Source: Laboratory of Dr. Khuloud Al-Jamal - King's College London

Mass spectrometry is an analytical chemistry technique that enables the identification of unknown compounds within a sample, the quantification of known materials, the determination of the structure, and chemical properties of different molecules.

A mass spectrometer is composed of an ionization source, an analyzer, and a detector. The process involves the ionization of chemical compounds to generate ions. When using inductively coupled plasma (ICP), samples containing elements of interest are introduced into argon plasma as aerosol droplets. The plasma dries the aerosol, dissociates the molecules, and then removes an electron from the components to be detected by the mass spectrometer. Other ionization methods such as electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) are used to analyze biological samples. Following the ionization procedure, ions are separated in the mass spectrometer according to their mass-to-charge ratio (m/z), and the relative abundance of each ion type is measured. Finally, the detector commonly consists in an electron multiplier where the collision of ions with a charged anode leads to a cascade of increasing number of electrons, which can be detected by an electrical circuit connected to a computer.

In this video, the procedure of ICP-MS analysis will be described by the detection of ⁵⁶Fe as an example.

1. Cleaning of Polycarbonate Tubes

1. Use polycarbonate tubes resistant to acidic solutions for sample digestion. In order to remove any contaminating trace of iron, fill all tubes with 5 mL of 0.1 M HCl.
2. Place tubes in a water bath for 1 h at 50 °C.
3. Wash the tubes with 5 mL of Milli-Q water and dry the tubes in an oven or chemical hood.

2. Sample Preparation and Digestion

1. Place 200 µL of sample in 1.8 mL of concentrated nitric acid (65

ICP-MS analysis of samples containing iron oxide nanoparticle is shown below. A standard curve was carried out using known concentration of ⁵⁶Fe (Figure 1). The correlation coefficient being close to 1 (R² = 0.999989) showed the good linear relationship between the sample concentrations and the intensity measured by the detector. Samples of interests showed values within the calibration range (Figure 2). The concentrations calculated by the software were then adjusted according to the d

The environmental and geological fields represent the first use for ICP-MS for example to measure contaminants present in water, in the soil, or in the atmosphere. The presence of contaminants at high concentration in tap water such as Fe, Cu, or Al can be monitored using ICP-MS.

The medical and forensic science fields also use ICP-MS detection. In case of suspicion of a metal poisoning such as arsenic, samples such as blood and urine can be analyzed using ICP-MS. This technique can al