The Measurement of VOCs in Flowing Water
We have recently been asked to build a headspace GC system for the analysis of volatile organic compounds in an industrial waste water stream.
This work is close to completion and it would be good to say something about what we have done.
We set-up an Agilent GC-MSD/FID with a dual-head GERSTEL MultiPurpose Sampler and fitted the MPS with a flow-cell.
In our laboratory, we simulated the flowing sample stream using gravity to move water from a glass reservoir into a waste bottle via our flow-cell.
The flow-cell consists of a stainless-steel chamber fitted with inlet and outlet ports and a septum port that we can access with a syringe.
The MPS is fitted with two syringe heads, one with a heated headspace syringe and one with an unheated syringe for liquid handling.
At pre-determined intervals, the right-hand head takes a 1ml aliquot of water from the flow-cell and puts this into a 10ml headspace vial.
Next, the same syringe adds internal standard to the sample vial.
Then the sample vial is transported to the agitator where it is heated and mixed so that VOCs from the water sample equilibrate with the headspace in the vial.
Once equilibrium has been achieved, the injection syringe removes 0.5ml of headspace and injects this into the GC.
The sequence is repeated continuously and the GC goes on to produce a report detailing the concentrations of the volatile organics in the stream of water over time.
Right now we have this system working in our Cambridge laboratory. If you have a similar application and would like to see it in action, please call us on +44 (0)1223 279210 or email: firstname.lastname@example.org.