Monitoring of liquid matrices by Gas Chromatography using a simplified and enhanced headspace sampling system

Chromatotec Group® is specialized in the manufacturing of automated Gas Chromatographs (autoGCs) for online monitoring of Volatile Organic Compounds (VOCs) at trace and ultra-trace levels. Besides its standard solutions for gas analysis in ambient air and industrial, odor, oil & gas, emission and process applications, Chromatotec® is permanently involved in new turn-key solution developments.

New cylinder-free auto-GC-FID range

Reliable and certified results from an all-in-one unit without gas cylinders: this was the design challenge that Chromatotec achieved to satisfy market expectations for VOCs monitoring. Objective was to simplify the perception of Gas Chromatography considered sometimes as too complex approach for on-site applications as requiring gas for carrier gas.
AutoGC analyzers with Flame Ionization Detection (FID) allow the speciation of VOCs with exceptional sensitivity and linear response for wide concentration ranges (ppt to %) in automatic routine mode. When comparing lab GC-FID with auto-GC-FID used in the field for online monitoring systems, users may be concerned with the on-site use of hydrogen (H2) and the complexity of cylinder management. Indeed, FID detectors require a H2/air flame and, in the case of cylinders, must be changed before exhaustion, or else risk interrupting analyses while also decreasing the usable amount of gas. In terms of safety, gas cylinders are bulky and heavy so personnel must be trained on how to move and secure them.
To solve these problems, gas generators are used, instead gas cylinders, in the first fully- automatic, standalone, cylinder-free, auto-GC-FID system manufactured by Chromatotec. These configurations allow to provide reliable and representative results with standalone analytical solutions.
 

Headspace sampling system

Recently, Chromatotec has entered the world of liquid sample analysis. Instruments can be coupled with an enhanced online sampling device: a headspace sampling system designed to extract representative compounds from the liquid phase.
The vaporized sample can be preconcentrated using a trap to achieve quantification at very low concentration levels (ppb and/or ppm). Then, it is injected automatically and in continuous mode into the airmoVOC WMS auto-GC analyzer. Speciation of VOCs is done with GC-FID analyzer. The complete system allows online analysis without human intervention.

Applications

This technology can be used for a wide variety of applications. The airmoVOC WMS has been deployed for many types of VOCs with up to 50 compounds from US EPA 502-2 and/or in industries in France and China for the quantification of benzene, toluene, ethylbenzene and xylene isomers (BTEX), a class of VOCs present in petroleum products, in oily wastewater or activities such as oil extraction. BTEX are present in these effluents because of their water solubility and polarity.
These contaminants may reach groundwater by infiltration from discharge systems, which leads to important health and environmental issues. They contribute significantly to the formation of ozone. They can also have adverse effects on human health due to the well-known toxicity of several compounds, such as benzene (carcinogen) and toluene (central nervous system toxicant). People can therefore be exposed to BTEX through contaminated drinking water.
Accurate and continuous monitoring and quantification of BTEX in water is critical to improve the understanding of the exposure to toxicants, and hence improve people’s safety. The airmoVOC WMS autoGC system automatically quantifies VOCs in water, including BTEX, to stay in compliance with wastewater discharge regulations from environmental protection agencies, by taking remedial actions if maximum limits are exceeded.
When analyzing industrial the water from the recovery network, cyclonic filters may be installed upstream to ensure the removal of particles. Such system can be also used to analyze other aqueous liquid samples such as drinking water or to quantify impurities in wastewater from other industrial applications, such as the polymer industry.

Conclusions

The performance of the cylinder-free auto-GC-FID system with headspace sampling system is highlighted by its main features:
• Low cost of ownership: Only distilled water and ambient air are needed. The integrated generators provide the FIDs total gas consumption requirement (30 mL/min H2 and 180 mL/min air).
• Improved safety: No compressed hydrogen cylinders are required.
• Complete autonomy: The FID detector can be operated continuously, avoiding the exchange of empty cylinders.
• Better sensitivity: “Zero grade” gases without hydrocarbon impurities for lower noise level and greater column protection.
• Analyzes a wide range of EPA 502.2 (purge and trap + CPG FID) compounds.
• Ability to detect VOCs at very low levels in liquid or gaseous samples (for industrial or ambient air quality monitoring without the headspace sampling system).
• Saves space: The analyzer and both generators are housed in an all-in-one wall-mounted cabinet.
• Enhanced ease of use: The measurement system performance evaluation is completed with internal calibration using NIST traceable permeation tube technology to provide automatic data validation.
This fully automatic, user-friendly system does not require specialized personnel to operate. You’ll only need to ensure proper power supply and to set up proper sampling lines to operate and obtain reliable and representative analysis without molecules losses.