Configuration of anti-pollution system for non-methane total hydrocarbon automatic sampler

The detection of non-methane hydrocarbons demands extremely high purity of the sample, as even trace amounts of cross-contamination can directly lead to distorted detection data. The automatic sampler for non-methane hydrocarbons, equipped with a comprehensive anti-pollution system, addresses multiple aspects from sample transfer and pipeline cleaning to sample chamber protection, ensuring accurate and reliable detection results. It is suitable for various sample testing needs, including ambient air, exhaust gas, and water quality.

1. Anti-pollution in pipeline transmission: low adsorption + full inert treatment

Selection of inert material pipeline

Key components such as the sample injection pipeline and the dosing loop are made of polytetrafluoroethylene (PTFE) or passivated stainless steel. These materials have strong surface inertia and extremely low adsorption for hydrocarbon substances, thus preventing sample loss or contamination caused by adsorption in the pipeline during transmission.

The pipeline interface adopts a double-ferrule sealing design, ensuring seamless connection without dead spaces. This design prevents sample residue and infiltration of external air, thereby avoiding interference from hydrocarbon impurities in the air that could affect the detection results.

Diverting and emptying design

An independent shunt evacuation channel is configured. After each sample injection, the system automatically evacuates the residual sample in the pipeline quickly, and simultaneously introduces high-purity nitrogen to purge the pipeline. The purge flow rate and duration can be set as required to ensure no residual sample in the pipeline.

For the detection of high-concentration samples, it supports a large split ratio mode to reduce the residence time of high-concentration samples in the pipeline and minimize the risk of cross-contamination.

II. Anti-pollution of sample injection chamber: closed purging + automatic cleaning

Closed sample injection chamber structure

The sample injection chamber adopts a fully enclosed design, and the interior of the chamber is also treated with inert passivation, effectively preventing the entry of external air, dust, and other impurities.

The chamber is equipped with an independent carrier gas protection channel, which continuously introduces high-purity nitrogen to form a protective gas curtain, preventing the adsorption of hydrocarbon substances inside the chamber and inhibiting the oxidation of the chamber's inner walls.

Fully automatic cavity cleaning function

Integrated multi-mode cleaning program, supporting dual cleaning with solvent cleaning and carrier gas purging:

Solvent cleaning: It can be externally connected to cleaning agents such as methanol and n-hexane to automatically flush the chamber and sample injection needle, dissolving residual high-boiling-point hydrocarbon substances;

Carrier gas purging: After cleaning, introduce high-temperature, high-purity nitrogen (temperature adjustable to 150℃) to quickly dry the chamber and pipelines, avoiding residual cleaning agents from interfering with subsequent testing.

The cleaning process can be customized according to the type of sample, and an enhanced cleaning procedure can be automatically triggered after the detection of highly contaminated samples.

III. Anti-pollution of sample injection needle: dedicated cleaning position + anti-hanging liquid design

Independent cleaning station configuration

Equipped with a dedicated sample injection needle cleaning station, including a cleaning solution bath and a purging channel. After each sample injection, the sample injection needle automatically moves to the cleaning station, first immerses in the cleaning solution to repeatedly aspirate and clean the inner wall, then cleans the outer wall through external spraying, and finally dries with high-purity nitrogen gas.

The cleaning solution can be automatically replaced to prevent contamination due to repeated use and ensure cleaning effectiveness.

Design of anti-hanging liquid sampling needle

The use of highly polished needle tips and inner wall treatment processes reduces sample residue on the wall; the needle shaft is equipped with an anti-adsorption coating to further reduce the adsorption of hydrocarbon substances.

The lifting and puncturing speed of the sampling needle is precisely controllable, avoiding debris generated during puncturing the sample bottle from falling into the cavity and causing additional contamination.

IV. Sample anti-pollution: Isolated sample position + anti-volatilization protection

Isolated sample tray design

The sample tray adopts a partitioned isolation structure, where samples of different batches and concentrations are placed separately to avoid contamination of adjacent low-concentration samples after evaporation of high-concentration samples.

Some models are equipped with independent sample sealing caps, ensuring that uninjected samples remain sealed at all times, reducing sample evaporation and preventing the intrusion of external impurities.

Low temperature control sample position (optional)

For volatile liquid samples, a low-temperature temperature control sample position can be configured to stabilize the sample temperature within a set range (such as 4°C), reduce the evaporation rate of the sample, and minimize concentration changes and chamber contamination caused by evaporation.

V. Application value of anti-pollution system

The full-process anti-pollution configuration enables the non-methane hydrocarbon automatic sampler to meet the precise detection requirements of low-concentration samples, with stable blank sample detection values below the method detection limit. In batch sample detection, there is no need for frequent manual cleaning and maintenance, which not only improves detection efficiency but also ensures data consistency. It is widely applicable to daily detection work in environmental monitoring stations, third-party testing institutions, and chemical enterprises.