Determination of halogens via molecules in the air-acetylene flame using high-resolution continuum source absorption spectrometry: Part I. Fluorine

The particular capabilities of a high-resolution continuum source absorption spectrometer were exploited to the determination of halogens in an ordinary air-acetylene flame. In the first part of the studies, a simple method was developed, which allows the determination of fluorine by measuring GaF molecular absorption. The molecules are generated in the presence of an excess of Ga in the flame. Under such conditions, all fluorine is converted into GaF, yielding an evaluable signal for the fluorine determination. Molecular bands of GaF were found between 211 and 214 nm; the strongest absorption band head at 211.248 nm was examined in detail to prove its applicability to analytical measurements. To this end, potential chemical and spectral interferences were tested, using various highly concentrated acids and metallic salt solutions. Since no serious interferences were found, the new method proved to be very reliable. As limit of detection, 1 mg L-1 fluorine in the presence of 10 g L-1 Ga was achieved, using a measurement time of five seconds. The linear dynamic range covers more than three orders of magnitude. Accuracy and precision were verified by analysis of a standard reference material (BCR No. 33). (c) 2006 Elsevier B.V. All rights reserved.