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Analysis of Trace Elements in Table Salt Using
ICPMS-2050
Kosuke Naka
Inductively Coupled Plasma Mass Spectrometer ICPMS-2050
Sample Preparation
The robustness of the ICPMS-2050 to sample matrix effects was
evaluated using table salt, a food with a particularly high matrix
concentration.
Unspiked Sample
An unspiked sample was prepared by weighing out approx. 0.2
g of table salt, adding 2.5 mL of nitric acid, 0.25 mL of
hydrochloric acid, and making the mixture up to 50 mL with
pure water. The final concentration of table salt in the unspiked
sample was approx. 0.4 %, the nitric acid concentration was 5 %
v/v, and the hydrochloric acid concentration was 0.5 % v/v.
Spiked Sample
A spiked sample was prepared by weighing out approx. 0.2 g of
table salt, adding 2.5 mL of nitric acid, 0.25 mL of hydrochloric
acid, adding commercially available single-element standard
solutions of Al, Cr, Mn, Ni, Cu, Zn, As, Se, Mo, Cd, Sn, Hg, Tl, and
Pb, then making the mixture up to 50 mL with pure water.
Method Blank
A method blank was prepared by combining 2.5 mL of nitric
acid with 0.25 mL of hydrochloric acid and making the mixture
up to 50 mL with pure water.
Fig. 1 ICPMS-2050 and AS-20 Equipment
Table 1 Target Element Concentrations in Calibration Standards
Elements
Calibration Standard (µg/L)
STD1 STD2 STD3 STD4
Cr, Ni, As, Se, Mo, Cd,
Sn, Tl, Pb
0 1 5 10
Hg 0 0.1 0.5 1
Al, Mn, Cu, Zn, 0 10 50 100
Nitric acid 5 % v/v
Hydrochloric acid 0.5 % v/v
Standard Samples
Calibration Standards
Calibration standards were prepared by combining
commercially available single-element standard solutions of Al,
Cr, Mn, Ni, Cu, Zn, As, Se, Mo, Cd, Sn, Hg, Tl, and Pb and adding
nitric acid and hydrochloric acid. The concentration of the target
elements in each calibration standard is shown in Table 1.
Internal Standard Solution
An internal standard solution was prepared by combining
commercially available single-element standard solutions of Sc,
Ge, Rh, Ir, and Bi and adding nitric acid to 5 % v/v and
hydrochloric acid to 0.5 % v/v. The final concentration of Sc, Ge,
Rh, Ir, and Bi in the internal standard solution was 2 mg/L.
Initial Calibration Verification (ICV) and Continuing
Calibration Verification (CCV) Samples
ICV and CCV samples were prepared with the same target
element concentrations as STD3 in Table 1.
Continuing Calibration Blank (CCB) Sample
A CCB sample was prepared with the same target element
concentrations as STD1 in Table 1.
Equipment Configuration and Analytical
Conditions
The configuration of the ICP-MS system is shown in Table 2. To
reduce running costs, analysis was performed with a mini-torch
that consumes less argon gas than a typical plasma torch. To
reduce the labor involved in sample preparation, the internal
standard sample was added online using an online internal
standard kit.
The analytical conditions used are shown in Table 3. A complex
investigation of conditions was avoided by using the analytical
conditions from a preset method in LabSolutions™ ICPMS.
Elements in table salt can be accurately analyzed over a long period of time.
Reduced running costs due to a mini-torch that uses less argon gas
Avoids a complex investigation of conditions by using the analytical conditions from preset methods.
Introduction
The Codex general standard for contaminants and toxins in
food and feed (Codex) establishes requirements for levels of
toxic metal elements in foods
1)
. Inductively coupled plasma
mass spectrometry (ICP-MS) systems can perform highly
sensitive quantitative determination of multiple elements
simultaneously, making them suited to the analysis of even
trace amounts of toxic metal elements in foods.
Food samples are typically high-matrix samples that can often
impact the clogging of torch or interfaces such as skimmer
cone, non-spectral interference, and long-term stability in ICP-
MS analysis.
This Application News uses the ICPMS-2050 (Fig. 1) to analyze
table salt, a food with a particularly high matrix concentration.
This analysis was performed using a mini-torch that features low
argon gas consumption. The long-term stability and spike
recovery were assessed based on the Food and Drug
Administration (FDA) Elemental Analysis Manual (EAM) Section
4.7
2)
.
