Secondary quantitative analysis

Quantitative analysis by SIMS is difficult because of matrix effects. The yield of secondary ions depends strongly on the chemical and electronic characteristics of the sample. For example, the yield of Al, Cr, and V are about 10 greater for... 

XRF nowadays provides accurate concentration data at major and low trace levels for nearly all the elements in a wide variety of materials. Hardware and software advances enable on-line application of the fundamental approach in either classical or influence coefficient algorithms for the correction of absorption and enhancement effects. Vendors software packages, such as QuantAS (ARL), SSQ (Siemens), X40, IQ+ and SuperQ (Philips), are precalibrated analytical programs, allowing semiquantitative to quantitative analysis for elements in any type of (unknown) material measured on a specific X-ray spectrometer without standards or specific calibrations. The basis is the fundamental parameter method for calculation of correction coefficients for matrix elements (inter-element influences) from fundamental physical values such as absorption and secondary fluorescence. UniQuant (ODS) calibrates instrumental sensitivity factors (k values) for 79 elements with a set of standards of the pure element. In this approach to inter-element effects, it is not necessary to determine a calibration curve for each element in a matrix. Calibration of k values with pure standards may still lead to systematic errors for unknown polymer samples. UniQuant provides semiquantitative XRF analysis [242]. 

Quantitative analysis of protein IR and VCD spectra in terms of the fractional components (FC) of their secondary structure has taken different approaches, as noted earlier. The FTIR approach of assigning frequencies to specific components can, in principle, identify amounts of unordered structure in a protein fold. The viability of this approach... 

In addition to absorption problems, measurements will be affected by secondary fluorescence and scattered radiations which will enter the detector and increase the general background. Detection limits under optimum conditions (a heavy element in a light matrix) may be as low as 10 ppm. Quantitative analysis is however difficult below the 20-100 ppm region if a reasonable precision (5% or better) is to be obtained. 

Expression (4-2) accounts qualitatively for the observed variations of secondary ion yields with ionization potential. It also describes correctly that the yields of positive secondary ions from metals increase when molecules such as CO or oxygen, which increase the work function, cover the surface. Although the model elegantly predicts a number of trends correctly, it is not detailed enough to be a basis for quantitative analysis of technical samples. 

The substantial effect of secondary breakup of droplets on the final droplet size distributions in sprays has been reported by many researchers, particularly for overheated hydrocarbon fuel sprays. 557 A quantitative analysis of the secondary breakup process must deal with the aerodynamic effects caused by the flow around each individual, moving droplet, introducing additional difficulty in theoretical treatment. Aslanov and Shamshev 557 presented an elementary mathematical model of this highly transient phenomenon, formulated on the basis of the theory of hydrodynamic instability on the droplet-gas interface. The model and approach may be used to make estimations of the range of droplet sizes and to calculate droplet breakup in high-speed flows behind shock waves, characteristic of detonation spray processes. 

Siggia, S., Hanna, J. G., and Kervenski, J. R. Quantitative analysis of mistures of primary, secondary, and tertiary aromatic amines. Anal. Chem., 1950, 22, 1295-1297. 

In contrast to SIMS, in SNMS - where the evaporation and ionization processes are decoupled -the matrix effects are significantly lower, because the composition of sputtered and post-ionized neutrals corresponds more closely to the composition in the solid sample (compared to the sputtered secondary ions in SIMS), which means the RSCs of elements vary by about one order of magnitude. Consequently, a semi-quantitative analysis by SNMS can also be carried out if no suitable matrix matched CRM is available. This is relevant for thin film analysis, especially for the determination of elemental concentration profiles in depth, for studying the stoichiometric composition of thin films and interdiffusion effects. 

M. S. Wagner, M. Shen, T. A. Horbett and D. G. Castner, Quantitative analysis of binary adsorbed protein films by time-of-flight secondary ion mass spectrometry, J. Biomed. Materials Res., 64A(1), 2003, 1-11. 

One of the common methods for studying the interaction of radicals with retarders is to decompose an initiator, such as azofsobutyronitrile, in the presence of an additive and to carry out product analysis. If the solutions are dilute and if several rather similar products are formed, quantitative analysis by conventional methods is exceedingly difficult especially if only part of the initiator is allowed to decompose in order to minimise the importance of secondary reactions. Problems of this sort can be solved by the method of isotope dilution analysis if labelled reagents are used. 

Marotti, G., Favia, A., and Zambonin Zallone, A. Quantitative analysis on the rate of secondary bone mineralization. Calc. Tiss. Res. 10, 67—81 (1972). 

In secondary ion mass spectrometry (SIMS) the sample surface is sputtered by an ion beam and the emitted secondary ions are analyzed by a mass spectrometer (review Ref. [360]). Due to the sputtering process, SIMS is a destructive method. Depending on the sputtering rate we discriminate static and dynamic SIMS. In static SIMS the primary ion dosis is kept below 1012 ions/cm2 to ensure that, on average, every ion hits a fresh surface that has not yet been damaged by the impact of another ion. In dynamic SIMS, multiple layers of molecules are removed at typical sputter rates 0.5 to 5 nm/s. This implies a fast removal of the topmost layers of material but allows quantitative analysis of the elemental composition. 

Muddiman, D. C., Gusev, A. I., and Hercules, D. M. (1996). Application of secondary ion and matrix-assisted laser desorption-ionization time-of-flight mass spectrometry for the quantitative analysis of biological molecules. Mass Spectrom. Rev. 14 383-429. 

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