Study of matrix effects using an adjustable chamber volume in a torch-integrated sample introduction system (TISIS) in ICP-AES

Abstract

In the present work, the recently designed torch integrated sample introduction system (TISIS) is characterized in terms of ICP-AES analytical figures of merit and matrix effects, and compared with a system dedicated to the analysis of low sample volumes (i.e., a micronebulizer, MicroMist, coupled to a low inner volume cyclonic spray chamber, Cinnabar). A double pass spray chamber was also used as a reference system. The TISIS design was modified with respect to the original in order to adjust the cavity inner volume to the analysis requirements. Four different volumes were tested (5, 9, 15 and 20 cm³). For the two latter ones, a mobile polyethylene body was adapted to the torch base. By modifying the position of this body, the volume of the chamber between the nebulizer and the injector torch could be adjusted. The liquid flow rates tested ranged from 20 to 200 µl min⁻¹. At the lowest Q_l studied, the solvent evaporation was very intense and, thus, the TISIS chamber acted as an evaporation cavity. At 200 µl min⁻¹, filtering of the aerosol took place inside the TISIS, and its cavity performed as an actual spray chamber. The results, corresponding to the determination of the tertiary aerosols, demonstrated that the injector played a more important role for the TISIS than for the Cinnabar spray chamber. The ICP-AES sensitivities and limits of detection reached with the TISIS were of the same order as those found for the Cinnabar and better than those obtained for the double pass spray chamber. Wash out times for TISIS depended on the cavity/chamber inner volume. At 20 µl min⁻¹, for a 20 cm³ volume, they were similar to those for the Cinnabar, whereas for the 9 cm³ volume, they were about 30 s shorter. In all cases, the wash out times for the TISIS were lower than those for the double pass spray chamber. The matrix, steady state effects were evaluated for nitric and sulfuric acid solutions, and the non--spectroscopic interferences for the TISIS were found to be less severe than those for both the Cinnabar and the double pass spray chamber.