Separation and preconcentration of Cr(VI) as ion associate using solid phase extraction
| Autoři | |
|---|---|
| Rok publikování | 2000 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | Collection of Czechoslovak Chemical Communications |
| Fakulta / Pracoviště MU | |
| Citace | |
| Obor | Analytická chemie, separace |
| Klíčová slova | Hexavalent chromium; solid phase extraction; ion associate; flame emission spectrometry |
| Popis | A method of separation and preconcentration of Cr(VI) was developed based on sorption on modified silica gel (C18) of an ion associate of Cr(VI) anion with a quaternary base. The study was performed with the following quaternary onium salts: [1-(ethoxycarbonyl)-pentadecyl]trimethylammonium bromide, 1-hexadecylpyridinium chloride, benzyl(dodecyl)dimethylammonium bromide, butyl(triphenyl)phosphonium bromide and tetraphenylarsonium chloride. Benzyl(dodecyl)dimethylammonium bromide was found the optimum ion-pairing reagent. Sample containing Cr(III) and Cr(VI) in the presence of 0.005 mol/l of benzyl(dodecyl)dimethylammonium bromide was pumped with a peristaltic pump through the column containing the sorbent. The optimum pH range 4-5 was maintained with 0.05 mol/l phosphate buffer. Elution was accomplished using 95 vol.% ethanol and the recovery of Cr(VI) was (96 +/- 6)% in the concentration range 0.005-1 mg/l of Cr(VI); even in a tenfold excess of Cr(III) the recovery of Cr(VI) was 99.8% with the relative standard deviation of repeatability about 2.4% Cr in the eluate was determined by emission flame spectrometry (Cr I 425.435 nm) in an air-acetylene or N2O-acetylene flame with the limits of detection 10 or 2 ng/ml, respectively. Hence, with a typical preconcentration factor of 200, the limits of detection in natural aqueous samples were 50 and 10 pg/ml, respectively. Calibrations were linear at least up to 10 mg/l. |
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