, most of the headspace vials made of borosilicate glass are inert enough to satisfy the analysis of most samples.
In quantitative analysis, the exact value compared to β is required, which requires us to know the exact volume (volume) of the vial, rather than simply sampling the manufacturer's nominal volume. An easy way to do this is to weigh the empty bottle with a balance and then fill it with water and weigh it. The exact volume of the vial can be calculated from the density of the water at the weighing temperature (eg 0.9971 g/ml at 25 ° C). Experiments have shown that there is an error of about 1% between the nominal volume and the real volume of a commercially available headspace vials. For the same batch of vials, the true volume of 5 of them can be accurately determined, and the average volume can be used as the actual volume of the batch of vials.
The volume of commercially available sample vials is 5-20ml. Which one to choose, one depends on the requirements of the headspace sampler instrument, and the second depends on the sample condition. The liquid sample is used in an extra 10 ml, and the left and right vials can meet the requirements, because the sensitivity of the analysis depends on the concentration of the component to be tested in the headspace gas, or depending on the ratio of β rather than the sample. Therefore, with large volume vials, if β is unchanged, the analytical sensitivity will not improve. Solid samples require larger sample vials because of the large volume of the sample itself (larger sample sizes ensure representativeness of the sample).
The third factor to consider is the HPLC column. When packed in a packed column, large-diameter column, or capillary column, the injection volume is typically 0.5-2 ml, which requires a large vials. When the capillary column is used without split injection, the injection volume often does not exceed 0.25 ml, so a small volume of sample vials is sufficient.
This is the end of the introduction of How do I choose the autosampler vials in headspace-gas chromatography analysis. I hope it can help you.
