Gas displacement and dynamic compensation sampling method in headspace analysis

Abstract

The invention relates to a gas displacement and dynamic compensation sampling method in headspace analysis, comprising the following steps: (1) configuring double needles having an inlet gas carrier hole and an air outlet hole; (2) placing a sample in a sample bottle and sealing the sample; (3) inserting the double needles into the sample bottle, feeding carrier gas into the sample bottle throughthe inlet gas carrier hole, exhausting the air in the sample bottle out of the sample bottle through the air outlet hole to finish gas displacement so that the sample bottle is in a closed state; and(4) heating the sample so that a component to be tested in the sample and the partial pressure in the headspace part are balanced, pressurizing the sample with carrier gas, communicating the air outlet hole with a gas chromatograph through a feeding pipeline, wherein the sample gas flows into the feeding pipeline through the air outlet hole, the carrier gas enters into the sample bottle through the inlet gas carrier hole, and pressure in the sample bottle is stable to achieve dynamic compensation sampling. The method can ensue that the sample is automatically isolated from oxygen and not oxidized under the heating condition, and ensure short sampling time, high testing precision and favorable repeatability in the subsequent headspace extracting process.

Description

Technical field: [0001] The invention relates to a headspace analysis method, in particular to a gas replacement and dynamic compensation sampling method for headspace analysis. Background technique: [0002] Headspace analysis is to put a gas, liquid or solid sample into a closed container, and form an equilibrium between the sample and the gas above it. Based on a fundamental law of physics, volatile compounds inherent in the sample will appear above it in gaseous form. The relative concentrations between the two phases will depend on the partial pressures of these compounds. We can analyze volatile organic compounds without the interference of non-volatile substances only by extracting a part of the gas phase substances. This is the headspace analysis method. The sample organic volatiles in the airtight headspace bottle will volatilize into the upper space after heating. In the traditional headspace analysis, after the sample gas in the upper part of the sample bottle ...

AI Technical Summary

Problems solved by technology

[0007] 2) Due to the large contact surface causing sample loss, it needs to be rebalanced outside the sample bottle, and the running time is long;

[0008] 3) To change the injection volume, the sample loop must be replaced

Images