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

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Detail(s)

Original languageEnglish
Pages (from-to)3985-3990
Journal / PublicationEnvironmental Science and Technology
Volume36
Issue number18
Publication statusPublished - 15 Sep 2002

Abstract

A new cloud-point extraction and preconcentration method using a cationic surfactant, Aliquat-336 (tricaprylyl-methylammonium 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 extra ction efficiency were also studied.

Citation Format(s)

Cloud-point extraction and preconcentration of cyanobacterial toxins (microcystins) from natural waters using a cationic surfactant. / Man, Ben Kwok-Wai; Lam, Michael Hon-Wah; Lam, Paul K. S.; Wu, Rudolf S. S.; Shaw, Glen.

In: Environmental Science and Technology, Vol. 36, No. 18, 15.09.2002, p. 3985-3990.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review