Analysis semiquantitative

If your data quality objectives for accuracy and precision are less stringent, ICP-MS offers a very rapid semiquantitative mode of analysis. This technique enables you to automatically determine the concentrations of up to 75 elanents in an unknown sample, without the need for calibration standards. There are slight variations in the way different instruments approach semiquantitative analysis, but the general principle is to measure the entire mass spectrum, without specifying individual elanents or masses. It relies on the principle that each element s natural isotopic 

FIGURE 13.3 In semiquantitative analysis, a small group of elements are used to update the reference response curve to improve the accuracy as the sample matrix changes. 

Practical Guide to ICP-MS A Tutorial for Beginners, Second Edition 

The other thing to be wary of with semiquantitative analysis is the spectral complexity of unknown samples. If you have a spectrally rich sample and are not making any compensations for spectral overlaps close to the analyte peaks, it could possibly give you a false-positive for that element. Therefore, you have to be very cautious when reporting semiquantitative results on completely unknown samples. They should be characterized first, especially with respect to the types of spectral interferences generated by the plasma gas, the matrix, and the solvents/acids/chemicals used for sample preparation. Collision/reaction cells/interfaces can help in the reduction of some of these interferences, but extreme care should be taken, as these devices are known to have no effect on some polyatomic interferences, and in some cases can increase the spectral complexity by generating other interfering complexes. 

If your data quality objectives for accuracy and precision are less stringent, ICP-MS offers a very rapid semiquantitative mode of analysis. This technique enables you 

This process is often called semiquantitative analysis using external calibration, and like traditional quantitative analysis using external standardization, works extremely well for samples that have a similar matrix. However, if you are analyzing samples containing widely different concentrations of matrix components, external calibration does not work very well because of matrix-induced suppression effects on the analyte signal. If this is the case, semiquant using a variation of standard addition 

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H. W. Fishbum, Jr., and W. E. DiU, Jr., "A Method for the Semiquantitative Analysis and Identification of Mixed Phases of Manganese Dioxide," paper presented at the Power Sources Conference, Atlantic City, N.J., May 10, 1961. 

Zinc smelters use x-ray fluorescence spectrometry to analyze for zinc and many other metals in concentrates, calcines, residues, and trace elements precipitated from solution, such as arsenic, antimony, selenium, tellurium, and tin. X-ray analysis is also used for quaUtative and semiquantitative analysis. Electrolytic smelters rely heavily on AAS and polarography for solutions, residues, and environmental samples. 

It is clear from the RSF data shown in Figure 2 that even without the use of RSFs, a semiquantitative analysis accurate to within an order of magnitude is quite possible, and GDMS indeed will provide full coverage of the periodic table. The analysis of a material of unknown composition will be elementally complete to trace levels, with no glaring omissions that may eventually return to haunt the end user of the material. 

One of the important advantages of ICPMS in problem solving is the ability to obtain a semiquantitative analysis of most elements in the periodic table in a few minutes. In addition, sub-ppb detection limits may be achieved using only a small amount of sample. This is possible because the response curve of the mass spectrometer over the relatively small mass range required for elemental analysis may be determined easily under a given set of matrix and instrument conditions. This curve can be used in conjunction with an internal or external standard to quantily within the sample. A recent study has found accuracies of 5—20% for this type of analysis. The shape of the response curve is affected by several factors. These include matrix (particularly organic components), voltages within the ion optics, and the temperature of the interffice. 

The authors of [33] considered their liquid Newtonian. Going back to Fig. 3 and its discussion, it becomes clear that this theory is fully applicable in qualitative and even semiquantitative analysis of thermoplastic foaming. 

Table 7-12. Semiquantitative Analysis of a Rare-Earth Mixture by X-ray Emission Spectrography...

Tracheal aspirate cultures (semiquantitative analysis of pathogenic bacteria)... 

Medhurst AD et al. The use of TaqMan RT-PCR assays for semiquantitative analysis of gene expression in CN S tissues and disease models. J Neurosci Methods 2000 98 9-20. 

