ICP optical emission spectrophotometers (also known as ICP-OES) have been in widespread use for the past 25 years and have evolved into one of the most flexible methods of inorganic analysis. The characteristics of this device are frequently compared to those of atomic absorption spectrophotometers. Argon inductively coupled plasma spectrometers have an excitation temperature of 5000 to 7000 K, which efficiently excites many elements. This is in contrast to atomic absorption spectrophotometers, in which the excitation temperature of an air-acetylene flame measures between 2000 and 3000 K. Additionally, the use of an inert gas like argon makes icp optical emission spectrometer more difficult to generate oxides and nitrides.
One technique for conducting optical emission spectrometry is known by its acronym ICP, which stands for inductively coupled plasma
An analysis sample's component parts (atoms) become excited when energy from an external plasma source is introduced to the sample from the outside
When the excited atoms settle back down to their original low energy state, emission rays, also known as spectrum rays, are released
The wavelengths of the emission rays that correspond to the photons are then measured
The location of the photon rays is used to determine the type of element, and the intensity of the rays is used to determine the amount of each element
In order to produce plasma, argon gas must first be pumped into the torch coil, and then a high-frequency electric current must be passed through the work coil, which is located at the very end of the torch tube. Ionization of argon gas and production of plasma are accomplished by utilizing the electromagnetic field that is produced in the torch tube as a result of the high frequency current. The excitation-emission of the sample makes use of the energy contained in this plasma, which has a high temperature and a high electron density (10000K). Through the slender tube located in the middle of the torch tube, atomized samples of solutions are introduced into the plasma.
ICP-OES's Analytical and Chemical Characteristics
The atomic absorption spectrophotometers that are used for purposes comparable to those of the ICP-OES can be differentiated from one another by the following features.
Simultaneous, sequential analysis of multiple elements possible
A significant portion of the linear portion of the analytical curve
Fewer opportunities for chemical interference or ionization interference, which makes it possible to analyze high-matrix samples
A high level of sensitivity (the lower limit of detection for the majority of elements is 10 ppb or lower).
High number of measurable elements; elements that are challenging to analyze using atomic absorption spectrometry, such as Zr, Ta, rare earth, P, and B, can be analyzed with relative ease using this method.
Unchanging
The structure and properties of the light source plasma are the primary sources from which the majority of the aforementioned characteristics are derived.
Equipment
A light source unit, a spectrophotometer, a detector, and a data processing unit are the components that make up the apparatus used for ICP optical emission spectrometry. There are several different kinds of apparatus that can be differentiated by the spectrophotometer and detector that they use. Figure 1 depicts the most common form of this phenomenon.
Sequential type
The most common configuration for this type is a spectrophotometer that contains a Czerny-Turner monochrometor and a detector that contains a photomultiplier. In order to obtain accurate readings for a number of constituents, this apparatus sequentially modifies the wavelength setting of the spectrophotometer. This results in a rather lengthy measurement time; however, because its spectrophotometers have a high resolution, it is advantageous for the measurement of high-matrix samples.
Simultaneous Type
In spectrophotometers of this type, an echelle cross disperser is typically used as the detector, and a semi-conductor detector, such as a CCD, is used in the instrument. By utilizing a combination of prism and echelle diffraction grating, the echelle cross disperser is able to two-dimensionally disperse light that falls within a measurable wavelength range. The use of a CCD detector in conjunction with an echelle cross disperser makes it possible to perform multi-element measurements at any wavelength. The high-speed measurement capability of this apparatus is without a doubt the most notable aspect of its design. In a normal setting, measurements take between one and two minutes, and they provide data on all 72 of the measurable elements.
Various Submissions
Material analysis is one of the most important applications fields for inductively coupled plasma optical emission spectrometry (ICP-OES). An examination of a sample of steel can be seen in the following example.
Equipment: Sequential Type ICP-OES, SPS3000*Sample: JSS Standard Steel Sample 150, 0.5 grams dissolved in 100 milliliters of a mixed acid consisting of chloric and nitric acids.
Standard solution: 0.5 grams of pure iron, 99.99 percent, dissolved in 100 milliliters of solution is used as a blank, and the standard curve is created by using standard solutions of eight different elements that have been measured (matrix matching).
Conditions for the analysis:When dealing with a sample that has a high matrix, spectral overlap with the matrix element, which in this case is iron, can occur. As a result, the spectral profile needs to be inspected, and the most appropriate analysis wavelength needs to be selected for measurement.
The chart displays the results from the three samples that were measured in addition to the value that was certified for the standard sample. The results show that there is an extremely high level of congruence.
