Chlorine isotope determination via the monitoring of the AlCl molecule by high-resolution continuum source graphite furnace molecular absorption spectrometry – a case study

Abstract

This work investigates the possibility of obtaining isotopic information via the monitoring of the absorption spectra of a gaseous diatomic molecule generated in a graphite furnace and using a high-resolution (approx. 1.5 pm per pixel) monochromator (HR CS GFMAS). To test this concept, Cl was chosen as analyte and AlCl as the target species. The results demonstrate that, unlike what occurs with atomic spectra, under optimum conditions it is possible to acquire isotopic information by HR CS GFMAS in a straightforward way, as it is feasible to observe band heads for each Cl isotope (actually, for Al 35 Cl and Al 37 Cl) that are separated, i.e., they act like two different molecules absorbing at different wavelengths.The method proposed, based upon addition of both Pd and Al and the selection of peak height values, enables Cl isotopic analysis with precision values around 2% RSD for solutions with Cl contents at the mg L -1 level. Accurate values, within this uncertainty, can be directly obtained without requiring any method for mass bias correction. The potential of 2 isotope dilution for calibration is also explored, and it is proven how this approach can help in providing accurate results in situations where the occurrence of chemical interferences, a case frequently encountered for the HR CS GFMAS technique, hampers the use of other calibration approaches, as demonstrated for water analysis.

Quo vadishigh-resolution continuum source atomic/molecular absorption spectrometry?

“…53 A potential solution for such a situation based on the use of isotope dilution will be discussed later. 54,55 Recently, the use of TlBr has been proposed for Br determination, 56 as well as the use of CaI and SrI for I determination. 57 In any case, for these two elements, more research on the use of different molecules is needed.…”

“…However, it has been proposed more recently that, if instead of using HR CS AAS, HR CS MAS is chosen, isotopic analysis potential could be enhanced. 54 This seems like a logical evolution for two reasons: i) MAS is an important area of research in this particular field of high-resolution continuum source, as discussed before, because diatomic molecules can be formed and their spectra resolved; ii) it has been already shown for laser induced breakdown spectrometry (LIBS) by Russo et al that the monitoring of molecular spectra provides higher isotopic shifts. 64,65 Therefore, the same idea could also be applied to HR CS MAS.…”

“…InFigure 1B, the spectrum obtained for CRM NIST 975a ( 35 Cl 75.774 %) is shown in black, and the one obtained for CRM AE642 ( 37 Cl 98.122 %) is highlighted in red. Reproduced with permission of the RSC (http://pubs.rsc.org/en/content/articlehtml/2015/ja/c5ja00055f) 54.…”

Development of a fast screening method for the direct determination of chlorinated persistent organic pollutants in fish oil by high-resolution continuum source graphite furnace molecular absorption spectrometry

“…However, only a few analytical techniques have shown some capacity for the determination of chlorine with relative sensitivity and accuracy, mainly for complex matrices, using direct determination. Among these techniques are electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) (Antes et al, 2013; Gois, Pereira, Welz, & Borges, 2014; Gois, Pereira, Welz, & Borges, 2015), laser induced plasma spectrometry (LIPS)(Kaski, Häkkänen, & Korppi-Tommola, 2004), X-ray fluorescence spectrometry (XRF)(Doyle, Saavedra, Tristão, Nele, & Aucélio, 2011), and more recently also highresolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS)(Bechlin, Ferreira, & Gomes Neto, 2017;Enders et al, 2016;Guarda et al, 2017;Heitmann, Becker-Ross, Florek, Huang, & Okruss, 2006;Nakadi, da Veiga, Aramendia, Garcia-Ruiz, & Resano, 2015;Ozbek & Akman, 2016;Pereira et al, 2015;Pereira et al, 2014;Welz, Vale, Pereira, Castilho, & Dessuy, 2014). The last technique is a very robust tool with a high tolerance for complex matrices due to the use of a graphite tube furnace, which makes possible the analysis of liquids, slurries and solid samples.…”

Determination of Chlorine in Crude Oil Emulsified via the MgCl Molecule by HR‑CS MAS

“…16,17 Chlorine determination by high-resolution continuum source molecular absorption spectrometry (HR-CS MAS) has been accomplished by detection of several diatomic molecules. 16,18 The most widely reported in the literature is AlCl [19][20][21][22][23][24][25] due to its high energy bond and well separated band heads, making it effective the background correction. 17,26 Strontium monochloride (SrCl) was applied for chlorine determination in different types of samples (coal, milk, animal organs and tissues, and wheat flour).…”