Water quality — Determination of microcystins — Method using liquid chromatography and tandem mass spectrometry (LC-MS/MS) (ISO 22104:2021)
This document specifies a method for the quantification of twelve microcystin variants (microcystin-LR, -LA, -YR, -RR, -LY, -WR, -HtyR, -HilR, -LW, -LF, [Dha7]-microcystin-LR, and [Dha7]-microcystin-RR)in drinking water and freshwater samples between 0,05 µg/ l to 1,6 µg/ l. The method can be used todetermine further microcystins, provided that analytical conditions for chromatography and massspectrometric detection has been tested and validated for each microcystin. Samples are analysed byLC-MS/ MS using internal standard calibration.This method is performance based. The laboratory is permitted to modify the method, e.g. increasingdirect flow injection volume for low interference samples or diluting the samples to increase the upperworking range limit, provided that all performance criteria in this method are met.Detection of microcystins by high resolution mass spectrometry (HRMS) as an alternative for tandemmass spectrometry (MS/ MS) is described in Annex A.An alternative automated sample preparation method based on on-line solid phase extraction coupledto liquid chromatography is described in Annex B.When instrumental sensitivity is not sufficient to reach the method detection limits by direct flowinjection, a solid phase extraction clean-up and concentration step is described in Annex C.
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