Characterization of a microwave microstrip helium plasma with gas-phase sample introduction for the optical emission spectrometric determination of bromine, chlorine, sulfur and carbon using a miniaturized optical fiber spectrometer

Abstract

Continuous flow generation of Br 2, Cl 2 and H 2S coupled to a low-power 2.45 GHz microwave microstrip He plasma exiting from a capillary gas channel in a micro-fabricated sapphire wafer with microstrip lines has been used for the optical emission spectrometric determination of Br, Cl and S using a miniaturized optical fiber CCD spectrometer. Under optimized conditions, detection limits (3σ) of 330, 190 and 220 μg l − 1 for Br, Cl and S, respectively, under the use of the Br II 478.5 nm, Cl I 439.0 nm and S I 469.0 nm lines were obtained and the calibration curves were found to be linear over 2 orders of magnitude. In addition, when introducing CO 2 and using the rotational line of the CN molecular band at 385.7 nm the detection limit for C was 4.6 μg l − 1 . The procedure developed was found to be free from interferences from a number of metal cations and non-metal anions. Only the presence of CO 3 2− and CN − was found to cause severe spectral interferences as strong CN and C 2 molecular bands occurred as a result of an introduction of co-generated CO 2 and HCN into the plasma. With the procedure described Br, Cl and S could be determined at a concentration level of 10–30 mg l − 1 with accuracy and precision better than 2%.