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

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 microg/m(3) 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 microg (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 microg As/m(3) with those achieved by the reference method (CT-GC-ICP-MS).

Rapid analysis of volatile arsenic species released from lake sediment by a packed cotton column coupled with atomic fluorescence spectrometry

“…9,16,17 Generally, volatile arsenic species can be separated by gas chromatographic (GC) systems 11,18 and detected by inductively coupled plasma mass spectrometry (ICP-MS) or mass spectrometry (MS). [19][20][21] Although some methods for volatile arsenic speciation have been reported in the past, new analytical methods for volatile arsenic species in various real samples are still needed for the requirements of sample collection and rapid analysis. Feldmann et al 20,21 trapped volatile arsenic compounds in natural gas and the headspace of soils by a chemotrapping technique and analyzed them by AFS and ICP-MS.…”

“…[19][20][21] Although some methods for volatile arsenic speciation have been reported in the past, new analytical methods for volatile arsenic species in various real samples are still needed for the requirements of sample collection and rapid analysis. Feldmann et al 20,21 trapped volatile arsenic compounds in natural gas and the headspace of soils by a chemotrapping technique and analyzed them by AFS and ICP-MS. In order to investigate the mechanism of arsenic biotransformation and methylation by bacteria, Qin et al…”

Toxicity of Methylated Bismuth Compounds Produced by Intestinal Microorganisms toBacteroides thetaiotaomicron, a Member of the Physiological Intestinal Microbiota

“…Thus, an alternative approach was developed based on passive TMBi chemotrapping using silver nitrate-coated silica beads analogous to a method recently introduced for the sampling of volatile arsenic and selenium species by Uroic et al [19]. The B. thetaiotaomicron culture located in the inner tube was replaced by the chemotrap and the bismuth content of the chemotrap after 48 h of incubation was analysed by ICP-MS; 1.64 ± 0.04 nmol Bi were trapped by AgNO 3 -coated silica beads corresponding to 33 nM TMBi in the gas phase, which is quite similar to the MIC 50 of TMBi.…”

“…Volatile TMBi was trapped by using silica beads coated with silver nitrate modified from Uroic et al [19]. These beads were placed over night in a 1% silver nitrate solution and then dried at 40°C.…”

Exploration of Detection Technology about Arsenic Content in Natural Gas and Application

“…29 Those solids blocked the quartz membrane, declined concentration of the absorbent, and blocked the gas channel, which could be seen in field 2 clearly.…”