Abstract
High-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GF-MAS) was employed for determining adsorbable organic chlorine (AOCl) in water. Organic chlorine was indirectly quantified by monitoring the molecular absorption of the transient aluminum monochloride molecule (AlCl) around a wavelength of 261.42 nm in a graphite furnace. An aluminum solution was used as the molecular-forming modifier. A zirconium coated graphite furnace, as well as Sr and Ag solutions were applied as modifiers for a maximal enhancement of the absorption signal. The pyrolysis and vaporization temperatures were 600 °C and 2300 °C, respectively. Non-spectral interferences were observed with F, Br, and I at concentrations higher than 6 mg L-1, 50 mg L-1, and 100 mg L-1, respectively. Calibration curves with NaCl, 4-chlorophenol, and trichlorophenol present the same slope and dynamic range, which indicates the chlorine atom specificity of the method. This method was evaluated and validated using synthetic water samples, following the current standard DIN EN ISO 9562:2004 for the determination of the sum parameter adsorbable organic halides (AOX) for water quality. These samples contain 4-chlorophenol as the chlorinated organic standard in an inorganic chloride matrix. Prior to analysis, organic chlorine was extracted from the inorganic matrix via solid-phase extraction with a recovery rate >95%. There were no statistically significant differences observed between measured and known values and for a t-test a confidence level of 95% was achieved. The limits of detection and characteristic mass were found to be 48 and 22 pg, respectively. The calibration curve was linear in the range 0.1-2.5 ng with a correlation coefficient R2 = 0.9986.
Highlights
Chlorinated organic compounds are well known as persistent water pollutants.[1,2] Currently, the Stockholm Convention on Persistent Organic Pollutants (POPs) formally recognizes several of them.[3]
Organic chlorine was indirectly quantified by monitoring the molecular absorption of the transient aluminum monochloride molecule (AlCl) around a wavelength of 261.42 nm in a graphite furnace
The standard DIN EN ISO 9562:2004 regulates the analysis of chlorine and other halogen atoms in water samples into one AOX parameter.[16,21]
Summary
Chlorinated organic compounds are well known as persistent water pollutants.[1,2] Currently, the Stockholm Convention on Persistent Organic Pollutants (POPs) formally recognizes several of them.[3] Despite their toxicity and consequent regulations by European and U.S authorities,[4,5,6] they are still used as pesticides (DDT type, polychlorinated cyclodienes, and biphenyls) in industry,[7,8] as non-polar solvents and polymers (phenols, chloromethanes and chloroethanes, vinyl chlorides, and dibenzodioxins),[9] and as products and by-products from the. Several analytical methods have been reported for the total determination of organochlorinated compounds in water using routine analytical techniques like ion chromatography,[15] gravimetric titration, and potentiometry.[16,17] the chemical conversion of the organic chlorine into an appropriate form for analysis (i.e., as chloride ions in solution) is necessary for these methods, which is time-consuming and prone to contamination. More sophisticated analytical methods like ICPMS or ICP-OES, which do not require pretreatment of the sample, are compromised by the memory effect of the halogen atom in the plasma torch, and they typically need certi ed reference materials or matrix-matched standards for calibration and bias correction.[18,19] the strongest absorption and emission lines of chlorine lie below the vacuum UV spectral range, which creates a technical challenge for its quanti cation
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