Evaluation of two atomisation modes for direct determination of molybdenum in complex matrices by ultrasonic slurry sampling–electrothermal atomic absorption spectrometry

Abstract

Tube wall (TWA) and L’vov platform (LPA) atomisations were compared for the direct determination of molybdenum (Mo) in coal fly ash by slurry sampling–electrothermal atomic absorption spectrometry (ETAAS). For both atomisation modes eight chemical modifiers were tested, namely HNO 3, Pd(NO 3) 2, Mg(NO 3) 2, Pd + Mg(NO 3) 2, reduced Pd, BaF 2, Ir and HF. The interfering effects of major and minor concomitants of samples on Mo signals and memory effects were also evaluated. BaF 2 and Pd(NO 3) 2 + Mg(NO 3) 2 mixture were selected for TWA and LPA, respectively. Standard addition calibration is needed in both cases. The best peak performance, memory effect reduction, within-run precision (6% versus 9% R.S.D.), and sensitivity ( m o = 7.5 pg versus 15.2 pg) were achieved with TWA compared to LPA. Both atomisation modes gave good analytical recoveries (94–102%), but the analysis of a certified coal fly ash (NIST SRM 1633a) only was accurate using TWA. Additionally, the urban dust NIST SRM 1629a was analysed.