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- Posts: 113
- Joined: Wed Jun 08, 2016 7:38 pm
- Location: Shropshire, UK
I am currently involved in a project looking to investigate the contamination of water with metaldehyde, a common pesticide used for slug and snail control in many parts of the world, but seem to be having some issues with the instrumental analysis.
The extraction and analysis method I have been using is described in pages 8 to 13 of the UK Environment Agency's methods paper, found here: http://webarchive.nationalarchives.gov.uk/20140328104725/http://www.environment-agency.gov.uk/static/documents/Research/Metaldehyde-226b.pdf. However, I'm having some issues replicating their instrumentation settings and ultimately the reported limits of detection.
Firstly, within the document linked above the authors state they used helium as the carrier gas at a rate of 30 ml/sec, however I'm unsure how that translates into ml/min as it seems the flow would be insanely fast?
Secondly, the authors state they injected 1 ul of sample using a pulsed splitless method, however they don't give any further detail. The GC asks for the pressure and duration of the pulse, which I can't replicate. Any suggestions?
I'm guessing that I'm struggling to replicate their LODs because I can't fully replicate their instrumentation settings accurately. I am unable to detect any metaldehyde below 10 ug/L at present, but as the EU limit for metaldehyde in drinking water is 0.1 ug/L this isn't good enough for my study.
Does anyone have any suggestions as how to progress?
Thanks,
Joe
Potentially useful papers:
http://pubs.rsc.org/-/content/articlepdf/2017/ew/c7ew00039a
http://www.mdpi.com/2073-4441/7/6/3057/htm
GC-MS instrumentation used by me:
Agilent 7890 B Gas Chromatograph coupled to an Agilent 5977 A Mass Spectrometer