Determination of chlorine via the CaCl molecule by high-resolution continuum source graphite furnace molecular absorption spectrometry and direct solid sample analysis

Abstract

This work investigates the possibilities of high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of Cl in solid samples via the CaCl molecule and measurement of its molecular absorption. The method proposed is based on addition of 400µg Ca as molecule-forming reagent and of 20µgPd as chemical modifier, which helps to stabilize the analyte and enhances sensitivity. The molecular spectrum for CaCl offers different lines with different limits of detection and linear ranges, which permitted to analyze solid samples with different Cl contents. The lowest limit of detection (0.75ng Cl, corresponding to 0.75µgg for a typical sample mass of 1mg) could be achieved by combination of three of the most sensitive lines in the vicinity of 620.862nm, while the amplest linear range (up to 860ng Cl) was achieved by selection of the less sensitive line at 377.501nm. The method developed enabled the direct determination of Cl in solid samples using simple external calibration with aqueous standards. Good precision (5-9% RSD) and accuracy was attained in a series of certified samples of very different nature (i.e. coal, iron oxide, polyethylene, human hair, pine needles, rice flour and milk) and with very different Cl contents, ranging from about 50µgg to 1% (w/w) Cl. The method appears as particularly useful for Cl determination in samples with elevated Ca contents, for which biased results with other diatomic molecules, such as AlCl or SrCl, may be obtained.

High-resolution continuum source atomic absorption spectrometry: a review of current applications

“…143 Solid-sampling fl ame AAS (HR-CS-F AAS) has a number of limitations associated with the sensitivity of determination and interference. Therefore, atomic absorption analysis of solid samples can be best done using HR-CS graphite furnace atomic absorption spectrometry (HR-CS-GF AAS) (see Refs 19,22,23,[27][28][29][43][44][45][47][48][49]58,70,73,76,77,89,101,102,108,116,126,131,132).…”

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

“…Actually, one review on the determination of non-metals published in 2014 noted the surprisingly low number of papers devoted to Cl determination via HR CS MAS, despite the importance of this element. 4 Three new molecules have been proposed in this period to accompany the ones previously explored (AlCl, 38 InCl, 48 and SrCl 49 ), namely CaCl, 50 GaCl 51 and MgCl. 52 Having different molecules to choose from for every particular application is important.…”

“…Moreover, Ca is an element present at high contents in many types of samples (e.g., biological), so it could be a strong interference if any other molecule is targeted instead. 50 Use of Ca also represents some disadvantages in practice, as this element is well-known to deteriorate the lifetime of the graphite parts. 43 Determination of Br and, particularly, of I are more challenging because their bonds with metals are much less strong than those of F and Cl.…”

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

“…This molecule is monitored at 635.862 nm and displays detection limits that are similar to certified values. 21,[27][28][29] A method for chlorine determination through CaCl molecule at the wavelength of 621.146 nm was developed by Guarda et al 30 and applied it to different types of certified reference materials (coal, iron oxide, polyethylene, human hair, pine needles, rice flour and milk). The same molecule was used by Bechlin et al 31 for chlorine quantification in cement samples at wavelength 621.145 nm, employing direct solid sampling analysis.…”