Improvement of the Limits of Detection for P, S, and Ca Nanoparticle Size in the Absence of Dissolved Analyte Using a Mixed-Gas Plasma in Single-Particle Inductively Coupled Plasma-Mass Spectrometry

摘要

Addition of nitrogen (N-2) to the plasma (outer) flow increases the power density of the plasma, which reduces matrix effects and may aid in the atomization and ionization of nanoparticles (NPs). For the first time, this work reports the limits of detection of NP diameter (LoD(size)) for 37 elements in the absence of dissolved analyte using single particle inductively coupled plasma-mass spectrometry (spICP-MS) with argon (Ar) plasma as well as Ar-N-2 and Ar-N-2-H-2 mixed-gas plasmas. For each plasma, the selected operating conditions provided a compromise in sensitivity for multielemental analysis. Despite this compromise, the Ar plasma provides significantly lower LoD(size) than previously reported using a different instrument brand. The Ar plasma also provides significantly lower LoD(size) than the mixed-gas plasmas, except for S-33, P-31, and Ca-44, where oxygen scavenging by N-2 within the Ar-N-2 plasma significantly improved LoD(size). With the Ar-N-2-H-2 plasma, an accompanying loss of sensitivity largely negated the LoD(size) improvement from oxygen scavenging. Further improvement of LODsize for S, P, and Ca can be expected from optimizing the Ar-N-2 mixed-gas plasma for the individual determination of each element.