User Benefits
Application
News
Fig. 1 ICPMS-2040/2050 and AS-20
Sample
Stainless steel certified reference material NSTM SUS570-1
(Nippon Steel Technology Co., Ltd.)
Introduction
In high-performance metallic materials such as steel, material
properties are strongly influenced by trace element
concentrations, making their proper control extremely important.
Conventionally, inductively coupled plasma atomic emission
spectrometry (ICP-AES) has been widely used for trace element
analysis in metallic materials. In Japan, steel samples have been
controlled and analyzed based on JIS G 1201
1)
and JIS G 1258.
2)
Recently, however, as metallic materials have become
increasingly sophisticated, there has been a growing need to
control elements at concentrations below those that can be
addressed by conventional methods.
Inductively coupled plasma mass spectrometry (ICP-MS) is known
as a highly sensitive technique for trace element analysis, but in
the past it was not always suitable for analyzing high-matrix
samples such as metals. In recent years, however, improvements
in sample introduction systems, including gas dilution technology,
have made it possible to apply ICP-MS to high-matrix samples as
well.
This article describes the trace element analysis of certified
reference materials for steel using the Aerosol Dilution System
installed as standard in the ICPMS-2050 (Fig. 1). By reducing the
amount of sample introduced into the plasma through gas
dilution, matrix-induced decreases in signal intensity and signal
drift could be effectively suppressed, enabling stable analytical
results. The results are presented below.
Table 1 Concentrations in Calibration Standards
Even high-matrix metal samples can be analyzed using the Aerosol Dilution System.
Trace elements in steel can be analyzed simultaneously under a single He collision mode, reducing analysis time.
Operating costs can be reduced by using a mini torch, which reduces argon consumption.
Trace Elements Analysis in Steel by ICP-MS
Yuichiro Matsui
Inductively Coupled Plasma Mass Spectrometer
Elements
STD1
(µg/L)
STD2
(µg/L)
STD3
(µg/L)
STD4
(µg/L)
P, Cu, Sn 0 50 250 1000
Sb, Te, Pb, Bi 0 2 10 40
Nitric acid 1.5 mL / 50 mL
Hydrochloric acid 1.5 mL / 50 mL
Sample Preparation
1. Approximately 0.5 g of the sample was weighed into a
fluororesin vessel, and 15 mL of a mixed acid consisting
of hydrochloric acid and nitric acid in a 1:1 (v/v) ratio was
added.
2. After heating on a hot plate at 80 °C for 90 minutes, the
temperature was raised to 150 °C, and heating was
continued for an additional 90 minutes.
3. After cooling to room temperature, the digested solution
was transferred and diluted to a final volume of 50 mL
with pure water.
4. 10 mL of the solution prepared in step 3 was taken, 3 mL
of the mixed acid was added, and the solution was
diluted to a final volume of 50 mL with pure water.
These operations were performed three times simultaneously
using the same certified reference material, and triplicate
sample solutions were prepared.
Standard Preparation
Calibration Standards
Calibration standards were prepared by mixing commercially
available single-element standard solutions and adding nitric
acid and hydrochloric acid. The concentrations of the target
elements in each calibration standard are shown in Table 1.
Internal Standards
An internal standard solution was prepared by mixing single-
element standard solutions of In and Tl, followed by the
addition of nitric acid and hydrochloric acid to match the acid
composition of the calibration standards. The concentration of
each internal standard element was 1000 µg/L. During analysis,
the internal standard solution was introduced using the
automatic internal standard addition kit.
Configurations and Analytical Conditions
Table 2 lists the instrument configurations. To reduce operating
costs, the analysis was performed using a mini torch, which
consumes less argon than a conventional torch. In this study,
only helium (He) was used to remove spectral interferences.
Although ICPMS-2050 was used for this analysis, a similar
analysis can also be performed with ICPMS-2040, which is
dedicated to collision mode. All target elements in this study
can be analyzed under a single set of cell conditions using He as
the collision gas, eliminating the need to change cell conditions
depending on the element and thereby shortening the analysis
time.
In addition, because a 0.2 % stainless steel solution was
introduced directly, each parameter was optimized to maintain
a robust plasma in the presence of the matrix. The analytical
conditions are shown in Table 3.
