title: Determination of halogens in coal after digestion using the microwave-induced combustion technique.
abstract: The microwave-induced combustion (MIC) technique was applied for coal digestion and further determination of bromide, chloride, fluoride, and iodide by ion chromatography (IC). Samples (up to 500 mg) were combusted at 2 MPa of oxygen. Combustion was complete in less than 50 s, and analytes were absorbed in water or (NH(4))(2)CO(3) solution. A reflux step was applied to improve analyte absorption. Accuracy was evaluated for Br, Cl, and F using certified reference coal and spiked samples for I. For Br, Cl, and F, the agreement was between 96 and 103% using 50 mmol L(-1) (NH(4))(2)CO(3) as the absorbing solution and 5 min of reflux. With the use of the same conditions, the recoveries for I were better than 97%. Br, Cl, and I were also determined in MIC digests by inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry, and F was determined by an ion-selective electrode with agreement better than 95% to the values obtained using IC. Temperature during combustion was higher than 1350 degrees C, and the residual carbon content was lower than 1%. With the use of the MIC technique, up to eight samples could be processed simultaneously, and a single absorbing solution was suitable for all analytes and determination techniques (limit of detection by IC was better than 3 microg g(-1) for all halogens).
authors.affiliation: Departamento de Química, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil. flores@quimica.ufsm.br
authors.forename: Erico M M
authors.initials: EM
authors.lastname: Flores
authors.forename: Marcia F
authors.initials: MF
authors.lastname: Mesko
authors.forename: Diogo P
authors.initials: DP
authors.lastname: Moraes
authors.forename: Juliana S F
authors.initials: JS
authors.lastname: Pereira
authors.forename: Paola A
authors.initials: PA
authors.lastname: Mello
authors.forename: Juliano S
authors.initials: JS
authors.lastname: Barin
authors.forename: Günter
authors.initials: G
authors.lastname: Knapp