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Subcritical water as an eluent for flow analysis systems including solid-phase extractionтезисы доклада
- Авторы: Statkus M., Goncharova E., Gorbacheva S., Tsysin G.
- Сборник: 21st International Conference on Flow Injection Analysis and Related Techniques. Book of Absracts
- Тезисы
- Год издания: 2017
- Место издания: VVM Publishing Lld Ст-Петербург
- Первая страница: 43
- Последняя страница: 43
- Аннотация: In the recent years there is a considerable interest in replacing organic eluents in HPLC separations with so-called subcritical water. Pressurized hot (liquid) water at 150-250 °C was shown to be similar in elution strength to ambient temperature water-acetonitrile mixtures of various compositions. It makes possible to use subcritical water as a replacement for organic solvents also in flow analysis systems including solid-phase extraction. We will review some literature publications on this problem, as well as present our own research. The present report is devoted to study and development of the on-line and off-line coupling of SPE and HPLC via subcritical water desorption. We have used porous graphitic carbon (PGC) column for solidphase extraction of analytes from water samples and octadecylsilica (ODS) column for HPLC separation. HPLC separation was carried out at ambient temperature with water-acetonitrile eluent. Phenol, its chloro- and nitro- derivatives, mono- and dialkyl phthalates were used as model substances. The developed procedure includes the following steps. First, solid-phase extraction of analytes on PGC column is carried out. Then, analytes are eluted by subcritical water at 150-250 °C and 30-60 bar; the effluent flow is cooled. In on-line mode the effluent is passed through HPLC column, where peak focusing takes place. Finally, HPLC separation by water-acetonitrile mixture at ambient temperature is carried out. Chromatographic peak widths were compared for three cases: direct injection HPLC analysis; desorption with water-acetonitrile mixture; desorption with subcritical water with subsequent focusing. It was found out that the third approach resulted in narrow peaks comparable to peaks obtained by direct injection. Desorption with water-acetonitrile resulted in excessive peak broadening. Analyte stability during desorption was studied for a group of analytes that are known to undergo hydrolysis at high temperatures: mono- and dialkylphthalates were chosen as model analytes. It was found out that desorption at temperatures higher than 150 °C result in partial hydrolysis of most of the studied phthalates. This problem could be avoided by carrying out desorption at lower temperatures, compensating for lower elution strength by adding 5-l 0% of acetonitrile to the elution solvent. We have applied so-called solvation parameters model for description and prognosis of retention of analytes during desorption. System constants were obtained for PGC and subcritical water in temperature range of 150-200 oc and water-methanol or water-acetonitrile mixtures at ambient temperature for comparison. These constants were used for prognosis of desorption efficiency for several analyte groups.
- Добавил в систему: Цизин Григорий Ильич