Semiquantitative analysis. In a preliminary investigation, the analysis using Eq. (1) of space relaxation data, obtained by testing under shift conditions the catalyst at high oxidation state by a CO, H O, N. mixture at constant PH 0 = °>40 bar and various p and at different temperature leve s between 180°C and 260 C, resulted in the following kinetic parameters for the power law rate r = k-p Q ... 

Figure 9.7 Sensitivity (ion counts per second/concentration in ppb) as a function of mass number in ICP-MS analysis. A semiquantitative analysis for elements not available as standards can be carried out by interpolating from such a graph.

If it is not possible to include a particular element in the calibration solutions, it is possible to perform a semiquantitative analysis. This uses the response of those elements which are in the calibration solution, but predicts the sensitivity (defined as cps/concentration) for the missing element(s) by interpolating between the sensitivities of known elements. By plotting sensitivity against mass for all the elements present in the calibration solutions (Fig. 9.7) and fitting a curve through the points, it is possible to predict the sensitivity of the instrument for any particular mass number, and hence use this sensitivity to convert cps to concentration at that mass number. As can be seen from the figure, however, this is a very crude approximation, and any data produced in this way must be treated with some caution. 

Graphs in Chapter 11 have shown that, at skeletal level, the diversity of natural products is highest for the Indo-Pacific area. Although a similar semiquantitative analysis for the actual metabolites is difficult to make, the trend is expected to be the same because of the highly interacting forms of life, semiochemicals in coral reefe should prove an even more common system of communication than in... 

An alternative to quantitative analysis by ICP-MS is semiquantitative analysis, which is generally considered as a rapid multielement survey tool with accuracies in the range 30-50%. Semiquantitative analysis is based on the use of a predefined response table for all the elements and a computer program that can interpret the mass spectrum and correct spectral Interferences. This approach has been successfully applied to different types of samples. The software developed to perform semiquantitative analysis has evolved in parallel with the instrumentation and, today, accuracy values better than 10% have been reported by several authors, even competing with typical ones obtained by quantitative analysis. The development of a semiquantitative procedure for multielemental analysis with ICP-MS requires the evaluation of the molar response curve in the ICP-MS system (variation of sensitivity as a function of the mass of the measured isotope) [17]. Additionally, in the development of a reliable semiquantitative method, some mathematical approaches should be employed in order to estimate the ionisation conditions in the plasma, its use to correct for ionisation degrees and the correction of mass-dependent matrix interferences. 

J. I. Garcia-Alonso, M. MonLcs-Bayon and A. Sanz-Medel, Environmental applications using ICP-MS semiquantitative analysis, in Plasma Source Mass Spectrometry New Development and Applications, ed. G. Holland and S. D. Tanner, Royal Society of Chemistry, Cambridge, 1999, pp. 95-107. 

Schierle and Otto [63] used a two-layer perceptron with error back-propagation for quantitative analysis in ICP-AES. Also, Schierle et al. [64] used a simple neural network [the bidirectional associative memory (BAM)] for qualitative and semiquantitative analysis in ICP-AES. 

Laprevote, O., Girard, C., Das, B.C., Laurens, A., and Cave, A. Desorption of lithium complex of acetogenins by fast atom bombardment application to semiquantitative analysis of crude extracts. Analusis, 21, 207, 1993. 

K. Niemax, Laser Ablation—Reflections on a Very Complex Technique for Solid Sampling, Fresenius J. Anal. Chem. 2001,370, 332. A major challenge for laser ablation-mass spectrometry is quantitative analysis. One scheme achieves semiquantitative analysis without standards by comparing the signal from each element with the total mass spectrometric signal A. M. Leach and... 

G. M. Hieftje, Standardless Semiquantitative Analysis of Metals Using Single-Shot Laser Ablation Inductively Couple Plasma Time-of-Flight Mass Spectrometry, Anal. Chem. 2001, 73, 2959. 

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