Multi-element determination

Within the confines of the present volume it is not possible to provide a detailed discussion of instrumentation for atomic fluorescence spectroscopy. An instrument for simultaneous multi-element determination described by Mitchell and Johansson53 has been developed commercially. Many atomic absorption spectrophotometers can be adapted for fluorescence measurements and details are available from the manufacturers. Detailed descriptions of atomic fluorescence spectroscopy are to be found in many of the volumes listed in the Bibliography (Section 21.27). 

Bermejo-Barrera P, I Ernanuez-Nocelo S, Moreda-PiSeiro A and Bekmejo-Barrera A (1999) Useftilness of enzymatic hydrolysis procedures based on the use of pronase E as sample pre-treatment for multi-element determination in biological materials. J Anal At Spcctrom 14 1893-1900. 

Simultaneous or sequential multi-elemental determination capability (up to 100 ppm)... 

In a typical MIP-MS instrument, the ICP portion is replaced with one of a variety of microwave discharge sources, usually a fairly standardised (modified) Beenakker cavity connected to a microwave generator. The analytical MIP at intermediate power (<500 W) is a small and quiet plasma source compared with the ICP. The mass spectrometer needs no major modifications for it to be interfaced with the MIP. With MIP used as a spectroscopic radiation source, typically consisting of a capillary (1mm i.d.), a power of 30-50 W and a gas flow below 1 L min 1, multi-element determinations are possible. By applying electrodeposition on graphite electrodes, ultratrace element determinations are within reach, e.g. pg amounts of Hg. 

Applications A method for multi-element determination of major elements in commercial and in-house prepared polymer/additive formulations by MIP-AES after microwave digestion with nitric acid has been reported [212], The precision obtained varied between 2 and 4.5 %, depending on the element determined. 

Holmes, L.J., Robinson, V. J., Makinson, P. R. and Livens, F. R. (1995). Multi-element determination in complex matrices by inductively coupled plasma-mass spectrometry (ICP-MS). Science of the Total Environment 173 345-350. 

Zheng, J., Goessler, W., Geiszinger, A., et al. (1997). Multi-element determination in earthworms with instrumental neutron activation analysis and inductively coupled plasma mass spectrometry a comparison. Journal of Radioanalytical and Nuclear Chemistry 223 149-155. 

The current generation of inductively coupled plasma emission spectrometers provide limits of detection in the range of 0.1-500pg L 1 in solution, a substantial degree of freedom from interferences and a capability for simultaneous multi-element determination facilitated by a directly proportional response between the signal and the concentration of the analyte over a range of about five orders of magnitude. 

To exploit the possibility of rapid multi element determinations by modem sequential ICP instruments the pre-concentration procedure must be carried out off-line. Knapp et al. [4i] have developed a microprocessor-controlled preconcentration instrument that performs various preconcentration regimes. In order to demonstrate the options available, trace elements have been concentrated in brines and in standard reference... 

Intensive instrumental and analytical methods research performed during the 1970 s has clearly contributed to the confidence with which current research results are reported. Examination of recent literature shows that research protocols have departed from simplistic single element studies and have incorporated more realistic experimental designs that include multi-elemental determinations. 

As discussed before, quadrupole based ICP-MS allows multi-element determination at the trace and ultratrace level and/or isotope ratios in aqueous solutions in a few minutes as a routine method with detection limits of elements in the sub pgml-1 range and a precision for determined trace element concentration in the low % range (RSD - relative standard deviation). The precision for isotope ratio measurements varies between 0.1% and 0.5% RSD. This isotope ratio precision is sufficient for a multitude of applications, e.g., for evidence of contamination of sample with depleted or enriched uranium in urine (this technique is used in the author s laboratory in a routine mode14) or the isotope dilution technique for the quantitative determination of trace element and species concentration after doping the sample with enriched isotope spikes. 

Today, as a direct solid-state analytical technique, dc GDMS is more frequently applied for multi-element determination of trace contaminants, mostly of high purity metallic bulk samples (or of alloys) especially for process control in industrial laboratories. The capability of GDMS in comparison to GD-OES (glow discharge optical emission spectrometry) is demonstrated in a round robin test for trace and ultratrace analysis on pure copper materials.17 All mass spectrometric laboratories in this round robin test used the GDMS VG 9000 as the instrument, but for several... 

