Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10529713 | Analytica Chimica Acta | 2005 | 9 Pages |
Abstract
Microwave energy has been novelty applied to speed up a tetramethylammonium hydroxide (TMAH) alkaline digestion of seaweed samples and to assist distillation of iodine from seaweed alkaline digests. Iodide in the alkaline digests from seaweed and distilled iodine, reduced back to iodine in a hydroxylamine hydrochloride solution, was determined by a catalytic spectrophotometric method based on the catalytic effect of iodide on the oxidation of As(III) by Ce(IV) in H2SO4/HCl medium (Sandell-Kolthoff reaction). The determination of iodide was directly performed in the alkaline digests, while total iodine was assessed by analyzing the hydroxylamine hydrochloride solution after the distillation process. Microwave-assisted alkaline digestion was performed using 7.5 mL of TMAH and irradiating samples at 670 W for two 5.5 min steps. Microwave-assisted distillation was carried out using 4.0 mL of the alkaline digest and 3 mL of a 2.2 M hydrochloric acid and 0.05% (m/v) sodium nitrite solution, with a microwave power at 670 W for two 90 s steps. The distillate (iodine vapor) was bubbled in 10 mL of a 500 μg mLâ1 hydroxylamine hydrochloride solution (accepting solution). The linear calibration ranges were 0.30-20.0 and 0.40-20.0 μg Lâ1 for iodide determination and total iodine determination, respectively. The limit of detection was 9.2 μg gâ1 for iodide and 28.5 μg gâ1 for total iodine. Repeatability of the overall procedures, expressed as R.S.D. for 11 determinations, was 2.6% for 196.3 μg gâ1 of iodide measured after microwave-assisted alkaline digestion, and 5.8% for 954.3 μg gâ1 of total iodine by microwave-assisted alkaline digestion followed by microwave-assisted distillation. Finally, accuracy of the methods was assessed by analyzing the NIST-09 (Sargasso) certified reference material and the methods were applied to the determination of iodide and total iodine in different Atlantic edible seaweed samples with satisfactory results.
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Diego Gamallo-Lorenzo, MarÃa del Carmen Barciela-Alonso, Antonio Moreda-Piñeiro, Adela Bermejo-Barrera, Pilar Bermejo-Barrera,