Plasma emission spectroscopy calibration

Total tin was determined by continuous on-line hydride generation followed by direct current plasma emission spectroscopy. Interfacing the hydride generation-DC plasma emission spectrometric system with high performance liquid chromatography allowed the determination of tin species. Detection limits, sensitivities and calibration plots were determined. 

In Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), a gaseous, solid (as fine particles), or liquid (as an aerosol) sample is directed into the center of a gaseous plasma. The sample is vaporized, atomized, and partially ionized in the plasma. Atoms and ions are excited and emit light at characteristic wavelengths in the ultraviolet or visible region of the spectrum. The emission line intensities are proportional to the concentration of each element in the sample. A grating spectrometer is used for either simultaneous or sequential multielement analysis. The concentration of each element is determined from measured intensities via calibration with standards. 

In the inductively coupled plasma atomic emission spectroscopy (ICPAES) method (ASTM DD 5600), a sample of petroleum coke is ashed at 700°C (1292°F) and the ash is fused with lithium borate. The melt is dissolved in dilute hydrochloric acid, and the resulting solution is analyzed by inductively coupled plasma atomic emission spectroscopy using aqueous calibration standards. Because of the need to fuse the ash with lithium borate or other suitable salt, the fusibility of ash may need attention (ASTM D1857). 

An easy calibration strategy is possible in ICP-MS (in analogy to optical emission spectroscopy with an inductively coupled plasma source, ICP-OES) because aqueous standard solutions with well known analyte concentrations can be measured in a short time with good precision. Normally, internal standardization is applied in this calibration procedure, where an internal standard element of the same concentration is added to the standard solutions, the samples and the blank solution. The analytical procedure can then be optimized using the internal standard element. The internal standard element is commonly applied in ICP-MS and LA-ICP-MS to account for plasma instabilities, changes in sample transport, short and long term drifts of separation fields of the mass analyzer and other aspects which would lead to errors during mass spectrometric measurements. 

M. L. Griffiths, D. Svozil, P. J. Worsfold, S. Denham and E. H. Evans, Comparison of traditional and multivariate calibration techniques applied to complex matrices using inductively coupled plasma atomic emission spectroscopy, J. Anal. At. Spectrom., 15, 2000, 967-972. 

The analyst uses ICP-OES (inductively coupled plasma, optical emission spectroscopy) to measure twenty different metal ions in solution. To fully calibrate the instrument requires the preparation and measurement of 100 individual calibration standards (five point calibration per element). It would be impracticable for an analyst to calibrate the instrument daily. The instrument is calibrated at regular intervals (say fortnightly) by the analyst. In the intervening time, the calibration for each metal ion is checked by the use of a set of drift correction standard solutions. Minor corrections can then be made to the calibration to allow for day-to-day drift. 

For colloids with a physically adsorbed surfactant or cca, the adsorption isotherm is important. The adsorbant concentration on the particle surface can be measured by infrared spectroscopy using diffuse reflectance and by ESCA. Absolute concentrations are difficult to determine with ESCA on "rough" surfaces, and a calibration point is required with other techniques. The change of the concentration of adsorbant in solution after adsorption on the colloid surfaces can be detected by elemental analysis of supernatant with plasma emission or atomic absorption if adsorbant contains specific element(s). When colloids are sterically stabilized, the effectiveness of the stabilization can be evaluated with solvent-nonsolvent techniques and with temperature studies ( 25,26). 

In atomic emission spectroscopy flames, sparks, and MIPs will have their niche for dedicated apphcations, however the ICP stays the most versatile plasma for multi-element determination. The advances in instrumentation and the analytical methodology make quantitative analysis with ICP-AES rather straightforward once the matrix is understood and background correction and spectral overlap correction protocols are implemented. Modern spectrometer software automatically provides aids to overcome spectral and chemical interference as well as multivariate calibration methods. In this way, ICP-AES has matured in robustness and automation to the point where high throughput analysis can be performed on a routine basis. 

Metal ions were detected using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES, Optima 8000 Perkin Elmer). The argon and air flow rate was adjusted to 12 lit/min and 1.2 lit/min, respectively. Two ICP standard solutions were used to do the calibration curves. 

In flame emission spectroscopy, the concentration of electronically excited atoms in the cooler, outer part of the flame is lower than in the warmer, central part of the flame. Emission from the central region is absorbed in the outer region. This selfabsorption increases with increasing concentration of analyte and gives nonlinear calibration curves. In a plasma, the temperature is more uniform, and self-absorption is not nearly so important. Table 20-4 states that plasma emission calibration curves are linear over five orders of magnitude compared with just two orders of magnitude for flames and furnaces. 

While a deviation from a straight line calibration is often predictable in principle from physical theory, a quantitative account is usually lacking there is no known reason why a true calibration graph should be a quadratic function or higher order polynomial. Indeed they are often of a somewhat different shape. This leads to a degree of lack of fit between the true function and the fitted function. Figure 2.23 shows an example, where a quadratic function has been fitted to closely spaced data of the slightly different shape typical of inductively coupled plasma atomic emission spectroscopy (ICP-AES) calibrations. 

Ayyalasomayajula et employed LIBS for the analysis of slurry samples. Three calibration models were developed using univariate calibration, multiple linear regression (MLR) and PLS. The LIBS analytical results obtained from the PLS model best fit the results obtained from inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. 

Fig. 8.28 (a-c) KCl (a) and NCI (b) plasma. Solid curves are absorption spectra Dashed curves are emission spectra measured. Calibration curve for K contents in NaCl measured using absorption spectroscopy (c)... 

See also Atomic Absorption, Methods and Instrumentation Atomic Absorption, Theory Atomic Emission, Methods and Instrumentation Atomic Spectroscopy, Historical Perspective Calibration and Reference Systems (Regulatory Authorities) Environmental Applications of Electronic Spectroscopy Food Dairy Products, Applications of Atomic Spectroscopy Food Science, Applications of Mass Spectrometry Food Science, Applications of NMR Spectroscopy Inductively Coupled Plasma Mass Spectrometry, Methods X-Ray Fluorescence Spectrometers X-Ray Fluorescence Spectroscopy, Applications. 

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