Improving Accuracy in Inductively Coupled Plasma-Quadrupole Mass Spectrometry: The Interference Standard Method

Author(s)

Donati, George L. ; Amais, Renata S. ; Nobrega, Joaquim A.

• Document type: Journal article
• Source: Spectroscopy; v. N/A, p. 4-pg., 2013-02-01.

Abstract

One of the main limitations with inductively coupled plasma mass spectrometry (ICP-MS) is related to the occurrence of spectral interferences. Considering the relatively low resolution presented by quadrupole-based mass spectrometry (ICP-QMS), sensitivity and accuracy can be compromised by interfering ions formed in the plasma. Several strategies have been proposed to overcome the problem, and the most successful ones are based on high-resolution instruments, mixed-gas plasmas, or collision-reaction cells and interfaces. A different approach was recently proposed based on the idea that interfering polyatomic ions and some plasma naturally occurring Ar species present similar behaviors. The so-called interference standard method (IFS) uses the analytical to IFS signal ratio associated with external calibration to minimize the interfering species contribution to the analytical signal, thereby improving ICP-QMS accuracy. In this work, the efficiency of the IFS method in the determination of Si is evaluated. A 130% recovery was found for Si-28 determined in a standard reference material (Typical Diet, NIST 1848a) using the conventional external calibration method without any interference correction. Such high recovery is a result of spectral interferences caused by molecular ions such as N-2(+) and (CO+)-C-12-O-16. On the other hand, no statistically significant difference at a 95% confidence level was found between reference- and IFS-determined values using the (ArH+)-Ar-36 or Ar-38(+) probes. Limits of detection of 6.0, 5.0, and 8.0 mu g/L were calculated for determinations at m/z 28 or using the 28/37 and 28/38 signal ratios, respectively. Possible mechanisms responsible for the IFS method efficiency also are discussed here. (AU)

• FAPESP's process: 10/17387-7 - Assessment of spectroanalytical techniques and sample preparation procedures for the determination of sulfur in biodiesel and diesel blends
• Grantee: Renata Stábile Amais
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 06/59083-9 - Inductively coupled plasma mass spectrometry: fundamentals and applications
• Grantee: Joaquim de Araújo Nóbrega
• Support Opportunities: Research Projects - Thematic Grants