Cloud-point extraction and preconcentration of cyanobacterial toxins (microcystins) from natural waters using a cationic surfactant

Ben Kwok-Wai MAN, Michael Hon-Wah LAM, Paul K. S. LAM, Shiu Sun Rudolf WU, Glen SHAW

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41 Citations (Scopus)

Abstract

A new cloud-point extraction and preconcentration method using a cationic surfactant, Aliquat-336 (tricaprylylmethylammonium chloride), has been developed for the determination of cyanobacterial toxins, microcystins, in natural waters. Sodium sulfate was used to induce phase separation at 25°C. The phase behavior of Aliquat-336 with respect to concentration of Na₂SO₄ was studied. The cloud-point system revealed a very high phase volume ratio compared to other established systems of nonionic, anionic, and cationic surfactants. At pH 6-7, it showed an outstanding selectivity in analyte extraction for anionic species. Only MC-LR and MC-YR, which are known to be predominantly anionic, were extracted (with averaged recoveries of 113.9 ± 9% and 87.1 ± 7%, respectively). MC-RR, which is likely to be amphoteric at the above pH range, was not detectable in the extract. Coupled to HPLC/UV separation and detection, the cloud-point extraction method (with 2.5 mM Aliquat-336 and 75 mM Na₂SO₄ at 25 °C) offered detection limits of 150 ± 7 and 470 ± 72 pg/mL for MC-LR and MC-YR, respectively, in 25 mL of deionized water. Repeatability of the method was 7.6% for MC-LR and 7.3% for MC-YR. The cloud-point extraction process can be completed within 10-15 min with no cleanup steps required. Applicability of the new method to the determination of microcystins in real samples was demonstrated using natural surface waters collected from a local river and a local duck pond spiked with realistic concentrations of microcystins. Effects of salinity and organic matter (TOC) content in the water sample on the extraction efficiency were also studied. Copyright © 2002 American Chemical Society.

Original languageEnglish
Pages (from-to)3985-3990
JournalEnvironmental Science and Technology
Volume36
Issue number18
DOIs
Publication statusPublished - 2002

Citation

Man, B. K.-W., Lam, M. H.-W., Lam, P. K. S., Wu, R. S. S., & Shaw, G. (2002). Cloud-point extraction and preconcentration of cyanobacterial toxins (microcystins) from natural waters using a cationic surfactant. Environmental Science and Technology, 36(18), 3985-3990. doi: 10.1021/es020620v

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