Chemical product testing institution

The testing center currently possesses domestically advanced high-resolution 400M nuclear magnetic resonance spectrometers, along with a complete set of Agilent series large-scale analytical instruments including liquid chromatography-mass spectrometry (LC-MS), gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC), and gas chromatography (GC).

Introduction to Several Injection Methods for Gas Chromatographs

The function of the injection system in a gas chromatograph is to introduce samples directly or after special treatment into the vaporization chamber or chromatographic column of the instrument for analysis.

Based on different functions, it can be categorized as follows:

1. Manual Injection System: Microsyringe

Manual injection involves using a microsyringe to draw a certain volume of gas or liquid sample and injecting it into the gas chromatograph for analysis. It is widely applicable for the analysis of thermally stable gases and liquid samples with boiling points generally below 500°C. There are various types of microsyringes for gas chromatography, and different syringes can be selected based on sample properties.

2. Solid-Phase Microextraction (SPME) Injector

Solid-phase microextraction is a sample pretreatment technology invented in the 1990s. It can be used to extract organic compounds from liquid or gas matrices. The extracted samples can be manually injected into the vaporization chamber of the gas chromatograph for thermal desorption and vaporization, followed by analysis in the chromatographic column. This technique is particularly suitable for the analysis of organic compounds in water.

3. Liquid Autosampler

The liquid autosampler is used for the injection of liquid samples, enabling automated operation, reducing human injection errors, and lowering manual operating costs. It is suitable for the analysis of batch samples.

4. Valve Injection System

Gas Injection Valve:

Using a valve for gas sample injection not only ensures good quantitative reproducibility but also isolates the sample from ambient air, preventing contamination. Manual injection using a syringe struggles to achieve these two aspects. Systems employing valve injection can combine multiple columns and valves for specialized analyses. The sample loop volume of a gas injection valve is generally above 0.25 milliliters.

Liquid Injection Valve:

Liquid injection valves are typically used for online sampling and analysis of liquid samples in setups. Their sample loops usually have a groove volume of approximately 0.1–1.0 microliters at the valve core.

5. Purge and Trap System

Used for the enrichment of volatile organic compounds in solid, semi-solid, and liquid sample matrices and their direct introduction into the gas chromatograph for analysis.

6. Thermal Desorption System

Used for the capture of volatile organic compounds in gas samples, followed by thermal desorption and introduction into the gas chromatograph for analysis.

7. Headspace Sampler System

The headspace sampler is primarily used for the analysis of volatile organic compounds in solid, semi-solid, and liquid sample matrices, such as VOCs in water, aroma components in tea, and residual monomers in synthetic polymer materials.