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Chinese EPA Method HJ 734 was released in 2014. It defines a procedure for sampling and analysis of VOCs in stationary source emissions, by using sampling onto sorbent tubes followed by TD–GC–MS analysis.

What’s involved in HJ 734?

HJ 734 was developed to determine VOCs in stationary source emissions. The method requires the monitoring of 24 polar and non-polar VOCs.

This method recommends that sampling is carried out using TD tubes with three types of sorbent packing:

  • Tenax GR (30 mm) and Carbopack B (25 mm)
  • Carbopack B (30 mm) and Carboxen 1000 (10 mm)
  • Carbopack C (13 mm), Carbopack B (25 mm) and Carboxen 1000 (13 mm), or equivalent performance.

Samples are either collected in a bag and then transferred to the tube, or pumped directly onto the tube. The tube is then analyzed by TD–GC–MS to determine the levels of VOCs present.

Complying with HJ 734

A challenge for analysts needing to comply with HJ 734 is presented by the high concentration and high humidity of industrial emissions.

However, Markes’ TD100-xr and UNITY–ULTRA-xr thermal desorbers fully meet the requirements of HJ 734, providing flexible split ratios and a dry-purging function to ensure low detection limits without interference from airborne moisture. Preloaded instrument parameters within Markes’ TD software further simplify the process of complying with the method.