Permanent modification in electrothermal atomic absorption spectrometry - advances, anticipations and reality

A review with 80 refs. Permanent modification is an important recent development in chem. modification techniques which is promising in view of increasing sample throughput with 'fast' programs, reducing reagent blanks, preliminary elimination of unwanted modifier components, compatibility with online and in situ enrichment, etc. An overview of this approach based on the authors' recent research and scarce literature data is given, revealing both success and failure in studies with permanently modified surfaces (carbides, nonvolatile noble metals, noble metals on carbide coatings, etc.), as demonstrated in examples of direct electrothermal at. absorption spectrometric (ETAAS) applications to biol. and environmental matrixes and vapor generation (VG)-ETAAS coupling with in-atomizer trapping of hydrides and other analyte vapors. Permanent modifiers exhibit certain drawbacks and limitations such as: poorly reproducible treatment technologies - eventually resulting in poor tube-to-tube repeatability and double or multiple peaks; impaired efficiency compared with modifier addn. to each sample aliquot; relatively short lifetimes; limitations imposed on temp. programs, the pyrolysis, atomization and cleaning temps. being set somewhat lower to avoid excessive loss of modifier; applicability to relatively simple sample solns. rather than to high-salt matrixes and acidic digests; side effects of overstabilization, etc. The most important niches of application appear to be the use of permanently modified surfaces in coupled VG-ETAAS techniques, anal. of org. solvents and exts., concs. and fractions obtained after enrichment and/or speciation sepns. and direct ETAAS detns. of highly volatile analytes in relatively simple sample matrixes. [on SciFinder (R)]