Abstract
A new indirect method has been developed for the determination of sulphuric acid and sulphur dioxide by flame atomic absorption spectrometry, thereby extending the range of application of AAS to some non-metallic substances. Under certain atomization conditions in air-acetylene flame, the absorbance signal of some alkali earth metal salts, such as magnesium shows significant dependence from the anions present. For instance, Mg(ClO4)2 produces almost ten times higher absorbance than MgSO4 in the same concentration, and this phenomenon is due to the thermal differences of these alkali earth salts. When sulphuric acid is added to Mg(ClO4)2 solutions, a continuously decreasing FAAS calibration series is obtained. Using this method unknown sulphuric acid concentration can be determined in samples. The presence of other acids - except phosphoric acid - does not interfere, since they are evaporated during the dry aerosol formation in the flame.The limit of detection for sulphuric acid and sulphur dioxide is 22 µg/m3 and 14 µg/m3. The limit of detection for the obtained solution is 0.11 mg/L and 0.07 mg/L for sulphuric acid and sulphur dioxide using 50 min sampling time at 1 L/min air suction rate into 10 ml appropriate liquid, respectively (enrichment factor = 5000 with respect to volume). The linear range is 0.5 – 5.0 mg/L.The recovery of spiked samples are 98%. The SO2 and SO32− salts can be similarly determined by this method based on the quantitative absorption of SO2 in H2O2, which yields sulphuric acid. The sulphate content of the solutions was determined by turbidimetric and ion chromatographic methods and the results were in good agreement with the developed method.
Published Version
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