Determination of fulvic acids in water samples of Hungarian caverns

Tatár, Enikő; Csintalan, Eszter; Mihucz, Victor G.; Tompa, Károly; Pöppl, L.; Záray, Gyula

doi:10.1016/s0026-265x(02)00045-0

Cited by 5 publications

(2 citation statements)

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“…One of the major problems observed in the cloud point extraction of humic substances is due to the presence of ionizable carboxylic and hydroxyl groups in their structure, which makes it difficult to improve the extraction efficiency, especially when hydrophobic media are used such as XAD resin and activated carbon. 17,38 In those cases, usually the pH value has to be lowered below 2, in order to protonate the humic substances and obtain hydrophobic species which can be extracted. However, even by applying these changing conditions on the original sample, it has been observed that FA is not completely extracted 38,39 due to the higher polar character of FA in comparison with HA.…”

Section: Effect Of the Cationic Surfactant On The Extraction At Diffe...mentioning

confidence: 99%

“…17,38 In those cases, usually the pH value has to be lowered below 2, in order to protonate the humic substances and obtain hydrophobic species which can be extracted. However, even by applying these changing conditions on the original sample, it has been observed that FA is not completely extracted 38,39 due to the higher polar character of FA in comparison with HA. Moreover, the structure and aggregation of the humic substances and their metal complexation potential, as well as the ability to immobilize toxic hydrophobic organic compounds within the humic micelle, depend on pH.…”

Section: Effect Of the Cationic Surfactant On The Extraction At Diffe...mentioning

confidence: 99%

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Trace humic and fulvic acid determination in natural water by cloud point extraction/preconcentration using non-ionic and cationic surfactants with FI-UV detection

Wuilloud

Sadi

et al. 2003

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A preconcentration and determination method for humic and fulvic acids at trace levels in natural water samples was developed. Cloud point extraction was successfully employed for the preconcentration of humic acid (HA) and fulvic acid (FA) prior to the determination by using a flow injection (FI) system coupled to a spectrophotometric UV-Vis detector. The quantitative extraction of HA and FA within the pH range 1-12 was obtained by neutralization of the anionic charge on the humic substances with a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB). This generated a hydrophobic species that was subsequently incorporated (solubilized) into the micelles of a non-ionic surfactant polyethylene glycol, tert-octylphenyl ether (Triton X-114). The FI method for HA and FA determination was developed by injection of 100 microl of the extracted surfactant-rich phase using an HPLC pump with spectrophotometric detection at 350 nm. A 50 ml sample solution preconcentration allowed an enrichment factor of 167. The limit of detection (LOD) obtained under the optimal conditions was 5 microg l(-1). The precision for ten replicate determinations at 0.2 mg l(-1) HA was 3.1% relative standard deviation (RSD), calculated from the peak heights. The calibration using the preconcentration system for HA and FA was linear with a correlation coefficient (r2) of 0.9997 at levels near the detection limits up to at least 1 mg l(-1). The method was successfully applied to the determination of HA and FA in natural water samples (river water).

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Section: Effect Of the Cationic Surfactant On The Extraction At Diffe...mentioning

confidence: 99%