Direct multielemental analysis

Huang, C. and Beauchemin, D. (2003) Direct multielemental analysis of human serum by ICP-MS with on-line standard addition using flow injection. J. Anal. At. Spectwm., 18,951-2. 

Barany, E., Bergdahl, I. A., Schutz, A., Skerfving, S., and Oskarsson, A. (1997) Indnctively coupled plasma mass spectrometry for direct multielemental analysis of diluted human blood and serum. J. Anal. At. Spectrom., 12,1005-9. 

The extension of inductively coupled plasma (ICP) atomic emission spectrometry to seawater analysis has been slow for two major reasons. The first is that the concentrations of almost all trace metals of interest are 1 xg/l or less, below detection limits attainable with conventional pneumatic nebulisation. The second is that the seawater matrix, with some 3.5% dissolved solids, is not compatible with most of the sample introduction systems used with ICP. Thus direct multielemental trace analysis of seawater by ICP-AES is impractical, at least with pneumatic nebulisation. In view of this, a number of alternative strategies can be considered ... 

Inductively coupled plasma (ICP) and direct current plasma (DCP) atomic emission spectrometry have become widely accepted techniques for simultaneous multielemental analysis. These techniques are highly sensitive and have a very wide dynamic range. A wealth of information is contained in the emission signal, including several atomic and ionic emission lines for each element in the sample. In even the simplest sample, there are thousands of observable spectral lines. To make full use of this enormous spectral information the analyst requires an instrument capable of observing a very wide spectral range simultaneously, preferably from 190 nM to 800 nM with a resolution of approximately 0.01 nM. 

Simple, low-dispersion monochromators or even interference filters are used for most flame emission applications since few atomic line spectral interferences are expected as a result of the limited population of the higher-lying excited states. For high-temperature sources such as ICPs, higher-dispersion spectrometers are typically used. Instruments set up to do simultaneous multielemental analysis can use direct readers with PMT detection. However, most modern detections systems for this type of source for simultaneous multielemental analysis employ a high-dispersion eschelle grating spectrometer and an array detector such as a CCD or CID. 

The main problem in carrying out total multielemental determinations in milk (as in other biological samples) is the nature of the matrix, which may interfere with the analytical technique employed for the measurement. In this sense, pretreatment of the samples becomes necessary so as to minimize matrix effects as much as possible (e.g., by destroying the organic matrix). An alternative to such destructive acid attacks is the direct analysis in milk whey samples by simply diluting the sample previously obtained by centrifugation. The main preparation procedures for milk samples (whole, skimmed, or freeze-dried) can be classified as follows (a) use of diluted solutions in order to minimize matrix and molecular... 

Mass spectrometry is one of the most powerful multielemental determination methods, allowing the estimation of non-pollution levels in a multielement run. In field-desorption MS, 10 pg Tl could be detected in 2, L of non-ashed sample solution (homogenized rat brain) by means of an isotope dilution technique (Schulten et al., 1978), offering possibilities of microlocal trace analysis. Ionization of CHCI3 extracts from plant cytosols with Ar" (secondary ion MS) enabled the detection of dimethylthallium-t- directly in the mass spectrum (Gunther and Umland, 1989). 

X-ray fluorescence is a non-destructive and multielemental analytical technique. Because of its excellent analytical sensitivity and spatial resolution under micro-beam conditions, the technique is capable of microscopic analysis, supplying information about two-dimensional (2D) distributions of trace elements. The technique can, thus, be used for imaging trace elements in biological specimens, and for the direct determination of trace elements in protein bands after slab-gel electrophoresis (GE), which is the benchmark for high-resolution protein separation, particularly in 2D format. Therefore, XRF is a useful technique for metallomics and metalloproteomics studies. 

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