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Issue 12, 2009
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Chemotrapping-atomic fluorescence spectrometric method as a field method for volatile arsenic in natural gas

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Abstract

Volatile arsenic compounds in natural gas, existing in the form of trimethylarsine (TMAs), have been determined using gas cryo-trapping gas chromatography coupled to inductively coupled plasma-mass spectrometry (CT-GC-ICP-MS). The results from a number of different gas wells revealed a huge concentration spread ranging from below the detection limit of 0.2 up to 1800 µg/m3 TMAs (as As) in the gas. Due to the toxicity and corrosive nature of these arsines, they need near real time monitoring via a method that can easily be implemented on site, i.e. during gas exploitation. Here, we introduce a novel method which utilises silver nitrate impregnated silica gel tubes for quantitative chemotrapping of trimethylarsine (TMAs) from a natural gas matrix. Subsequent elution with hot nitric acid followed by online photo-oxidation hydride generation atomic fluorescence spectrometry (HG-AFS) is used for the determination of TMAs gas standards in nitrogen and natural gas samples, respectively. The chemotrapping method was validated using CT-GC-ICP-MS as a reference method. The recovery of arsenic from nitrogen or natural gas matrix ranged from 85 to 113% for a range of 20 to 2000 ng As. Trapping efficiency was >98%, from the methods LOD of 20 ng to 4.8 µg (absolute amount As) with sample sizes of 0.02 and 2 L gas. Method performance was established by comparing the results obtained for eight natural gas samples containing between 1 and 140 µg As/m3 with those achieved by the reference method (CT-GC-ICP-MS).

Graphical abstract: Chemotrapping-atomic fluorescence spectrometric method as a field method for volatile arsenic in natural gas

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Publication details

The article was received on 06 Jul 2009, accepted on 28 Aug 2009 and first published on 25 Sep 2009


Article type: Paper
DOI: 10.1039/B913322D
J. Environ. Monit., 2009,11, 2222-2230

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    Chemotrapping-atomic fluorescence spectrometric method as a field method for volatile arsenic in natural gas

    M. K. Uroic, E. M. Krupp, C. Johnson and J. Feldmann, J. Environ. Monit., 2009, 11, 2222
    DOI: 10.1039/B913322D

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