Decomposition trace analysis

An important analysis regarding toxicological and legal requirements of flavourings is the control of heavy metal contaminations. Most of the heavy metals show toxic effects in humans, even in trace quantities. Their determination can only be accomplished using trace analysis techniques. In practice, the different analytical techniques Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) have been employed successfully. Both methods require complete dissolution of the sample by decomposition. 

Knapp G (1990) Mechanised methods of sample decomposition in trace and ultra-trace analysis. Anal Proceed 27 112-114... 

Decomposition of materials for trace analysis in the cement industry. In Stoeppler M, ed. Sampling and Sample Preparation, Practical Guide for Analytical Chemists, pp. 183-198. Springer-Verlag, Berlin. 

Tolg G (1983) Role of sample decomposition and preconcentration in elemental trace analysis. Pure Appl. Chem 55 1989-2006. 

Decomposition of these stone formations using nitric acid and perchloric acid, followed by a few drops of hydrofluoric acid in a microwave oven should be the method of choice for trace analysis of these stone formations using most analytical methods requiring the sample in solution. 

Neumann, C., Eichinger, P. (1991) Ultra-trace analysis of metaUic contaminations on silicon wafer surfaces by vapour phase decomposition/total reflection X-ray fluorescence (VPD/TXRF). Spectrochimica Acta Part B Atomic Spectroscopy, 46,1369-1377. 

Particularly in trace analysis, and in the absence of standard samples for calibration purposes, there still is no satisfactory alternative to relying at lea.st initially on wet-chemical multistep procedures. This entails a detour consisting of sample decomposition with subsequent separation and enrichment of the analyte(s) of interest relative to interfering matrix constituents. A suitable form of the analyte(s) is then subjected to the actual determination step, which may ultimately involve one or more of the direct instrumental methods of analysis. 

When solids need to be analyzed, samples have to be dissolved. Sample decomposition methods range from simple dissolution in aqueous solutions to treatment with strong and oxidizing acids. In all sample dissolution and pretreatment work for ASS, attention must be paid to all the problems which be set trace elemental analytical chemistry. This includes precautions for avoiding contamination from the reagents, the vessels used, and from the laboratory atmosphere (->Trace Analysis). All... 

Figure B2.1.8 Dynamic absorption trace obtained with the dye IR144 in methanol, showing oscillations arising from coherent wavepacket motion (a) transient observed at 775 mn (b) frequency analysis of the oscillations obtained using a linear prediction, smgular-value-decomposition method.

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