Periodic acid, detection properties

Chemoselective hydrogen-bonded acid polymers are at the heart of many electronic nose chemical point detection sensor systems. These polymers selectively adsorb chemical agents or explosives over extended periods of time (minutes, hours, days). Relatively thick polymer films and/or hyperporous structures allow rapid vapor sorption. Material properties are selected to allow vapor sorption, but not desorption, at ambient conditions. Heating allows the trapped agent to be released for analyses. 

To control the completion of the operation, the whole process is repeated. Quantitative removal of the Ddz-group in the first reaction period is indicated during repetition by a constant zero line on the recording. In several cases, because of the shape of the kinetic curve we were able to detect not only extended reaction times, but even incomplete removal of the protective group in the first reaction period which clearly indicated alterations in the solvation properties of the peptide-on-polymer and the necessity for repetition of the process. The quantitative determination of the Ddz-fission product is performed spectroscopically in the filtrates collected during deprotection. The results of those measurements yield directly the amount of amino acid incorporated to the polymer-bound peptide in the preceding synthesis step. Since the accuracy of the determination depends on the spectroscopic measurement and not on the reliability of an additional chemical reaction, the quality of this analysis is better than that of any other method of test. 

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