Khalaf V.A. Sorption pre-concentration and determination of phenol, 1-naphthole and 2,4,6-trinitrophenol using chemically modified silicas. – Manuscript.

Thesis for Candidate of chemical science degree with specialization in 02.00.02. - Analytical chemistry. – Kyiv National Taras Shevchenko University, Kyiv, 2006.

The Ph. D. thethis is devoted to investigation of chemically modified silicas containing groups of aryldiazonium salts, 2,3,5-triphenyltetrazole and Triton X-100. Phenols hold an important place among organic pollutants, which need to be constantly monitored in waters and in places of military activities. Sampling of phenol matrix is conducted with solid phase extragents (SPE) with further high performance liquid chromatography or gas chromatography analysis.  Application of the known SPE usually is ineffective as it doesn’t give the possibility to provide full extraction of the analyt (microcontents) in the matrix media. Therefore SPE application needs further progress in their selectivity. In the stated work was proposed a rate of modified silicas for extraction of activated and deactivated phenols. Two methods were proposed for extraction of the activated phenols. The first approach is based on heterogeneous azo-coupling reaction of phenols with aryldiazonium salts bonded on the silica surface. For this purpose p-aminoacetophenone and m-aminophenilarsonic acid were used. First reagent was covalently bonded on the silica, while second was bonded by the ion-exchange on the silica with covalently grafted quaternary ammonium salt. These diazo-couplers were transferred into aryldiazonium salts, which were stabilized with potassium tetrafluoroborate and were azo-coupled with phenols in aqua media. Complete adsorption of 1-naphthol, 2-naphthol, and resorcinol from water takes place at pH 6-9, while phenol and pirocatechin react with immobilized aryldiazonium salts at pH³ 8-9. In both of the described methods formation of immobilized azo-compounds as a result of SPE reaction with phenol leads to a drastic change in the sorbent’s color. The second approach is based on a direct interaction of phenols with 4-nitrophenyldiazonium tetrafluoroborate in aqua media and its further extraction by modified silica with polyoxyethylene isooctylphenol groups in the presence of cationic surfactant. The capacity of silicas containing groups of Triton X-100 to phenol is up to 25 μmol/g. Rapid determination of activated phenols in water by combined solid-phase extraction – diffuse reflectance spectroscopy was developed for silicas with aryldiazonium salts groups and polyoxyethylene isooctylphenol silica. Azo-dyes of phenol and 1-naphthole on polyoxyethylene isooctylphenol silica surface allowed to develop simple procedure for their desorption with further liquid chromatography/mass spectrometry or photometric analysis.

For the selective pre-concentration of deactivated phenols a new silica-based material with the grafted 2,3,5-triphenyltetrazole was proposed. This method is based on the formation of molecular charge-transfer complexes of 2,3,5-triphenyltetrazole (p-donor) with picric acid (p-acceptor) in the phase of the adsorbent. Complete adsorption of 2,4,6-trinitophenols from water is take place at pH 4-8. The capacity of proposed adsorbent is up to 70 μmol/g. Proposed SPE is suitable for high performance liquid chromatography or photometric analysis of 2,4,6-trinitrophenol after its desorption by acetonitrile.

Key words: analysis, phenols, pre-concentration, adsorption, chemically-modified silicas.