Elemental Analyzer

Elemental analysis (EA) refers to detecting the compositional elements of the target and determining how much of each element there is. Elemental analysis is broadly grouped into organic analysis—in which organic compounds are analysed in fields such as pharmaceuticals and biotechnology—and inorganic analysis—in which the composition and impurities of industrial materials are analysed.

When the organic compound subjected to analysis is a mixture, analysis is performed via purification. For example, the solubility in a solvent is investigated or the purity is investigated by isolating the targeted component via distillation and then physical properties such as melting point, boiling point, and spectrum are measured. In this manner, the molecular formula is determined by subjecting the compositional elements to qualitative and quantitative analyses and measuring their molecular weights. Organic analysis is useful in the functional expression of cutting-edge materials in fields such as pharmaceuticals, biotechnology and electronics.

Because inorganic analysis can be applied to all materials handled in inorganic chemistry, the types of elements and their number are far greater than organic materials. Hence, inorganic analysis is widely used in industrial fields where diverse materials and components are handled. Inorganic qualitative analysis is the method used to determine the types of components such as atomic species, groups of atoms, molecular species and isotopes within inorganic materials. This analysis is performed qualitatively or via detection. The analysis method used to determine the amount of contained components is called inorganic quantitative analysis. Quantitative analysis is used in a variety of industries for chemical analysis of industrial materials, direct analysis of solid samples, microanalysis of pharmaceuticals and biological samples, analysis of ion components in electronics fields such as semiconductors and fields such as secondary batteries.

This section introduces typical inorganic analysis techniques and principles of analysis equipment.

Also known as inductively coupled plasma mass analysis, this mass analysis method uses argon plasma for ionisation. With this method most elements can be ionised at a rate of 90% or higher. First, the sample solution is converted into an aerosol and inserted into the plasma. The elements within the sample solution dissolve, vaporise, atomise and are ionised. Then, they pass the sampling interface and are drawn into the mass analysis section which is subject to a high vacuum. These elements are focused by an ion lens, separated by a mass spectrometer and measured by a detector.

This form of atomic emission spectroscopy uses high-frequency inductively coupled plasma (ICP) as its light source. The sample solution is converted into an aerosol and inserted into high-temperature argon plasma for measurement. Spectroscopy of the light emitted when an element returns to its ground state provides a qualitative analysis of the element from the wavelength of the light and a quantitative analysis of the element from the intensity of the light. Many types of elements can be measured, and this method is used in the composition analysis that identifies the metallic elements in thin films. Analysis equipment is available in sequential types, which measure a single element with high resolution, and multi-channel types, which use multiple CCDs to simultaneously measure multiple elements.

This method uses a graphite kiln for converting the sample into a solution or atomisation within the frame to heat the measurement sample and atomise its elements (atom vaporisation). The element to measure is then permeated with light at an appropriate wavelength. The atoms at their ground state absorb this light and are excited. The element concentration is measured according to the amount of light absorbed by the element under measurement. Because a dilute acid aqueous solution is used for the measurement sample, solid samples must undergo appropriate pre-processing.

In this analysis method, the sample is irradiated with X-rays (primary X-rays). Then, the excited fluorescent X-rays (secondary X-rays) are detected to qualitatively and quantitatively measure the element. When the sample is subjected to X-rays, the inner shell electrons jump out to the outer shell, creating vacancies. The element is measured from its characteristic fluorescent X-ray which is generated from the energy difference when electrons move to fill these vacancies. Different methods are used depending on the element to measure. Wavelength-dispersive X-ray fluorescence spectroscopy (WDX) separates and detects the fluorescent X-rays with crystals and energy-dispersive X-ray fluorescence spectroscopy (EDX) detects the fluorescent X-rays with a semiconductor detector.

In this method, the surface of a solid sample is exposed to concentrated laser light which evaporates and micronises the sample. The sample is then inserted into plasma via carrier gas for analysis and ionisation. Measuring these ions with a mass spectrometer makes it possible to investigate the elements of the localised parts of the sample.

Capillary Electrophoresis (CE)—which qualitatively and quantitatively investigates inorganic ions as well as organic acids and amines with low molecular weight in aqueous solutions, and Ion Chromatography—which measures acids and bases in solid samples with water extracted and gaseous samples with solutions collected, are also available.

The analysis methods introduced above all require significant pre-processing that are time-consuming and require a skilled user to perform. LIBS analysis significantly simplifies the identification of inorganic materials by eliminating the need for pre-processing (vacuum, cross-sectioning, etc.). Information such as the analysis principle, characteristics, types and applications of this method are explained below.