Species-specific isotope-ratio measurements of volatile tin and antimony compounds using capillary GC–ICP–time-of-flight MS

Abstract

The analytical performance of an axial inductively-coupled-plasma time-of-flight mass spectrometer (ICP-TOFMS) as a detector for fast transient chromatographic signals resulting from the coupling to capillary gas chromatography (CGC) was investigated. A cryotrapping GC-ICP-TOFMS method for the determination of volatile metal(loid) compounds (VOMs) in gases was used and the suitability of the TOF mass analyzer for multielemental speciation analysis and multi-isotope ratio determinations was studied in terms of accuracy and precision. Isotope ratios 118Sn/120Sn and 121Sb/123Sb have been determined in in-house gas standard atmospheres in Tedlar bags at two different levels (100 pg and 1 ng) for different elemental species (SnH4, MeSnH3, Me2SnH2, Me3SnH, BuSnH3, SbH3, and MeSbH2). A limitation arising from counting statistics in both detection modes could be shown. A solution containing rhodium (10 ng mL(-1)) and cadmium (40 ng mL(-1)) was introduced simultaneously to the GC outlet. Rhodium acts as a continuous internal standard and Cd is used for mass-bias correction (by measuring the 111Cd/113Cd ratio). The detection system in both pulse counting and analog mode was examined. The best attainable precision was established for Me2SnH2 (analog mode, 12 replicates, 1 ng, RSD 0.34%, accuracy 0.31%) whereas most other species ranged between 0.4 and 0.5% RSD if higher concentrations were used. The limitations of the pulse counting system are clearly seen, with peak heights of more than 2000 counts reaching saturation (for an integration time of 100 ms), which reduces the accuracy of isotope ratio determinations. A dozen VOM could be detected in an aged landfill gas sample; several unidentified Sn compounds were present. Although their isotope ratios are within the confidence value of the standards, it is not yet clear if the acquired precision is good enough to identify isotopic fractionation of metal(loid)s through biovolatilization processes. With the precision achieved, the combination of cryotrapping GC and ICP-TOFMS is a powerful tool for monitoring volatile multi-element species in multi-tracer experiments and isotope dilution methodology.

An Overview of Analytical Applications of Time of Flight-Mass Spectrometric (TOF-MS) Analyzers and an Inductively Coupled Plasma-TOF-MS Technique

“…The benefits of using a capillary GC ICP-TOF-MS for the detection of volatile components of gaseous samples (tin and antimony compounds) in terms of accuracy and precision have been considered. 130 The RSD of 0.34% for Me2SnH2 and of 0.4 -0.5% for the other species determined were reported. Analytical performance of a LECO Renaissance ICP-TOF-MS instrument for the detection of tetramethyltin (TMT), tetraethyltin (TET) and tetraethyllead (TEL) separated by gas chromatography has been evaluated.…”

“…Exceptional attributes of ICP-TOF-MS, such as high speed of data acquisition, an ability to obtain a full elemental analysis in a time-frame suited to a transient inlet system and significantly better, as compared with widely used quadrupole ICP-MS, the precision of the measurements generate increasing interest in the technique. The ICP-TOF-MS has been successfully coupled to LA, [120][121][122][123][124][125][126] ETV, 127 GC, [128][129][130][131][132] liquid chromatography, 133,134 CE 135,136 and FIA. [137][138][139][140][141] Detailed reviews of the development and analytical performance of TOF-MS combined with ICP ion source have been presented.…”

“…The attractiveness of ICP-TOF-MS detectors for transient concentration variable signals produced by high speed chromatographic techniques has been confirmed in a speciation analysis of various organometallic (tin, lead) and volatile tin and antimony compounds (GC [128][129][130][131][132] ), and metalloproteins (HPLC [132][133][134] ). Low femtogram DLs and a dynamic range of greater than six orders of magnitude have been reported.…”

A method for monitoring and controlling reproducibility of intensity data in complex electrospray mass spectra: A thermometer ion-based strategy

“…This effect can be pronounced for instruments employing time-todigital converter (TDC)-based signal digitizers [48,49], although this has become less of a concern as the dynamic range of the instruments has increased with the use of ADC-based digitizers. However, a more subtle, yet equally critical, effect impacts peaks of low abundance during the detection/digitization process.…”

Investigations into the role of methylcobalamin and glutathione for the methylation of antimony using isotopically enriched antimony(V)

“…The preparation of a gas standard by HG and the analysis by CT-CF-GC-ICP-MS is described elsewhere. 27 Gas-samples were analysed using a quadrupole-ICP mass spectrometer (Spectromass 2000, Spectro Analytical).…”