Trace impurities in noble metal nanoclusters, used for the fabrication of highly oriented arrays on crystalline bacterial surface layers on a substrate for future nanoelectronic applications, can influence the material properties.25 Reliable and sensitive analytical methods are required for fast multi-element determination of trace contaminants in small amounts of high purity platinum or palladium nanoclusters, because the physical, electrical and chemical properties of nanoelectronic arrays (thin layered systems or bulk) can be influenced by impurities due to contamination during device production25 The results of impurities in platinum or palladium nanoclusters measured directly by LA-ICP-MS are compared in Figure 9.5. As a quantification procedure, the isotope dilution technique in solution based calibration was developed as discussed in Chapter 6. 

ICP-MS is well suited for the multi-element determination of trace impurities in different types of water samples, such as drinking water, rain, sea, river, groundwater and also waste water samples (and in addition, highest purity water as required for microelectronics) due to its excellent detection limits from the pg m I 1 to Ig m I 1 concentration range. This powerful and sensitive mass spectrometric technique is applied in routine measurement programs for characterization of water quality and determination of pollution in many laboratories worldwide. 

Multi-element determination of REE concentrations by quadrupole based ICP-MS... 

Consequently, the contamination danger can be minimized. Furthermore, isotope dilution analysis with LA-ICP-MS can be used as a microlocal analytical technique for multi-element determination in thin layers or nanowires of high purity platinum and palladium nanoclusters on DNA. LA-ICP-MS allows microlocal analysis for studying the elemental distribution in layered systems and bulk material. 

An accurate determination of copper and zinc traces in human serum samples from the International Measurement Evaluation Programme-17 launched by IRMM (Geel) has been made by isotope dilution TIMS.38 An analytical method for the multi-element determination of metals (Ti, V, Cr, Co, Ni and Mo) potentially released from dental implants and prostheses into human body fluids (in blood and urine) by ICP-MS (double-focusing sector field instrument and quadrupole instrument with octopole collision cell) for medical studies was developed in Sanz-Medel s group.39 The Cr and Co concentrations found in blood samples of patients with chromium-cobalt based alloy varied in the sub-p,gl 1 range and were not significantly higher than the basal levels found by other authors.40... 

At present, advanced mass spectrometric techniques have been successfully established among a multitude of quite different analytical methods as very powerful tools which are increasingly being employed for high tech research topics and for daily routine analyses in many laboratories worldwide. Numerous different applications in various fields of use, as demonstrated in the several chapters of this book, illustrate the excellent current capability of inorganic mass spectrometry in the multi-element determination of elements in a wide dynamic range (from % range for determination of stoichiometries, e.g., in layered materials, down to the extreme ultratrace level, e.g., in environmental research, speciation analysis and isotope ratio measurements). 

Multi-element determination of dissolved metals at ultratrace level may be performed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). U.S. EPA s Methods 200.8 and 1638 present a methodology for measuring trace elements in waters and wastes by the above technique. Sample is acid digested and the solution is introduced by pneumatic nebulization into a radio-frequency plasma. The elements in the compounds are atomized and ionized. The ions are extracted from the plasma through a differentially pumped vacuum interface and separated by a quadrupole mass spectrometer by their mass to charge ratios. The mass spectrometer must have a resolution capability of 1 amu peak width at 5% peak height. 

In spite of the problems associated with the new solid state detectors there is no question that they are extremely useful in multi-element determinations and in many cases eliminate the need of time-consuming... 

However, any spectrometer that uses CS and a double monochromator with an echelle grating makes it possible to reach any line within an extremely short period of time of much less than 1 s, as both the grating and the prism are stepper-motor controlled. This feature allows a fast sequential multi-element determination to be performed with the great advantage that flame conditions and burner... 

M. M. Castineira, R. Brandt, A. von Bohlen, Development of a procedure for the multi-element determination of trace elements in wine by ICP-MS, Anal. Bioanal. Chem., 370 (2001), 553-558. 

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