Air Segmented Discrete Introduction in Inductively Coupled Plasma Mass Spectrometry

Abstract

An assessment of some advantages and disadvantages of ICP-MS analysis using air segmented discrete sample introduction was performed. Air segmented discrete introduction (ASDI) was effected with two small air bubbles placed between the sample and the washing solvent and was carried out by an in-house built device. Sampling by ASDI was compared with continuous introduction and flow injection, testing 12 isotopes simultaneously (²⁷Al, ⁵⁵Mn, ⁶³Cu, ⁶⁴Zn, ⁷⁵As, ¹⁰³Rh, ¹¹⁴Cd, ¹¹⁵In, ¹³⁰Te, ¹³³Cs, ²⁰⁵Tl, ²⁰⁸Pb). The main benefit of the ASDI mode is the elimination of dispersion, leading to sensitivity enhancement at the same injection frequency and long-term stability compared with flow injection. Although small volumes (104–300 µl) were injected, slightly increased signals (‘hyper signals’) were observed with ASDI compared with continuous nebulization. Hyper signals up to 15% were observed for isotopes with low and medium ionisation potentials (<7.7 eV) and a variety of masses. For the elements tested at a 104 µl injection, the ASDI-ICP-MS detection limits were improved by a factor of ≈3 (peak maximum) compared with the same volume introduced by flow injection and were similar to those of continuous sample introduction.